Storm Of May Research Articles

Midlatitude mesosphere and lower thermosphere variations during the extreme gannon geomagnetic storm in May 2024

Recent studies based upon both observations and numerical simulations have indicated the impacts of the intense geomagnetic storms induced by Coronal Mass Ejections (CMEs) on the neutral dynamics in the mesosphere and lower thermosphere (MLT). Even in the midlatitude MLT, far equatorward of subauroral zone, significant variations were reported. Aurora is one of the major dynamic drivers in the MLT in high latitudes, but observations of the neutral dynamic variations under the aurora in the storm time MLT are sparse. The lack of such MLT observations during the presence of aurora leads to a critical gap in the understanding of upper atmospheric dynamics. In this paper, we present the unprecedented observations under the aurora during the Gannon Geomagnetic Storm in May 2024 by the Na Doppler lidar at Utah State University (42°N, 112°W) and the Advanced Mesospheric Temperature mapper (AMTM) at the nearby Bear Lake observatory (BLO). Significant warming (as much as ∼50 K) accompanied by fast equatorward flow in the lower thermosphere (up to ∼100 m/s changes in the meridional wind above 100 km altitude) were observed. The temperature enhancement (∼10 K) of the hydroxyl layer during the same period is also captured by the AMTM. Intriguingly, significant storm time depletion of sodium (Na) abundance on the topside of the mesospheric Na layer above 105 km, as much as more than 80%, was also observed. These observations provide insight for future investigations on the MLT responses to the intense geomagnetic storms, especially the role of aurora in these events.

The impact of the Gannon Storm of May 2024 on the radiation fields at aviation altitudes and in low earth orbits

In May 2024 the strongest geomagnetic storm since the Halloween storms of 2003 occurred. Media reported worldwide about the space weather situation and its effects on the infrastructure. Of particular interest were reports claiming severe effects on the radiation exposure at aviation altitudes, although no data supporting this assertion were available at that time. In this work the different aspects that affect the radiation exposure at aviation altitudes are discussed for the event. Furthermore, the corresponding dose rates are evaluated and compared to data from Low Earth Orbit. Model calculations indicate an additional contribution to the radiation field at aviation altitudes due to this extraordinary space weather situation, although the dose rates were still in the lowest category D0 of the space weather D-index, i.e., within the dose rate variation of a solar cycle.

Global Ionospheric Response During Extreme Geomagnetic Storm in May 2024

The main idea of the present study is to investigate in detail the time evolution of the spatial inhomogeneities connected with the ionospheric response to the geomagnetic storm registered in the period of 10–11 May 2024. The obtained ionospheric anomalies represented by the relative deviations of the global Total Electron Content (TEC) data have been utilized in the analysis. The used global TEC data have been converted to a coordinate system with a modip latitude and geographical longitude. In addition to the maps illustrating the global spatial distribution of the geomagnetically forced ionospheric anomalies, a presentation of the observed longitudinal structures by sinusoidal approximation has also been used. The resulting positive and negative responses have been studied depending on the magnetic latitude, local times and the behavior of the geomagnetic activity parameters during the considered event. The interpretation takes into account the known mechanisms for the effect of the geomagnetic storm on the electron density. A special attention is focused on the differences in the two hemispheres at high and mid latitudes, where a simultaneous direct impact of the particle precipitation and the change in the temperature regime of the neutral atmosphere has been assumed. The low-latitude response as a result of the Equatorial Ionization Anomaly (EIA) associated with Disturbed Dynamo Electric Fields (DDEFs) and its relationship with local time has also been considered.

Synoptic Conditions at Pressure Different Levels for the Dust Storm of May/ 2022 Over Iraq

This study examines the severe dust storm from May 12-16/2022,culminating on May 15, with a comprehensive analysis and explanation. The weather maps from the National Oceanic and Atmospheric Administration (NOAA) and the European Centre for Medium-Range Weather Forecasts (ECMWF) weather maps were used to identify systems and patterns that contributed to the storm's activity, continuity, and tracking as well as maps of pressure compounds and wind vectors in levels 1000 and 850 mbar that appear with the dust state for the same days accompanied by tracking patterns in the middle of the turbosphere 500 mbar to give a comprehensive analytical view of climate conditions at each level of pressure and higher systems supportive of their persistence on the surface. The northwesterly winds are the main factor that carries dust over long distances. The eastern desert in Syria, the Empty Quarter in the Kingdom of Saudi Arabia, the desert of western Iran, and the desert region of western Iraq are among the main sources of dust In its atmosphere. Based on weather maps of the surface and upper levels of storm days, the concentration of dust reached very high levels in Iraq's airspace and surrounding countries, including Egypt, Jordan, Lebanon, Palestine, and Syria. The intensity of the dust gradually decreased as the area was affected by wet westerly winds with relatively low temperatures and a relative increase in wind speeds due to the impact of the study area on the atmospheric decline centered around the Turkish island of Cyprus.

Report on the effects of the May 2024 Mother's day geomagnetic storm observed from Chile

This study investigates the extreme geomagnetic storm of May 10–15, 2024, utilizing data from the SER ground-based station in Chile and the DSCOVR satellite. The methodology involves calculating the horizontal magnetic field (H), filtering geomagnetic data using a Butterworth filter, and conducting cross-correlation analysis between solar wind parameters and Pc5 pulsations. The storm, starting with a sudden storm commencement triggered by a coronal mass ejection around 18:00 UT on May 10, exhibited a main phase lasting about 8 h, followed by a recovery phase starting on May 11. The extreme storm exhibited abrupt fluctuations in the interplanetary magnetic field data and solar wind parameters, inducing a depression in the geomagnetic field H-component reaching ΔH ∼ −551 nT at the SER station. Throughout the storm, solar wind parameters such as density, speed, and temperature exhibited varied ranges, with significant changes observed in all storm phases. Notably, during the initial and main phases, cross-correlation analysis unveiled robust associations between Pc5 pulsations and solar wind parameters such as density and speed, with maximum R values reaching 0.98 for both phases.

Modeling the Simultaneous Dropout of Energetic Electrons and Protons by Magnetopause Shadowing

AbstractMagnetopause shadowing (MPS) effect could drive a concurrent dropout of radiation belt electrons and ring current protons. However, its relative role in the dropout of both plasma populations has not been well quantified. In this work, we study the simultaneous dropout of MeV electrons and 100s keV protons during an intense geomagnetic storm in May 2017. A radial diffusion model with an event‐specific last closed drift shell is used to simulate the MPS loss of both populations. The model well captures the fast shadowing loss of both populations at L* > 4.6, while the loss at L* < 4.6, possibly due to the electromagnetic ion cyclotron wave scattering, is not captured. The observed butterfly pitch angle distributions of electron fluxes in the initial loss phase are well reproduced by the model. The initial proton losses at low pitch angles are underestimated, potentially also contributed by other mechanisms such as field line curvature scattering.

Weathering the storm: Decreased activity and glucocorticoid levels in response to inclement weather in breeding Columbian ground squirrels

Inclement weather can rapidly modify the thermal conditions experienced by animals, inducing changes in their behavior, body condition, and stress physiology, and affecting their survival and breeding success. For animals living in variable environments, the extent to which they have adapted to cope with inclement weather is not established, especially for hibernating species with a short active season that are constrained temporally to breed and store energy for subsequent hibernation. We examined behavioral (foraging activity) and physiological (body mass and fecal cortisol metabolites) responses of Columbian ground squirrels (Urocitellus columbianus), small hibernating rodents inhabiting open meadows in Rocky Mountains, to 3 events of inclement weather (two snow storms in May 2021 and May 2022, one heavy rainfall in June 2022). We found that individuals adapted to inclement weather conditions by (1) reducing above-ground activity, including foraging, (2) decreasing the mobilization of stored resources as indicated by a decrease in the activity of the hypothalamo-pituitary-adrenal (HPA) axis and lower fecal cortisol metabolites in the hours/days following periods of inclement weather; and (3) compensating through increased foraging and more local activity when favorable conditions resumed. As a result, body mass and growth did not decrease following short periods of inclement weather. Columbian ground squirrels were well-adapted to short periods of inclement weather, coping via modifications of their behavior and the activity of the HPA axis.

50 years of beach–foredune change on the southeastern coast of Australia: Bengello Beach, Moruya, NSW, 1972–2022

A fifty-year time series of high-resolution field-surveyed beach profiles from a southeast Australian ocean beach was analysed to determine spatial and temporal variability and changes in beach–foredune morphology at annual to decadal time scales. Data from 452 surveys obtained at two to six-weekly intervals was available from four closely spaced (within 422 m) cross-shore profiles in the centre of a 6 km long beach. Each profile extended 110–130 m seaward from a dune datum at ~5 m Australian Height Datum (AHD) to mean sea level (MSL). Morphometric indicators examined included beach–foredune sand volume, four shore position contours at 0 m AHD (MSL) +1 m, +2 m, +3 m AHD, and across-shore topographic changes. Five phases of different beach/foredune conditions were identified, two in the 1970s, and three in the following four decades. After a brief accretion period (phase 1) major storms in May–June 1974 caused the loss of over 100 m3/m from each profile and a 50–60 m landward shift of the MSL shoreline. The substantial sand deficit lasted for the next five years with average beach volumes of 134 m3/m followed by incremental accretion of 120 m3/m from 1979 to 1982 (phase 2). In the next 12 years (phase 3, 1982–1994) the beach maintained high volumes averaging 268 m3/m. This declined by 45–60 m3/m in the mid 1990s (phase 4). Since 2002 (phase 5) sand stored above MSL has averaged 279 m3/m, ~10 m3/m greater than at any time since surveys began although the volume gradually declined in the decade prior to 2022. Morphological changes and shifts in shoreline position have accompanied volumetric changes. An incipient dune developed during the 1980s at the site of the 1970s foreshore later to become an established, vegetated foredune. Comparison of results with other long-term beach profile sites in Europe, Japan and USA showed some differences most notably Bengello exhibits no consistent seasonal summer-winter cycle in beach volume. General similarities include lack of clear beach change evidence of decadal–scale sea level rise, and all locations contend with the impacts of storms. Bengello averages 15 storms per year (H sig ≥3.0 m) and in the fifty-year period there have been 21 major events (H max >10 m) all of which have caused substantial erosion. Recovery times have varied from a few months to over 5 years. The net effect of these erosion-recovery events over 1972–2022 has not resulted in beach recession.

Ionospheric-Thermospheric responses to the May and September 2017 geomagnetic storms over Asian regions

This paper presents the longitudinal dependence of ionospheric responses from Global Navigation Satellite System (GNSS) derived Total Electron Content (TEC) during two intense geomagnetic storms of May and September 2017. The GNSS-TEC is retrieved from four stations installed at the verge of low to mid-latitude Asian regions of Pakistan and China. Two ionospheric enhancements were observed during the storm of May 2017. The first one at local noon–afternoon during the storm main phase on 28 May was due to the southward turning of Interplanetary Magnetic Field (IMF-Bz) and eastward Prompt Penetration Electric Field (PPEF), with the maximum TEC enhancement at Wuhan. The second one at nighttime during the recovery phase of the storm on 29 May triggered ionospheric variations, mainly due to the later southward turning of the IMF-Bz as the Asian regions, were on the nightside with the westward PPEF. Negative storm time ionospheric responses were observed on 30 May, related to the change of the thermospheric composition as O/N2 depletion. Moreover, a significant increase in TEC was recorded during the main phase of the storm on 8 September 2017. This enhancement corresponded with the eastward PPEF and an increase in the O/N2. The TEC increment was also observed during the recovery phase on 9 September in the Pakistani stations. A minor storm on 7 September also gave rise to TEC enhancements, especially in western regions. However, the negative phase was registered from 9 to 10 September at each station because of the changes in the thermospheric composition as O/N2 depletion.

Statistical study and corresponding evolution of plasmaspheric plumes under different levels of geomagnetic storms

Abstract. Using observations of Van Allen Probes, we present a statistical study of plasmaspheric plumes in the inner magnetosphere. Plasmaspheric plumes tend to occur during the recovery phase of geomagnetic storms. Furthermore, the results imply that the occurrence rate of observed plasmaspheric plume in the inner magnetosphere is larger during stronger geomagnetic activity. This statistical result is different from the observations of the Cluster satellite with much higher L shells in most orbital periods, which suggests that the plasmaspheric plume near the magnetopause tends to be observed during moderate geomagnetic activity (Lee et al., 2016). In the following, the dynamic evolutions of plasmaspheric plumes during a moderate geomagnetic storm in February 2013 and a strong geomagnetic storm in May 2013 are simulated through group test particle simulation. It is obvious that the plasmaspheric particles drift out on open convection paths due to sunward convection during both geomagnetic storms. It seems that the outer plasmaspheric particles exhaust the energy available to them sooner, and the plasmasphere shrinks faster during strong geomagnetic storms. As a result, the longitudinal width of the plume is narrower, and the plume is limited to lower L shells during the recovery phase of strong geomagnetic storm. The simulated evolutions may provide a possible interpretation for the occurrence rates: Van Allen Probes tend to observe plumes during stronger geomagnetic storms, and the Cluster satellite with higher L shells tends to observe plumes during moderate geomagnetic storms.

Atmospheric transport of microplastics during a dust storm

Dust storms are common events in arid and semi-arid regions that have a wide range of impacts on the environment and human health. This study addresses the presence, characteristics and potential sources of microplastics (MPs) in such events by analysing MPs deposited with dust particles in the metropolis of Shiraz, southwest Iran, following an intense storm in May 2018. At 22 locations throughout the city, MP concentrations on a number basis ranged from 0.04 to 1.06 per g of dust (median = 0.31 MP g−1). Particles were mainly fibrous, with a mean diameter of about 20 μm and >60% under 100 μm in length, and polymer makeup was dominated by nylon, polypropylene and polyethylene terephthalate. Examination of selected MPs by scanning electron microscopy revealed varying degrees of weathering and contamination by extraneous geogenic particles amongst the samples. Using published MP concentrations in urban dusts and remote, arid soils, we estimate that between about 0.1 and 5% of MPs deposited by the dust storm are derived from local sources within the metropolis, with the remainder arising from more distant sources. HYSPLIT modelling, satellite imagery and published geochemical signatures of regional dust particles suggest that the deserts of Saudi Arabia constitute the principal distal and transboundary source. Dust storms may represent a significant means by which MPs are transported and redistributed in arid and semi-arid environments and an important source of MPs to the oceans.

Relative Contribution of ULF Waves and Whistler‐Mode Chorus to the Radiation Belt Variation During the May 2017 Storm

AbstractWe investigate the time and location where ULF waves and whistler‐mode chorus contributed to the net flux enhancement of relativistic electrons during the magnetic storm of May 2017. During the early recovery phase, both ULF and chorus waves contribute to the enhancement of relativistic electron fluxes, but ULF waves play roles of the inward diffusion. During the late recovery phase, both Van Allen Probe‐B and Arase show that whistler‐mode chorus contributes to the flux enhancement confined in the L‐value. The CRCM coupled with BATS‐R‐US simulation qualitatively reproduces the global evolution of ULF waves. Although the electron flux is underestimated by the simulation, this study reveals a large anisotropy of hot electrons in the region where whistler‐mode chorus waves were actually observed by satellites. In addition, the estimated magnetic field curvature on the dayside is small during the recovery phase. Furthermore, we investigate the control of wave evolution. Both observations and the simulation suggest that the observed ULF waves in the frequency range of ∼2–5 mHz are excited by the enhancement of the solar wind dynamic pressure. Observations also indicate that whistler‐mode chorus on the nightside is predominantly excited by hot electrons with temperature anisotropy, whereas the dayside chorus is enhanced by the change of the magnetic field line configuration. The estimated spatial distributions of electron anisotropy and magnetic field curvature provide an explanation for the presence of enhanced whistler‐mode chorus in the dusk sector, which is far from the usual location of wave generation.

The Unusual Severe Dust Storm of May 2018 Over Northern India: Genesis, Propagation, and Associated Conditions

AbstractOn the evening of May 02, 2018, an unusually severe dust storm (DS) from a convective system, which developed over the Thar Desert, struck northwest India resulting in more than 100 casualties. Analysis of its genesis from surface measurements and reanalysis data indicates that this DS was “Haboob” type which are formed when strong downdrafts from a convective system reaches the surface in arid regions. Surface observations show that this DS was accompanied by a sharp drop in temperature and visibility and increase in relative humidity. Model simulation at convective‐permitting scale reveals the complex structure of dust transport in space and time. In contrast to the generally observed dust storms over the Indo‐Gangetic Plain being mostly associated with westerly wind bringing dust from Southwest Asia and Eastern Africa, this particular DS was triggered by strong easterly wind. The moisture‐laden easterly wind at the surface level colliding against the dry westerlies from the desert region along a steep front resulted in strong convection over northwest India leading to the formation of strong downdrafts. This, in turn, was largely due to the positioning of the upper level jet stream, which modulated the location and the strengths of surface lows and highs. The importance of this study is that while recent studies indicate that dust aerosol over India is on the decline partly due to reduction in westerly wind strength, the present work shows that anomalous easterlies can provide an alternate pathway to intense dust storms over the region.

Reconstruction of Magnetospheric Storm‐Time Dynamics Using Cylindrical Basis Functions and Multi‐Mission Data Mining

AbstractFirst results are presented of the modeling of magnetospheric storm events, based on: (i) a new method to represent the magnetic field by means of the so‐called cylindrical basis functions, (ii) the data mining approach by Sitnov et al. (2008); https://doi.org/10.1029/2007ja013003, and (iii) upgraded and extended pool of multi‐mission data taken in 1995–2019. The study is focused on the low‐latitude magnetospheric domain in the distance range 3–18RE bounded by field line shells with footpoint latitudes ±70°. The magnetic configurations are reconstructed from data subsets, selected from the grand database by the nearest‐neighbor method, using both interplanetary data and the ground disturbance indices. A strong storm of May 27–29, 2017, has been studied in relation to its effect on the reconfiguration of the low‐latitude magnetosphere. The modeling reproduces the main features of the magnetosphere dynamics in terms of the geomagnetic field depression/compression and extremely variable field line stretching. The initial contraction of the magnetosphere during the storm sudden commencement results in a local transient surge of the inner tail current and a dramatic antisunward discharge of the magnetic flux. As the storm progresses, the ring current buildup results in a strongly depressed magnetic field in the inner magnetosphere, which expels the magnetic flux to larger distances and increases the field line connection across the more distant tail plasma sheet. At the same time, a strong dawn‐dusk asymmetry is developed due to the formation of the duskside partial ring current, in agreement with previous independent results.

Plasma depletions lasting into daytime during the recovery phase of a geomagnetic storm in May 2017: Analysis and simulation of GPS total electron content observations

This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm. By analyzing GPS data collected in Japan, we investigate temporal variations in the horizontal two-dimensional distribution of total electron content (TEC) during the geomagnetic storm. The SYM-H index reached −142 nT around 08 UT on 28 May 2017. TEC depletions extending up to approximately 38°N along the meridional direction appeared over Japan around 05 LT (LT = UT + 9 hours) on 29 May 2017, when TEC rapidly increased at sunrise due to the solar extreme ultraviolet (EUV) radiation. The TEC depletions appeared sequentially over Japan for approximately 8 hours in sunlit conditions. At 06 LT on 29 May, when the plasma depletions first appeared over Japan, the background TEC was enhanced to approximately 17 TECU, and then decreased to approximately 80% of the TEC typical of magnetically quiet conditions. We conclude that this temporal variation of background plasma density in the ionosphere was responsible for the persistence of these plasma depletions for so long in daytime. By using the Naval Research Laboratory: Sami2 is Another Model of the Ionosphere (SAMI2), we have evaluated how plasma production and ambipolar diffusion along the magnetic field may affect the rate of plasma depletion disappearance. Simulation shows that the plasma density increases at the time of plasma depletion appearance; subsequent decreases in the plasma density appear to be responsible for the long-lasting persistence of plasma depletions during daytime. The plasma density depletion in the top side ionosphere is not filled by the plasma generated by the solar EUV productions because plasma production occurs mainly at the bottom side of the ionosphere.

WRF-Chem v3.9 simulations of the East Asian dust storm in May 2017: modeling sensitivities to dust emission and dry deposition schemes

Abstract. Dust aerosol plays an important role in the radiative budget and hydrological cycle, but large uncertainties remain for simulating dust emission and dry deposition processes in models. In this study, we investigated dust simulation sensitivity to two dust emission schemes and three dry deposition schemes for a severe dust storm during May 2017 over East Asia using the Weather Research and Forecasting model coupled with chemistry (WRF-Chem). Results showed that simulated dust loading is very sensitive to different dry deposition schemes, with the relative difference in dust loading using different dry deposition schemes ranging from 20 %–116 %. Two dust emission schemes are found to produce significantly different spatial distributions of dust loading. The difference in dry deposition velocity in different dry deposition schemes comes from the parameterization of collection efficiency from impaction and rebound effect. An optimal combination of dry deposition scheme and dust emission scheme has been identified to best simulate the dust storm in comparison with observation. The optimal dry deposition scheme accounts for the rebound effect and its collection efficiency from impaction changes with the land use categories and therefore has a better physical treatment of dry deposition velocity. Our results highlight the importance of dry deposition schemes for dust simulation.

Formation of Ionospheric Irregularities in the East Siberian Region during the Geomagnetic Storm of May 27–28, 2017

Results of studying different-scale ionospheric irregularities on the basis of multi-instrumental data, obtained in the East Siberian region of Russia during the geomagnetic storm of May 27–28, 2017, are presented. Spatial inhomogeneities of electron density in the ionosphere were observed through data from ground-based receivers of signals of global navigational satellite systems and on the basis of direct measurements of electron density in low-orbit satellites. An intense radio aurora was seen in UHF radar data just after the initial phase of geomagnetic storm. At the same time, we recorded fluctuations of the total electron content from data of GPS receivers and the presence of E-layer irregularities by data of the ionosonde in Norilsk. The time of irregularity recording by different instruments is consistent with the spatiotemporal changes in field-aligned currents of the second zone, obtained from data of AMPERE low-orbit satellite system.

Dust Heterogeneous Reactions during Long-Range Transport of a Severe Dust Storm in May 2017 over East Asia

Dust aerosol has important climate and environmental effects, which could be changed by internally mixing with anthropogenic aerosol as a result of heterogeneous reactions; however, the importance of these reactions is not fully understood yet. In this study, synergetic observations and an air quality model were used to analyze the transport of a severe dust storm and its impacts on nitrate and sulfate levels over East Asia between 3 and 11 May 2017. The model successfully reproduced the occurrence and transport of the dust storm compared to dust RGB imageries of the Himawari-8 satellite and dust extinction coefficients observed by LIDAR. The model also reasonably simulated the variations of observed nitrate and sulfate concentrations, and the results indicated that the dust heterogeneous reactions were dominant pathways for nitrate formation, but they had limited contribution for sulfate in both fine and coarse mode in Fukuoka, Japan. Dust nitrate formed rapidly after leaving China, and the highest period-averaged concentration of dust nitrate (>5 μg m−3) was shown over the Yellow Sea. Based on model results; we found that the mass ratio of dust nitrate to dust aerosol could reach 10% over the Pacific Ocean. Our results confirmed the importance of heterogeneous reactions on compositions of dust particles.

The Great Storm of May 1921: An Exemplar of a Dangerous Space Weather Event

AbstractWe reconstruct the timeline of the extreme space weather event of May 1921, reviewing a wealth of reports from scientific literature, databases, newspaper reports, and reports by historians and astronomers. A series of coronal mass ejections (CMEs) bombarded Earth between 13 and 16 May, as shown by a series of sudden commencements observed across the global network of magnetometers. These CMEs produced three major periods of geomagnetic activity. The first period followed the arrival of two CMEs on 13 May. These may have cleared much density from the inner heliosphere, enabling a subsequent CME to travel quickly to Earth and cause intense activity. Continuing moderate magnetic activity following the first period may also have preconditioned the magnetosphere so it responded strongly to that later CME. This arrived late on 14 May, driving a short period of very intense activity early on 15 May, including technological impacts indicative of strong geoelectric fields. Another CME arrived early on 16 May, driving intense activity similar to that on 13 May. We show how these impacts fit with scientific observations to give a timeline that can be used in worst‐case studies/benchmarks. We also show that some impacts were probably coincidental with the storm, but due to more prosaic faults. This sequence of preconditioning, intense geoelectric fields, and their impacts, plus coincidental faults, makes the 1921 event an excellent basis for building space weather scenarios. Such scenarios are vital scientific input to the development and implementation of policies for mitigation of severe space weather.

Analyses of geospace response to the geomagnetic storm in May 2017

Strong geomagnetic storm occurred since 15:37UT May 27th, 2017. The analysis result showed that, the corona mass ejection (CME) on May 23rd transformed into magnetic cloud while travelling towards the Earth, the B z component of which stayed continually below −10 nT, and reached minimum value of −20.71 nT. Under effect of the interaction between the B z component and the magnetic field in the magnetopause, the minimum value of SYM-H index reached −142 nT. Plenty of the global ionosonde stations observed ionospheric disturbances. Comprehensive study of the ionosonde, TIMED-GUVI observation and TEC assimilation data revealed that, such ionospheric storm showed apparent hemispheric asymmetries, neutral composition (N2, O2) disturbance may be the primary cause of the negative storm, while the positive storm may be caused by the upward effect of equatorward thermospheric wind or the increase of the neutral density ratio O/N2. The enhancement of the thermospheric atmosphere density during the geomagnetic storm caused the significant acceleration of the altitude decay speed of low orbit satellites, which was in good correspondence with the change of the HPI index.