Auroral Particle Precipitation Research Articles

The Polarity of IMF By Strongly Modulates Particle Precipitation During High‐Speed Streams

AbstractRecent studies have suggested that the interplanetary magnetic field (IMF) component modulates particle precipitation during solstices, or periods of high dipole tilt . So far this explicit IMF ‐effect has only been shown in statistical studies. Here we analyzed a sequence of high‐speed stream (HSS) driven events of auroral ( keV) and medium energy ( keV and keV) particle precipitation. We show that when HSSs are comparable in terms of IMF and solar wind parameters, they can lead to systematically stronger particle precipitation in individual events when the signs of and are opposite. We also perform a superposed epoch analysis of 485 HSSs giving further evidence that the ‐effect is especially significant during HSSs. This is likely due to the persistent IMF polarity during HSSs. We show evidence that the dependence in particle precipitation is caused by a similar dependence in substorm occurrence.

Investigation of Ionospheric Small‐Scale Plasma Structures Associated With Particle Precipitation

AbstractWe investigate the role of auroral particle precipitation in small‐scale (below hundreds of meters) plasma structuring in the auroral ionosphere over the Arctic. In this scope, we analyze together data recorded by an Ionospheric Scintillation Monitor Receiver (ISMR) of Global Navigation Satellite System (GNSS) signals and by an All‐Sky Imager located in Longyearbyen, Svalbard (Norway). We leverage on the raw GNSS samples provided at 50 Hz by the ISMR to evaluate amplitude and phase scintillation indices at 1 s time resolution and the Ionosphere‐Free Linear Combination at 20 ms time resolution. The simultaneous use of the 1 s GNSS‐based scintillation indices allows identifying the scale size of the irregularities involved in plasma structuring in the range of small (up to few hundreds of meters) and medium‐scale size ranges (up to few kilometers) for GNSS frequencies and observational geometry. Additionally, they allow identifying the diffractive and refractive nature of fluctuations on the recorded GNSS signals. Six strong auroral events and their effects on plasma structuring are studied. Plasma structuring down to scales of hundreds of meters is seen when strong gradients in auroral emissions at 557.7 nm cross the line of sight between the GNSS satellite and receiver. Local magnetic field measurements confirm small‐scale structuring processes coinciding with intensification of ionospheric currents. Since 557.7 nm emissions primarily originate from the ionospheric E‐region, plasma instabilities from particle precipitation at E‐region altitudes are considered to be responsible for the signatures of small‐scale plasma structuring highlighted in the GNSS scintillation data.

Online system for analyzing currents in the upper ionosphere according to Swarm satellite data

In this paper, we describe the TeslaSwarm online system [http://aleph.gcras.ru/teslaswarm] for visualizing field-aligned currents in the upper ionosphere, using data from Swarm low-orbit satellites. The system provides researchers with a simple and convenient tool for event selection and detailed analysis of currents and electromagnetic fields in the upper ionosphere. The system user can select satellite passages over a given region, visualize the geomagnetic field structure and field-aligned currents, compare the pattern of field-aligned currents with the auroral particle precipitation map, using the OVATION-Prime model, and save the selected parameters in a file in text format. We demonstrate advantages of the developed system over its foreign analogues. In practice, the collection and pre-processing of raw data for experiments make up about 80 % of all work with data. The proposed online system largely saves the user from the most time-consuming work of choosing the required satellite passage segments and calculating the characteristics of interest from raw measurements.

A Survey of Magnetic Field Line Curvature in Jovian Dawn Magnetodisc

AbstractThe Jovian magnetosphere is highly dynamic, influenced by both solar wind and internal processes associated with the rapid planetary rotation and Io's volcanic activities. Accompanying the mass and energy circulations driven by the magnetospheric dynamics, the magnetic configuration also changes dramatically. One of the crucial parameters to characterize the magnetic configuration is magnetic field line curvature (FLC), which generally describes how stretched the field line is. The curvature is pivotal to influence particle behaviors, for example, pitch angle scattering which may lead to auroral particle precipitation. In this work, a method is proposed to investigate the real‐time magnetic FLC in Jovian current sheet using the magnetic field data from the Juno spacecraft. The results indicate that the FLC scattering of ions and relativistic electrons are common in Jovian magnetosphere, providing a crucial insight to understand the particle behaviors.

Онлайн система для анализа токов в верхней ионосфере по данным спутников Swarm

In this paper, we describe the TeslaSwarm online system [http://aleph.gcras.ru/teslaswarm] for visualizing field-aligned currents in the upper ionosphere, using data from Swarm low-orbit satellites. The system provides researchers with a simple and convenient tool for event selection and detailed analysis of currents and electromagnetic fields in the upper ionosphere. The system user can select satellite passages over a given region, visualize the geomagnetic field structure and field-aligned currents, compare the pattern of field-aligned currents with the auroral particle precipitation map, using the OVATION-Prime model, and save the selected parameters in a file in text format. We demonstrate advantages of the developed system over its foreign analogues. In practice, the collection and pre-processing of raw data for experiments make up about 80 % of all work with data. The proposed online system largely saves the user from the most time-consuming work of choosing the required satellite passage segments and calculating the characteristics of interest from raw measurements.

Observations of 4.26 μm CO2 Auroral Emissions From AIRS Nadir Sounder Measurements

AbstractThe Atmospheric Infrared Sounder (AIRS) instrument onboard the NASA Aqua satellite is used to observe aurora associated with the CO2 4.26 μm emission. These observations are due to non‐local thermodynamic equilibrium (NLTE) resulting from the vibrational excitation of CO2, which arises in the process of auroral energetic particle precipitation, as opposed to the dayside NLTE occurring due to solar radiation. The observations are confirmed to be associated with aurora using the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) limb measurements and the SuperMAG Electrojet (SME) index. The high spectral resolution and low noise associated with the AIRS instrument allows for the emission spectrum to be calculated and confirmed to arise from CO2. Our new NLTE index values derived from AIRS provide the ability to globally measure auroral events associated with CO2 with a spatial resolution on the order of ∼13.5 km.

Classification and Distribution of the Dayside Ion Upflows Associated with Auroral Particle Precipitation

Two important phenomena of the solar wind–magnetosphere–ionosphere coupling are auroral particle precipitation and the formation of ions flowing upward from the ionosphere. They have opposite transport directions of energy and substance. Based on the observations of particle precipitation and ion drift from the DMSP F13 satellite in January and July 2005, the ionospheric ion upflows in dayside auroral oval (0600–1800 MLT) can be divided into five types according to the velocity of ion upflows and the spectrum characteristics of auroral particle precipitation, and the distribution for different types of ion upflows is studied. The results show that the ion upflows mainly occur in the geomagnetic latitude (MLAT) range of 70–80°.The main magnetospheric source region of ion upflows (type A and D) caused by the accelerated electron (mainly the soft electron) corresponds to Low Latitude Boundary Layer (LLBL) and Cusp, and ion upflows of type B and C (related to the process of ambipolar diffusion caused by electron acceleration) mainly occur in LLBL and Boundary Plasma Sheet (BPS), while ion upflows of type E without electron acceleration mainly occur in the central plasma sheet (CPS).The dawn–dusk asymmetry is obvious in the winter season, with the ion upflows mainly occurring on the dawn/dusk side ionosphere. However, the ion upflows in summer mainly occur at the magnetic noon, with a symmetric distribution centered at the magnetic noon. The occurrence of ion upflow in winter is significantly higher than that in summer, and it is significantly enhanced during the period of moderate geomagnetic activity. The upward region expands to the lower latitude when the geomagnetic activity is enhanced. The effect of interplanetary magnetic field (IMF) components has also been studied in this paper. When IMF Bx is negative, the upflow occurrence increases in the region of 1500–1800 MLT and 0600–0900 MLT, with the MLAT range below 70°. The direction of IMF By may lead to the high-incidence area reverse at the prenoon or postnoon region. The occurrence of ion upflows with the MLAT range below 75° increases significantly when IMF is southward. Type A ion upflow has the highest velocity of ion upflows, followed by type E, and type D has the lowest. The average velocity of ion upflows in winter is significantly higher than that in summer.

Transient energetic particles as the origin of the mid-infrared north polar hotspot of Jupiter

Since it was detected in 1980, Jupiter's 8-μm CH4 north polar hot spot (8CNPHS), ∼20 K warmer than the surrounding polar stratosphere, has been observed for four decades. Unlike normal auroral ovals (i.e., the bright rings of auroral emissions), it is usually filled with bright emission. The causes of both its shape and longevity are not understood, although several mechanisms have been proposed to explain its existence. In order to investigate the deriving mechanism of the 8CNPHS, we have observed the north polar regions near 3 μm, where line emission from another CH4 band as well as a C2H6 fundamental band occur. Using Gemini North/GNIRS in 2013, 2020, 2021, and 2022, we have detected transient 3-μm CH4 and/or C2H6 bright spots within the 8CNPHS, and occasionally no apparent bright spots. By comparing the emission from CH4 with that from C2H6, we demonstrate that the origin of the 8CNPHS must be due to transient and energetic magnetospheric particles, which can penetrate down to the hydrocarbon layers, heating the homopause (∼1 μbar level) and the stratosphere (∼1 mbar level) and energize the 8CNPHS. Based on our observations and analysis, we propose the following three mechanisms for maintaining and containing the decades long warmth of the 8CNPHS: 1) energetic and transient auroral particle precipitations warming the stratosphere of the 8CNPHS, 2) a longer radiative cooling time in the 8CNPHS stratosphere (∼6 months) compared to less than or equal to one month at the homopause, and 3) recently detected polar stratospheric jets likely associated with polar fronts, which resist the free flow of warm gas in the 8CNPHS to the surrounding polar regions. We show that other heating mechanisms proposed so far in the literature, such as Joule heating, polar haze heated by sunlight, etc., are only the secondary mechanisms that follow atmospheric ionization caused by energetic particle bombardment. Our finding of the magnetospheric-ionospheric-stratospheric coupling in the Jovian polar regions open the possibility of quantitatively refining 3-D global circulation models for the atmospheres of giant planets and exoplanets.

Ionospheric plasma structuring in relation to auroral particle precipitation

Auroral particle precipitation potentially plays the main role in ionospheric plasma structuring. The impact of auroral particle precipitation on plasma structuring is investigated using multi-point measurements from scintillation receivers and all-sky cameras from Longyearbyen, Ny-Ålesund, and Hornsund on Svalbard. This provides us with the unique possibility of studying the spatial and temporal dynamics of the aurora. Here we consider three case studies to investigate how plasma structuring is related to different auroral forms. We demonstrate that plasma structuring impacting the GNSS signals is largest at the edges of auroral forms. Here we studied two stable arcs, two dynamic auroral bands, and a spiral. Specifically for arcs, we find elevated phase scintillation index values at the poleward edge of the aurora. This is observed for auroral oxygen emissions (557.7 nm) at 150 km in the ionospheric E-region. This altitude is also used as the ionospheric piercing point for the GNSS signals as the observations remain the same regardless of different satellite elevations and azimuths. Further, there may be a time delay between the temporal evolution of aurora (e.g., commencement and fading of auroral activity) and observations of elevated phase scintillation index values. The time delay could be explained by the intense influx of particles, which increases the plasma density and causes recombination to carry on longer, which may lead to a persistence of structures – a “memory effect”. High values of phase scintillation index values can be observed even shortly after strong visible aurora and can then remain significant at low intensities of the aurora.

The role of particle precipitation on plasma structuring at different altitudes by in-situ measurements

The plasma in the cusp ionosphere is subject to particle precipitation, which is important for the development of large-scale irregularities in the plasma density. These irregularities can be broken down into smaller scales which have been linked to strong scintillations in the Global Navigation Satellite System (GNSS) signals. We present power spectra for the plasma density irregularities in the cusp ionosphere for regions with and without auroral particle precipitation based on in-situ measurements from the Twin Rockets to Investigate Cusp Electrodynamics-2 (TRICE-2) mission, consisting of two sounding rockets flying simultaneously at different altitudes. The electron density measurements taken from the multi-needle Langmuir probe system (m-NLP) were analyzed for the whole flight duration for both rockets. Due to their high sampling rates, the probes allow for a study of plasma irregularities down to kinetic scales. A steepening of the slope in the power spectra may indicate two regimes, a frequency interval with a shallow slope, where fluid-like processes are dominating, and an interval with a steeper slope which can be addressed with kinetic theory. The steepening occurs at frequencies between 20 Hz and 100 Hz with a median similar to the oxygen gyrofrequency. Additionally, the occurrence of double slopes increases where precipitation starts and throughout the rest of the flight. In addition, strong electron density fluctuations were found in regions poleward of the cusp, thus in regions immediately after precipitation. Furthermore, by investigating the integrated power of the fluctuations within different frequency ranges, we show that at low frequencies (10–100 Hz), the power is pronounced more evenly while the rocket encounters particle precipitation, while at high frequencies (100–1000 Hz) fluctuations essentially coincide with the passing through a flow channel.

On the Sources, Coupling and Energetics During Supersubstorms of the Solar Cycle 24

AbstractThe solar cycle 24 exhibited only four supersubstorms (SSSs) during three of the geomagnetic storms of May 2011, March 2012, and September 2017. A robust and quantitative analyses of these events is performed and the results show that multiple hits by the magnetic clouds with fast moving background solar wind plasma provided the conditions for occurrence of these events. The available solar wind energy, the magnetospheric input energy and the sink energies are estimated. The input energy dominates the total dissipation for shorter intervals of the SSSs, wherein, a dominance of Joule heating sink over the auroral particle precipitation and ring current sinks is revealed. However, for longer time intervals (6 months and more), the total dissipation supersedes the total input energy wherein, the auroral precipitation sink dominates. The contribution of the ring current sink is found at the lowest levels against a high percentage share (79%–91%) of ionospheric sink during the SSSs. Intriguingly, when the SSS expansion and the recovery phases are compared on dissipation terms, percentage share of the Joule heating (ring current) is found more during the later (former) phase. The input efficiencies are found at ∼3.05%, 4.95%, 3.98%, and 1.15%, and the dissipation efficiencies at 73.95%, 58.56%, 37.72%, and 77.94%, respectively during the four SSSs. The dissipation efficiency and the ratio of the sink energies are found to be inversely proportional to the intensity of the substorms. The energy partitioning in the magnetosphere‐ionosphere system also respond in a contrasting fashion to the different levels of substorms.

Advanced Classification of Ionospheric Troughs in the Morning and Evening Conditions

The separation and classification of ionospheric troughs in the winter evening and morning ionospheres of the southern hemisphere were performed using CHAMP satellite data for high solar activity (2000–2002). In the high-latitude ionosphere, the main ionospheric trough (MIT) was separated from the high-latitude trough (HLT). The separation was carried out using a thorough analysis of all the characteristic structures of the ionosphere in the framework of the auroral diffuse particle precipitation model. Two types of high-latitude troughs were identified: (1) a wide trough associated with zone II of diffuse precipitation on the poleward edge of the auroral oval and (2) a narrow trough of ionization, which is presumably associated with an electric field action. The poleward wall of MIT is as ever formed by diffuse precipitation in zone I on the equatorward edge of the auroral oval. The HLT and MIT separation is most difficult at the longitudes of the eastern hemisphere, where all structures are located at the highest latitudes and partially overlap. In the mid-latitude ionosphere, all the characteristic structures of the ionosphere were also identified and considered. MIT was separated from the ring ionospheric trough (RIT), which is formed by the decay processes of the magnetospheric ring current. The separation of MIT and RIT was performed based on an analysis of the prehistory of all geomagnetic disturbances during the period under study. In addition to the RIT, a decrease in the electron density equatorward of the MIT was found to be often formed at the America–Atlantic longitudes, which masks the MIT minimum. For completeness, all cases of a clearly defined polar cavity are also presented.

Advanced separation and classification of ionospheric troughs in midnight conditions

This study uses a novel approach to separate and classify different ionospheric troughs from CHAMP satellite data in the winter midnight ionosphere of the southern hemisphere at high solar activity (2000–2002). The main ionospheric trough (MIT) was separated from the high latitude trough (HLT). The separation was performed through an analysis of troughs in the frame of a model of the diffuse auroral particle precipitation. Two types of HLT were distinguished. In the mid-latitude ionosphere, the MIT was separated from the ring ionospheric trough (RIT), which is formed by the decay processes of the magnetospheric ring current. The separation was performed on the basis of an analysis of the prehistory of all geomagnetic disturbances for the period under study. In addition, a decrease in the electron density, which is superimposed on the MIT and masks its minimum position, is quite often observed at American and Atlantic longitudes near the Polar Circle.

An EISCAT UHF/ESR Experiment That Explains How Ionospheric Irregularities Induce GPS Phase Fluctuations at Auroral and Polar Latitudes

AbstractA limitation to the use of Global Navigation Satellite System (GNSS) for precise and real‐time services is introduced by irregularities in the ionospheric plasma density. An EISCAT UHF/ESR experiment was conducted to characterize the effect of electron density irregularities on temporal fluctuations in TEC along directions transverse to GPS ray paths in the high latitudes ionosphere. Two representative case studies are described: Enhancements in temporal TEC fluctuations originating (a) in the auroral ionosphere following auroral particle precipitation and (b) in the polar ionosphere following the drift of a polar patch as well as particle precipitation. The results indicate that the origin of enhancements in TEC fluctuations is due to the propagation through large‐to‐medium scale irregularities (i.e., ranging from few kilometres in the E region to few tens of kilometres in the F region) and occurring over spatial distances of up to approximately in the E region and up to approximately in the F region with a patchy distribution. Furthermore, the results indicate that enhancements in TEC fluctuations produced by polar plasma patches and particle precipitation occur over similar temporal scales, thus explaining the overall observation of higher phase scintillation indices in the high‐latitude ionosphere. The similarity in the temporal scales over which enhancements in TEC fluctuations occur in the presence of both particle precipitation and plasma patches suggests an intrinsic limitation in the monitoring and tracking of plasma patches through ground GNSS observations.

Variations in Cosmic Noise Absorption in Association With Equatorward Development of the Pulsating Auroral Patch: A Case Study to Estimate the Energy Spectra of Auroral Precipitating Electrons

AbstractThis study focused on a pulsating aurora event associated with aurora morphological changes in Fennoscandia in the early morning on March 7, 2017. A high‐speed sampling all‐sky camera captured equatorward development of the pulsating auroral patch in association with a substorm centered over the Greenland/North America region. Of particular interest in this event is the interconnection between the auroral intensity and the cosmic noise absorption (CNA) derived from three riometers aligned meridionally in Finland (from north to south: Ivalo, Sodankylä, and Rovaniemi). The analysis was made by dividing optical measurements into two oscillation components: longer and shorter than 40 s, that is, nonpulsating and pulsating auroral modulations. The interrelation between the auroral brightness and CNA showed a linear correlation. The inclination of the regression line changed with time depending on latitudes, which was interpreted as hardening or softening of the precipitating electron spectrum. Especially in the case of the low‐pass component, the inclination of the CNA‐vs‐intensity interrelation increased at the three riometer latitudes in the substorm recovery phase. On the other hand, for the high‐pass component, the inclination decreased at Rovaniemi (lower latitude) but remained uniform at Sodankylä (higher latitude). These features suggest that the precipitating electron spectrum has softened in the low‐pass or nonpulsating auroral component, but the spectrum has hardened in the high‐pass or pulsating auroral component on the lower latitude part of the auroral patch region. This study proposes a new application of riometer‐camera measurements to examine auroral particle precipitation.

Influence of different types of ionospheric disturbances on GPS signals at polar latitudes

Abstract. The comparative research of the influence of different types of auroral particle precipitation and polar cap patches (PCPs) on the global positioning system (GPS) signals disturbances in the polar ionosphere was done. For this purpose, we use the GPS scintillation receivers at Ny-Ålesund and Skibotn, operated by the University of Oslo. The presence of the auroral particle precipitation and polar cap patches was determined by using data from the EISCAT 42m radar on Svalbard. The optical aurora observations in 557.7 and 630.0 nm spectrum lines on Svalbard were used as well for the detection of ionospheric disturbances. The cusp identification was done with using SuperDARN (Hankasalmi) data. We consider events when the simultaneous EISCAT 42m and GPS data were available for the years 2010–2017, and in this paper we present, in detail, typical examples describing the overall picture, and we present the statistics for 120 events. We considered the dayside/cusp precipitation, substorm precipitation, daytime and nighttime PCPs, and precipitation associated with the interplanetary shock wave arrival. We demonstrate that substorm-associated precipitation (even without PCPs) can lead to a strong GPS phase (σϕ) scintillations up to ∼ 1.5–3 radians, which is much stronger than those usually produced by other types of considered ionosphere disturbances. The value of the substorm-phase scintillations in general correlate with the value of the geomagnetic field disturbance. But sometimes even a small geomagnetic substorm, when combined with the PCPs, produces quite strong phase scintillations. Cusp phase scintillations are lower than dayside PCPs scintillations. PCPs can lead to stronger ROT (rate of total electron content) variations than other types of ionosphere disturbances. So our observations suggest that the substorms and PCPs, being different types of the high-latitude disturbances, lead to the development of different types and scales of ionospheric irregularities.

Auroral E‐Region as a Source Region for Ionospheric Scintillation

AbstractAltitudinal source regions and generation mechanisms of ionospheric scintillation are investigated by employing the incoherent scatter radar (ISR) at Poker Flat, Alaska (PFISR) and nearby global positioning system (GPS) receivers. Analysis of PFISR and GPS observations during the September 2017 geomagnetic disturbances reveals that phase scintillation is seen during auroral disturbances, and can occur at any storm phase. Statistical comparisons of the rate of change of the total electron content (TEC) index (ROTI) with the amplitude (S4) and phase (σϕ) scintillation in July‐December 2017 show a significant increase with geomagnetic activity and considerable correlations between ROTI and σϕ, whereas S4 showed no noticeable increase or correlations. The PFISR‐GPS comparisons show that scintillation occurs when the electron density is enhanced in the auroral E‐region and is stronger for larger E‐region peak density and/or lower E‐region peak altitude. This implies that scintillation is stronger for more intense and/or deeper auroral particle precipitation. A detailed analysis of an event with a well‐defined and propagating E‐region density enhancement imaged by PFISR reveals that scintillation is stronger on the trailing edge of the density enhancement. This feature is discussed in the context of the gradient‐drift instability as a potential mechanism for generation of plasma density waves that scatter GPS radio signals and lead to scintillation. The results of this study add to the growing body of evidence that ROTI can be used as a proxy for phase scintillation and that the ionospheric E‐region is an important source region for ionospheric scintillation at auroral latitudes.

Data‐Driven Ensemble Modeling of Equatorial Ionospheric Electrodynamics: A Case Study During a Minor Storm Period Under Solar Minimum Conditions

AbstractThe dayside equatorial ionospheric electrodynamics exhibit strong variability driven simultaneously by highly changeable external forcings that originate from the solar extreme ultraviolet (EUV), magnetosphere, and lower atmosphere. We investigate this variability by carrying out comprehensive data‐driven ensemble modeling using a coupled model of the thermosphere and ionosphere, with the focus on the vertical E × B drift variability during a solar minimum and minor storm period. The variability of vertical E × B drift in response to the changes and uncertainty of primary forcings (i.e., solar EUV, high‐latitude plasma convection and auroral particle precipitation, and lower‐atmospheric tide and wave forcing) is investigated by ensemble forcing sensitivity experiments that incorporate data‐driven stochastic perturbations of these forcings into the model. Second, the impact of assimilating FORMOsa SATellite‐3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT‐3/COSMIC) electron density profiles (EDPs) on the reduction of uncertainty of the modeled vertical E × B drift variability resulting from inadequately specified external forcing is revealed. The Communication and Navigation Outage Forecasting System (C/NOFS) ion drift velocity observations are used for validation. The validation results support the importance of the use of a data‐driven forcing perturbation methods in ensemble modeling and data assimilation. In conclusion, the solar EUV dominates the global‐scale day‐to‐day variability, while the lower atmosphere tide and wave forcing is critical to determining the regional variability. The modeled vertical E × B drift is also sensitive to the magnetospheric forcing. The ensemble data assimilation of FORMOSAT‐3/COSMIC EDPs helps to reduce the uncertainty and improves agreement of the modeled vertical E × B drifts with C/NOFS observations.

Magnetosphere‐Ionosphere Coupling via Prescribed Field‐Aligned Current Simulated by the TIEGCM

AbstractThe magnetosphere‐ionosphere (MI) coupling is crucial in modeling the thermosphere‐ionosphere (TI) response to geomagnetic activity. In general circulation models (GCMs) the MI coupling is typically realized by specifying the ion convection and auroral particle precipitation patterns from for example, empirical or assimilative models. Assimilative models, such as the Assimilative Mapping of Ionospheric Electrodynamics, have the advantage that the ion convection and auroral particle precipitation patterns are mutually consistent and based on available observations. However, assimilating a large set of diverse data requires expert knowledge and is time consuming. Empirical models, on the other hand, are convenient to use, but do not capture all the observed spatial and temporal variations. With the availability of Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) data, there is an opportunity for employing field‐aligned currents (FAC) in GCMs to represent the MI coupling. In this study, we will introduce a new method which enables us to use observed FAC in GCMs and solve for the interhemispherically asymmetric electric potential distribution. We compare Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) simulations of a geomagnetic storm period using the new approach and two other often‐used methods for specifying MI coupling based on empirical and assimilative high latitude electric potentials. The comparison shows general similarities of the TI storm time response and improved temporal variability of the new method compared to using empirical models, but results also illustrate substantial differences due to our uncertain knowledge about the MI coupling process.

Influence of the Ionosphere on the Parameters of the GPS Navigation Signals during a Geomagnetic Substorm

The influence of geomagnetic activity on slips of navigation signals of the global positioning system (GPS), as well as an increase in the amplitude of jumps in the total electron content at high latitudes, has been studied in detail. It is shown that the navigation signal of the L2 frequency is subject to more frequent malfunctions than the L1 frequencies, both in calm conditions and during geomagnetic disturbances. The probability of total electron content jumps is higher than the probability of phase slips at the L1 and L2 frequencies. The maximum disruptions and the frequency of large jumps in the total electron content are observed during the recovery phase of the geomagnetic substorm. The data from the whole-sky camera, magnetometers, and the interplanetary magnetic field used in this study make it possible to monitor the time evolution of a substorm and to study it in detail. The indicated features of the signal behavior are apparently caused by the precipitation of auroral particles, which usually occur during geomagnetic substorms in high latitude regions.