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Coronal mass ejection

A coronal mass ejection (CME) is a large expulsion of plasma and magnetic field from the Sun's corona, forming a massive bubble of magnetized plasma that propagates through the heliosphere at high speeds.^[1] These events release up to a billion tons of coronal material, accelerated to velocities ranging from 200 to 3,000 kilometers per second, far exceeding the typical solar wind speed of about 400 km/s. First observed in 1971 using space-based coronagraphs, CMEs are a key driver of solar activity and space weather. The frequency of CMEs follows the Sun's 11-year solar cycle, occurring roughly once per week at solar minimum and increasing to two or three per day near solar maximum.^[5] When directed toward Earth, a CME can take 3 to 5 days to arrive, interacting with Earth's magnetosphere to trigger geomagnetic storms that disrupt power grids, satellite operations, and communications systems.^[6]^[7] These storms arise from the merging of the CME's magnetic fields with Earth's, inducing strong electrical currents that can corrode pipelines and overload transformers.^[1]^[7] In extreme cases, such as the February 2022 event, CMEs have led to the loss of dozens of satellites due to atmospheric drag from heated upper layers.^[8] Monitoring CMEs is crucial for space weather forecasting, with missions like NASA's Solar Dynamics Observatory and Parker Solar Probe providing detailed observations of their initiation, propagation, and impacts.^[9] While most CMEs disperse harmlessly in interplanetary space, Earth-directed ones pose risks to technology-dependent infrastructure, underscoring the need for predictive models to mitigate potential disruptions.^[10]

Fundamentals

Definition and Overview

A coronal mass ejection (CME) is defined as a large-scale expulsion of plasma and magnetic fields from the Sun's corona into the heliosphere.^[11] These events involve the ejection of magnetized plasma structures, often appearing as expanding bubbles or loops in coronagraph observations.^[12] Typical CMEs eject approximately $10^{15} to $10^{16} grams of coronal material at speeds ranging from 250 km/s to 3000 km/s.^[13]^[11] In terms of scale, CMEs can expand to angular widths exceeding 120 degrees as viewed from the Sun, corresponding to physical sizes up to about 0.5 AU by the time they reach Earth's orbit, and they carry embedded magnetic flux on the order of $10^{21} to $10^{22} Mx.^[14] The total energy released in a CME, primarily stored in the magnetic field, ranges from $10^{25} to $10^{32} ergs, with kinetic energy contributing significantly to the overall budget.^[14] This magnetic origin underscores the role of solar magnetic reconfiguration in driving these ejections.^[15] CMEs are distinct from other solar phenomena, such as solar flares, which involve intense bursts of electromagnetic radiation and accelerated particles from magnetic reconnection but do not entail substantial mass ejection.^[16] Unlike prominences—dense, relatively stationary clouds of cool plasma suspended in the corona by magnetic loops—CMEs represent dynamic, propagating eruptions that can incorporate prominence material but are characterized by their outward propagation and heliospheric impact.^[17]^[18]

Physical Properties

Coronal mass ejections (CMEs) consist primarily of coronal plasma, comprising protons, electrons, and alpha particles (helium nuclei), along with trace heavy ions such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron.^[19]^[20] Near the Sun, the plasma density in these ejections typically ranges from $10^{-17} to $10^{-15} g/cm³, reflecting variations in the low-coronal environment from which the material is expelled.^[21]^[22] The magnetic structure of CMEs is characterized by flux ropes, in which helical magnetic fields twist around a central axial field, forming a coherent bundle of field lines.^[23]^[24] The polarity of this helical component often opposes that of the leading edge, contributing to the overall twisted configuration observed in eruptions.^[25] Magnetic energy densities within these structures can reach up to $10^4 J/m³, representing a significant portion of the stored energy available for release during the ejection.^[26] CMEs feature multi-temperature plasma profiles, with the core maintaining temperatures around $10^6 K while the surrounding sheath is cooler, influenced by the ambient coronal conditions.^[21]^[27] Their average propagation speeds range from 400 to 800 km/s, though faster events can drive fast-mode shocks ahead of the ejecta, compressing and heating the interplanetary medium.^[28]^[29] The kinetic energy of a CME, which quantifies its dynamic impact, is expressed by the equation

E_k = \frac{1}{2} M v^2

where M is the total mass of the ejected plasma and v is its speed; this form illustrates the quadratic scaling of energy with velocity, emphasizing the role of faster ejections in delivering greater heliospheric influence.^[30]

Formation and Dynamics

Origins in the Solar Corona

The solar corona, the Sun's outermost atmospheric layer, features an extremely low plasma density of approximately $10^8 to $10^9 particles per cubic centimeter and temperatures ranging from 1 to 2 million Kelvin, creating a tenuous, hot environment where thermal pressure is minimal compared to magnetic forces.^[31]^[32] These conditions allow magnetic fields to dominate the plasma dynamics, structuring the corona into filamentary features such as loops and open field regions that guide solar wind outflow.^[33] The corona's magnetic complexity arises primarily in active regions, localized areas of intense magnetic activity often associated with sunspots—dark, cooler photospheric patches where concentrated magnetic flux emerges from the solar interior. Within these active regions, prominences—dense, cool plasma threads suspended against gravity in magnetic field dips—and arcade-like structures of overlying loops form potential source regions for coronal mass ejections (CMEs), where magnetic shear from photospheric motions builds up free energy. Sheared fields, twisted by differential rotation and convection, introduce instabilities that can lead to eruptive events when the stored magnetic energy exceeds equilibrium thresholds. In the coronal plasma, behavior is largely governed by ideal magnetohydrodynamics (MHD), enforcing the frozen-in condition where field lines move with the plasma; however, non-ideal effects enable magnetic reconnection, a diffusive process that breaks and rejoins field lines, releasing energy rapidly.^[34] Observational and simulation evidence indicates that reconnection in the solar corona proceeds at a fast rate, with the normalized inflow speed v_{\rm in} / v_A \approx 0.1, where v_{\rm in} is the reconnection inflow velocity and v_A the Alfvén speed, facilitating the onset of CMEs. Helmet streamers represent quasi-steady coronal structures, comprising closed bipolar magnetic arcades capped by oppositely directed open fields that form a neutral current sheet, often overlying active regions or prominences.^[35] These streamers delineate the boundary between opposite-polarity coronal holes and are frequent sites of CME eruptions, particularly from their cusp regions at the apex, where reconnection can open closed fields and eject plasma.^[35] The stability of these cusps relies on the balance of magnetic tension and pressure, but accumulated shear or external perturbations can trigger breakout reconnection, initiating the expulsion process.

Initiation and Acceleration

Coronal mass ejections (CMEs) initiate through several proposed mechanisms involving the destabilization of magnetic structures in the solar corona. One prominent model is the catastrophic loss of equilibrium in pre-existing magnetic flux ropes, where gradual photospheric motions build up magnetic shear until the system reaches a critical point, leading to a sudden reconfiguration and eruption. In this scenario, the flux rope, suspended above the photosphere by overlying magnetic fields, undergoes a rapid upward acceleration once equilibrium is lost, releasing stored magnetic energy. This model, developed by Lin and Forbes, emphasizes the role of global magnetic topology changes without requiring external reconnection triggers. Another key initiation mechanism is tether-cutting reconnection, in which magnetic reconnection occurs at the base of a sheared arcade, severing restraining "tethers" that hold the flux rope in place and allowing it to erupt. Proposed by Antiochos et al., this process begins with reconnection between oppositely directed fields near the polarity inversion line, forming a flux rope that expands outward as further reconnection ejects the structure. The model explains the frequent association between CMEs and flares, as the reconnection also drives plasma heating. Additionally, the kink instability can trigger eruptions in highly twisted flux ropes, where the helical deformation of the magnetic field exceeds a critical twist threshold of approximately 2.5π to 3.5π (about 1.25 to 1.75 turns), leading to non-axisymmetric perturbations that destabilize the structure. Simulations by Török and Kliem demonstrate that this ideal magnetohydrodynamic instability initiates a helical motion, often transitioning to full ejection if the overlying field is sufficiently weak. Following initiation, CMEs undergo an impulsive acceleration phase primarily driven by the Lorentz force, \mathbf{J} \times \mathbf{B}, where the current density \mathbf{J} interacts with the magnetic field \mathbf{B} to propel the plasma outward. This phase propels the ejecta to initial speeds of 100–500 km/s within the inner corona, with acceleration rates typically ranging from 100–500 m/s². A simplified expression for the acceleration a in this magnetically dominated regime is a \approx \frac{(B^2 / 4\pi \rho)^{1/2}}{r}, where \rho is the plasma density and r is the heliocentric distance, highlighting the inverse dependence on distance as magnetic tension diminishes. The eruption onset occurs over timescales of minutes to hours, often preceded by a pre-eruptive slow rise phase lasting tens of minutes to hours at velocities of 10–50 km/s, during which the flux rope ascends quasi-statically before rapid acceleration.^[36]^[37]^[36]^[38] Observational indicators of initiation and early acceleration include coronal dimming regions and extreme ultraviolet (EUV) waves. Dimming regions manifest as localized decreases in EUV and soft X-ray intensity, reflecting the evacuation of plasma as the CME lifts off, with mass losses estimated at 10^{15}–10^{16} g. These dimmings often appear transiently near the eruption site and serve as footprints of the departing flux rope. Concurrently, EUV waves—large-scale propagating disturbances at speeds of 200–1000 km/s—radiate from the eruption site, interpreted as fast-mode magnetosonic waves or plasma compressions excited by the expanding CME. These signatures, detectable via instruments like SDO/AIA, provide early warnings of the event's onset.^[39]^[40]^[41]

Propagation and Interactions

As coronal mass ejections (CMEs) propagate through interplanetary space, they expand radially due to the lower density of the ambient solar wind compared to the corona, increasing their angular width and overall size as they move outward.^[11] This expansion is accompanied by deceleration primarily from aerodynamic drag forces exerted by the solar wind, which slows faster-moving CMEs while accelerating slower ones toward the solar wind speed. The speed evolution can be approximated in drag-based models as v(t) \approx v_0 + \int -\frac{C_d \rho_{sw} A}{M} (v - v_{sw})^2 \, dt, where v_0 is the initial speed, C_d is the drag coefficient (typically ≈1 for empirical fits), \rho_{sw} is the solar wind density, A is the cross-sectional area, M is the CME mass, and v_{sw} is the solar wind speed; this results in a nonlinear decrease in speed for fast CMEs.^[42] Interactions between CMEs and the heliosphere further modify their propagation. When multiple CMEs are ejected in close succession, they can collide, leading to inelastic mergers where the trailing faster CME catches up to the leading slower one, compressing structures and potentially enhancing shock strengths or altering magnetic properties.^[43]^[44] Additionally, CMEs may experience deflection from their radial path due to gradients in ambient solar wind streams, such as corotating interaction regions, which can steer non-central CMEs eastward or westward depending on the heliospheric current sheet configuration.^[45] In the heliosphere, fast CMEs with speeds exceeding approximately 400–500 km/s relative to the solar wind drive forward shocks that accelerate particles and compress the preceding solar wind.^[46] As CMEs evolve into interplanetary CMEs (ICMEs) farther from the Sun, they exhibit characteristic signatures such as bidirectional flows of suprathermal electrons, indicating trapped plasma along open magnetic field lines connected to the Sun.^[47] Travel times to Earth vary significantly with initial speed, ranging from as little as 15–18 hours for the fastest events (up to ~3000 km/s) to several days for slower ones (~250 km/s).^[11]

Morphology and Classification

Structural Features

Coronal mass ejections (CMEs) typically exhibit a characteristic three-part structure when observed in white-light coronagraph images, consisting of a bright leading edge, a low-density cavity, and a dense core embedded within the cavity. The leading edge represents compressed plasma piled up ahead of the erupting material, often forming a shock front that enhances electron density and Thomson scattering. The cavity is a region of relatively low electron density, interpreted as the volume occupied by a twisted magnetic flux rope, while the core comprises denser prominence or filament material that trails within this cavity. This model, first widely recognized through observations from the Solar and Heliospheric Observatory (SOHO), provides a framework for understanding the internal organization of CMEs near the Sun.^[48]^[49]^[50] In terms of size and shape, CMEs display angular widths ranging from approximately 20° to 120° as measured from the Sun-Earth line in coronagraph observations, with many events showing an average width around 45°. These structures are inherently three-dimensional and often asymmetric due to radial expansion and interactions with the ambient solar wind, leading to broader lateral extents compared to their initial coronal footprints. The asymmetry arises from non-uniform expansion, where the flanks of the CME spread more rapidly than the apex, resulting in a fan-like or loop-like morphology in stereoscopic views.^[51]^[52]^[53] Internally, the flux rope within the cavity features helical magnetic field windings, with the degree of twist varying based on the pre-eruptive coronal configuration, as evidenced by signatures in both remote imaging and in-situ measurements. At the leading edge, material pile-up creates a high-density sheath that contrasts sharply with the cavity's lower density, observable through electron density variations in white-light images where the front appears brighter due to enhanced scattering. These density contrasts highlight the layered nature of CMEs, with the core's prominence plasma often showing filamentary substructures trailing the rope.^[54]^[55]^[56] As CMEs propagate, their structure evolves into a widening cone approximation, where the angular width increases with heliocentric distance due to self-similar expansion, facilitating simplified geometric modeling for forecasting arrival times at Earth. This conical evolution captures the overall radial and lateral growth, though real asymmetries persist from the low corona.^[57]^[58]

Types and Observational Signatures

Coronal mass ejections (CMEs) are classified primarily by their morphology and apparent angular width as observed in white-light coronagraph imagery. Loop-like CMEs, the most common type, display a characteristic three-part structure: a bright leading edge formed by piled-up coronal plasma, a lower-density cavity often enclosing a filament or prominence, and a brighter core representing the erupting magnetic flux rope. These structures typically appear as expanding arcade-like loops with angular widths less than 120 degrees, propagating radially from their solar source regions.^[26] Partial-halo CMEs exhibit angular widths between 120 and 360 degrees, encircling only a portion of the coronagraph's occulting disk and often indicating limbward or partially Earth-directed eruptions. In contrast, full-halo CMEs appear to surround the entire occulting disk with a 360-degree apparent width, resulting from projection effects when the CME propagates nearly toward the observer, such as events aimed at Earth. Stealth CMEs represent a distinct category, lacking prominent low-coronal signatures in extreme ultraviolet (EUV) or X-ray observations; they emerge without associated flares, dimmings, or post-eruption arcades, yet are detectable in coronagraphs as broad, diffuse ejections originating from quiet-Sun regions or active-region peripheries.^[59]^[60]^[61] Key observational signatures of CMEs span multiple wavelengths and detection methods. In white-light coronagraphs, such as those aboard the Solar and Heliospheric Observatory (SOHO), CMEs are imaged via Thomson scattering of photospheric light by free electrons in the ejected plasma, revealing their density enhancements and overall envelope up to several solar radii. Radio signatures include type II bursts, generated by magnetohydrodynamic shocks ahead of the CME propagating through the corona and interplanetary medium, manifesting as slowly drifting frequency emissions from metric to decametric wavelengths. In-situ measurements by spacecraft like Wind or ACE at 1 AU identify CME passages through bidirectional suprathermal electron flows, prolonged southward interplanetary magnetic fields, and low plasma beta conditions within magnetic clouds—coherent, force-free structures comprising about one-third of CMEs.^[26]^[62]^[63] Multi-wavelength observations complement coronagraph data by tracing CME evolution across the solar atmosphere. Soft X-ray emissions from instruments like the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory highlight reconnection sites and hot plasma associated with CME drivers, often preceding the white-light ejection by minutes. EUV imaging reveals coronal dimmings—regions of depleted density due to mass loss—and expanding loops or supra-arcade downflows linked to the eruption. Recent missions such as NASA's Parker Solar Probe and ESA's Solar Orbiter have provided close-range and multi-viewpoint observations, revealing finer details of flux rope morphology and early structural evolution near the Sun as of 2023–2025. Infrared observations, particularly in the near- to mid-IR range, can detect CME interactions with zodiacal dust or provide spectral diagnostics of cooler ejecta components through lines like those from Fe IX or Si X, aiding in multi-thermal modeling of the plasma.^[64]^[65]^[66]^[67] Observing CMEs presents challenges due to inherent limitations in remote-sensing techniques. Projection effects in two-dimensional coronagraph images distort the true three-dimensional geometry, leading to overestimation of speeds for limb events or underestimation of widths for near-disk-center eruptions, which complicates kinematic reconstructions. Non-radial propagation further complicates detection, as CMEs may deflect from their initial radial paths due to interactions with the ambient solar wind or large-scale magnetic fields, resulting in asymmetric expansion or unexpected arrival times at 1 AU. These issues underscore the value of stereoscopic viewpoints from missions like STEREO, enhanced by recent data from Parker Solar Probe and Solar Orbiter, for mitigating biases in single-observer data.^[68]^[69]

Relation to Solar Activity

Solar Cycle Variation

Coronal mass ejections (CMEs) display a pronounced variation in occurrence rate tied to the 11-year solar cycle, with the frequency increasing dramatically from solar minimum to maximum. During solar minimum, the rate averages approximately 0.2 CMEs per day, while at solar maximum, it rises to about 3–5 CMEs per day, reflecting heightened solar magnetic activity. Over the course of a full solar cycle, observations indicate a total of roughly $10^4 CMEs, underscoring the cycle's role in driving eruptive events from the Sun's corona.^[26] The properties of CMEs also evolve systematically with the solar cycle phase. At solar maximum, CMEs are typically faster, with speeds exceeding those at minimum by factors of 1.5–2, and wider in angular extent, often spanning greater heliographic widths due to more complex coronal structures. Latitude distributions shift notably: during minimum, CMEs predominantly originate at high latitudes near the solar poles, forming polar crown filaments, but migrate equatorward during the rising and maximum phases, aligning with the equatorward drift of sunspot activity known as Spörer's law.^[70]^[71] Statistical analyses from the SOHO/LASCO coronagraph provide key benchmarks for these variations, reporting an overall average CME speed of 470 km/s and a typical ejected mass of $10^{15} g across observed events. The CME occurrence rate correlates moderately with the sunspot number, yielding a Pearson correlation coefficient of approximately r \approx 0.7, indicating that solar surface magnetism is a primary driver of ejection frequency. Longer-term patterns suggest additional modulation by the 22-year Hale cycle, where reversals in the Sun's global magnetic polarity influence CME production rates between consecutive 11-year cycles, potentially leading to asymmetries in activity levels during odd- versus even-numbered cycles.^[72]

Associations with Flares and Eruptions

Coronal mass ejections (CMEs) are frequently associated with solar flares, particularly those classified as M- or X-class based on GOES soft X-ray measurements, where approximately 50-60% of such flares are accompanied by a CME.^[73] This association is understood through the standard magnetic reconnection model, in which both phenomena originate from the same reconnection site in the solar corona, where twisted magnetic fields release stored energy, accelerating plasma and producing the observed emissions and ejections.^[74] In this framework, the reconnection process drives the impulsive energy release seen in flares while simultaneously destabilizing overlying magnetic structures, leading to the expulsion of coronal material as a CME.^[75] CMEs are also commonly linked to filament eruptions, where cool, dense plasma threads suspended in the corona—known as prominences or filaments—disappear and contribute material to the ejecta. Observations indicate that more than 80% of filament eruptions result in a CME, with the filament often serving as the bright core of the three-part structure observed in white-light coronagraphs.^[76] In the symbiotic eruption model, the filament's destabilization through magnetic reconnection triggers both the flare's radiative output and the CME's propagation, as the erupting filament material interacts with the surrounding hot coronal plasma to form the overall ejecta.^[77] Temporally, the soft X-ray signature of a flare typically precedes the visible onset of the associated CME by several minutes, reflecting the rapid energy release that initiates the ejection process.^[78] The peak soft X-ray flux during these events serves as a reliable proxy for the CME's mass ejection rate, with stronger fluxes correlating to faster and more massive ejections due to enhanced reconnection-driven acceleration.^[79] Not all flares produce CMEs; confined flares, which lack an associated ejection, often occur in regions with strong overlying magnetic fields that constrain the plasma and prevent breakout. These events are characterized by localized energy release without large-scale field reconfiguration, resulting in no observable CME in coronagraph imagery.^[80] Such confinement is more prevalent in smaller active regions where the magnetic arcade is robust enough to resist eruption.^[81]

Space Weather Impacts

Effects on Earth's Environment

When a coronal mass ejection (CME) reaches Earth, its interaction with the magnetosphere begins with compression of the magnetopause, the boundary between the solar wind and Earth's magnetic field. The southward component of the interplanetary magnetic field (B_z) embedded in the CME facilitates magnetic reconnection at the dayside magnetopause, allowing solar wind plasma and energy to enter the magnetosphere. This process injects approximately 10^{12} W of power into the magnetosphere during geomagnetic storms, enhancing magnetospheric convection and overall energy loading.^[82]^[83] The influx of energy and particles from reconnection drives enhanced particle precipitation into the auroral zones, significantly amplifying auroral activity. During intense CME-driven storms, charged particles, primarily electrons, precipitate into the upper atmosphere, increasing the global auroral power to levels around 10^{11} to 10^{12} W, which can expand auroral displays to lower latitudes. This precipitation is modulated by the strength and duration of the southward B_z, leading to substorms and heightened electrodynamic coupling between the magnetosphere and ionosphere.^[84]^[85] CMEs also profoundly affect the dynamics of Earth's radiation belts by accelerating electrons to relativistic energies exceeding 1 MeV through wave-particle interactions, such as those involving chorus waves energized by the injected plasma. This acceleration fills the slot region between the inner and outer radiation belts (typically L-shells 2–3), which is normally depleted due to scattering losses, resulting in enhanced fluxes that persist for days to weeks post-storm. Such changes alter the overall structure and intensity of the Van Allen belts, with peak electron energies reaching up to several tens of MeV in extreme events.^[86]^[87] In the ionosphere, CME-induced disturbances manifest as enhancements in total electron content (TEC) and scintillation, driven by prompt penetration electric fields and thermospheric neutral wind forcing from magnetospheric energy deposition. These irregularities, often occurring in the equatorial and high-latitude regions, cause rapid fluctuations in ionospheric plasma density, leading to signal scintillation that impacts GPS accuracy by inducing phase delays and amplitude variations up to several TEC units. The disturbances peak within hours of CME arrival, correlating with the storm's intensity as measured by southward B_z duration.^[88]^[89]

Geomagnetic Storms and Technological Risks

Coronal mass ejections (CMEs) can trigger geomagnetic storms when their embedded magnetic fields interact with Earth's magnetosphere, leading to disturbances measured by indices such as the disturbance-storm time (Dst) index, which quantifies the strength of the equatorial ring current. Intense geomagnetic storms are typically defined by a Dst index below -100 nT, reflecting significant enhancement of the ring current due to injected plasma from the solar wind.^[90]^[91] These storms pose substantial risks to technological infrastructure through geomagnetically induced currents (GICs), which arise from rapid changes in Earth's magnetic field and flow through long conductive paths like power transmission lines. In power grids, GICs up to 100 A can saturate transformer cores, causing overheating, harmonic generation, and potential blackouts, as observed in events where grid operators had to disconnect lines to prevent cascading failures. Satellites face damage from high-energy particles associated with CMEs, which can penetrate shielding and degrade electronics or solar panels, leading to operational anomalies or total mission loss in vulnerable low-Earth orbit assets. Aviation encounters elevated radiation exposure during such storms, with crew and passengers at high altitudes receiving doses equivalent to multiple chest X-rays from secondary particles produced in the atmosphere, prompting route adjustments or flight delays to limit health risks.^[92]^[93]^[94]^[95] Mitigation strategies rely on space weather forecasting to provide advance warnings, with lead times for Earth-directed CMEs ranging from 15-18 hours for the fastest events to 2-4 days for typical ones, enabling protective actions like grid reconfiguration or satellite safing. The May 2024 geomagnetic storm, reaching G5 (extreme) levels with Dst minima around -412 nT, exemplified these risks by disrupting high-frequency radio communications, causing GPS signal scintillation affecting navigation, and increasing radiation doses on polar flights, though no major blackouts occurred due to timely alerts and monitoring.^[11]^[96]^[97]^[98] Similarly, the November 2025 geomagnetic storm, reaching G4 (severe) levels from multiple CMEs arriving around November 12, disrupted high-frequency radio communications and enhanced auroral displays to mid-latitudes, with no major infrastructure failures reported due to advance forecasting.^[99] A Carrington-level event, like the 1859 geomagnetic storm with an estimated Dst of around -850 nT (some estimates up to -1760 nT or as low as -900 nT), has a recurrence probability of approximately 1% per decade for Dst < -850 nT based on statistical analyses of historical and paleomagnetic records, potentially resulting in global economic losses exceeding $2 trillion from widespread power outages, satellite failures, and supply chain disruptions lasting months.^[100]^[101]

Halo CMEs and Detection Challenges

Halo coronal mass ejections (CMEs) are a subset of CMEs directed toward Earth, appearing in coronagraph observations as bright enhancements that encircle the entire occulting disk of the Sun, creating an illusion of a full solar disk halo. This visual effect occurs because the eruption is oriented limb-on relative to the observer, with the expanding plasma expanding symmetrically around the line of sight. Due to projection effects in two-dimensional imaging, the apparent speed of halo CMEs is systematically underestimated compared to their true three-dimensional propagation velocity, often by approximately 20% for events observed near the solar disk center.^[102]^[103] Detecting and characterizing halo CMEs presents significant challenges due to their ambiguous three-dimensional structure when viewed from a single vantage point, such as Earth's orbit. In coronagraph images, the superposition of foreground and background material obscures the true geometry, making it difficult to distinguish the eruption's actual width, orientation, and propagation direction, which can lead to misinterpretations of non-halo events as potential Earth-impacting halos and resultant false alarms in space weather alerts. To mitigate these issues, stereoscopic observations from missions like the Solar Terrestrial Relations Observatory (STEREO) enable three-dimensional reconstructions by providing simultaneous views from offset angles, allowing for more accurate de-projection and identification of the CME's core structure.^[104] Halo CMEs are particularly geoeffective, with approximately 71% of frontside halo events producing geomagnetic storms, largely attributable to their likelihood of carrying southward interplanetary magnetic fields (Bz) that facilitate efficient magnetic reconnection with Earth's magnetosphere. This high hit rate underscores their importance in space weather forecasting, though predictions of their arrival at Earth remain uncertain, with typical errors in transit time estimates ranging from 10 to 20 hours due to variability in solar wind interactions and initial velocity measurements.^[105]^[106] A notable recent example is the series of halo CMEs observed in May 2024 from active region AR 3664, which included multiple fast, Earth-directed eruptions following X-class flares, culminating in a G5-level geomagnetic storm from May 10 to 12—the strongest since 2003—and widespread auroral displays at low latitudes.^[107]^[108]

Observation and History

Early Discoveries and Traces

The earliest indications of coronal mass ejections (CMEs) emerged from 19th-century observations of geomagnetic storms, which hinted at solar material influencing Earth's magnetosphere. The most prominent example is the Carrington Event of September 1–2, 1859, during solar cycle 10, when astronomer Richard Carrington witnessed an intense white-light solar flare in a large sunspot group. Concurrently, physicist Balfour Stewart, director of the Kew Observatory, recorded a severe geomagnetic disturbance that disrupted telegraph systems worldwide, establishing a causal link between solar eruptions and terrestrial magnetic perturbations suggestive of ejected plasma streams. This event, the strongest geomagnetic storm in recorded history, underscored the potential for solar ejections to propagate through interplanetary space and impact Earth.^[109]^[110] In the pre-spacecraft era, additional indirect evidence accumulated from anomalous behaviors in comet tails and geomagnetic records. Discontinuities and sudden kinks in comet ion tails, observed as early as the mid-20th century, were attributed to transient bursts of high-speed solar corpuscular radiation interacting with the cometary plasma, distinct from the steady solar wind inferred by Ludwig Biermann in 1951. For instance, tail disruptions in comets like Morehouse (1908) and others were later reinterpreted as encounters with interplanetary shocks from solar ejections. Complementing this, magnetometer data revealed sudden commencements—abrupt positive deflections in Earth's horizontal magnetic field component—correlating with solar activity and interpreted as pressure pulses from arriving solar plasma clouds. These signatures provided conceptual groundwork for discrete mass ejections without direct solar imaging.^[111] Conceptual advancements in the mid-20th century further traced CME origins through radio emissions and chromospheric disturbances. In the 1940s, radio astronomy observations of solar bursts, pioneered by figures like Bernard Lovell at Jodrell Bank, indicated that intense metric-wavelength emissions arose from streams of ionized particles ejected from active regions, implying explosive mass loss from the corona. Building on this, the 1950s brought the discovery of Moreton waves by Robert Moreton, who documented large-scale, arc-like propagations in Hα emission across the solar disk at velocities exceeding 1000 km/s during major flares. These waves, spanning hundreds of thousands of kilometers, were recognized as chromospheric projections of fast-mode magnetohydrodynamic shocks in the corona, driven by eruptive events later identified as CMEs.^[112]^[111] A pivotal synthesis occurred in the 1970s with the first in-situ detections of interplanetary CMEs (ICMEs), confirming the ejection of coronal material into the heliosphere. Data from Pioneer spacecraft, such as Pioneer 10 launched in 1972, revealed plasma enhancements and bidirectional electron flows indicative of expanding magnetic structures. Similarly, Voyager 1 and 2, launched in 1977, observed ICMEs between 1 and 10 AU from 1977 to 1980, characterized by low plasma beta, enhanced magnetic fields, and compositional anomalies matching coronal signatures. These findings, including events like the August 1978 ICME studied across multiple probes, solidified the understanding that CMEs were massive, billion-tonne expulsions propagating at hundreds of km/s, reconciling earlier indirect traces with heliospheric dynamics.^[113]^[114]

Key Instruments and Missions

Ground-based instruments laid the foundation for CME observations by enabling indirect and direct views of solar eruptive phenomena. Bernard Lyot's coronagraph, invented in the early 1930s, created artificial solar eclipses to allow routine visible-light imaging of the corona from Earth's surface, marking a pivotal advance over eclipse-dependent sightings.^[115] Complementing optical methods, radio telescopes have detected type II and type IV bursts since the mid-20th century, which are signatures of shock waves and plasma emissions driven by CMEs propagating through the corona and interplanetary medium.^[116] Space-based missions revolutionized CME studies by providing uninterrupted, high-resolution observations free from atmospheric interference. The Orbiting Solar Observatory 7 (OSO-7), operational from 1971 to 1973, featured the first spaceborne coronagraph, which captured white-light images revealing 23 CME events and confirming their existence as dynamic solar phenomena.^[5] Building on this, the Skylab mission's coronagraph in 1973–1974 delivered the initial detailed optical imagery of over 110 CMEs, highlighting their morphologies, speeds, and associations with solar surface activity during a period of rising solar activity.^[71] The Solar and Heliospheric Observatory (SOHO), launched in 1995, has been instrumental in long-term monitoring through its Large Angle and Spectrometric Coronagraph (LASCO), which has cataloged more than 30,000 CMEs over nearly three decades.^[117] LASCO's C2 and C3 coronagraphs offer complementary fields of view spanning approximately 2 to 30 solar radii (R⊙), allowing comprehensive tracking of CME evolution from near-Sun launch to heliospheric propagation and enabling detailed analyses of their three-dimensional structures and kinematics.^[118] Subsequent missions enhanced stereoscopic and in-situ capabilities. The twin Solar Terrestrial Relations Observatory (STEREO) spacecraft, STEREO-A and STEREO-B, launched in 2006, provided the first three-dimensional views of CMEs by imaging events from opposing vantage points, revealing their true propagation geometries and internal complexities for over 4,500 eruptive events.^[119] Meanwhile, the Wind and Advanced Composition Explorer (ACE) spacecraft, positioned at the L1 Lagrange point since the mid-1990s, have delivered critical in-situ measurements of interplanetary CMEs (ICMEs), recording plasma, magnetic field, and compositional signatures to study their heliospheric impacts and geoeffectiveness.^[120]

Recent Advances and Simulations

The Parker Solar Probe has provided unprecedented in situ measurements of coronal mass ejections (CMEs) through its close approaches to the Sun, reaching distances as low as approximately 9.9 solar radii during its December 2024 perihelion. These encounters have enabled direct sampling of CME-driven shocks and associated phenomena, including sub-Alfvénic solar wind regions induced by CMEs, where plasma flows slower than the local Alfvén speed. For instance, data from the probe's eighth encounter in April 2021 onward revealed consistent sub-Alfvénic conditions linked to CME propagation, offering insights into the early evolution of these structures near the Sun. Additionally, 2024 observations captured nascent CMEs, including bursts of plasma release and Kelvin-Helmholtz instabilities within ejecta, highlighting turbulent mixing at shock interfaces. Complementing these findings, the Solar Orbiter mission, operational since 2021, has advanced multi-viewpoint imaging of CMEs using its suite of remote-sensing and in situ instruments, such as the Extreme Ultraviolet Imager (EUI) and the Solar Orbiter/HIS (SoloHI) coronagraph. High-resolution EUV and coronagraphic data from 2023 to 2025 have revealed asymmetric ejections, with east-west detection asymmetries in solar energetic particles exceeding 10 MeV, attributed to varying magnetic connectivity and CME geometries. For example, observations of the April 2023 CME that triggered Solar Cycle 25's first severe geomagnetic storm demonstrated non-uniform expansion and particle acceleration, informed by SoloHI's wide-field views from off-ecliptic vantage points. Joint analyses with Parker Solar Probe data, such as for the September 2022 CME, have modeled global structures, confirming flux rope configurations and radial evolution of interplanetary shocks at distances below 0.8 AU. Magnetohydrodynamic (MHD) simulations have seen significant improvements in forecasting CME propagation and interactions, with models like WSA-ENLIL integrating real-time solar wind data for 1-4 day predictions of arrival times at Earth. These simulations assimilate coronagraph observations to refine ambient solar wind backgrounds, achieving accurate estimates for events like the January 2025 CMEs. Recent 2025 studies focused on the May 2024 superstorm, driven by multiple interacting CMEs, used MHD frameworks to simulate their evolution, revealing how successive ejecta mergers amplified geomagnetic impacts through enhanced shock strengths and prolonged disturbances. Such models, including those in the Space Weather Modeling Framework, have demonstrated that three CMEs arrived nearly simultaneously at Earth, contributing to the event's extremity. Advances in understanding young Sun analogs include spectroscopic detections of multi-temperature CME signatures in pre-main-sequence stars. A 2025 study identified the first evidence of such ejections from the young G dwarf EK Draconis, a solar analog approximately 100 million years old, using Hubble Space Telescope and ground-based observations to trace hot plasma components across temperatures exceeding 10 million Kelvin. These findings, revealing filamentary eruptions akin to solar CMEs, suggest frequent mass loss in T Tauri-like phases, informing models of early solar activity and its effects on proto-planetary environments.

Notable Events

Historical Significant CMEs

The Carrington Event of September 1–2, 1859, stands as the most intense geomagnetic storm in recorded history, inferred to have been triggered by a massive coronal mass ejection (CME) following a powerful solar flare observed by Richard Carrington.^[121] This event produced widespread auroral displays visible as far south as the Caribbean and caused global disruptions to telegraph systems, including fires at operators' stations and induced currents that operated lines without batteries.^[122] Modern reconstructions estimate the storm's intensity at a disturbance-storm time (Dst) index of approximately −900 nT, with estimates ranging from −800 nT to −1,100 nT, far exceeding typical severe storms.^[123]^[124] On August 4, 1972, a Carrington-class solar event unleashed an ultra-fast CME associated with a nearly white-light flare, marking one of the earliest instances of such phenomena captured by space-based observations from the Orbiting Solar Observatory-7 (OSO-7) mission.^[125] The CME propagated at an average shock speed of around 2900 km/s, leading to a severe geomagnetic storm that intensified solar radiation and caused operational failures in at least seven satellites, including disruptions to telecommunications and power systems.^[126] This event highlighted the vulnerability of early space assets, with proton fluxes reaching levels that would have endangered Apollo astronauts if a mission had been underway.^[127] The March 13, 1989, geomagnetic storm originated from a filament eruption on the Sun that ejected a high-speed CME, resulting in one of the most significant power grid failures in modern history.^[128] The ensuing geomagnetic disturbances induced geomagnetically induced currents (GICs) that overwhelmed the Hydro-Québec transmission system, causing a nine-hour blackout affecting six million people across Quebec and parts of the northeastern United States.^[129] The storm peaked with a Dst index of -589 nT, underscoring the direct link between solar eruptions and terrestrial infrastructure risks.^[128] The Halloween solar storms of October–November 2003 featured a sequence of multiple X-class solar flares and associated CMEs from active region AR 0486, producing some of the most intense space weather of the space era.^[130] These events drove super-intense geomagnetic storms, with one reaching a Dst index of -383 nT, alongside solar energetic particle fluxes that elevated radiation levels to hazardous thresholds.^[131] Astronauts aboard the International Space Station were compelled to shelter in protected areas to mitigate radiation exposure, as proton event intensities approached S4 (severe) levels for extended periods.^[132]

Modern and Extreme Events

One of the most notable near-misses in recent solar history occurred on July 23, 2012, when a powerful coronal mass ejection (CME) erupted from active region AR1520 on the Sun's farside, narrowly avoiding a direct impact with Earth.^[133] This Earth-directed event traveled at speeds exceeding 2,000 km/s, with the associated shock wave reaching approximately 3,000 km/s as it propagated through interplanetary space, arriving at the STEREO-A spacecraft in just 19 hours.^[134] If it had struck Earth, models indicate it would have triggered an extreme geomagnetic storm with a Dst index of around -1,200 nT, rivaling the intensity of the 1859 Carrington Event and potentially causing widespread technological disruptions.^[135] In May 2024, a series of fast and interacting CMEs from active region AR3664 produced the strongest geomagnetic storm since 2003, classified as G5 on the NOAA scale from May 10 to 12.^[136] These CMEs, traveling at speeds up to 1,300 km/s, arrived in rapid succession, with their compressed magnetic fields enhancing the storm's severity and leading to prolonged auroral displays visible at unusually low latitudes, including as far south as 21°N.^[108] The event also induced significant atmospheric expansion, resulting in increased satellite drag that affected low-Earth orbit assets, with drag levels rising by factors of up to 10 times normal and necessitating orbital adjustments for hundreds of satellites.^[137] Recent simulations in 2025 have highlighted the potential devastation of Carrington-scale CMEs, particularly in multi-CME complexes where successive ejections clear interplanetary space, allowing subsequent events to accelerate and amplify impacts.^[138] European Space Agency (ESA) models from October 2025 predict that such a superstorm could increase satellite drag by 400%, potentially destroying or deorbiting the entire constellation of low-Earth orbit satellites through atmospheric heating and collision risks.^[139] These ENLIL-based simulations underscore the vulnerability of modern space infrastructure, estimating near-total satellite loss in a direct hit scenario comparable to the 1859 event.^[140] A striking example of modern CME scale was observed on October 21, 2025, when a massive farside eruption from a complex active region produced a spectacular CME captured by NOAA's GOES-16 coronagraph.^[141] Though non-Earth-directed, this event ejected billions of tons of plasma at high speeds, forming a vast halo-like structure visible in extreme ultraviolet imagery, illustrating the immense energy release—estimated at over 10^32 ergs—possible during solar maximum and the challenges in forecasting such remote ejections.^[141]

Stellar Analogues

CMEs in Other Stars

Observations of coronal mass ejections (CMEs) in stars other than the Sun rely primarily on indirect detection methods, as direct imaging is challenging due to the lack of spatial resolution for distant stars. In active stars such as RS CVn binaries, which are close binary systems with enhanced magnetic activity, CMEs are inferred from associated radio bursts and X-ray flares that indicate plasma ejections and magnetic reconnection events.^[142]^[143] These bursts, often in the decimeter to meter wavelength range, accompany flares and suggest shock waves driven by ejected material, similar to type II radio bursts observed in solar CMEs.^[144] Spectroscopic techniques have provided more direct evidence, particularly through Doppler shifts in emission lines that reveal outflowing plasma. In 2025, high-resolution far-ultraviolet (FUV) spectroscopy of the young Sun-like star EK Draconis captured the first multi-temperature signatures of a stellar CME, including hot plasma at approximately 100,000 K and cooler components indicative of a massive eruption following a superflare.^[64]^[145] This event, with an estimated mass of about 10^17 grams, highlights the feasibility of detecting CMEs in young G-type stars via line profile asymmetries in spectra from instruments like the Hubble Space Telescope. In November 2025, astronomers confirmed the first coronal mass ejection from a star other than the Sun using radio and X-ray observations of the M dwarf StKM 1-1262, marking a breakthrough in direct detection.^[146] Analogous multi-temperature plasma ejections have been identified in T Tauri stars, pre-main-sequence analogues to the early Sun, through combined X-ray and UV observations revealing dimming and outflow signatures during flare events.^[147] Frequency estimates for stellar CMEs vary by spectral type and activity level, with M-dwarfs exhibiting rates up to 10^3 to 10^4 times higher than the modern Sun due to their strong magnetic fields and frequent flaring.^[148] In these cool, low-mass stars, which dominate the stellar population, super-CMEs with kinetic energies ranging from 10^34 to 10^36 ergs occur regularly, often linked to superflares exceeding 10^34 ergs in radiated energy.^[149] For comparison, solar CMEs typically release 10^30 to 10^32 ergs, underscoring the enhanced eruptive activity in more magnetically dynamic stars.^[150] Detection challenges persist, as most evidence is indirect and requires distinguishing CME signatures from other flare-related phenomena. Enhancements in H-alpha line profiles, such as red asymmetries from accelerating plasma, serve as proxies for outflows in M-dwarfs and active giants, but contamination from chromospheric activity complicates interpretation.^[151] Similarly, ultraviolet dimmings—temporary decreases in EUV flux—indicate coronal mass loss in K- and M-type stars, yet these are subtle and demand high-cadence photometry to confirm association with ejections.^[152] Advances in machine learning applied to spectral data are improving the identification of these Doppler signatures across stellar samples.^[153]

Implications for Exoplanetary Systems

Coronal mass ejections (CMEs) from active stars pose significant threats to the atmospheres of close-in exoplanets, particularly those orbiting in the habitable zone of M dwarfs, by driving atmospheric erosion through high-energy particle impacts and enhanced escape processes. High-energy CMEs can strip volatiles such as hydrogen and oxygen from planetary atmospheres, with the mass loss rate per event approximated as Ṁ ≈ (E_CME / E_bind) M_atm, where E_CME is the energy of the CME, E_bind is the gravitational binding energy of the atmosphere, and M_atm is the atmospheric mass; this process is most severe for planets with low escape velocities and weak magnetic fields.^[154] Studies indicate that for M dwarf exoplanets, frequent CME impacts—up to 0.5 to 5 per day—can lead to substantial atmospheric mass loss, potentially eroding entire envelopes over gigayears.^[154] Beyond physical stripping, stellar CMEs introduce biosphere threats by delivering lethal radiation doses and inducing ozone depletion in Earth-like atmospheres on exoplanets. The charged particles in CMEs can penetrate planetary magnetospheres, increasing ionizing radiation levels that exceed survivable thresholds for surface life, with doses potentially reaching hundreds of times background levels during major events.^[155] In modeled Earth-analog atmospheres, CME-induced particle precipitation triggers NOx chemistry, depleting stratospheric ozone by up to 50% or more, thereby allowing harmful UV radiation to reach the surface and disrupt potential biological processes.^[156] The presence of frequent and energetic CMEs from active stars effectively reduces the width of habitable zones for exoplanets, as atmospheric retention becomes untenable closer to the star. For young, magnetically active stars similar to the early Sun, recent 2025 observations of massive CMEs from young solar-analog stars, such as EK Draconis, reveal that such events could have profoundly influenced planetary atmospheres in the early Solar System, providing clues to volatile delivery and loss mechanisms.^[157] Over stellar lifetimes, the cumulative effects of repeated CME-driven stripping can render worlds like Proxima b uninhabitable by progressively eroding protective atmospheres, with models suggesting that an unmagnetized Earth-like atmosphere around Proxima b could be fully eroded over approximately 100 million years due to combined stellar wind and CME activity.^[158] This long-term erosion underscores the challenges for habitability around flare-prone M dwarfs, where sustained particle bombardment limits the persistence of biospheres.^[159]

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Oct 23, 2018 · Measured speeds and widths of CMEs are desirable for SEP event forecasting, but X-ray flare events precede the associated CMEs and have shorter ...
[77]
On the Statistical Relationship Between CME Speed and Soft X-Ray ...
PDF | Both observation and theory reveal a close relationship between the kinematics of coronal mass ejections (CMEs) and the thermal energy.
[78]
A COMPARATIVE STUDY OF CONFINED AND ERUPTIVE FLARES ...
We investigate the distinct properties of two types of flares: eruptive flares associated with coronal mass ejections (CMEs) and confined flares without CMEs.
[79]
Statistical Study of Magnetic Topology for Eruptive and Confined ...
Feb 20, 2018 · The other 10 flares without CMEs were defined as “confined” flares. ... confined flares because of its stronger overlying coronal fields. A ...
[80]
Interaction of solar wind pressure pulses with the magnetosphere ...
Aug 29, 2012 · As remarked by Koskinen and Tanskanen [2002], a few times 1012 W of this power is believed to penetrate through the magnetopause, giving an ...
[81]
Energetics of the magnetosphere | Space Science Reviews
The sporadic power level of such events reaches the order of 3 × 1012 W. The role of magnetic merging in such releases of magnetic energy is briefly ...
[82]
Global geomagnetic response to the extreme geospace storm of ...
Jul 15, 2025 · The energy and power of the GSS of May 10–11, 2024, attained 6.5 × 1018 J and 0.4 × 1015 W, respectively. Such a storm is classified as extreme.
[83]
A comparison of the effects of CIR‐ and CME‐induced geomagnetic ...
Sep 9, 2014 · ... auroral power (HP) and mean atmospheric density per revolution ... CME storm precipitation may have occurred at a lower magnetic latitude.
[84]
Acceleration of Particles to High Energies in Earth's Radiation Belts
Oct 25, 2012 · 1986), and electrons with energies as high as 50 MeV have been reported in association with very strong CME-driven geomagnetic storms (Blake et ...
[85]
Dynamics of Electron Flux in the Slot Region and Geomagnetic Activity
Mar 25, 2021 · ... CME-driven geomagnetic storms, but also for the effects of the high speed solar wind streams, associated with co-rotating interaction region ...
[86]
TEC disturbances caused by CME-triggered geomagnetic storm of ...
May 30, 2024 · This study investigates the ionospheric response to a geomagnetic storm triggered by a Coronal Mass Ejection (CME) during 6–9 September 2017.
[87]
Influence of different types of ionospheric disturbances on GPS ...
Jul 20, 2021 · The UiO GNSS scintillation receiver is the standard GNSS ionospheric scintillation/TEC ... It was CME (coronal mass ejection) geomagnetic storm ...
[88]
Modeling the contributions of ring, tail, and magnetopause currents ...
Dec 4, 2010 · If the disturbance measured by the Dst index is mainly caused by the ring current equation (1) gives a relation between the Dst index and the ...
[89]
Machine learning models for predicting geomagnetic storms across ...
Oct 15, 2024 · A GmS, in terms of Dst index, is commonly defined as an event where the Dst index drops below a certain threshold, such as −50 nT or −100 nT, as ...
[90]
[PDF] Geomagnetic Storms and Their Impacts on the US Power Grid
This report describes the threat of geomagnetic storms on the Earth caused by solar activity and further discusses their impacts (past and future) on the U.S. ...
[91]
[PDF] Geomagnetic Storms and Long- Term Impacts on Power Systems
It is widely accepted that the sun can create geomagnetically induced currents (GIC) on the Earth that are potentially damaging to electric power equipment.
[92]
[PDF] Space Weather radiation impacts on aviation - UNOOSA
Jun 14, 2024 · The effects of radiation storms for aviation sectors are two-fold: increased radiation exposure to aircrew and passengers and single event ...
[93]
Validation of coronal mass ejection arrival-time forecasts by ...
Jan 6, 2021 · It takes about 2–4 days for the typical CMEs to reach the Earth from their onset. Therefore, our IPS-based forecast will work for most CMEs. The ...
[94]
The strongest geomagnetic superstorm in the last two decades
Feb 5, 2025 · The geomagnetic superstorm that occurred between May 10–15, 2024, was extremely intense, with the Dst index reaching a minimum of −412 nT and ...
[95]
Solar flares in May 2024 revealed Earth's vulnerability to space ...
Feb 12, 2025 · Solar flares in May 2024 revealed Earth's vulnerability to space weather · $500 million loss · Mass satellite migration · Aviation impact · Power ...
[96]
Probability estimation of a Carrington-like geomagnetic storm - Nature
Feb 20, 2019 · Thus, the estimated probability of occurrence of a Carrington event in the first decade after 1859 is 3.33%, which is 3.6 times greater than ...
[97]
Gray Swan in our sky: The multibillion-dollar threat of solar flares
Feb 25, 2025 · Lloyd's latest research estimates that global economic losses from a severe storm like this one could reach $2.4 trillion over a five-year ...Missing: recurrence probability
[98]
Correcting Projection Effects in CMEs Using GCS‐Based Large ...
Feb 19, 2024 · ... Halo CMEs, and found that 2D speeds underestimate 3D speeds by 20%. ... When the effects of projection are taken into account, the true speeds ...
[99]
Solar and heliospheric geoeffective disturbances - ScienceDirect.com
Called “halo” CMEs, owing to the Sun-centered circular patterns of light which form as the CMEs expand beyond the edge of the occulting disk (which blocks out ...
[100]
THREE-DIMENSIONAL STEREOSCOPIC ANALYSIS OF A ...
A three-dimensional (3D) reconstruction of the 2007 May 20 partial-halo coronal mass ejection (CME) has been made using STEREO/EUVI and STEREO/COR1 ...3. Observations · 4. Data Analysis And Results · 4.4. Synthesis Of O Vi...
[101]
Halo coronal mass ejections during Solar Cycle 24
Feb 13, 2018 · The optimal time interval between two subsequent CME eruptions, in order to have their intersection close to the Sun (≤ 20 RΘ), has been found ...
[102]
Updating Measures of CME Arrival Time Errors - Kay - 2024
Jul 12, 2024 · From 1702 arrival time predictions we find a bias of −2.5 hr, mean absolute error of 13.2 hr, and standard deviation of 17.4 hr The ...
[103]
Observational Overview of the May 2024 G5-Level Geomagnetic ...
The changes in near-Earth space environment due to these intense geomagnetic storms caused by strong solar activity can severely impact modern human technology.
[104]
Geomagnetic and Atmospheric Response to May 2024 Solar Storm
Dec 12, 2024 · The May 2024 solar storm, caused by CMEs, created a G5 geomagnetic storm, hitting Earth's magnetosphere and upper atmosphere, simulated by the ...<|control11|><|separator|>
[105]
[PDF] a brief history of cme science
Coronal Mass Ejection Speeds From Coronagraph Images and Interplanetary Characteristics of the Associated Interplanetary Coronal Mass Ejections', J. Geophys ...
[106]
History and development of coronal mass ejections as a key player ...
Mar 3, 2016 · CMEs are the most important players in solar terrestrial relationship as the root cause of severe weather in Earth's space environment.
[107]
A Historical Perspective on Coronal Mass Ejections - ResearchGate
In the 1940's the concept of corpuscular radiation from the sun was proposed and then in the 1950's used to explain the discontinuity in a comet tail. Parker's ...
[108]
Terminology of largeâ•'scale waves in the solar atmosphere - Wiley
Mar 15, 2005 · Gradually the term "Moreton wave". (sometimes also "Ramsey-Moreton wave") became widely used, as well as its synonym,. "flare wave," which was ...<|separator|>
[109]
Coronal mass ejections and their sheath regions in interplanetary ...
This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of ...
[110]
(PDF) Analysis of Voyager 1 and Voyager 2 in situ CME observations
This paper studies ICMEs detected by both Voyager spacecraft during propagation from 1 to 10 AU, with observations from 1977 to 1980. ICMEs are detected by ...
[111]
Coronal plasma diagnostics from ground‐based observations - Landi
Aug 31, 2016 · The invention of the coronagraph by Lyot [1932] made daily ground-based observations of the solar corona in the visible wavelength range a ...Missing: ejection | Show results with:ejection
[112]
Type II radio bursts and their association with coronal mass ...
In cycle 23, ≈79% type II bursts were associated with a white-light CME using our criteria, while in cycle 24, the percentage was considerably higher, ≈95%s.
[113]
SOHO LASCO CME CATALOG - CDAW DATA CENTER - NASA
This CME catalog is generated and maintained at the CDAW Data Center by NASA and The Catholic University of America in cooperation with the Naval Research ...A complete description of the... · Univ2020_12.html · Related LinksMissing: total | Show results with:total
[114]
LASCO Coronagraph | NOAA / NWS Space Weather Prediction Center
LASCO images have been used by the SWPC forecast office to characterize the solar corona heating and transient events, including CME's.
[115]
STEREO | Johns Hopkins University Applied Physics Laboratory
STEREO captured more than 13 million images of the Sun, providing detailed, 3D views of at least 4,500 CMEs and other solar eruptive events. STEREO-A ...
[116]
Advancing in situ modeling of ICMEs: New techniques for new ...
Jan 10, 2013 · The focus of this paper is to better exploit the available multispacecraft observations by combining measurements from STEREO with those from ...
[117]
[PDF] Duration and Extent of the Great Auroral Storm of 1859
Within -17 hours later the Earth experienced the massive auroral display of September 2-3 from a coronal mass ejection (CME). The Great Storm in 1859 occurred ...Missing: details | Show results with:details
[118]
When Solar Storms Attack: Space Weather and our Infrastructure
Oct 19, 2015 · The 1859 Carrington Event, the largest geomagnetic storm in recorded history, crippled a large portion of the telegraph system at the time, ...Missing: details | Show results with:details
[119]
The extreme magnetic storm of 1–2 September 1859 - AGU Journals
Jul 3, 2003 · The auroral sightings were as low as 23° magnetic latitude (Hawaii and Santiago), and the storm index was estimated to be −1760 nT. The Colaba ...
[120]
On the Little‐Known Consequences of the 4 August 1972 Ultra‐Fast ...
Oct 25, 2018 · The 4 August 1972 flare, shock, and geomagnetic storm are components of a Carrington-class event The event was associated with a nearly ...
[121]
[PDF] SOLAR ENERGETIC PARTICLE VARIATIONS
for the 1972 August 4 event shown in Figure 1. How- ever, the average speed of the shock, from the Sun to the Earth, in this event was 2900 km/s. This is ...
[122]
9 Houston, We Could Have a Problem | Storms from the Sun
In 1972, solar flares caused radio issues, auroras in the US, and power problems. If Apollo astronauts were exposed, they might not have survived.
[123]
A 21st Century View of the March 1989 Magnetic Storm - Boteler
Oct 10, 2019 · On 13 March 1989, the largest magnetic storm of the last century caused widespread effects on power systems including a blackout of the Hydro-Québec system.Abstract · Introduction · Interplanetary Conditions · Discussion
[124]
A Scary 13th: 20 Years Ago, Earth Was Blasted with a Massive ...
Mar 13, 2009 · Violent space weather treated many to a fantastic display of colorful auroras, but damaged power grids left six million Canadians in the dark.
[125]
[PDF] Halloween Storms - CDAW
Oct 27, 2003 · The Dst index shows three super-intense storms, the first two occurring around the time of very high solar wind speed and the third one ...
[126]
[PDF] Extreme Solar Eruptions and their Space Weather Consequences
The CMEs had speeds exceeding 2000 km/s and produced super magnetic storms (Dst < -200 nT) when they arrived at Earth. The Halloween solar eruptions thus ...
[127]
Remembering the Great Halloween Solar Storms | News
Oct 31, 2023 · At the height of the storms, astronauts aboard the International Space Station had to take cover from the high radiation levels, which had only ...
[128]
A major solar eruptive event in July 2012: Defining extreme space ...
Sep 19, 2013 · On 23 July 2012, solar active region 1520 (~141°W heliographic longitude) gave rise to a powerful coronal mass ejection (CME) with an initial ...Abstract · Introduction · Solar and Solar Wind... · Discussion<|separator|>
[129]
A BLAST WAVE MEDIATED BY SOLAR ENERGETIC PARTICLES
May 22, 2013 · On 2012 July 23, a very fast CME was launched from the Sun at about 0208 ± 2 minutes UT, as detected by the STEREO SECCHI (Howard et al. 2008) ...
[130]
Near Miss: The Solar Superstorm of July 2012 - NASA Science
Jul 22, 2014 · Their paper, entitled "A major solar eruptive event in July 2012," describes how a powerful coronal mass ejection (CME) tore through Earth orbit ...
[131]
Severe and Extreme (G4-G5) Geomagnetic Storms Likely on 12 May ...
May 13, 2024 · Severe and Extreme (G4-G5) Geomagnetic Storms Likely on 12 May 2024 ... Another series of CMEs associated with flare activity from Region 3664 ...
[132]
Satellite Drag Analysis During the May 2024 Geomagnetic Storm
Jun 12, 2024 · Widespread auroral activity was reported to be visible during the peak enhancement as far south as 21 ∘ N latitude. Report issue for preceding ...
[133]
Carrington Class Coronal Mass Ejection - ENLIL Simulation of A ...
Aug 7, 2025 · These ejections range in speed between 200 km/s to up to 3000 km/s. At the highest speeds, these CMEs can travel faster than the background ...
[134]
Scientists prepare for solar storm that could wipe out satellites
Oct 27, 2025 · ESA scientists estimated that satellite drag could rise by 400 percent during the CME phase. This would increase collision risk, reduce ...
[135]
The next solar superstorm could wipe out 'all our satellites,' new ...
Oct 30, 2025 · Worrying new simulations show that a solar storm on par with the infamous Carrington Event could potentially wipe out every single satellite ...
[136]
Sun's far side erupts in satellite image photo of the day for Oct. 29 ...
Oct 29, 2025 · A massive coronal mass ejection erupted from the sun's far side late on Oct. 21, 2025 and was captured by a NOAA coronagraph.
[137]
Radio Emission from the Sun and Stars: New Insights into Energetic ...
... CMEs while type III radio bursts are commonly associated with impulsive flares. ... radio emission from both RS CVn binaries and classical flare stars. The ...
[138]
Stellar flares | Living Reviews in Solar Physics
Apr 24, 2024 · These stellar flares are bursts of electromagnetic radiation from X-ray to radio wavelengths, and they occur on most stars with outer convection zones.
[139]
An MHD Simulation of the Possible Modulations of Stellar CMEs ...
Apr 3, 2025 · ... detecting and characterizing coronal mass ejections from other stars. A radio burst is a short period when stellar coronal radio emission is ...An Mhd Simulation Of The... · 2.1 Star-Planet Interaction... · 2.2 Flux Rope Model For The...
[140]
Astronomers Detect Coronal Mass Ejections from Young Sun-Like Star
Oct 28, 2025 · These observations provide the first evidence of a multi-temperature CME from EK Draconis. “We found that hot plasma of 100,000 K was ...
[141]
Coronal Mass Ejections from Young Suns: Insights from Solar ... - arXiv
Oct 25, 2025 · Nearly simultaneous NICER X-ray observations revealed possible coronal X-ray dimming, which is a different CME signature representing the ...
[142]
Stellar coronal mass ejections – I. Estimating occurrence ...
Mass estimates of observed stellar CME events range from 1015 to 1019 g and line-of-sight velocities from ∼100 to 5800 km s−1. The masses are comparable to ...Missing: m³ | Show results with:m³
[143]
Extreme energetic particle events by superflare-associated CMEs ...
Mar 25, 2022 · Theoretical models suggest that stellar superflares can be associated with energetic confined CMEs forming within active regions and halo-type ...
[144]
[PDF] Magnetic Interaction of a Super-CME with the Earth's Magnetosphere
CMEs with energies ≥ 1034 ergs we will refer to as super-CMEs. ... Our Sun is a magnetically active star that exhibits CMEs with kinetic energies in the range.
[145]
Red Asymmetry of H α Line Profiles during the Flares on the Active ...
Feb 22, 2024 · Here we report the capture of a possible CME or chromospheric condensation on the RS CVn-type star II Pegasi (II Peg) using high-resolution ...
[146]
Probable detection of an eruptive filament from a superflare ... - Nature
Dec 9, 2021 · Discovery of multi-temperature coronal mass ejection signatures from a young solar analogue ... T Tauri stars in Chamaeleon. Astron. Astrophys.
[147]
Detecting coronal mass ejections with machine learning methods
Jan 15, 2024 · We present a possibility to find stellar CMEs with the help of high-resolution solar spectra.
[148]
PROBABILITY OF CME IMPACT ON EXOPLANETS ORBITING M ...
V374 Peg's strong magnetic fields can trap CMEs at the M dwarfs's ... M dwarf CME mass distribution to determine the probability and frequency of CME impacts.<|separator|>
[149]
Observations and detectability of young Suns' flaring and CME ...
Observationally constrained rates of Coronal Mass Ejections (CMEs) of young solar analogues are still lacking, as those require dedicated monitoring. We present ...
[150]
(PDF) 3D modelling of the impact of stellar activity on tidally locked ...
The impacts of the stellar flares are seen in the generation of an ozone layer around 20-25 km. The impact of the CMEs is seen in the depletion of ozone above ...
[151]
https://iopscience.iop.org/article/10.3847/1538-4357/ad1928
[152]
(PDF) Is Proxima Centauri b habitable? -- A study of atmospheric loss
We address the important question of whether the newly discovered exoplanet, Proxima Centauri b (PCb), is capable of retaining an atmosphere over long periods ...
[153]
An Earth-like atmosphere may not survive Proxima b's orbit
Jul 31, 2017 · The scientists show that with the highest thermosphere temperatures and a completely open magnetic field, Proxima b could lose an amount equal ...