Preserving the chronological record of geomagnetic ‘solar’ storms that impact Earth’s biosphere, against the Sun’s future disturbances – a hardened record documenting protracted solar activity, safeguarding this essential space climate knowledge for posterity to continue to learn to live with our ‘stormy’ stare.




On 1–2 September 1859, Earth experienced a ‘curious’ geo-atmospheric event. Vibrant auroras brazenly danced outwards from the planet’s polar regions, illuminating the night sky sufficiently for people and animals to confuse this encroaching light for the imminent dawn. These concerning auroras were observable even at lower latitudes in the equatorial tropics, showering energetic purples, reds, blues, and rich green hues across south-central Mexico, Cuba, Hawaii, Queensland, southern Japan and China. The eerie radiance unnerved many who witnessed the strange glow, some believing the light to be of supernatural origin, while others reportedly harnessed the unanticipated illumination to read their local newspapers at nightime. Telegraphs sizzled to life with an abhorrent spectrum of interference, sometimes electrocuting station operators who risked touching their equipment. Early telegraph services were also documented to function without an attached battery power supply, while other circuits failed as the pylons uncontrollable sparked and burst into flames. Compass needles reportedly went haywire and spun frantically; becoming futile in locating magnetic North. These strange phenomena were reported worldwide, occurring across a fleeting window of mere days, before ceasing and fading into a mystery. This curious tale would later become known as the infamous ‘Carrington Event’.


The Sun supports all terrestrial life cycles, such as the circadian rhythm, and many geochemical cycles across the Earth’s dynamic biosphere. However, our local star itself also undergoes its own cyclic solar maximum period; a timeframe where fierce surface activity and emissions can erupt outwards into the encapsulating Solar System, influencing everything from the density of [and fluctuations in] the prevailing solar winds, to radically influencing the atmospheric conditions of worlds dozens of light-minutes away from the Sun’s own photosphere. Known alternatively as the Schwabe or sunspot cycle, each period lasts for an average length of 11 years (all recorded cycles fall between 9.0–13.6 years, but the length of a Solar Cycle is still contested, and no two cycles are alike). Presently, we are situated in Solar Cycle 25 which began during December 2019, with the first recorded Solar Cycle commencing from February 1755. Over the course of these 11-year cycles, levels of solar radiation and ejection of stellar material, the frequency and scale of sunspots, solar flares, and coronal loops all demonstrate patterns in fluctuation; from a period of minimum activity, to a period of a maximum activity, and then back to minimum activity – demarcating a natural end for a ‘typical’ 11-year cycle.

Throughout the documented fluctuations within a standard Solar Cycle, the quantity [and decay] of sunspots releases prodigious amounts of magnetic flux across the Sun’s outer photosphere. This flux forms ‘loops’ of magnetic knots that violently oppose, twist, and contort around one another, comparable to twisting a sphere of rubber bands, wrapping up elastic tension energy with each unbearable twist. Torsions of opposing polarity can eventually ‘snap’ however; suddenly releasing the burden of magnetic energy held within the outer corona. The re-configuring of stresses from this process of ‘Magnetic Reconnection’ subsequently discharges intensive bursts of energy and clouds of magnetically-bound plasma outwards, before the breaking points, now free of their vexing magnetic troubles, reassert themselves to a lower (and balanced) energy state. These natural disturbances within the Sun’s magnetic field increase the amount of stellar material hurtling outwards from the corona; causing associated phenomena such as density fluctuations in the solar winds, Solar Flares (intense bursts of electromagnetic radiation, mostly in non-visible frequencies), and sometimes Coronal Mass Ejections (CME – expulsions of magnetically-charged plasma) of varying intensities to erupt – re-distributions of stellar mass and energy with the potential to affect the Solar System.

Occurrences like this are simply known under the blanket terms of a solar or ‘geomagnetic storm’, but such showers, travelling in our direction, arrive at Earth in three distinctive stages. Firstly, high-energy sunlight, mostly x-rays and ultraviolet light, ionises Earth's upper atmosphere about 8 minutes after departing the Sun’s corona; interfering with orbital telecommunications equipment and navigation services that varyingly operate across radio frequencies. Thereafter, a radiation storm washes over the Earth’s magnetosphere like a tidal wave, creating potentially dangerous living conditions for unprotected astronauts, about 23 minutes to two hours after departing the Sun. Finally, but not always after a Solar Flare, a CME, consisting of a slower moving cloud of charged particles (i.e. plasma), reaches Earth’s magnetosphere after several hours or days of transit. This material can violently react with Earth’s magnetosphere, inducing widespread electromagnetic interference across electrical systems, and compacting the daylight-facing geomagnetic field lines, while stretching out the night-facing side of this protective cocoon into a long, diametric ‘tail’ away from the Sun. If geomagnetic storms are compared with a conventional chemical explosion, solar flares may be described as the initial ‘flash of light’, the ensuing pressure shockwave as the radiation shower, and finally the enduring heat wave as a CME after-wave which continues to bombard onlookers after the detonation. Depending upon the intensity of a stellar eruption, this solar bombardment can stretch Earth’s own magnetic tail to the point of snapping; dragging some of this plasma back with it towards our planet’s poles – in the process, creating bright auroras and inducing global electromagnetic interference. Most flares and ensuing geomagnetic storms are of moderate energetic output (with a classification system established to measure intensities according to the peak flux of X-rays at a specified frequency range), but there have been documented cases of intensive ‘super’ storms (class ‘X’-level events) that can reach beyond our protective magnetosphere.

Shortly before noon on 1st September 1859 during the maximum period in the 10th Solar Cycle, the amateur astronomer Richard Carrington (independently, also Richard Hodgson) began sketching a large sunspot region through his brass telescope when he observed an intensive, bright flash. His fortuitous observation would later be documented as the earliest confirmed sighting of the still-theorised solar flare, but his discovery would also be recalled as the most intensive geomagnetic storm encountered within recorded human history. Carrington studiously made note of his unique discovery and began recording his experience for later publication. After 17.6 hours (due to the transit delay of the cloud of magnetic plasma), the expelled CME material hit the Earth’s magnetosphere, stretching it’s tail towards breaking point. Ricocheting backwards after the magnetosphere tail snapped, the influx of charged stellar material rapidly induced currents across the Ionosphere, thereafter translating this energy into Geo-Magnetically Induced Currents (GICs) on the upper surface of our planetary crust. These GICs then created widespread electric disruptions to telecommunication systems and, in some cases, caused extensive damage to these early networks. Electronic systems sparked uncontrollably as the incoming charged particles induced electromagnetic currents throughout the physical telegraph cables from ground-level, overcharging networks to the point of failure. Consequently, Earth fell silent in the wake of this widespread disruption to telegraph lines. Damage, however, was ‘minimal’ due to the limited global reliance on telegraph services at the time – electrical networks which bore the brunt of this ‘abnormal’ geomagnetic storm. Yet, the event continues to be cited as a cautionary tale to encourage heliophysics research, electrical grid resiliency and other safeguarding measures for our high-tech macro-societies.

The uncomfortable truth, however, is that Solar Storms of varying intensity, and the impacts resulting from stellar flares and CME, are a common occurrence for the Earth’s magnetosphere. In fact, at the time of writing, a moderate G-1 class solar storm is presently washing over our planet, with predicted disruptions to satellite services from this “direct hit” anticipated, along with expected aurora activity, and frantic media coverage. Concentrations of Carbon-14 within tree rings and Beryllium-10 (among other isotopes) in ice cores, alongside several other proxy resources, all paint a similar picture; stellar material has long interacted with the past biochemistry of the terrestrial surface, and quite often. This evidentiary well of Carbon-14 isotopes alone has been used to reconstruct the last 11,400 years of sunspot activity; demonstrating the deep-time implications for these geomagnetic storms, and their capability to continually influence life on and across the Earth – from satellite disruptions and electronic interference, to widespread distribution of more damaging radiations.

Since 1859, less-intense bursts of solar material have also interfered with terrestrial life over the succeeding decades. In March 1989, a geomagnetic storm was responsible for disruptions to the entire power grid of Quebec City. In August 1972, a solar storm caused severe technological disruptions throughout North America and the Pacific regions, including the accidental detonation of over 4000 [U.S.] magnetic-influence sea mines near North Korea, as well as triggering alarms on Vela nuclear detonation detection satellites. A milder geomagnetic storm in February 2022 also led to the failure, and destructive reentry, of 40 SpaceX Starlink satellites. Numerous solar storms of varying intensity between these documented ‘extreme’ instances have often washed over our planet, triggering stronger auroral activity, and extending these vibrant lights downwards towards the tropics, while damaging both orbital and ground-based services. Surveillance by STEREO-A and other solar observatory satellites (like DISCOVR, SOHO, and GOES) have revealed that ‘Carrington-level’ geomagnetic storms are also much more common than previously assumed within our meagre recorded history of Solar Cycles; the Ultrafast CME on 23rd July 2012 being perhaps the most distinguished event, narrowly missing Earth by mere days (due to the Sun’s own rotation rate not directly intersecting with our planet’s orbit).

Solar storms are but one facet of ‘Space Climate’ that regularly reshapes lives and lifestyles on Earth. Yet, these storms are perhaps the most significant local stellar phenomenon that may inflict serious damage to electronic systems on a global scale, disrupting the balances of social order and civil unity along with supply chain issues for vital resources (e.g., water pumps, power distribution etc.), while also incurring severe economic damage in the fallout for our globally interconnected civilisations. Geomagnetic storms are a regular – and inescapable – property of our ‘stormy’ stellar neighbourhood, essentially guaranteeing Earth will encounter bombardments of flares and CME to varying degrees of intensity, and into perpetuity. Probability estimates vary for predicting the next Carrington-level geomagnetic storm occurring in the imminent decade, about 12% of a chance per year, but it is certainly a question of when, not if, and how prepared humanity is for this fateful encounter. The Carrington flare was previously assumed to be a once in 150 (or 500) year geomagnetic storm, yet the July 2012 CME calls into question this very prediction.

In recognising these realities, our attention immediately shifts to questioning when the next CME will violently wash over our planet, and how prepared our civilisation will be for such an eventual calamity. A detailed 2013 risk assessment by Lloyds and AER (Atmospheric and Environmental Research) concludes that a Carrington-level geomagnetic storm is both inevitable, and may cause the catastrophic outage of the aging United States power grid for anywhere between 16 days and 1–2 years, with an estimated cost of $0.6–2.6 trillion to repair all damaged transformers across the U.S. grid. Preventative measures that may mitigate widespread damage have been proposed (with expensive upfront costs), but ‘hardening the grid’ against such super storms has proceeded at a slower pace than it expected. Moreover, advanced warning of an incoming violent solar storm provides mere hours of notice for a global ‘switch off’ of grids to avoid the most detrimental damage, but only if this event is observed and reported within sufficient timeframes. For this reason alone, numerous space agencies and ground institutes, including the SWPC and the U.S. Air Force, cast a near-constant gaze towards our nearby star, looking for pre-emptive signs of a damaging ‘Earth-directed’ stellar belch. Learning to live with our ‘stormy’ star is perhaps the most prudent defensive measure we can hope to adopt, while mitigating steps continue to be pioneered against our Sun’s most disruptive impulses.

As part of the After the Horizon initiative, the foundation is presently compiling an extensive catalogue of historic solar storms, their measured intensities, observational data (if available), perceived fallout across terrestrial environments, and also general Solar Cycle statistics in the interest of both maintaining knowledge, and access to, these crucial resources for further scientific study. This process is part of a concerted, multidisciplinary effort to preserve this crucial information for the benefit of future scientific investigations as our knowledge of local solar storms continues to mature with each bombardment we witness, and duly record. The intention of this archive is principally custodial in nature, ensuring a ‘hard-copy’ of all materials and data remains available – and accessible – for sustained study of our in-situ stellar environment. In addition to this focus, this cataloguing effort sets a precedent for folding extended observations of our Sun, and heliophysics in general, into the realm of other long-term experimental practices; providing vital observational data across generational scales for our local stellar body, while possibly conserving this information against the very phenomenon that may, one unfortunate day, irreparably damage digital resources for posterity (the ‘digital oblivion’ as it has become varingly described). This Solar Storm initiative is also considered a counterpart feature for our established ‘Climate Recording’ programme; conserving crucial environmental data that will not remain viable for future observations, or repeatable testing, as sampling sources (such as ice cores, and dendrochronology) naturally degrade over deep time.

Notes to the catalogue: The index simply documents materials that have been recorded by a number of historical archives, journalists, academics, instrumentation experts, and also contemporary space agencies for the purposes of heliophysics research. Any large divergences in figures are noted after the defined ‘formally-accepted’ observation data; properties agreed upon by an established majority of observational institutes. No judgements or independent assessments for the risk profile associated with any of the listed solar storms have been completed, nor does the foundation actively employ observational equipment for heliophysics studies. The entire catalogue remains an active document, subject to updates, amendments, and further peer-review, in addition to the inclusion of future observational data for the next significant solar storms.

Page last updated: 20 Jul 2022