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Solar cycle 10

Solar cycle 10 was the tenth recorded solar cycle since systematic observations began in 1755, spanning from the solar minimum in December 1855 (smoothed sunspot number of 6.0) to the minimum in March 1867.^[1] It peaked at a smoothed sunspot number of 186.2 in February 1860, marking it as one of the stronger cycles in the modern observational record.^[1] This period of heightened solar activity is most famously associated with the Carrington Event of September 1–2, 1859, the largest geomagnetic storm ever recorded, triggered by a massive solar flare and coronal mass ejection that produced widespread auroras visible as far south as the Caribbean and disrupted early telegraph systems globally.^[2]^[3] The cycle's ascending phase lasted about 4 years and 2 months from minimum to maximum, while the descending phase extended roughly 7 years and 1 month, yielding a total duration of 11 years and 3 months—close to the typical 11-year periodicity of solar cycles.^[4] With its high sunspot maximum well above the long-term average of around 140, cycle 10 exemplified robust solar magnetic activity during the mid-19th century, contributing to increased frequencies of solar flares, prominences, and geomagnetic disturbances.^[1] Observations during this era, though limited by technology, advanced understanding of solar-terrestrial interactions, particularly through eyewitness accounts of auroral displays and the first documented white-light flare by Richard Carrington.^[3] In a modern context, such activity would pose significant risks to satellites, power grids, and communications, underscoring the event's enduring relevance in space weather studies.

Cycle Overview

Duration and Phases

Solar Cycle 10 commenced in December 1855, marking the ascent from the sunspot minimum that concluded Solar Cycle 9, with a smoothed sunspot number of approximately 6 at the onset.^[1] This cycle concluded in March 1867, as it transitioned into the minimum phase preceding Solar Cycle 11, characterized by a smoothed sunspot number of about 9.9.^[1] The overall duration spanned 11.3 years, aligning with the typical length observed in solar cycles, though it exhibited a distinctive double-peak structure in its activity profile.^[1]^[5] The cycle's numbering as the tenth in the sequence was established by Swiss astronomer Johann Rudolf Wolf, who reconstructed solar activity records dating back to 1755 to systematically catalog cycles starting from that baseline year.^[6] This methodology provided a foundational framework for tracking solar variability through sunspot observations. The rising phase extended from 1855 to 1860, during which sunspot numbers progressively increased toward the cycle's maximum.^[1] Following this peak, the declining phase unfolded from 1860 to 1867, gradually diminishing activity until reaching the subsequent minimum.^[1] This phased progression underscored the oscillatory nature of solar magnetic activity inherent to the 11-year cycle.

Peak Sunspot Activity

Solar Cycle 10 exhibited one of its most intense phases during its maximum, characterized by elevated sunspot activity that marked it as a period of significant solar dynamism. The peak of this activity, as measured by the 13-month smoothed monthly mean sunspot number, reached 186.2 in February 1860.^[4] This value represents the highest point in the cycle's progression, derived from systematic observations compiled by early astronomers such as Rudolf Wolf and later standardized by the Solar Influences Data Analysis Center (SIDC).^[7] The maximum displayed irregularity through a double-peaked structure, with an initial peak in late 1859—specifically October, when the monthly mean sunspot number hit 218—followed by a secondary rise culminating in July 1860 at 222.^[8] This pattern, common in some solar cycles due to hemispheric asymmetries in sunspot emergence, contributed to the cycle's overall irregularity and prolonged high activity phase.^[8] The 13-month smoothing technique applied to daily and monthly sunspot counts from historical records helps mitigate short-term fluctuations, providing a reliable indicator of the cycle's amplitude while preserving trends from pre-telescopic and early telescopic era data.^[9] In comparison to other solar cycles, Cycle 10's maximum amplitude of 186.2 ranks it 12th highest among the 24 cycles with recorded data up to Cycle 24, placing it among the stronger historical cycles, particularly notable before the advent of more comprehensive modern observations in the 20th century.^[1] The cycle concluded with a transition to a quiet phase, marked by a minimum smoothed sunspot number of approximately 9.9, signaling the onset of diminished activity leading into Cycle 11.^[4]

Solar Observations

Sunspot Records

Sunspot monitoring during Solar Cycle 10, which extended from December 1855 to March 1867, primarily involved daily visual inspections using telescopes by dedicated astronomers. Rudolf Wolf, director of the Zurich Observatory, played a central role in these efforts, systematically recording sunspot counts to extend historical series back to the 17th century.^[10] These observations employed a relative sunspot number formula, W = k(10g + f), where g represented the number of sunspot groups, f the total individual spots, and k a correction factor adjusted for observer and instrumentation differences.^[10] Johann von Lamont contributed complementary geomagnetic data from Munich, which Wolf later correlated with sunspot variations to strengthen cycle periodicity evidence.^[11] The Zurich Observatory's records formed the foundational dataset for the International Sunspot Number series, initiated by Wolf in the mid-19th century to standardize global observations.^[10] This series aggregated daily reports, emphasizing group counts for consistency despite varying observer reliability. During the cycle's declining phase and transition to Solar Cycle 11, a total of 406 spotless days were recorded, reflecting extended periods of solar quiescence from February 1860 onward.^[12] Nineteenth-century sunspot recording faced significant challenges, including inconsistent global coverage with many days unobserved, particularly outside Europe.^[13] Reliance on a limited network of European astronomers like Wolf and Schwabe led to potential biases, as non-European data was scarce until later reconstructions.^[13] Additionally, the absence of photographic techniques—only introduced sporadically after 1858—meant all data depended on subjective visual sketches, complicating precise area measurements and position accuracy.^[13] As Solar Cycle 10 progressed, sunspot groups exhibited a systematic latitudinal drift, originating at mid-to-high latitudes around 20°–30° and migrating equatorward to within 2°–10° by cycle's end, in accordance with Spörer's law of sunspot zone evolution.^[14] This trend highlighted the cycle's hemispheric asymmetry and the gradual concentration of activity near the solar equator, drawn from digitized records spanning 1826–1867.^[14]

Early Flare Observations

During Solar Cycle 10, which spanned 1855 to 1867 and featured exceptionally high solar activity with a peak smoothed sunspot number of 186.2 in February 1860, observers began noting sporadic white-light brightenings associated with sunspot groups, reflecting the cycle's increased visibility of solar dynamics. These early reports in the 1850s were incidental to broader sunspot monitoring, as systematic flare detection was not yet established, but the cycle's intense activity provided more opportunities for such phenomena to be captured visually. Richard Carrington's pioneering sketches of sunspot complexes, conducted daily from November 1853 at his Redhill observatory, offered the first detailed records of their dynamic evolution, hinting at rapid structural changes that foreshadowed eruptive events. His work documented the migration, rotation, and morphological shifts in sunspot groups, revealing the Sun's surface as far from static and setting the stage for recognizing transient brightenings as distinct solar phenomena.^[15]^[16] These early observations relied solely on visual projection methods, as spectroheliographs for spectral analysis were not invented until 1868 by Norman Lockyer and Pierre Janssen. The noted brightenings typically manifested as brief, intense flashes in the umbrae of sunspots, enduring only a few minutes and appearing as localized white-light enhancements against the darker penumbrae. Such characteristics distinguished them from longer-lasting features like prominences, which were primarily observed during eclipses.^[17] Flare-like events appeared more prevalent during the cycle's rising phase, aligning with escalating sunspot numbers toward the 1860 maximum, though precise frequency counts were impossible without modern instrumentation and awaited quantification in subsequent cycles like Cycle 12. This era's records, despite their limitations, established flares as a unique class of solar eruptive activity separate from prominences or routine sunspot variability, with many instances likely unrecorded due to inconsistent monitoring. The 1859 white-light flare exemplified these traits amid the cycle's peak activity.^[18]

The Carrington Event

The September 1859 Solar Flare

On September 1, 1859, British astronomers Richard Carrington and Richard Hodgson independently observed a remarkable solar phenomenon while sketching a prominent sunspot group in the Sun's northern hemisphere.^[19]^[20] Carrington, at his private observatory in Redhill, Surrey, noted the event around 11:18 UT during routine solar monitoring.^[21] This sighting marked the first unambiguous documentation of a white-light solar flare, providing direct visual evidence of explosive solar activity previously unobserved.^[22]^[20] The flare manifested as an intense outburst of white light spanning two adjacent sunspots within the group, appearing as two brilliant kernels that emerged suddenly and moved rapidly across the photosphere.^[21] Carrington described the illumination as "fully equal to that of direct sunlight," with the kernels traversing a distance of approximately 35,000 miles in about 5 minutes before fading.^[23]^[24] Hodgson, observing from London, corroborated the event, reporting a "very brilliant star of light, much brighter than the sun's surface."^[21] This rapid evolution highlighted the flare's dynamic nature, distinguishing it from typical sunspot variability. The event unfolded in a complex active region that had been developing since late August, with the sunspot group becoming visible around August 28 and growing to cover about 2,300 millionths of the solar hemisphere by early September.^[19] This region emerged near the ascending phase of Solar Cycle 10, approximately 5 months before the cycle's maximum, amid increasing solar activity.^[22]^[1] Retrospective analyses estimate the flare's radiative energy release at approximately $5 \times 10^{32} ergs, classifying it as an X45-class event in modern soft X-ray terms—one of the most energetic flares recorded, though calibrations rely on historical accounts rather than contemporary instruments.^[19]^[21] Observations were conducted using projected images of the Sun through refracting telescopes onto screens, allowing safe sketching without direct viewing to avoid eye damage.^[20]^[21]

The Resulting Geomagnetic Storm

The geomagnetic storm triggered by the coronal mass ejection (CME) associated with the September 1, 1859, solar flare commenced approximately 17.6 hours after the flare's observation, beginning in the early hours of September 2, 1859, in universal time, with its most intense phase peaking later that day.^[25] The storm's rapid onset was characterized by a sudden impulse in Earth's magnetic field, followed by a prolonged main phase lasting through September 2 and into September 3, marking it as one of the most abrupt and extended disturbances in recorded history.^[21] This event stands as one of the most intense geomagnetic storms on record, with recent reconstructions (as of 2024) estimating a disturbance-storm time (Dst) index equivalent of approximately -900 nT, far surpassing typical severe storms that reach -100 to -200 nT.^[26] Ground-based magnetometer observations, such as those at the Colaba Observatory in India, recorded horizontal magnetic field deviations of approximately 900 nT.^[26] The mechanism involved the CME's exceptionally high propagation speed of around 2000 km/s, enabling it to traverse the approximately 150 million kilometers to Earth in record time and compress the magnetosphere, initiating a sudden storm commencement followed by a deep main phase driven by enhanced ring current and magnetopause currents.^[25] The storm significantly intensified the auroral electrojet, with enhanced ionospheric currents extending to unusually low latitudes, contributing to the overall magnetic perturbations observed worldwide.^[27] Compared to modern events, this storm's severity dwarfs even the strongest 20th-century disturbances, such as the 1989 Quebec storm (Dst ≈ -589 nT), and statistical models estimate a recurrence probability of about 1% per decade for an event of similar magnitude.^[28]

Terrestrial Impacts

Auroral Phenomena

During Solar Cycle 10 (1855–1867), intense auroral activity was observed during periods of elevated sunspot numbers, with multiple geomagnetic storms producing widespread displays, though the events of late August and early September 1859 were unparalleled in extent and brilliance.^[3] These displays were driven by charged particle precipitation from the solar wind into Earth's ionosphere, where collisions with atmospheric gases excited emissions visible as auroras, and the exceptional storm intensity expanded the auroral oval equatorward to unprecedented latitudes.^[27] The particle influx was particularly strong during the 1859 storms, resulting in prolonged visibility at low geomagnetic latitudes for up to 42 hours on September 2–3.^[27] The auroras of 1859 were reported globally, visible as far equatorward as Colombia (approximately 12°N) from aboard the ship St. Mary's and in Hawaii (21°N), locations where such phenomena are exceedingly rare.^[29]^[30] Their brightness exceeded that of moonlight, allowing newspapers to be read by the light alone in regions like New York and Honolulu.^[3] Eyewitnesses described pulsating rays, undulating curtains, and coronas in vivid crimson, blood-red, green, and orange hues, with the sky appearing as if aflame or lit by a perpetual sunset.^[3] Multiple intense displays occurred between August 28 and September 2, 1859, beginning with a brilliant red aurora on August 28–29 that illuminated the northern horizon across Europe and North America, followed by an even more spectacular event on September 2–3 featuring converging cones of light and waves extending to the zenith.^[3]^[27] Newspaper accounts from Europe, such as The Times in London reporting luminous waves to the zenith, North America, including the New York Times detailing blood-red glows bright enough for reading, and Australia, where the Melbourne Argus described red glares over the city, captured the awe of observers who termed it the "great auroral storm."^[3] In Tasmania, the Hobart Town Mercury noted the most magnificent aurora ever seen, with red and green bands visible for hours.^[3] These reports underscore the event's rarity and scale within Cycle 10, far surpassing typical auroral visibility confined to high latitudes.^[3]

Effects on Telegraph Networks

During the intense geomagnetic storms of late August and early September 1859, part of Solar Cycle 10, telegraph networks across Europe and North America experienced widespread failures due to geomagnetically induced currents (GICs) from rapid changes in Earth's magnetic field.^[31] These currents rendered many lines inoperable for hours, as the induced electricity overwhelmed or neutralized the standard battery power, making transmission impossible in places like Paris and Philadelphia.^[3] In some cases, operators discovered that the GICs were strong enough to power the systems without batteries; for instance, in Boston on September 2, lines functioned using this "auroral current" for about two hours, reportedly better than with conventional batteries connected.^[3] This vulnerability highlighted the nascent electrical infrastructure's susceptibility to solar-terrestrial interactions, briefly referenced as arising from the solar flare and coronal mass ejection observed by Richard Carrington.^[32] Specific incidents underscored the severity of these disruptions. In Pittsburgh on August 28, sparks and streams of fire erupted from telegraph instruments, posing fire hazards to equipment.^[31] Operators faced physical dangers, including severe electric shocks; one account from Washington, D.C., described a worker being stunned by a spark leaping from their forehead to the telegraph sounder.^[3] In Brussels, the disturbance caused bells on instruments to ring spontaneously, while in Norway, paper at a telegraph station ignited from sparks during the September 2-3 event.^[31] These effects stemmed from GICs flowing through long conductive lines, varying by orientation and grounding, and affected an estimated 125,000 miles of global telegraph wire.^[3] The storms' reach extended globally, with reports from as far as Bombay, where a significant magnetic disturbance disrupted operations at local observatories on September 2, though no direct auroral current linkage was confirmed.^[31] In Europe, Paris stations saw needles in constant motion, interrupting service, while planning for transatlantic cables—already challenged by prior failures—faced added concerns over potential GIC vulnerabilities in extended undersea lines.^[32] Beyond telegraphs, ships at sea reported compass deviations due to the intense magnetic fluctuations, providing early evidence of solar influences on navigation.^[31]

References

[1]
Solar Cycles Min/Max | SIDC
Dates of the minima and maxima of past solar cycles, with the corresponding sunspot number, based on the 13-month smoothed monthly sunspot number time series.
[2]
Near Miss: The Solar Superstorm of July 2012 - NASA Science
Jul 22, 2014 · ... Carrington Event of Sept. 1859, named after English astronomer Richard Carrington who actually saw the instigating flare with his own eyes.
[3]
[PDF] Eyewitness Reports of the Great Auroral Storm of 1859
Aug 5, 2005 · The first event began on August 28* and the second began on. September 2"d. It is the storm on September 2"d that results from the Carrington- ...
[4]
Cycles durations | SIDC
Cycle durations are shown in a table with minimum and maximum values, based on 13-month smoothed monthly mean sunspot numbers.
[5]
One Possible Reason for Double-Peaked Maxima in Solar Cycles
Sep 26, 2013 · As shown in this figure, the duration of the maximum of Solar Cycle 10 is about 2.42 years (from 1859.08 to 1861.50) and for Solar Cycle 20, the ...
[6]
Sunspot Numbers | NCEI - NOAA
Johann Rudolf Wolf (1816-1893). In 1848 Rudolf Wolf devised a daily method of estimating solar activity by counting the number of individual spots and groups ...
[7]
Sunspot Number | SIDC
### Extracted Link
[8]
Temporal and Spatial Evolutions of a Large Sunspot Group and ...
Aug 29, 2019 · The storms around the Carrington event occur almost in the maximum of Solar Cycle 10. ... double peak of the monthly mean value of the ...
[9]
https://www.sidc.be/SILSO/infosnmstot
[10]
Inconsistency of the Wolf sunspot number series around 1848
The tremendous work by Rudolf Wolf of Zürich in the second half of the 19th century resulted in creation of the first official sunspot number series, known as ...
[11]
[PDF] Johann von Lamont (1805-1879): A pioneer in geomagnetism
The cirumdecadal periodicity in the geomagnetic field was first identified by Lamont and was subsequently correlated with sunspots and solar activity by Wolf in.
[12]
Spotless Days | SIDC
Jul 5, 2022 · The baseline is again the month with the 10th spotless day after solar cycle maximum. Any spotless days happening more than 12 months before ...
[13]
[PDF] Historical Sunspot Observations: A Review - arXiv
These observations should allow us to know the number, position, and area of sunspots as well as some relevant episodes (Maunder Minimum, optical flares, etc.).
[14]
Wings of the butterfly: Sunspot groups for 1826–2015
Here we present a new extended butterfly diagram of sunspot group occurrence since 1826, using the recently digitized data from Schwabe (1826–1867) and Spörer ...<|separator|>
[15]
Observations of the spots on the sun from November 9, 1853, to ...
Sep 14, 2009 · Observations of the spots on the sun from November 9, 1853, to March 24, 1861, made at Redhill ; Publication date: 1863 ; Topics: Sunspots.Missing: dynamic changes
[16]
A modern reconstruction of Carrington's observations (1853-1861)
Mar 9, 2021 · The focus of this article is a re-count of Richard Carrington's original sunspot observations from his book drawings (Carrington,1863)Missing: dynamic changes
[17]
Flare Observations | Living Reviews in Solar Physics
Dec 9, 2016 · Since September 1, 1859, when R. C. ... The coronal source has been observed to emit hard X-rays even in the pre-flare phase before footpoints ...<|control11|><|separator|>
[18]
The Solar Cycle | Living Reviews in Solar Physics
Carrington (1859) and Hodgson (1859) reported the first observations of a solar flare from white-light observations on September 1, 1859. While observing ...
[19]
The 1859 space weather event revisited: limits of extreme activity
The solar flare on 1 September 1859 and its associated geomagnetic storm remain the standard for an extreme solar-terrestrial event.
[20]
What Was the Carrington Event? | NESDIS - NOAA
Carrington is studying a group of sunspots (through dark filters that protect his eyes, of course). Around 11:00 AM, he sees a sudden flash of intense white ...
[21]
The extreme magnetic storm of 1–2 September 1859 - AGU Journals
Jul 3, 2003 · [2] The solar flare of 1 September 1859 was observed and reported by Carrington [1859] and Hodgson [1859] in the Monthly Notices of the ...
[22]
[PDF] Duration and Extent of the Great Auroral Storm of 1859
On September 1,1859, Richard Carrington and fichard Hodgson, while observing a large sunspot group independently, were the first to observe a white light ...
[23]
An extreme coronal mass ejection and consequences for the ...
Jan 13, 2014 · The transit time of the Carrington event was ~17.5 h. If higher ICME speeds than assumed here are possible, then the time duration could be ...
[24]
Duration and extent of the great auroral storm of 1859 - PMC - NIH
On September 1, 1859, Richard Carrington and Richard Hodgson, while observing a large sunspot group independently, were the first to observe a white light flare ...<|control11|><|separator|>
[25]
Probability estimation of a Carrington-like geomagnetic storm - Nature
Feb 20, 2019 · The Carrington event is the largest known example of geomagnetic storm, occurred by the end of August and early September 1859 and is associated ...
[26]
[1508.06365] The Grand Aurorae Borealis Seen in Colombia in 1859
Aug 26, 2015 · The geomagnetic storm, generated by the solar-terrestrial event, had such a magnitude that the auroral oval expanded towards the equator, ...Missing: Hawaii | Show results with:Hawaii
[27]
East Asian observations of low-latitude aurora during the Carrington ...
The magnetic storm caused worldwide observations of auroras, even at very low latitudes, such as Hawaii, Panama, or Santiago. Available magnetic-field ...
[28]
(PDF) The super storms of August/September 1859 and their effects ...
Telegraph operation in Europe was severely affected by the initial magnetic disturbance. In North America, 5 or 6 hours behind in local time, this initial ...
[29]
The Carrington Solar Flares of 1859: Consequences on Life - NIH
Oct 30, 2014 · The beginning of September 1859 was the occasion of the first and unique observation of a giant solar white light flare, auroral displays were ...