Moderate Geomagnetic Storm Research Articles

Space Weather Environment During the SpaceX Starlink Satellite Loss in February 2022

AbstractOn 3 February 2022, SpaceX Starlink launched and subsequently lost 38 of 49 satellites due to enhanced neutral density associated with a geomagnetic storm. This study examines the space weather conditions related to the satellite loss, based on observations, forecasts, and numerical simulations from the National Oceanic and Atmospheric Administration Space Weather Prediction Center (SWPC). Working closely with the Starlink team, the thermospheric densities along the satellite orbits were estimated and the neutral density increase leading to the satellite loss was investigated. Simulation results suggest that during the geomagnetic storm, pre‐launch Monte Carlo analyses performed by the Starlink team using empirical neutral density inputs from NRLMSISE‐00 tended to underestimate the impact relative to predictions from the operational coupled Whole Atmosphere Model and Ionosphere Plasmasphere Electrodynamics physics‐based model. The numerical simulation indicated this minor to moderate geomagnetic storm was sufficient to create 50%–125% density enhancement at altitudes ranging between 200 and 400 km. With the increasing solar activity of Solar Cycle 25, satellites in low‐Earth orbit are expected to experience an increasing number of thermospheric expansion events. Currently, no alerts and warnings issued by SWPC are focused on satellite users concerned with atmospheric drag and related applications. Thus, during geomagnetic storms, it is crucial to establish suitable alerts and warnings based on neutral density predictions to provide users guidance for preventing satellite losses due to drag and to aid in collision avoidance calculations.

Modeling Radiation Belt Electron Dropouts During Moderate Geomagnetic Storms Using Radial Diffusion Coefficients Estimated With Global MHD Simulations

AbstractMain phase flux dropouts often promote depletion of the outer electron radiation belt. The quantification of the contributions of various loss mechanisms to MeV electron dropouts has not yet been elucidated in detailed case studies for moderate geomagnetic storms. This work focuses on quantifying radial diffusion to study relativistic electron flux losses observed by Van Allen Probes during two moderate storms in 2017. The events are identified as Case 1 (27 March), with losses deep in L, and Case 2 (21 November), with less deep losses. Event‐specific radial diffusion coefficients (DLL) were calculated from global magnetohydrodynamic (MHD) fields simulated by the SWMF/BATS‐R‐US. The MHD‐DLL was used as an input to radial diffusion simulations of both events for relativistic electrons. For the outer boundary conditions defined at L* = 6, electron fluxes measured by GOES‐15 at geosynchronous orbit were converted to phase space densities (PSDs) and then calibrated against the Van Allen Probe A measurements. Using these calibrated PSD of GOES‐15 at the outer boundary and event‐specific MHD‐DLL, the main phase dropout is well captured with radial diffusion simulation for Case 2, but not for the deep dropout in Case 1 down to L* < 4.5. Scaling MHD‐DLL based on validations of the MHD waves against in situ wave observations improves the simulation results of Case 1, but still does not fully resolve its deep dropout. However, analyzing the uncertainty of simulated PSD imposed by the uncertainty in the scaled MHD‐DLL, it was found that outward radial diffusion could still account for the losses at L* < 4.5.

Importance of lower atmospheric forcing and magnetosphere-ionosphere coupling in simulating neutral density during the February 2016 geomagnetic storm

During geomagnetic storms a large amount of energy is transferred into the ionosphere-thermosphere (IT) system, leading to local and global changes in e.g., the dynamics, composition, and neutral density. The more steady energy from the lower atmosphere into the IT system is in general much smaller than the energy input from the magnetosphere, especially during geomagnetic storms, and therefore details of the lower atmosphere forcing are often neglected in storm time simulations. In this study we compare the neutral density observed by Swarm-C during the moderate geomagnetic storm of 31 January to 3 February 2016 with the Thermosphere-Ionosphere-Electrodynamics-GCM (TIEGCM) finding that the model can capture the observed large scale neutral density variations better in the southern than northern hemisphere. The importance of more realistic lower atmospheric (LB) variations as specified by the Whole Atmosphere Community Climate Model eXtended (WACCM-X) with specified dynamics (SD) is demonstrated by improving especially the northern hemisphere neutral density by up to 15% compared to using climatological LB forcing. Further analysis highlights the importance of the background atmospheric condition in facilitating hemispheric different neutral density changes in response to the LB perturbations. In comparison, employing observationally based field-aligned current (FAC) versus using an empirical model to describe magnetosphere-ionosphere (MI) coupling leads to an 7–20% improved northern hemisphere neutral density. The results highlight the importance of the lower atmospheric variations and high latitude forcing in simulating the absolute large scale neutral density especially the hemispheric differences. However, focusing on the storm time variation with respect to the quiescent time, the lower atmospheric influence is reduced to 1–1.5% improvement with respect to the total observed neutral density. The results provide some guidance on the importance of more realistic upper boundary forcing and lower atmospheric variations when modeling large scale, absolute and relative neutral density variations.

Unveiling the Space Weather During the Starlink Satellites Destruction Event on 4 February 2022

AbstractOn 4 February 2022, 38 Starlink satellites were destroyed by the geomagnetic storm, which brought significant financial, aerospace and public influences. In this letter, we reveal the space weather process during 3–4 February 2022 geomagnetic disturbances, from the Sun all the way to the satellite orbiting atmosphere. Initiated by an M1.0 class flare and the following coronal mass ejection (CME), a moderate geomagnetic storm was stimulated on 3rd February by the CME arrival at Earth. Subsequently, another moderate storm was triggered on 4th February by the passage of another CME. Model simulations driven by solar wind show that the first geomagnetic storm induced around 20% atmospheric density perturbations at 210 km altitude on 3rd February. The unexpected subsequent storm on 4th February led to a density enhancement of around 20%–30% at around 210 km. The resulting atmospheric drag can be even larger, since the regional density enhancement was over 60% and the satellite orbits were continuously decaying. This event brings forth the urgent requirements of better understanding and accurate prediction of the space weather as well as collaborations between industry and space weather community.

Intense Equatorial Electrojet and Counter Electrojet Caused by the 15 January 2022 Tonga Volcanic Eruption: Space‐ and Ground‐Based Observations

AbstractWe present space‐ and ground‐based multi‐instrument observations demonstrating the impact of the 2022 Tonga volcanic eruption on dayside equatorial electrodynamics. A strong counter electrojet (CEJ) was observed by Swarm and ground‐based magnetometers on 15 January after the Tonga eruption and during the recovery phase of a moderate geomagnetic storm. Swarm also observed an enhanced equatorial electrojet (EEJ) preceding the CEJ in the previous orbit. The observed EEJ and CEJ exhibited complex spatiotemporal variations. We combine them with the Ionospheric Connection Explorer neutral wind measurements to disentangle the potential mechanisms. Our analysis indicates that the geomagnetic storm had minimal impact; instead, a large‐scale atmospheric disturbance propagating eastward from the Tonga eruption site was the most likely driver for the observed intensification and directional reversal of the equatorial electrojet. The CEJ was associated with strong eastward zonal winds in the E‐region ionosphere, as a direct response to the lower atmosphere forcing.

Disappearance of the Polar Cap Ionosphere During Geomagnetic Storm on 11 May 2019

AbstractMulti‐instrument data from Jang Bogo Station (JBS) in Antarctica were utilized to study ionospheric responses to the 11 May 2019 moderate geomagnetic storm. These include Vertical Incident Pulsed Ionospheric Radar (VIPIR)/Dynasonde, Fabry‐Perot Interferometer (FPI), GPS vertical total electron content (vTEC), and magnetometer. The VIPIR/Dynasonde observed long‐lasting (>11 hr) severe depletion of the electron density in the F‐region ionosphere over JBS. During the depletion interval, GPS TEC also correspondingly decreased, FPI neutral temperature was significantly enhanced, and the polar magnetic field variations showed positive and negative excursions in the Y (east) and Z (vertical) components, respectively. GK‐2 A satellite, located ∼2.5 hr west of JBS, observed negative magnetic field perturbations in the azimuthal BD component at geosynchronous orbit during the depletion of ionospheric plasma. Such a BD perturbation at geosynchronous orbit is due to the field‐aligned currents flowing out of the ionosphere. From these observations we suggest that transpolar ionospheric currents connected to the field‐aligned currents flowing on a substorm wedge‐shaped circuit act as a source of polar atmospheric heating during the moderate geomagnetic storm interval and that elevated heavy molecular gases (O2 and N2) by atmospheric heating contribute to the electron density depletion via increased recombination rate.

Findings of the unusual plasma bubble occurrences at dawn during the recovery phase of a moderate geomagnetic storm over the Brazilian sector

In this work, we observe for the first time the unusual pre-sunrise Equatorial Plasma Bubbles (EPBs) during a moderate geomagnetic storm recovery phase caused by the High-Speed Solar Wind Stream (HSS) on February 17, 2015, over the Brazilian sector. Therefore, this study aims to explain the generation mechanism of this uncommon event, which started at 08:00 UT on February 18, 2015. We used Multiple Global Navigation Satellite Systems (Multi-GNSS, GPS, and GLONASS) data to produce two-dimensional maps of the Rate Of TEC index (ROTI) that show EPB features elongated in magnetic meridians. Also, Digisonde data from São Luís (2.53° S, 44.30° W, dip angle: 8.57°), Boa Vista (12.81° N, 60.67° W, dip angle: 33.71°), and Campo Grande (20.44° S, 54.64° W, dip angle: 25.98°), and magnetometer data at São Luís and Eusébio (3.89° S, 38.45° W, dip angle: 17.96°). Our analysis shows that the unusual pre-sunrise plasma bubbles lasted longer after sunrise, around 1 h. Finally, we showed that these EPBs are likely driven by a disturbance wind dynamo effect, which helps to understand the role of the external factors in EPBs development.

Using Temporal Relationship of Thermospheric Density With Geomagnetic Activity Indices and Joule Heating as Calibration for NRLMSISE‐00 During Geomagnetic Storms

AbstractThe responses of thermospheric densities to geomagnetic activity indices and Joule heating are analyzed during 265 geomagnetic storms and can be used to calibrate the model NRLMSISE‐00 with neutral mass density observed at 400 km based on the CHAMP satellite from 2002 to 2008. In this work, the geomagnetic activities at high and low latitudes are identified by AE indices and Dst indices. During geomagnetic storms, Joule heating and its impacts on the thermospheric density are calculated by the Weimer‐2001 electric potential model and the DMSP spacecraft. The results show that the response of thermospheric density to both AE and Dst index takes a longer time as geomagnetic storms intensify. During weak and moderate storms, density delays AE indices for about 0–1 hr, while it is 2–4 hr for intense storms. In addition, the time differences between Dst indices and AE indices increase as storms intensify. During weak and moderate geomagnetic storms, the difference in the time corresponding to Dst indices with the time when AE indices peak is only 1–2 hr, while it increases to 3–5 hr for the intense storms. Furthermore, the calibration of the NRLMSISE‐00 model results can reproduce the storm‐time thermospheric density well, with the Mean Relative Error (MRE) between density observation and model decreasing from 40% to 10% after the correction.

Assessing the Impact of Weak and Moderate Geomagnetic Storms on UK Power Station Transformers

AbstractIt is well documented that space weather can impact electricity infrastructure, and several incidents have been observed in recent decades and directly linked to large geomagnetic storms (e.g., the Hydro Québec incident in 1989). However, less is understood about the impact of lower‐level geomagnetically induced currents on the health of transformers in the long term. In this study, the long term impact of geomagnetic activity on 13 power station transformers in the UK is investigated. Dissolved gas measurements from 2010 to 2015 were used to look for evidence of a link between degradation of the transformer and heightened levels of the global SYM‐H index and as measured at Eskdalemuir magnetometer station in southern Scotland. First, case studies of the most significant storms in this time period were examined using dissolved gas analysis methods, specifically the Low Energy Degradation Triangle. These case studies were then augmented with a statistical survey, including Superposed Epoch Analysis of multiple storm events. No evidence of a systematic space weather impact can be found during this time period, likely owing to the relatively quiet nature of the Sun during this epoch and the modernity of the transformers studied.

Three‐Dimensional Reconstruction of Tongue of Ionization During the 11 October 2010 Geomagnetic Storm and Evolution Analysis With TIEGCM

AbstractThe three‐dimensional computerized ionospheric tomography (3DCIT) technique that fused multisource data is used to reconstruct the spatial distribution of tongue of ionization (TOI) appeared over Greenland during a moderate geomagnetic storm on 11 October 2010. The reconstruction results are validated with observations from the constellation observing system for meteorology, ionosphere, and climate radio occultations and two ionosonde stations, which show good agreements. The 3DCIT images indicated a zone of high electron density (magnitude of ∼5 TECU) that crossed northern Greenland and electrons were input into the polar region in the anti‐sunward direction after aggregating at midlatitudes, which formed a TOI. The images also revealed that the TOI magnitude was larger in the upper ionosphere ssand lower at 300 and 500 km but still noticeable. Below 300 km, the TOI was difficult to detect. The simulation result of the Thermosphere‐Ionosphere‐Electrodynamic General Circulation Model (TIEGCM) also showed the same TOI structure. Then, we combined the measured ionospheric data and term‐by‐term analysis of the ion continuity formula in TIEGCM to further identify the principal TOI formation mechanisms. We assume that the dominant TOI formation mechanism is electric field transport, which is offset by ambipolar diffusion and neutral wind transport. Furthermore, the uplift of electrons and the insignificant effect of other physical processes explained the insignificant TOI in lower ionosphere.

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.

Van Allen Probes Observations of Symmetric Stormtime Compressional ULF Waves.

Previous spacecraft studies showed that stormtime poloidal ultralow‐frequency (ULF) waves in the ring current region have an antisymmetric (second harmonic) mode structure about the magnetic equator. This paper reports Van Allen Probes observations of symmetric ULF waves in the postnoon sector during a moderate geomagnetic storm. The mode structure is determined from the presence of purely compressional magnetic field oscillations at the equator accompanied by strong transverse electric field perturbations. Antisymmetric waves were also detected but only very late in the recovery phase. The symmetric waves were detected outside the plasmasphere at L = 3.0–5.5 and had peak power at 4–10 mHz, lower than the frequency of the local fundamental toroidal standing Alfvén wave. During the wave events, the flux of protons was enhanced at energies below ∼5 keV, which appears to be a prerequisite for the waves. The protons may provide free energies to waves through drift resonance instability or drift compressional instability, which occur in the presence of radial gradients of plasma parameters.

Effects of Subauroral Polarization Streams on the Equatorial Electrojet During the Geomagnetic Storm on 1 June 2013: 2. The Temporal Variations

AbstractUsing ground‐based magnetic field measurements and numerical simulations from the Thermosphere‐Ionosphere Electrodynamic General Circulation Model (TIEGCM), a first paper (Zhang, Yamazaki, et al., 2021, doi: https://doi.org/10.1029/2021JA029681; under review) introduced the potential roles of disturbance dynamo electric field due to subauroral polarization streams (SAPS) on the equatorial electrojet (EEJ) during a moderate geomagnetic storm on 1 June 2013. Our second study investigated the temporal responses of equatorial electrojet to SAPS. At noon, the residual EEJ (ΔEEJ) owing to SAPS flows westward, that is, counter equatorial electrojet (CEJ). The temporal variation of CEJ excited by the dynamo electric field was basically consistent with that by SAPS, and the effects of zonal wind were larger than those of meridional wind. The relative time delay of CEJ and SAPS was related to the propagation time of disturbance wind from mid‐latitudes to low‐latitudes. It took 2–3 hr for SAPS‐related disturbance wind to propagate to the equatorial region and change the polarity of EEJ. The influence of meridional winds on the temporal variations of ΔEEJ is related to the generation of eastward currents at mid‐latitudes, which can accumulate the positive charges at dusk terminator and then generate a westward electric field at lower latitudes.

Ionospheric irregularities during disturbed geomagnetic conditions over Argentinian EIA region

Ionospheric irregularities can severely degrade radio communication and navigation systems. Geomagnetic storms may affect the generation of these irregularities in a way that is not yet fully understood. To improve the forecasting of this phenomenon, we need to study the ionosphere in different regions of the world, and in particular in the equatorial ionization anomaly (EIA) where irregularities are usually more intense. This study analyses the effect of geomagnetic storms on ionospheric irregularities. We examined the occurrence of irregularities at the southern crest of the EIA in Argentina (Tucumán, 26.9°S, 294.6°E, dip latitude 15.5°S) during three intense and one moderate geomagnetic storm of different solar sources, between 2015 and 2018. We used data from an ionosonde, a Global Positioning System receiver and magnetometers. Ionogram spread-F, the F-layer bottom side (h'F), the critical frequency of the F2-layer (foF2), the rate of TEC index and the S4 scintillation index were analysed. The data show irregularities were present as range spread-F and moderate TEC fluctuations in one storm: 27 May 2017 (a coronal mass ejection CME-driven storm occurred on local winter), and were absent in the other events. We suggest that eastward disturbance dynamo electric field and over-shielding prompt penetration electric fields may create favourable conditions for developing these irregularities, whereas westward storm time electric fields might inhibit the growth of irregularities during the other storms considered. During co-rotating interaction region CIR-driven storms, the westward disturbance dynamo electric field may be associated with the non-occurrence of irregularities.

Forecasting Geomagnetic activity (Dst Index) using the ensemble kalman filter

ABSTRACT A novel Ensemble Kalman Filter (EnKF) method is adopted to make reliable forecasts of geomagnetic activity (Dst index) for real-time applications. In this method, an educated estimate (forecast) of Disturbance storm time (Dst) is made based on the ring current dynamics like injection and decay rates. This estimated Dst is further updated with the assimilation of real-time Dst values or ∆H values from a single ground based magnetometer observations. The forecasted Dst values by this EnKF method are validated with the true Dst during the severely disturbed period that consists of 2 super (Dst< -250 nT), 8 intense (Dst< -100 nT), and 13 moderate geomagnetic storms (Dst< -50 nT). It is found that the EnKF method implemented in this work offers the best accurate forecast of Dst with a root mean square error (RMSE) and regression coefficient (R) of 4.3 nT and 0.99, respectively.

Observation of the ionosphere by ionosondes in the Southern and Northern hemispheres during geospace events in October 2021

The paper presents the results of ionospheric observations performed over the Ukrainian Antarctic Akademik Vernadsky station and Millstone Hill (USA). Ionospheric parameters such as peak electron density and height (hmF2 and NmF2) in October 2021 are shown and discussed. The results of the comparative analysis between observations and predictions of the International Reference Ionosphere 2016 (IRI-2016) model are presented. The main objectives of this work are an investigation of the ionosphere response to space weather effects in the Northern and Southern hemispheres in the American longitudinal sectorusing ionosondes located at the Vernadsky station and near the magnetically conjugate region – Millstone Hill, and a comparison of observations with the model. The F2-layer peak height was calculated from ionograms obtained by ionosonde using subsequent electron density profile inversion. Diurnal variations of hmF2 and NmF2 were calculated using a set of sub-models of the IRI-2016 model for comparison with experimental results. A strong negative response of the ionosphere to the moderate geomagnetic storm on October 12, 2021 was revealed over the Vernadsky station and Millstone Hill. During October 21–31, 2021, the gradual night-to-night increase in NmF2 (by a factor of ~2) was observed over the Vernadsky station. It was found that the IRI hmF2 sub-models (SHU-2015 and AMTB-2013) provide a relatively good agreement with the observed variations of hmF2 in the daytime and nighttime for almost the entire investigated period over both the Vernadsky station and Millstone Hill. The largest deviations for both IRI hmF2 sub-models occurred during the nighttime of geomagnetically disturbed periods. The IRI NmF2 submodels (URSI and CCIR) generally agree with the observations. However, observations and model predictions differ somewhat in the geomagnetically disturbed periods. According to the results of the standard deviation calculations, it cannot be concluded that any of the IRI-2016 sub-models is better than the others. The hypotheses on the possible reasons for the differences in the modeled and observed variations of hmF2 and NmF2 are proposed and discussed in the frame of well-known ionospheric storms’ mechanisms. The results obtained in this paper demonstrate the peculiarities of the ionosphere in different hemispheres of the American longitude sector under geomagnetically quiet and disturbed conditions and provide one more validation of the modern empirical international reference models of the ionosphere.

Effects of the 12 May 2021 Geomagnetic Storm on Georeferencing Precision

In this work, we present the positioning error analysis of the 12 May 2021 moderate geomagnetic storm. The storm happened during spring in the northern hemisphere (fall in the south). We selected 868 GNSS stations around the globe to study the ionospheric and the apparent position variations. We compared the day of the storm with the three previous days. The analysis shows the global impact of the storm. In the quiet days, 93% of the stations had 3D errors less than 10 cm, while during the storm, only 41% kept this level of accuracy. The higher impact was over the Up component. Although the stations have algorithms to correct ionospheric disturbances, the inaccuracies lasted for nine hours. The most severe effects on the positioning errors were noticed in the South American sector. More than 60% of the perturbed stations were located in this region. We also studied the effects produced by two other similar geomagnetic storms that occurred on 27 March 2017 and on 5 August 2019. The comparison of the storms shows that the effects on position inaccuracies are not directly deductible neither from the characteristics of geomagnetic storms nor from enhancement and/or variations of the ionospheric plasma.

MHD‐Test Particles Simulations of Moderate CME and CIR‐Driven Geomagnetic Storms at Solar Minimum

AbstractAs part of the Whole Heliosphere and Planetary Interactions initiative, contrasting drivers of radiation belt electron response at solar minimum have been investigated with MHD‐test particle simulations for the May 13–14, 2019 Coronal Mass Ejection (CME)‐shock event and the August 30–September 3, 2019 high speed solar wind interval. Both solar wind drivers produced moderate geomagnetic storms characterized by a minimum Dst = −65 nT and −52 nT, respectively, with the August ‐ September event accompanied by prolonged substorm activity. The latter, with characteristic features of a Corotating Interaction Region (CIR)‐driven storm, produced the hardest relativistic electron spectrum observed by Van Allen Probes during the last two years of the mission, ending in October 2019. MHD simulations were performed using both the Lyon‐Fedder‐Mobarry global MHD code and recently developed GAMERA model coupled to the Rice Convection Model, run with measured L1 solar wind input for both events studied, and coupled with test particle simulations, including an initial trapped and injected population. Initial electron Phase Space Density (PSD) profiles used measurements from the Relativistic Electron Proton Telescope and MagEIS energetic particle instruments on Van Allen Probes for test particle weighting and updating of the injected population at apogee. Results were compared directly with measurements and found to reproduce magnetopause loss for the CME‐shock event and increased PSD for the CIR event. The two classes of events are contrasted for their impact on outer zone relativistic electrons near the end of Solar Cycle 24.

Analysis of the first four moderate geomagnetic storms of the year 2015

This essay investigates the first four moderate geomagnetic activities (the 04 January storm, the 07 January storm, the 17 February storm, and the 24 February storm) of 2015 in the 24th solar cycle. The essay attempts to understand these storms with the aid of zonal geomagnetic indices. It predicts the zonal geomagnetic indices (Dst, ap, AE) of the storms by an artificial neural network model. The phenomena that occurred in January and February are discussed by taking into account the solar wind parameters (Bz, E, P, N, v, T) and the zonal geomagnetic indices obtained from NASA. In the study, after glancing at the general appearance of the year 2015, which is exhibited with too small errors, binary correlations of the variables are indicated by the covariance matrix and the hierarchical cluster of the variables is presented by at dendrogram. The artificial neural network model is governed by the physical principles in the paper. The model uses the solar wind parameters as inputs and the zonal geomagnetic indices as outputs. The causality principle forms the models by cause–effect association. The back propagation algorithm is specified as Levenberg–Marquardt (trainlm), and 35 neural numbers are utilized in the artificial neural network. The neural network model predicts the Dst, ap, and AE indices of January and February geomagnetic storms with an accuracy that deserves discussion. The R correlation coefficients of the Dst, ap, and AE indices reach up to 98.9%. In addition to reliable accuracy, the parameters affecting the R correlation coefficients agree with the literature. Estimating the geomagnetic activities may support interplanetary works.

Deriving column-integrated thermospheric temperature with the N<sub>2</sub> Lyman–Birge–Hopfield (2,0) band

Abstract. This paper presents a new technique to derive thermospheric temperature from space-based disk observations of far ultraviolet airglow. The technique, guided by findings from principal component analysis of synthetic daytime Lyman–Birge–Hopfield (LBH) disk emissions, uses a ratio of the emissions in two spectral channels that together span the LBH (2,0) band to determine the change in band shape with respect to a change in the rotational temperature of N2. The two-channel-ratio approach limits representativeness and measurement error by only requiring measurement of the relative magnitudes between two spectral channels and not radiometrically calibrated intensities, simplifying the forward model from a full radiative transfer model to a vibrational–rotational band model. It is shown that the derived temperature should be interpreted as a column-integrated property as opposed to a temperature at a specified altitude without utilization of a priori information of the thermospheric temperature profile. The two-channel-ratio approach is demonstrated using NASA GOLD Level 1C disk emission data for the period of 2–8 November 2018 during which a moderate geomagnetic storm has occurred. Due to the lack of independent thermospheric temperature observations, the efficacy of the approach is validated through comparisons of the column-integrated temperature derived from GOLD Level 1C data with the GOLD Level 2 temperature product as well as temperatures from first principle and empirical models. The storm-time thermospheric response manifested in the column-integrated temperature is also shown to corroborate well with hemispherically integrated Joule heating rates, ESA SWARM mass density at 460 km, and GOLD Level 2 column O/N2 ratio.