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When there is a temporary disturbance of earth’s magnetosphere, then a geomagnetic storm (or solar storm) has occurred. It is caused by a solar wind shock wave and/or cloud of a magnetic field that interacts with the Earth's magnetic fields. The interaction of Interplanetary Magnetic Fields (IMF) of the sun with the earth’s magnetic fields in opposite directions is known as magnetic reconnection (Yousif, 2014). Magnetic reconnection (often referred as "reconnection") is the breaking and reconnecting of oppositely directed magnetic field lines in plasma at a neutral point which leads to converting the magnetic field energy into plasma kinetic and thermal energy. It occurs either in the day-time (day reconnection) where the sunward convection near the polar cusps allows energised particles to be transmitted earthward or night-time (tail reconnection) where particles injected into the magnetosphere are saturated, thus releasing stored energy in the form of auroral substorms. Sokolov (2011) suggested that a geomagnetic storm can be determined by changes in the Disturbed-storm time (Dst). However, not all geomagnetic storms have an initial phase and not all sudden increase in Dst or SYM-H are followed by a geomagnetic storm. This paper attempts to determine what are responsible for magnetic reconnections in the solar cycle 24 considering a low solar activity year 2009 and a high solar activity year 2012. We have to classify the geomagnetic storms using the Dst indices and rearrange the IMF Bz according to its negative, neutral and positive values. We measured the correlation between Bz and solar wind using a 1-min resolution OMNIweb dataset. Thereafter, establish the factors responsible for magnetic reconnections. We analysed 39 and 202 geomagnetic storms in 2009 and 2012 respectively considering the Dst indices and IMF Bz values of each month obtained from the OMNIWeb Database. Our results showed that geomagnetic storms occurred in 10% and 45% of days in the year 2009 and 2012 respectively which implies they were frequent and intense due to high solar activity caused by the frequent occurrence of coronal mass ejections (CMEs) and interplanetary coronal mass ejections (ICMEs) in the year 2012 than in the year 2009. This study also revealed that negative Bz occurrences were 47.54% and 52.18% in 2009 and 2012 respectively. Thus, the more intense the geomagnetic storms, the more Bz would go south and the more magnetic reconnections and subsequently auroral substorms which can increase radiation doses for occupants of transpolar flights, disruption of shortwave radio communications, distortion of compass readings in polar regions, failure of electrical transmission lines, increased corrosion in long pipelines, anomalies in the operations of communications satellites, and potentially lethal dosages of radiation for astronauts in interplanetary spacecraft.

The largest geomagnetic storm in solar cycle 24 is investigated from the dual perspective of (1) solar source – solar wind – geomagnetic storm chain and (2) the hazardous induced response as shown by the surface electric field. The study is based on heliospheric magnetic field and solar wind data, on one hand, and on recorded 1-min geomagnetic data from the INTERMAGNET network of European geomagnetic observatories, on the other. The lateral distribution of the induced electric response for the European continent during the considered storm is shown, and the timing of the maximum induced horizontal geoelectric vector is discussed in terms of specific moments of the storm development.

Geomagnetic indices are routinely used to characterize space weather event intensity. The DST index is well resolved, but is only available over 5 solar cycles. The aa index extends over 14 cycles but is highly discretized with poorly resolved extremes. We parameterize extreme aa activity by the annual averaged top few % of observed values, show these are exponentially distributed and they track annual DST index minima. This gives a 14 cycle average of ~ 4% chance of at least one great (DST nT) storm and ~ 28% chance of at least one severe (DST nT) storm per year. At least one DST=‐809 [‐663,‐955] nT event in a given year would be a 1:151 year event. Carrington event estimate DST ~ ‐850 nT is within the same distribution as other extreme activity seen in aa since 1868 so that its likelihood can be deduced from that of more moderate events. Events with DST ≲ ‐1000 nT are in a distinct class, requiring special conditions.

Few studies have collected and analyzed the astronomical events recorded in Arabic literature. In this paper, we present some additional events reported in four Arabic historical sources that could be classified as an aurora. These observations occurred from 9th to 20th century and cover a large geographic area: North Africa, Arabian-Peninsula and Middle-East. Some of them were observed at very low geomagnetic latitude, such as the event seen in Yemen in AD 1919 that can be considered as one of the lowest latitude auroras ever documented by Arabic scholars. In the same Yemenite source, the author describes a twilight phenomenon of 1883 October 03–November 01 which can be considered as an atmospheric-optical phenomenon arising from the major explosive eruptions of Krakatoa in 1883 August 26–27. We also noticed that one of the events which was seen for 7 days coincide probably with the prolonged manifestation of auroras of 1870 September 24–25. Including published records, we compiled a so far most complete catalog of potential auroral candidates in the Arabic sources. This data set can be used in order to study the solar activity variations and magnetic storms in the historical past. One of the interesting auroras was seen in Mecca ($\sim17^{\circ}$ MLAT) in 1872 February 04. This event is further evidence for the equatorward extension of auroral display and the planetary consequences of the great geomagnetic storm of 1872. Finally, it should be underlined that no aurora observations were recorded during the Maunder minimum (MM).

The largest variations in the plasma and fields that comprise the inner regions of the Earth’s space environment, or the magnetosphere, occur during geomagnetic storms and are related to the intensification of the ring current, the magnetically trapped charged particles that partially or fully encircle the Earth inside of ∼7 Earth radii. This chapter provides a historical introduction to the ring current and geomagnetic storms that have been investigated for more than 100 years. An overview of the relationship of the ring current to solar wind drivers and the development and decay of the ring current, in terms of the Sun-Earth connection is presented. Major space weather effects triggered by geomagnetic storms are briefly summarized. These effects intensify during extreme events, like the largest recorded geomagnetic storm that occurred in September 1859, known as the Carrington Event. Less severe storms have occurred since then, still causing many disruptions.

On 1 September 1859, occurred one of the most intense geomagnetic storm that has been documented in recent history. This storm is known as the Carrington Event. On the morning September 1st at arou...

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.

The Earth's atmosphere and the Earth's magnetic field protects local life by shielding us against Solar particle flows, just like the sun's magnetic field deflects cosmic particle radiation. Generally, magnetic fields can affect terrestrial life such as migrating animals. Thus, terrestrial life is connected to astronomical interrelations between different magnetic fields, particle flows and radiation. Mass strandings of whales have often been documented, but their causes and underlying mechanisms remain unclear. We investigated the possible reasons for this phenomenon based on a series of strandings of 29 male, mostly bachelor, sperm whales (Physeter macrocephalus) in the southern North Sea in early 2016. Whales’ magnetic sense may play an important role in orientation and migration, and strandings may thus be triggered by geomagnetic storms. This approach is supported by the following: (1) disruptions of the Earth's magnetic field by Solar storms can last about 1 day and lead to short-term magnetic latitude changes corresponding to shifts of up to 460 km; (2) many of these disruptions are of a similar magnitude to more permanent geomagnetic anomalies; (3) geomagnetic anomalies in the area north of the North Sea are 50–150 km in diameter; and (4) sperm whales swim about 100 km day−1, and may thus be unable to distinguish between these phenomena. Sperm whales spend their early, non-breeding years in lower latitudes, where magnetic disruptions by the sun are weak and thus lack experience of this phenomenon. ‘Naïve’ whales may therefore become disoriented in the southern Norwegian Sea as a result of failing to adopt alternative navigation systems in time and becoming stranded in the shallow North Sea.

Space weather events produce variations in the electric current in the Earth's magnetosphere and ionosphere. From these high-altitude atmospheric regions, resulting geomagnetically induced currents (GICs) can lead to fluctuations in ground currents that affect the electric power grid and potentially overload transformers during extreme storms. The most extreme geomagnetic storm on record, known as the 1859 Carrington event, was so intense that ground-based magnetometers were saturated at high magnetic latitudes. The most reliable, unsaturated observation is the hour resolution data from the Colaba Magnetic Observatory in India. However, higher-frequency components—fluctuations at second through minute time cadence—to the magnetic field can play a significant role in GIC-related effects. We present a new method for scaling higher-frequency observations to create a realistic Carrington-like event magnetic field model, using modern magnetometer observations. Using the magnetic field model and ground conductivity models, we produce an electric field model. This method can be applied to create similar magnetic and electric field models for studies of GIC effects on power grids.

An increase in the solar magnetic field gives rise to the number of visible sunspots in the Earth facing side of the Sun. This tends to impact the Earth’s magnetic field. Occurrence of a geomagnetic storm depends on the interaction of magnetic fields of both the Sun (captured in solar wind) and the Earth. The energy of the sun is given out in the form of high-speed solar wind, solar flares, coronal mass ejections (CMEs), solar uV light and energetic particles (MeV). The effect of such geomagnetic storms is borne by the trans-ionospheric message carrying signal and affects both satellite navigation and radio communication systems on Earth. Moreover, the ionosphere, being a refractive and dispersive medium, adds as a source of error to the message signal. Thus, it becomes important to study the effect of space weather activities on GNSS signal and try to overcome its impact. This paper studies the impact of one such solar storm in the mid-high latitude region during the winter solstice of 2015 on GPS and high-frequency airplane communication. A case study of an event that occurred in Stockholm, Sweden on the 4 November 2015 has been investigated using the geomagnetic and satellite geometric parameters, and the total electron content (TEC) variation in the ionosphere. The analysis undertaken in this paper demonstrates the importance of understanding the serious threats solar activity poses to GNSS and its related applications on Earth, which can have rippling effects on industries which are evidently reliable on space technology.

Although knowing the occurrence frequency of severe space weather events is important for a modern society, it is insufficiently known due to the lack of magnetic or sunspot observations, before the Carrington event in 1859 known as one of the largest events during 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{\deg} magnetic latitude. The equatorward boundary of the auroral oval is estimated to be 33.0{\deg} invariant latitude (ILAT), which is comparable to the storms on 25/26 September 1909 (~31.6{\deg} ILAT, minimum Dst of -595 nT), 28/29 August 1859 (~36.5{\deg} ILAT), and 13/14 March 1989 (~40{\deg} 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 on March 1582 was severe. We also found that the storm on March 1582 lasted, at least, for three days by combining European records. 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 a first ICME could have cleaned up interplanetary space to make the following ICMEs more geo-effective, as probably occurred in the Carrington and Halloween storms., Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Society; main text 10 pages, reference 5 pages, appendix 4 pages, 2 tables, and 6 figures

A statistical analysis of the relation between exceptional solar events and daily numbers of deaths in the Czech Republic is presented. In particular, we concentrate on diseases of the nervous system (group VI from ICD-10—International Statistical Classification of Diseases and Related Health Problems 10th Revision) and diseases of the circulatory system (group IX from ICD-10). We demonstrate that the neurological diseases exhibit greater instability during the period of rising and falling solar activity. We study the daily numbers of deaths, separately for both sexes and two age groups (under 39 and 40+), during the Solar Cycles No. 23 and No. 24. We focus on exceptionally strong solar events in this period, such as the “Bastille Day event” on 14 July 2000, “Halloween solar storm” on 28 October 2003, and events on 7 January 1997, 2 April 2000, and on 7 September 2005. Special attention is paid to “St. Patrick’s Day storm” on 17 March 2015, the strongest geomagnetic storm of the Solar Cycle No. 24 that occurred following a coronal mass ejection (CME). We investigate the changes in the daily numbers of deaths during 1 month before and 1 month after these exceptional solar events. We take specific storm dynamics of their geophysical parameters into consideration. It has been verified that, for diseases of the nervous system, women are generally more sensitive than men. On the contrary, this differences between men and women have not been found for diseases of the circulatory system. Our findings suggest that the impact of the hazardous space weather conditions on human health depends on the specific dynamic and strength of the solar storm.

A statistical study has been performed on all the geomagnetic storm events caused by Coronal Mass Ejections (CMEs) which are associated with flares from January 2010 to December 2012. The following results are obtained. The sources of the CMEs mentioned above are distributed mainly from 45°E to 45°W on the solar surface, accounting 78.95% of the total events, and most of them are distributed in the western hemisphere, thus the sources of CMEs located in the western hemisphere are more likely to cause geomagnetic effects. The X-class flares are more likely to be associated with geomagnetic effects, and geomagnetic storms will be observed in two or three days after the eruption of 60% of X-class flares, while the flares of other classes have a much lower probability to associate with geomagnetic effects, less than 10% for all of them. By analyzing all the X-class flares erupted during this period on the solar disk, it is found that for the X-class flares located from 45°E to 45°W in heliographic longitude, if there are no large-scale disturbances on the solar surface nor the accompanied CMEs during the eruptions, the probability of occurrence of geomagnetic storms after the flares will be very small. Therefore, a new method to forecast the geomagnetic storms by analyzing the observed solar image data has been proposed.

The Sun, the only star in our solar system, is an essential energy source for all human activities as well as the entire Earth biosphere. Galileo discovered the existence of sunspots in 1610, and 200 years later, Schwabe proved that our home star?s activities follow a cycle of 11 years. Using high-tech devices, scientists and engineers have gained a clearer vision of solar activities and are now better able to discern the sun?s behavior. Known solar activities include a combination of sunspots, solar flares, and coronal mass ejections. Solar activity occurs in peaks, with roughly equal intervals between them. The sun interacts significantly with Earth?s magnetosphere. Extraordinary solar activities (or solar storms) can severely interfere with Earth?s magnetospheric and ionospheric electrical current system, causing rapidly changing Earth surface potential (ESP). The destructive consequences become more evident with the ever-increasing propagation of electrical and electronic equipment. The first recorded example of the negative effects of solar activity on human society was an unprecedented solar storm that raged from 28 August through 2 September 1859 (cycle 10), in which telegraph systems all over Europe and North America failed.

This chapter explores how the thermosphere and ionosphere (T-I) might respond to extreme solar events. Three different scenarios are considered: (1) an increase in solar UV and EUV radiation for a number of days, (2) an extreme enhancement in the solar X-rays and EUV radiation associated with a flare, and (3) an extreme CME driving a geomagnetic storm. Estimating the response to the first two scenarios is reasonably well defined, and although they would certainly impact the T-I system, those impacts could potentially be mitigated. In contrast, the response to an extreme geomagnetic storm is significantly more complicated, making the response much more uncertain, and mitigation more challenging. The question is, if an 1859 Carrington-level CME hit Earth, how might the thermosphere and ionosphere respond? Firstly, the response would be dependent upon how the magnetosphere reacts and channels the energy into the upper atmosphere. The assumption is the magnetospheric convection and auroral precipitation inputs would look similar to the 2003 Halloween or 2000 Bastille Day storms, but stronger and more expanded towards middle latitudes. For a Halloween or Bastille-level geomagnetic storm, the sequence of physical processes in the thermosphere and ionosphere are mostly understood, and the physics-based models have been tuned for this level of event. For an extreme solar storm, it is unclear what the magnitude of the driving forces would be, and if the T-I response would be a natural linear extrapolation or if nonlinear processes would begin to dominate. A numerical simulation has been performed with a coupled thermosphere ionosphere model to quantify the likely response to an extreme geomagnetic storm. The simulation predicts the neutral atmosphere would experience horizontal winds of 1500 m s−1, vertical winds exceeding 150 m s−1, and large increases in neutral density with the “top” of the thermosphere (where collisions no longer dominate) rising to well above 1000 km. The expansion of the atmosphere during an extreme event and the increase in neutral density has the direct effect of enhancing drag on a spacecraft, changing its orbit, and raising the uncertainty of its position. With the proliferation of space debris, the challenge of collision avoidance is of mounting concern, which further raises the importance of accurate orbit prediction. Predicting the ionosphere response is more challenging because there is significant uncertainty in quantifying some of the other driver-response relationships, such as the magnitude and shielding time-scale of the penetration electric field, and the possible feedback to the magnetosphere. Total electron content at mid latitude could exceed 1000 TEC units, which together with steep gradients and more structure will severely impact critical communications and satellite navigation accuracy.

Extreme space weather events, while rare, can have a substantial impact on our technologically-dependent society. And, although such events have only occasionally been observed, through careful analysis of a wealth of space-based and ground-based observations, historical records, and extrapolations from more moderate events, we have developed a basic picture of the components required to produce them. Several key issues, however, remain unresolved. For example, what limits are imposed on the maximum size of such events? What are the likely societal consequences of a so-called “100-year” solar storm? In this review, we summarize our current scientific understanding about extreme space weather events as we follow several examples from the Sun, through the solar corona and inner heliosphere, across the magnetospheric boundary, into the ionosphere and atmosphere, into the Earth’s lithosphere, and, finally, its impact on man-made structures and activities, such as spacecraft, GPS signals, radio communication, and the electric power grid. We describe preliminary attempts to provide probabilistic forecasts of extreme space weather phenomena, and we conclude by identifying several key areas that must be addressed if we are better able to understand, and, ultimately, predict extreme space weather events.

We present a detailed study on a solar storm occurred on 2014 January 7. By using the remote-sensing observations of solar activities at multiple wavelengths from the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO), the eruptions of the solar flare and coronal mass ejection (CME) are investigated. Based on the measurement of energetic protons from the Geostationary Operational Environmental Satellite (GOES) and the in-situ plasma measurement from the Advanced Composition Explorer (ACE) at the solar-terrestrial L1 point, the solar energetic particle (SEP) event and interplanetary CME (ICME) accompanied by the solar storm, and the shock driven by the ICME are analyzed. The influence of the solar storm on the geomagnetic fields is also analyzed with the ground-based magnetic data. The results in this study show that: (1) The initial time of impulsive phase of the solar flare and the ejection time of the CME are temporally in accordance with each other. (2) The solar protons are mainly accelerated by the CME-driven shock, rather than by the magnetic reconnection in the flare, and the protons are released when the CME travels to 7.7 solar radius. (3) The widths of the interplanetary shock sheath and the ICME itself are derived to be 0.22 AU and 0.26 AU, respectively. (4) The interplanetary shock and the ICME give rise to substorms and aurora, whereas no obvious geomagnetic storm is detected. The reason is that the ICME does not contain a regular structure of magnetic cloud (MC) or evident southward component of magnetic field.

An examination is made of the hypothesis that the statistics of magnetic storm maximum intensities are the realization of a lognormal stochastic process. Weighted least squares and maximum likelihood methods are used to fit lognormal functions to −Dst storm time maxima for years 1957–2012; bootstrap analysis is used to established confidence limits on forecasts. Both methods provide fits that are reasonably consistent with the data; both methods also provide fits that are superior to those that can be made with a power-law function. In general, the maximum likelihood method provides forecasts having tighter confidence intervals than those provided by weighted least squares. From extrapolation of maximum likelihood fits: a magnetic storm with intensity exceeding that of the 1859 Carrington event, −Dst ≥ 850 nT, occurs about 1.13 times per century and a wide 95% confidence interval of [0.42, 2.41] times per century; a 100 year magnetic storm is identified as having a −Dst ≥ 880 nT (greater than Carrington) but a wide 95% confidence interval of [490, 1187] nT.

The shock wave of the traveling mass of solar energetic particles causes geomagnetic storms that may disrupt the Earth’s magnetosphere. In the present paper, we have analyzed five major geomagnetic storms (disturbance storm time

A large variation in 14C around AD 775 has been considered to be caused by one or more solar super-flares within one year. We critically review all known aurora reports from Europe as well as the Near, Middle, and Far East from AD 731 to 825 and find 39 likely true aurorae plus four more potential aurorae and 24 other reports about halos, meteors, thunderstorms etc., which were previously misinterpreted as aurorae or misdated; we assign probabilities for all events according to five aurora criteria. We find very likely true aurorae in AD 743, 745, 762, 765, 772, 773, 793, 796, 807, and 817. There were two aurorae in the early 770s observed near Amida (now Diyarbakir in Turkey near the Turkish-Syrian border), which were not only red, but also green-yellow – being at a relatively low geomagnetic latitude, they indicate a relatively strong solar storm. However, it cannot be argued that those aurorae (geomagnetic latitude 43 to 50°, considering five different reconstructions of the geomagnetic pole) could be connected to one or more solar super-flares causing the 14C increase around AD 775: There are several reports about low- to mid-latitude aurorae at 32 to 44° geomagnetic latitude in China and Iraq; some of them were likely observed (quasi-)simultaneously in two of three areas (Europe, Byzantium/Arabia, East Asia), one lasted several nights, and some indicate a particularly strong geomagnetic storm (red colour and dynamics), namely in AD 745, 762, 793, 807, and 817 – always without 14C peaks. We use 39 likely true aurorae as well as historic reports about sunspots together with the radiocarbon content from tree rings to reconstruct the solar activity: From AD ∼733 to ∼823, we see at least nine Schwabe cycles; instead of one of those cycles, there could be two short, weak cycles – reflecting the rapid increase to a high 14C level since AD 775, which lies at the end of a strong cycle. In order to show the end of the dearth of naked-eye sunspots, we discuss two more Schwabe cycles until AD ∼844. The 14C record (from both Intcal and Miyake et al. 2013a) is anti-correlated to auroral and sunspot activity, as expected from solar wind modulation of cosmic rays which produce the radiocarbon. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A complex solid torus model was developed in order to be able to study an extreme solar storm, the so-called "Great Storm" or "New York Railroad Storm" of May 1921, when neither high spatial and time resolution magnetic field measurements, solar flare nor coronal mass ejection observations were available. We suggest that a topological change happened in connection with the occurrence of the extreme solar storm. The solar storm caused one of the most severe space weather effects ever.

The ionospheric irregularities on St. Patrick's day (17 March 2015) at Chiang Mai and Chumphon stations are affected by the strongest of the 24th solar storm cycle. The ionogram data in this research is obtained from the frequency modulated/carrier waves (FM/CW) ionosonde at Chiang Mai station and near the magnetic equator, namely, Chumphon station. The parameters in this research include the critical frequency of F2 layer, the virtual height of F layer, and the maximum height of F2 layer. Overall, we found that the ionosphere layer at Chiang Mai and Chumphon stations are disturbed by the geomagnetic storm. The result indicate that the radio frequency transmission is affected by geomagnetic storm at both stations and the observation differ from the median value is specified in part of the percentage of coefficient deviation.

The great geomagnetic storm of August 28 through September 3,1859 is, arguably, the greatest and most famous space weather event in the last two hundred years. For the first time observations showed that the sun and aurora were connected and that auroras generated strong ionospheric currents. A significant portion of the world's 200,000 km of telegraph lines were adversely affected, many of which were unusable for 8 hours or more which had a real economic impact. In addition to published scientific measurements, newspapers, ship logs, and other records of that era provide an untapped wealth of first hand observations giving time and location along with reports of the auroral forms and colors. At its height, the aurora was described as a blood or deep crimson red that was so bright that one "could read a newspaper by." At its peak, the Type A red aurora lasted for several hours and was observed to reach extremely low geomagnetic latitudes on August 28-29 (-25") and on September 2-3 (-18"). Auroral forms of all types and colors were observed below 50" latitude for -24 hours on August 28-29 and -42 hours on September 2-3. From a large database of ground-based observations the extent of the aurora in corrected geomagnetic coordinates is presented over the duration of the storm event.

The solar flares, the speeds of shocks propagated in the solar-terrestrial space and driven by coronal mass ejections (CMEs), the heliographic longitudes and Carrington longitudes of source regions, and the geomagnetic storms, which are accompanied by the super solar proton events with a peak flux equal to or exceeding 10 000 pfu, have been studied by using the data of ground-based and space observations. The results show that the heliographic longitudes of source regions of super solar proton events distributed in the range from E30 to W75°. The Carrington longitudes of source regions of super solar proton events distributed in the two longitudinal belts, 130°∼220° and 260°∼320°, respectively. All super solar proton events were accompanied by major solar flares and fast CMEs. The averaged speeds of shocks propagated from the sun to the Earth were greater than 1 200 km/s. Eight super solar proton events were followed by major geomagnetic storms (Dst≤−100 nT), except that one super solar proton event was followed by a geomagnetic storm with the geomagnetic activity index Dst=−96 nT, a little smaller than that of major geomagnetic storms.

On the basis of geomagnetic storm index (minimum Dst index), we have considered nine events of coronal mass ejections (CMEs), solar flares, geomagnetic storms and other parameters during the active period of solar cycle 23 (year 1999–2005). We have examined the physics and phenomenology of CMEs and associated solar flares and their further association with geomagnetic storms. Observational results conclude that coronal mass ejections having faster speed (>1,000 km/s) mostly produce stronger geomagnetic storms.

Based on hourly data of solar energetic particles (velocity and density), interplanetary magnetic field (IMF) Bz component, and derived IMF orientations, e.g. IMF cone angle and clock angle, we studied their relations within 155 intense geomagnetic storms (Dst index less than -100 nT) during years 2009 to 2016 of solar cycle 24. The importance of negative and southward Bz was confirmed. It is suggested that strong geomagnetic storm also depends on IMF orientation angles, especially perpendicular IMF Bz. However, strong storms is not correlated with fast proton speed, which is aligned with perpendicular or parallel IMF cone angle. In the future, we can use those derived equations for prediction of solar storm.

[1] The recovery phase of the largest storms ever recorded has been studied. These events provide an extraordinary opportunity for two goals: (1) to validate the hyperbolic model by Aguado et al. (2010) for the recovery phase after disturbances as severe as the Carrington event or that related to the Hydro-Quebec blackout in March 1989, and (2) to check whether the linear relationship between the recovery time and the intensity of the storm still complies. Our results reveal the high accuracy of the hyperbolic decay function to reproduce the recovery phase of the magnetosphere after an extreme storm. Moreover, the characteristic time that takes the magnetosphere to recover depends in an exponential way on the intensity of the storm, as indicated by the relationship between the two parameters involved in the hyperbolic decay. This exponential function can be approached by a linear function when the severity of the storm diminishes.

The magnetic storm around 1859 September 2, caused by so-called Carrington flare, was the most intense in the history of modern scientific observations, and hence is considered to be the benchmark event for space weather. The magnetic storm caused worldwide observations of auroras even at very low latitudes such as Hawaii, Panama, or Santiago, and the available magnetic field measurement at Bombay, India, showed two peaks: the main was the Carrington event which occurred in day time in East Asia, and a second storm after the Carrington event which occurred at night in East Asia. In this paper, we present a result from surveys of aurora records in East Asia, which provides new information of the aurora activity of this important event. We found some new East Asian records of low latitude aurora observations caused by the storm which occurred after the Carrington event. The size of the aurora belt of the second peak of the Carrington magnetic storm was even wider than usual low-latitude aurora events., 2016/08/26 accepted for publication in PASJ. Due to the matter of license, we cannot show some figures on the preprint version. Please see the published version in PASJ for the figures

When solar storms strike, they weaken Earth's defenses against harmful radiation. New satellite measurements reveal just how much.

Two of the largest geomagnetic storms of the last decade were witnessed in 2015. On 17 March 2015, a coronal mass ejection‐driven event occurred with a Dst (storm time ring current index) value reaching −223 nT. On 22 June 2015 another strong storm (Dst reaching −204 nT) was recorded. These two storms each produced almost total loss of radiation belt high‐energy (E ≳ 1 MeV) electron fluxes. Following the dropouts of radiation belt fluxes there were complex and rather remarkable recoveries of the electrons extending up to nearly 10 MeV in kinetic energy. The energized outer zone electrons showed a rich variety of pitch angle features including strong “butterfly” distributions with deep minima in flux at α = 90°. However, despite strong driving of outer zone earthward radial diffusion in these storms, the previously reported “impenetrable barrier” at L ≈ 2.8 was pushed inward, but not significantly breached, and no E ≳ 2.0 MeV electrons were seen to pass through the radiation belt slot region to reach the inner Van Allen zone. Overall, these intense storms show a wealth of novel features of acceleration, transport, and loss that are demonstrated in the present detailed analysis., Key Points March and June 2015 storms offer insight into ultrarelativistic electron dynamicsImpenetrable barrier can be pushed inward, still isolates high‐E electrons from inner zoneMulti‐MeV electrons take 1‐2 days to appear following these strong driving events.

The Carrington storm in 1859 is considered to be the major geomagnetic disturbance related to solar activity. In a recent paper, Cid et al. (2015) discovered a geomagnetic disturbance case with a profile extraordinarily similar to the disturbance of the Carrington event at Colaba, but at a mid-latitude observatory, leading to a re- interpretation of the 1859 event. Based on those results, this paper performs a deep search for other 'Carrington-like' events and analyses interplanetary observations leading to the ground disturbances which emerged from the systematic analysis. The results of this study based on two Carrington-like events (1) reinforce the awareness about the possibility of missing hazardous space weather events as the large H-spike recorded at Colaba by using global geomagnetic indices, (2) argue against the role of the ring current as the major current involved in Carrington-like events, leaving field- aligned currents (FACs) as the main current involved, and (3) propose abrupt southward reversals of IMF along with high solar wind pressure as the interplanetary trigger of a Carrington-like event., Accepted in Journal of Space Weather and Space Climate (SWSC)

On March 31st. 2001, a coronal mass ejection pushed the subsolar magnetopause to the vicinity of geosynchronous orbit at 6.6 RE. The NASA/GSFC Community Coordinated Modeling Center (CCMe) employed a global magnetohydrodynamic (MHD) model to simulate the solar wind-magnetosphere interaction during the peak of this geomagnetic storm. Robertson et aL then modeled the expected 50ft X-ray emission due to solar wind charge exchange with geocoronal neutrals in the dayside cusp and magnetosheath. The locations of the bow shock, magnetopause and cusps were clearly evident in their simulations. Another geomagnetic storm took place on July 14, 2000 (Bastille Day). We again modeled X-ray emission due to solar wind charge exchange, but this time as observed from a moving spacecraft. This paper discusses the impact of spacecraft location on observed X-ray emission and the degree to which the locations of the bow shock and magnetopause can be detected in images.

Extreme historical and space era geomagnetic storms ( Δ H or Dst ≤ − 400 nT ) are studied in terms of their sunspot and Gleissberg solar cycle distributions. Interplanetary and magnetospheric processes associated with the Carrington storm are summarized and the intense storm of August 4, 1972 is discussed in the context of the possibility of having occurred as an extreme storm instead, if the polarity of the related magnetic cloud would have been opposite. We also discuss about superintense geomagnetic storms ( Dst ≤ − 250 nT ) that occurred in the space era, showing their solar cycle and seasonal distributions and also providing averages for the peak values of their main associated interplanetary parameters. A discussion about the possible occurrence of more Carrington type storms is also addressed.

We present a review on the interplanetary causes of intense geomagnetic storms (Dst≤−100 nT), that occurred during solar cycle 23 (1997–2005). It was reported that the most common interplanetary structures leading to the development of intense storms were: magnetic clouds, sheath fields, sheath fields followed by a magnetic cloud and corotating interaction regions at the leading fronts of high speed streams. However, the relative importance of each of those driving structures has been shown to vary with the solar cycle phase. Superintense storms (Dst≤−250 nT) have been also studied in more detail for solar cycle 23, confirming initial studies done about their main interplanetary causes. The storms are associated with magnetic clouds and sheath fields following interplanetary shocks, although they frequently involve consecutive and complex ICME structures. Concerning extreme storms (Dst≤−400 nT), due to the poor statistics of their occurrence during the space era, only some indications about their main interplanetary causes are known. For the most extreme events, we review the Carrington event and also discuss the distribution of historical and space era extreme events in the context of the sunspot and Gleissberg solar activity cycles, highlighting a discussion about the eventual occurrence of more Carrington-type storms.

The current notions of the solar-terrestrial relations responsible for the transport of solar disturbances and for the generation of magnetic storms on the Earth are briefly reviewed. The probability of generating magnetic storms by different solar and interplanetary phenomena is quantitatively estimated. The efficiencies of generating magnetic storms by different types of solar wind streams are compared.

Descriptions of eleven aurorae observed in the Canary Islands during the period 1770 – 2010 have been found in different documents. Most of them are coincident with periods of strong solar activity, with the geomagnetic latitude playing a minor role. Coronal mass ejections are the most probable solar source of these low-latitude events. The absence of low-latitude aurorae is verified in our sample during the Dalton Minimum and the first half of the twentieth century.

We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching −263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation.

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 242 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.

Thermospheric infrared radiance at 4.3 μm is susceptible to the influence of solar-geomagnetic disturbances. Ionization processes followed by ion-neutral chemical reactions lead to vibrationally excited NO + (i.e., NO + (v)) and subsequent 4.3 μm emission in the ionospheric E-region. Large enhancements of nighttime 4.3 μm emission were observed by the TIMED/SABER instrument during the April 2002 and October–November 2003 solar storms. Global measurements of infrared 4.3 μm emission provide an excellent proxy to observe the nighttime E-region response to auroral dosing and to conduct a detailed study of E-region ion-neutral chemistry and energy transfer mechanisms. Furthermore, we find that photoionization processes followed by ion-neutral reactions during quiescent, daytime conditions increase the NO + concentration enough to introduce biases in the TIMED/SABER operational processing of kinetic temperature and CO 2 data, with the largest effect at summer solstice. In this paper, we discuss solar storm enhancements of 4.3 μm emission observed from SABER and assess the impact of NO + (v) 4.3 μm emission on quiescent, daytime retrievals of Tk/CO 2 from the SABER instrument.

A retrospective analysis of the Russian magnetic observations of the Carrington event that occurred on September 2–3, 1859, has been performed. The conclusion has been made that this event was caused by the series of three recurrent eruptive solar flares during ∼40 h. The characteristics of the geomagnetic crochet, related to a considerable flux of the ionizing electromagnetic radiation during this flare, have been studied. The value and direction of a magnetic field disturbance, registered during the maximum of the geomagnetic storm of September 2, unambiguously indicate that all Russian stations were in the auroral oval zone, which was strongly expanded southward from its average position. The disturbance dependence on the station longitude—the absence of magnetometer pinning in Nerchinsk—is interpreted as the possible manifestation of a strong asymmetry in the effective contour of the current system, which was connected to the heliosphere and covered the disturbed magnetosphere and ionosphere during the short period that lasted only 1–3 h.

This paper presents an investigation of geomagnetic storm effects in the equatorial and middle-low latitude F-region in the West Pacific sector during the intense geomagnetic storm on 13–17 April, 2006. The event, preceded by a minor storm, started at 2130 UT on April 13 while interplanetary magnetic field (IMF) Bz component was ready to turn southward. From 14–17 the ionosphere was characterized by a large scale enhancement in critical frequency, foF2 (4∼6 MHz) and total electron content (TEC) (∼30TECU, 1TECU=1×1016el/m2) followed by a long-duration negative phase observed through the simultaneous ionospheric sounding measurements from 14 stations and GPS network along the meridian 120°E. A periodic wave structure, known as traveling ionospheric disturbances (TIDs) was observed in the morning sector during the initial phase of the storm which should be associated with the impulsive magnetospheric energy injection to the auroral. In the afternoon and nighttime, the positive phase should be caused by the combination of equatorward winds and disturbed electric fields verified through the equatorial F-layer peak height variation and modeled upward drift of Fejer and Scherliess [1997. Empirical models of storm time equatorial electric fields. Journal of Geophysical Research 102, 24,047–24,056]. It is shown that the large positive storm effect was more pronounced in the Southern Hemisphere during the morning-noon sector on April 15 and negative phase reached to lower magnetic latitudes in the Northern Hemisphere which may be related to the asymmetry of the thermospheric condition during the storm.

The Forbush effects associated with far western and eastern powerful sources on the Sun that occurred on the background of unsettled and moderate interplanetary and geomagnetic disturbances have been studied by data from neutron monitor networks and relevant measurements of the solar wind parameters. These Forbush effects may be referred to a special sub-class of events, with the characteristics like the event in July 2005, and incorporated by the common conditions: absence of a significant disturbance in the Earth vicinity; absence of a strong geomagnetic storm; slow decrease of cosmic ray intensity during the main phase of the Forbush effect. General features and separate properties in behavior of density and anisotropy of 10 GV cosmic rays for this subclass are investigated.

Hourly magnetic readings of H and D from six geomagnetic observatories in Finland and Russia were utilized for analysis of the time behavior of the extreme space weather event of August/September 1859. The observatories cover about 200° in longitude and magnetic latitudes 45–60°N. The August/September 1859 event consisted of two consecutive magnetic storms that started on August 28th and September 2nd, respectively. The latter and stronger is known as the “Carrington storm”. The August 28–29 storm was greatest at high latitudes (Sitka; magn. lat. 60°N) where field variations ( D ) of ±700 nT were recorded. On September 2 05–07 UT, exceptionally great magnetic disturbances occurred simultaneously worldwide. The largest magnetic field excursions were about 1500 nT (in D ) in a few hours. The disturbances (mainly positive) in H have clearly been even greater but the variometers went off scale. The maximum time derivative of the field was estimated to be about 30 nT/s. During the Carrington storm on September 2 (05–07 UT) the observatories were well inside the auroral oval and the disturbances (mostly positive) registered were connected with eastward flowing auroral electrojets and field-aligned currents. No magnetic signatures of the ring-current can be seen in the observations. However, simultaneous magnetic variations at the Colaba observatory (magn. lat. 10.5°N) near the Equator showed a deep depression (about −1600 nT) in H mostly due to ring-current effects.

We briefly review data on observations of the Sun, interplanetary medium, and magnetosphere, obtained by participants of the “Solar Extreme Events in 2004 (SEE’04)” collaboration before and during one of the strongest (4th in the 23rd solar cycle) magnetic storm of November 08, 2004 with Dst = - 373 nT .

During extreme solar events such as big flares or/and energetic coronal mass ejections (CMEs) high energy particles are accelerated by the shocks formed in front of fast interplanetary coronal mass ejections (ICMEs). The ICMEs (and their sheaths) also give rise to large geomagnetic storms which have significant effects on the Earth's environment and human life. Around 14 solar cosmic ray ground level enhancement (GLE) events in solar cycle 23 we examined the cosmic ray variation, solar wind speed, ions density, interplanetary magnetic field, and geomagnetic disturbance storm time index (D-st). We found that all but one of GLEs are always followed by a geomagnetic storm with D-st

On Thursday, September 1, 1859, the British astronomer Richard Carrington, for the first time ever, observes a spectacular gleam of visible light on the surface of the solar disk, the photosphere. The Carrington Event, as it is nowadays known by scientists, occurred because of the high solar activity that had visible consequences on Earth, in particular reports of outstanding aurorae activity that amazed thousands of people in the western hemisphere during the dawn of September 2. The geomagnetic storm, generated by the solar-terrestrial event, had such a magnitude that the auroral oval expanded towards the equator, allowing low latitudes, like Panama's 9$^\circ$ N, to catch a sight of the aurorae. An expedition was carried out to review several historical reports and books from the northern cities of Colombia, allowing the identification of a narrative from Monter\'ia, Colombia (8$^\circ$ 45' N), that describes phenomena resembling those of an aurorae borealis, such as fire-like lights, blazing and dazzling glares, and the appearance of an immense S-like shape in the sky. The very low latitude of the geomagnetic north pole in 1859, the lowest value in over half a millennia, is proposed to have allowed the observations of auroral events at locations closer to the equator, and supports the historical description found in Colombia. The finding of such chronicle represents one of the most complete descriptions of low-latitude sightings of aurorae caused by the Carrington Event., Comment: 26 pages, 10 figures. Accepted for publication in Advances in Space Research

The solar wind conditions of an extreme geomagnetic storm were examined using magnetic field observations obtained from geosynchronous satellites and the disturbance storm-time (Dst) index. During geosynchronous magnetopause crossings (GMCs), magnetic field variations at the magnetosheath, which is the modulated interplanetary magnetic field (IMF), were observed by geosynchronous satellite. The dawn to dusk solar wind electric field (VBS) was estimated from the Dst index by using an empirical formula for Dst prediction; these data were then used to estimate the IMF and solar wind speed. This method was applied in the analysis of an extreme geomagnetic storm event that occurred on March 13–14, 1989, for which no direct solar wind information was available. A long duration of the GMC was observed after the second storm sudden commencement (SSC) of this event. The solar flare possibly associated with the second SSC of this storm event was identified as the March 12 M7.3/2B flare. The IMF B z was estimated to be about −50 nT with a solar wind speed of about 960 km/s during the 5 h in which the main phase of the storm rapidly developed, assuming an Alfven Mach number (M A) during this period of more than 2.

The geomagnetic storm during the Carrington event, which occurred on 2 September 1859, displayed extremely rapid recovery. The geomagnetic field increased by approximately 650 nT/h at Bombay, India, and by >300 nT/h in 1-h averaged data. Although the rapid recovery is considered due to a sudden increase in the magnetopause current, a sudden decrease of the ring current, or/and a sudden enhancement of the ionospheric currents, this study focuses on the ring current decay. The Carrington rapid recovery had a time constant (approximately 1 h) comparable to the storm development (i.e., decrease in the geomagnetic field), indicating that energy loss from the ring current region is predominantly controlled by E × B convection transport which is responsible for energy input during the storm main phase. This feature has led us to a hypothesis that the flow-out of dense ring current ions and injections of tenuous plasma sheet ions caused the rapid decay of the ring current and in turn the storm rapid recovery. This study examines whether the Carrington rapid recovery can be explained by the flow-out effect. We extend the empirical Burton’s model to a model that takes into consideration a sudden change in solar wind density which is correlated with plasma sheet density. We first apply the extended Burton’s model to previously observed four intense magnetic storms (Dst minimum < −200 nT) for which solar wind data are available. Using the best fit parameters found by forward modeling, the extended model estimates the recovery of the Carrington storm. The estimate indicates that a solar wind structure with a density bump by approximately 100 cm[−3] (and southward interplanetary magnetic field (IMF) of 65 nT and solar wind speed of 1, 500 km/s) can cause the rapid recovery under a continuous southward IMF condition. We conclude that the flow-out effect plays a significant role in producing the rapid recovery of the Carrington storm.