Carrington Event Research Articles

International Legal and Ethical Issues of a Future Carrington Event: Existing Frameworks, Shortcomings, and Recommendations

Solar-geomagnetic superstorms like the 1859 Carrington Event pose significant risks to electrical power utilities and satellite infrastructure. Damage to this critical infrastructure could have sig...

Using the Index Over the Last 14 Solar Cycles to Characterize Extreme Geomagnetic Activity

AbstractGeomagnetic indices are routinely used to characterize space weather event intensity. The index is well resolved but is only available over five solar cycles. The index extends over 14 cycles but is highly discretized with poorly resolved extremes. We parameterize extreme activity by the annual‐averaged top few percent of observed values, show that these are exponentially distributed, and they track annual index minima. This gives a 14‐cycle average of 4% chance of at least one great ( nT) storm and 28% chance of at least one severe ( nT) storm per year. At least one nT event in a given year would be a 1:151 year event. Carrington event estimate nT is within the same distribution as other extreme activity seen in since 1868 so that its likelihood can be deduced from that of more moderate events. Events with nT are in a distinct class, requiring special conditions.

Capability of Geomagnetic Storm Parameters to Identify Severe Space Weather

Abstract The paper investigates the capability of geomagnetic storm parameters in the disturbance storm-time (Dst), Kp, and AE indices to distinguish between severe space weather (SvSW) that causes the reported electric power outages and/or telecommunication failures and normal space weather (NSW) that does not cause these severe effects in a 50 yr period (1958–2007). The parameters include the storm intensities DstMin (minimum Dst during the main phase, MP, of the storm), (dDst/dt)MPmax, Kpmax, and AEmax. In addition, the impulsive parameter is derived for the storms that are automatically identified in the Kyoto Dst and USGS is the integral of the modulus of the Dst from onset of the MP (MPO) to the DstMin. T MP is the MP duration from MPO to DstMin. The corresponding mean values and are also calculated. Regardless of the significant differences in the storm parameters between the two Dst indices, the IpsDst in both indices seems to identify four of the five SvSW events (and the Carrington event) in more than 750 NSW events that have been reported to have occurred in 1958–2007, while all other parameters separate one or two SvSWs from the NSWs. Using the Kyoto IpsDst threshold of −250 nT, we demonstrate a 100% true SvSW identification rate with only one false NSW. Using the false NSW event (1972 August 4), we investigate whether using a higher resolution Dst might result in a more accurate identification of SvSWs. The mechanism of the impulsive action leading to large IpsDst and SvSW involves the coincidence that the fast interplanetary coronal mass ejection velocity V contains its shock (or front) velocity and large interplanetary magnetic field Bz southward covering .

Radiocarbon Production Events and their Potential Relationship with the Schwabe Cycle

Extreme cosmic radiation events occurred in the years 774/5 and 993/4 CE, as revealed by anomalies in the concentration of radiocarbon in known-age tree-rings. Most hypotheses point towards intense solar storms as the cause for these events, although little direct experimental support for this claim has thus far come to light. In this study, we perform very high-precision accelerator mass spectrometry (AMS) measurements on dendrochronological tree-rings spanning the years of the events of interest, as well as the Carrington Event of 1859 CE, which is recognized as an extreme solar storm even though it did not generate an anomalous radiocarbon signature. Our data, comprising 169 new and previously published measurements, appear to delineate the modulation of radiocarbon production due to the Schwabe (11-year) solar cycle. Moreover, they suggest that all three events occurred around the maximum of the solar cycle, adding experimental support for a common solar origin.

Temporal and Spatial Evolutions of a Large Sunspot Group and Great Auroral Storms Around the Carrington Event in 1859

AbstractThe Carrington event is considered to be one of the most extreme space weather events in observational history within a series of magnetic storms caused by extreme interplanetary coronal mass ejections from a large and complex active region that emerged on the solar disk. In this article, we study the temporal and spatial evolutions of the source sunspot active region and visual aurorae and compare this storm with other extreme space weather events on the basis of their auroral spatial evolution. Sunspot drawings by Schwabe, Secchi, and Carrington describe the position and morphology of the source active region at that time. Visual auroral reports from the Russian Empire, Iberia, Ireland, Oceania, and Japan fill the spatial gap of auroral visibility and revise the time series of auroral visibility in middle to low magnetic latitudes. The reconstructed time series is compared with magnetic measurements and shows the correspondence between low‐latitude to mid‐latitude aurorae and the phase of magnetic storms. The spatial evolution of the auroral oval is compared with those of other extreme space weather events in 1872, 1909, 1921, and 1989 as well as their storm intensity and contextualizes the Carrington event, as one of the most extreme space weather events, but likely not unique.

Intensity and Impact of the New York Railroad Superstorm of May 1921

AbstractAnalysis is made of low‐latitude ground‐based magnetometer data recording the magnetic superstorm of May 1921. By inference, the storm was driven by a series of interplanetary coronal mass ejections, one of which produced a maximum pressure on the magnetopause of ~64.5 nPa, sufficient to compress the subsolar magnetopause radius to ~5.3 Earth radii. Over the course of the storm, low‐latitude geomagnetic disturbance exhibited extreme local time (longitude) asymmetry that can be attributed to substorm disturbance extending to low latitudes. The storm attained an estimated maximum −Dston 15 May of 907 ± 132 nT, an intensity comparable to that of the Carrington event of 1859. The May 1921 storm brought spectacular aurorae to the nighttime sky. It also interfered with and damaged telephone and telegraph systems associated with railroad systems in New York City and State. These later effects were due to a combination of three factors: the localized details of geomagnetic vector disturbance, the geographic expression of the Earth's surface impedance tensor, and the configurations and physical parameters of the electrical networks of the day.

Modeling a Carrington-scale Stellar Superflare and Coronal Mass Ejection from κ 1 Cet.

Observations from the Kepler mission have revealed frequent superflares on young and active solar-like stars. Superflares result from the large-scale restructuring of stellar magnetic fields, and are associated with the eruption of coronal material (a coronal mass ejection, or CME) and energy release that can be orders of magnitude greater than those observed in the largest solar flares. These catastrophic events, if frequent, can significantly impact the potential habitability of terrestrial exoplanets through atmospheric erosion or intense radiation exposure at the surface. We present results from numerical modeling designed to understand how an eruptive superflare from a young solar-type star, κ 1 Cet, could occur and would impact its astrospheric environment. Our data-inspired, three-dimensional magnetohydrodynamic modeling shows that global-scale shear concentrated near the radial-field polarity inversion line can energize the closed-field stellar corona sufficiently to power a global, eruptive superflare that releases approximately the same energy as the extreme 1859 Carrington event from the Sun. We examine proxy measures of synthetic emission during the flare and estimate the observational signatures of our CME-driven shock, both of which could have extreme space-weather impacts on the habitability of any Earth-like exoplanets. We also speculate that the observed 1986 Robinson-Bopp superflare from κ 1 Cet was perhaps as extreme for that star as the Carrington flare was for the Sun.

Occurrence of great magnetic storms on 6–8 March 1582

AbstractAlthough knowing the occurrence frequency of severe space weather events is important for the modern society, it is insufficiently known due to the lack of magnetic or sunspot observations, before the Carrington event in 1859, which is known as one of the largest events of the last two centuries. Here we show that a severe magnetic storm occurred on 8 March 1582, based on auroral records in East Asia. The equatorward boundary of auroral visibility reached 28.8° magnetic latitude. The equatorward boundary of the auroral oval is estimated to be 33.0° invariant latitude (ILAT), which is comparable to the storms on 25/26 September 1909 (∼31.6° ILAT, minimum Dst of −595 nT), 28/29 August 1859 (∼36.5° ILAT), and 13/14 March 1989 (∼40° ILAT, minimum Dst of −589 nT). Assuming that the equatorward boundary is a proxy for the scale of magnetic storms, we presume that the storm in March 1582 was severe. We also found, by combining Euroepan records, that the storm in March 1582 lasted at least three days. The auroral oval stayed at mid-latitude for the first two days and moved to low latitude (in East Asia) for the last day. It is plausible that the storm was caused by a series of ICMEs (interplanetary coronal mass ejections). We can reasonably speculate that the first ICME could have cleaned up interplanetary space to make the following ICMEs more geoeffective, as probably occurred in the Carrington and Halloween storms.

Detection of a giant white-light flare on an L2.5 dwarf with the Next Generation Transit Survey

Abstract We present the detection of a ΔV ∼ −10 flare from the ultracool L2.5 dwarf ULAS J224940.13−011236.9 with the Next Generation Transit Survey (NGTS). The flare was detected in a targeted search of late-type stars in NGTS full-frame images and represents one of the largest flares ever observed from an ultracool dwarf. This flare also extends the detection of white-light flares to stars with temperatures below 2000 K. We calculate the energy of the flare to be $3.4^{+0.9}_{-0.7}\times 10^{33}$ erg, making it an order of magnitude more energetic than the Carrington event on the Sun. Our data show how the high-cadence NGTS full-frame images can be used to probe white-light flaring behaviour in the latest spectral types.

Probability estimation of a Carrington-like geomagnetic storm

Intense geomagnetic storms can cause severe damage to electrical systems and communications. This work proposes a counting process with Weibull inter-occurrence times in order to estimate the probability of extreme geomagnetic events. It is found that the scale parameter of the inter-occurrence time distribution grows exponentially with the absolute value of the intensity threshold defining the storm, whereas the shape parameter keeps rather constant. The model is able to forecast the probability of occurrence of an event for a given intensity threshold; in particular, the probability of occurrence on the next decade of an extreme event of a magnitude comparable or larger than the well-known Carrington event of 1859 is explored, and estimated to be between 0.46% and 1.88% (with a 95% confidence), a much lower value than those reported in the existing literature.

Low-latitude Aurorae during the Extreme Space Weather Events in 1859

Abstract The Carrington storm (1859 September 1/2) is one of the largest magnetic storms ever observed, and it caused global auroral displays in low-latitude areas, together with a series of multiple magnetic storms from 1859 August 28 to September 4. In this study, we revisit contemporary auroral observation records to extract information on their elevation angle, color, and direction to investigate this stormy interval in detail. We first examine the equatorward boundary of the “auroral emission with multiple colors” based on descriptions of elevation angle and color. We find that their locations were 36.°5 ILAT on August 28/29 and 32.°7 ILAT on September 1/2, suggesting that trapped electrons moved to, at least, L ∼ 1.55 and L ∼ 1.41, respectively. The equatorward boundary of “purely red emission” was likely located at 30.°8 ILAT on September 1/2. If the “purely red emission” was a stable auroral red arc, it would suggest that trapped protons moved to, at least, L ∼ 1.36. This reconstruction with observed auroral emission regions provides conservative estimations of magnetic storm intensities. We compare the auroral records with magnetic observations. We confirm that multiple magnetic storms occurred during this stormy interval, and that the equatorward expansion of the auroral oval is consistent with the timing of magnetic disturbances. It is possible that the August 28/29 interplanetary coronal mass ejections (ICMEs) cleared out the interplanetary medium, making the ICME for the Carrington storm on September 1/2 more geoeffective.

A great space weather event in February 1730

Aims. Historical records provide evidence of extreme magnetic storms with equatorward auroral extensions before the epoch of systematic magnetic observations. One significant magnetic storm occurred on February 15, 1730. We scale this magnetic storm with auroral extension and contextualise it based on contemporary solar activity.Methods. We examined historical records in East Asia and computed the magnetic latitude (MLAT) of observational sites to scale magnetic storms. We also compared them with auroral records in Southern Europe. We examined contemporary sunspot observations to reconstruct detailed solar activity between 1729 and 1731.Results. We show 29 auroral records in East Asian historical documents and 37 sunspot observations.Conclusions. These records show that the auroral displays were visible at least down to 25.8° MLAT throughout East Asia. In comparison with contemporary European records, we show that the boundary of the auroral display closest to the equator surpassed 45.1° MLAT and possibly came down to 31.5° MLAT in its maximum phase, with considerable brightness. Contemporary sunspot records show an active phase in the first half of 1730 during the declining phase of the solar cycle. This magnetic storm was at least as intense as the magnetic storm in 1989, but less intense than the Carrington event.

The Great Space Weather Event during 1872 February Recorded in East Asia

Abstract The study of historical great geomagnetic storms is crucial for assessing the possible risks to the technological infrastructure of a modern society, caused by extreme space–weather events. The normal benchmark has been the great geomagnetic storm of 1859 September, the so-called “Carrington Event.” However, there are numerous records of another great geomagnetic storm in 1872 February. This storm, which occurred about 12 years after the Carrington Event, resulted in comparable magnetic disturbances and auroral displays over large areas of the Earth. We have revisited this great geomagnetic storm in terms of the auroral and sunspot records in historical documents from East Asia. In particular, we have surveyed the auroral records from East Asia and estimated the equatorward boundary of the auroral oval to be near 24.°2 invariant latitude, on the basis that the aurora was seen near the zenith at Shanghai (20° magnetic latitude, MLAT). These results confirm that this geomagnetic storm of 1872 February was as extreme as the Carrington Event, at least in terms of the equatorward motion of the auroral oval. Indeed, our results support the interpretation of the simultaneous auroral observations made at Bombay (10° MLAT). The East Asian auroral records have indicated extreme brightness, suggesting unusual precipitation of high-intensity, low-energy electrons during this geomagnetic storm. We have compared the duration of the East Asian auroral displays with magnetic observations in Bombay and found that the auroral displays occurred in the initial phase, main phase, and early recovery phase of the magnetic storm.

Possible Influence of Extreme Magnetic Storms on the Thermosphere in the High Latitudes

AbstractSolar and interplanetary events can create extreme magnetic storms, such as the Carrington storm in 1859 with intensity up to Dst ∼−1,760 nT. The influence of an idealized, smaller Carrington‐type storm on the thermosphere has been simulated using the nonhydrostatic Global Ionosphere‐Thermosphere Model. For the storm conditions we simulated, the solar wind BZ and velocity were −50 nT and 1,000 m/s, respectively. The corresponding cross polar cap potential reached 360 kV, and the hemispheric power was 200 GW. Consequently, the hemispheric integrated Joule heating exceeded 3,500 GW, which is more than 70 times higher than normal conditions. The thermosphere variations at high latitudes were examined through the comparison of three cases: reference, storm with geomagnetic energy enhancement only, and storm with both solar and geomagnetic energy enhancement. At 400‐km altitude, the neutral density increased by >20 times at certain locations and by >10 times globally averaged. The atmosphere experienced a temperature of 4000 K, more than 1,500 m/s horizontal wind, and exceeding 150 m/s vertical wind. In general, additional energy increase from solar irradiation resulted in 20–30% more perturbation in neutral density and temperature. The exobase (top boundary of the thermosphere) expanded to altitudes >1,000 km, and the buoyancy acceleration (difference between vertical pressure gradient force and gravity force) can be as large as 3 m/s2. The results will help to determine possible extreme responses to interplanetary coronal mass ejections for various phenomena occurring in geospace.

Observations of Low‐Latitude Red Aurora in Mexico During the 1859 Carrington Geomagnetic Storm

AbstractOne of the most intense geomagnetic storm that has been documented in recent history occurred on 1 September 1859. This storm is known as the Carrington Event. In the morning of 1 September at around 11:15 UT, Richard Carrington and Richard Hodgson observed in England, independently and for the first time, an intense white light solar flare. About 17 hr after this solar event, there occurred the strongest geomagnetic perturbation ever recorded as well as a greatly extended red aurora, which covered unusually at low latitudes. The red auroral display on 2 September was reported in regions where this kind of phenomena is very rare, like in Cuba and Hawaii. Until now however, it was not known to scientists that the low‐latitude red aurora is also registered in Mexico. At that time, Mexico was in a civil war, and there were very difficult conditions in where to establish astronomical and magnetic observatories. Nevertheless, the geomagnetic storm was observed with a maximum intensity between 7:00 and 8:00 UTC and was reported to a Mexican newspaper from five different locations (Mexico City, Querétaro, Guadalajara, Hidalgo, and Guanajuato) and registered also from at least in two additional sites (Michoacán and San Luis Potosí) in other historical documents. These records confirm that the Carrington geomagnetic storm was a global event with planetary repercussions, and that the Mexican low‐latitude region is susceptible to significant effects associated with intense space weather events.

Ground-based detection of G star superflares with NGTS

We present high cadence detections of two superflares from a bright G8 star (V = 11.56) with the Next Generation Transit Survey (NGTS). We improve upon previous superflare detections by resolving the flare rise and peak, allowing us to fit a solar flare inspired model without the need for arbitrary break points between rise and decay. Our data also enables us to identify substructure in the flares. From changing starspot modulation in the NGTS data we detect a stellar rotation period of 59 hours, along with evidence for differential rotation. We combine this rotation period with the observed \textit{ROSAT} X-ray flux to determine that the star's X-ray activity is saturated. We calculate the flare bolometric energies as $5.4^{+0.8}_{-0.7}\times10^{34}$ and $2.6^{+0.4}_{-0.3}\times10^{34}$ erg and compare our detections with G star superflares detected in the \textit{Kepler} survey. We find our main flare to be one of the largest amplitude superflares detected from a bright G star. With energies more than 100 times greater than the Carrington event, our flare detections demonstrate the role that ground-based instruments such as NGTS can have in assessing the habitability of Earth-like exoplanets, particularly in the era of \textit{PLATO}.

A Framework to Understand Extreme Space Weather Event Probability.

An extreme space weather event has the potential to disrupt or damage infrastructure systems and technologies that many societies rely on for economic and social well-being. Space weather events occur regularly, but extreme events are less frequent, with a small number of historical examples over the last 160 years. During the past decade, published works have (1) examined the physical characteristics of the extreme historical events and (2) discussed the probability or return rate of select extreme geomagnetic disturbances, including the 1859 Carrington event. Here we present initial findings on a unified framework approach to visualize space weather event probability, using a Bayesian model average, in the context of historical extreme events. We present disturbance storm time (Dst) probability (a proxy for geomagnetic disturbance intensity) across multiple return periods and discuss parameters of interest to policymakers and planners in the context of past extreme space weather events. We discuss the current state of these analyses, their utility to policymakers and planners, the current limitations when compared to other hazards, and several gaps that need to be filled to enhance space weather risk assessments.

Characteristics of Solar Proton Events Observed Near Earth and Stellar Activity Variations

AbstractWe could identify three categories of solar proton events (SPE) with distinct solar origin from an analysis of direct and indirect observations during the years 1561-2016 CE spanning 42 sunspot cycles. They are (i) 10 MeV SPE whose number of occurrences closely follow the sunspot cycles (ii) 30 MeV SPE which show secular changes with peaks near Gleissberg solar cycle minima and inferred to be associated with distinct enhancements in the efficiency of the solar dynamo and (iii) those associated with Impulsive and irregular solar activity changes such as the Carrington event of September 1859. The relevance of above results for stars exhibiting cyclic and irregular activity changes will be also discussed.

Statistics of Extreme Time‐Integrated Geomagnetic Activity

AbstractA statistical analysis of the time‐integrated Dst index is performed over 1958–2007. The tail of the probability distribution of extreme time‐integrated Dst events, which occur during strong geomagnetic storms, can be precisely fitted by a power law function with upper cutoff, apparently not exceeded even by the 1859 Carrington event. This time‐integrated Dst is expected to be a reasonable proxy for maximum densities of MeV electrons in the heart of the outer radiation belt, which are known to pose a serious threat to satellites. During such strong events, a correlation is found between the time‐integrated levels of various physical quantities, such as interplanetary magnetic field Bz, particle energy fluxes measured during injections in the magnetotail, geosynchronous ULF wave index, and geomagnetic activity in the inner magnetosphere, suggesting cumulative effects from successive disturbances.

Retrospective analysis of GLEs and estimates of radiation risks

28 February 2017 marked 75 years since the first confident registration of solar cosmic rays (SCRs), i.e., accelerated solar particles with energies from about 106to ~1010÷ 1011eV. Modern state of the problems related to the studies of Ground Level Enhancements (GLEs) of relativistic SCRs is critically analyzed based on available direct and proxy data. We are also taking into account extremely large fluxes of non-relativistic solar energetic particles (SEPs). Both kinds of SCR events are of great astrophysical and geo-scientific (geophysical) interests. A number of the GLE properties (total statistics, occurrence rate, longitude distribution, ranking of GLEs, a number of specific GLEs – so-called “rogue” SEP events etc.) are discussed in some detail. We note also the problems of GLE identification (definition) by ground-based observations, the difficulties in the studies of weak (“hidden”, or sub-) GLEs etc. One of serious challenges to the problem of radiation hazard in space is a lack of a clear, unambiguous relation between the fluxes (fluences) of relativistic SCR and non-relativistic SEPs. Special attention is paid to the recent debate on the validity, origin and properties of the “ancient” events AD775, AD994, AD1859 (Carrington event) and BC3372. We demonstrate that, in spite of existing uncertainties in proton fluences above 30 MeV, all of them are fitted well by a unique distribution function, at least, with the present level of solar activity. Extremely large SEP events are shown to obey a probabilistic distribution on their fluences with a sharp break in the range of large fluences (or low probabilities). The studies of this kind may be extended for periods with different levels of solar activity in the past and/or in the future. Dose rates at aircraft altitudes are also demonstrated during some GLEs. Several examples of using the SCR data and GLE properties in radiation prediction schemes are considered.