Studying the dynamics of electric currents and polar caps in ionospheres of two hemispheres during the August 17, 2001 geomagnetic storm

The magnetogram inversion technique (MIT), developed at ISTP SB RAS more than forty years ago, has been used until recently only in the Northern Hemisphere. In recent years, MIT has been improved and extended to make instantaneous calculations of 2D distributions of electric fields, horizontal and field-aligned currents in two polar ionospheres. The calculations were carried out based on one-minute ground-based geomagnetic measurements from the worldwide network of stations in both hemispheres (SuperMAG). In this paper, this extended technique is used in the approximation of uniform ionospheric conductance and is applied for the first time to calculations of equivalent and field-aligned currents in two hemispheres through the example of the August 17, 2001 geomagnetic storm. We have obtained the main and essential result: the advanced MIT-ISTP can calculate large-scale distributions of ionospheric convection and FACs in the Northern (N) and Southern (S) polar ionospheres with a high degree of expected hemispheric similarity between these distributions. Using the said event as an example, we have established that the equivalent and field-aligned currents obtained with the advanced technique exhibit the expected dynamics of auroral electrojets and polar caps in two hemispheres. Hall current intensities in polar caps and auroral electrojets, calculated from the equivalent current function, change fairly synchronously in the N and S hemispheres throughout the magnetic storm. Both (westward and eastward) electrojets of the N hemisphere are markedly more intense than respective electrojets of the S hemisphere, and the Hall current in the north polar cap is almost twice as intense as that in the south one. This interhemispheric asymmetry is likely to be due to seasonal conductance variations, which is implicitly contained in the current function. From FAC distributions we determine auroral oval boundaries and calculate magnetic fluxes through the polar caps in the N and S hemispheres. These magnetic fluxes coincide with an accuracy of about 5 % and change almost synchronously during the magnetic storm. In the N hemisphere, the magnetic flux in the dawn polar cap is more intense that that in the dusk one, and vice versa in the S hemisphere. These asymmetries (dawn–dusk and interhemispheric) in the polar caps are consistent with the theory of reconnection for IMF By>0 and with satellite images of auroral ovals; both of these asymmetries decrease during the substorm expansion phase.

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Geomagnetic method for automatic diagnostics of auroral oval boundaries in two hemispheres of Earth

Solar-Terrestrial Physics ◽

10.12737/stp-72202106 ◽

2021 ◽

Vol 7 (2) ◽

pp. 57-69

Author(s):

Yury Penskikh ◽

Sergey Lunyushkin ◽

Vyacheslav Kapustin

Keyword(s):

Input Data ◽

Large Scale ◽

Auroral Oval ◽

Software Implementation ◽

Automatic Method ◽

Current Function ◽

Ionospheric Convection ◽

Polar Caps ◽

Image Satellite ◽

Field Aligned Current

The ground-based automatic method for determining auroral oval (AO) boundaries developed by the authors [Lunyushkin, Penskikh, 2019] has been modified and expanded to the Southern Hemisphere. Input data of the method contains large-scale distributions of the equivalent current function and field-aligned current density calculated in the polar ionospheres of two hemispheres in a uniform ionospheric conductance approximation based on the magnetogram inversion technique and the geomagnetic database of the world network of stations of the SuperMAG project. The software implementation of the method processes large volumes of time series of input data and produces coordinates of the main boundaries of AO in both hemi- spheres: the boundaries of the ionospheric convection reversal, the AO polar and equatorial boundaries, the lines of maximum density of field-aligned currents and auroral electrojets. The automatic method reduces the processing time for a given amount of data by 2–3 orders of magnitude (up to minutes and hours) compared to the manual method, which requires weeks and months of laborious operator work on the same task, while both methods are comparable in accuracy. The automatic geomagnetic method has been tested for diagnostics of AO boundaries during the isolated substorm of August 27, 2001, for which the expected synchronous dynamics of polar caps in two hemispheres has been confirmed. We also show the AO boundaries identified are in qualitative agreement with simultaneous AO images from the IMAGE satellite, as well as with the results of the OVATION and APM models; the boundary of ionospheric convection reversal, determined by the geomagnetic method in two hemispheres, is consistent with the maps of the electric potential of the ionosphere according to the SuperDARN-RG96 model.

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Geomagnetic method for automatic diagnostics of auroral oval boundaries in two hemispheres of Earth

Solnechno-Zemnaya Fizika ◽

10.12737/szf-72202106 ◽

2021 ◽

Vol 7 (2) ◽

pp. 63-76

Author(s):

Yury Penskikh ◽

Sergey Lunyushkin ◽

Vyacheslav Kapustin

Keyword(s):

Input Data ◽

Large Scale ◽

Auroral Oval ◽

Software Implementation ◽

Automatic Method ◽

Current Function ◽

Ionospheric Convection ◽

Polar Caps ◽

Image Satellite ◽

Field Aligned Current

The ground-based automatic method for determining auroral oval (AO) boundaries developed by the authors [Lunyushkin, Penskikh, 2019] has been modified and expanded to the Southern Hemisphere. Input data of the method contains large-scale distributions of the equivalent current function and field-aligned current density calculated in the polar ionospheres of two hemispheres in a uniform ionospheric conductance approximation based on the magnetogram inversion technique and the geomagnetic database of the world network of stations of the SuperMAG project. The software implementation of the method processes large volumes of time series of input data and produces coordinates of the main boundaries of AO in both hemi- spheres: the boundaries of the ionospheric convection reversal, the AO polar and equatorial boundaries, the lines of maximum density of field-aligned currents and auroral electrojets. The automatic method reduces the processing time for a given amount of data by 2–3 orders of magnitude (up to minutes and hours) compared to the manual method, which requires weeks and months of laborious operator work on the same task, while both methods are comparable in accuracy. The automatic geomagnetic method has been tested for diagnostics of AO boundaries during the isolated substorm of August 27, 2001, for which the expected synchronous dynamics of polar caps in two hemispheres has been confirmed. We also show the AO boundaries identified are in qualitative agreement with simultaneous AO images from the IMAGE satellite, as well as with the results of the OVATION and APM models; the boundary of ionospheric convection reversal, determined by the geomagnetic method in two hemispheres, is consistent with the maps of the electric potential of the ionosphere according to the SuperDARN-RG96 model.

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Extended period of polar cap auroral display: auroral dynamics and relation to the IMF and the ionospheric convection

Annales Geophysicae ◽

10.1007/s00585-995-0854-9 ◽

1995 ◽

Vol 13 (8) ◽

pp. 854-862 ◽

Cited By ~ 5

Author(s):

V. G. Vorobjev ◽

S. V. Leontyev ◽

Ya. I. Feldstein

Keyword(s):

Large Scale ◽

Interplanetary Space ◽

Extended Period ◽

Auroral Oval ◽

Polar Cap ◽

Substorm Activity ◽

Convection Patterns ◽

Northern And Southern Hemispheres ◽

Birkeland Currents ◽

The Imf

Abstract. An unusually extended period (5 h) of polar cap auroral display on 3 August 1986 is examined. Auroras have been investigated using ground-based data as well as measurements from the IMP-8 spacecraft in interplanetary space and simultaneous observations from the polar-orbiting satellites Viking and DE-1 in the northern and southern hemispheres, respectively. It is found that visible Sun-aligned arcs are located inside the transpolar band of the θ-aurora observed from the satellite in ultraviolet wavelengths. The transpolar band can contain several Sun-aligned arcs that move inside the band toward the morning or evening side of the auroral oval independent of the direction of the band movement. Intensifications of polar cap auroras with durations of up to about 30 min are observed. No change has been found in either IMF parameters or substorm activity that can be related to these intensifications. The θ-aurora occurred during a 2-h period when the B z-component of the IMF was negative. A tendency is noted for dawnward (duskward) displacement of the transpolar band when By>0 (By<0) in the southern hemisphere. Simultaneous observations of auroral ovals during interplanetary Bz<0, By<0 and Bx>0 in both hemispheres and convection patterns for Bz<0 and By<0 have been displayed using satellite and ground-based measurements. It was found that the transpolar band of the <theta>-aurora in the sunlit hemisphere was situated in the region of large-scale downward Birkeland currents.

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Polar substorm on 7 December 2015: preonset phenomena and features of auroral breakup

Annales Geophysicae ◽

10.5194/angeo-38-901-2020 ◽

2020 ◽

Vol 38 (4) ◽

pp. 901-918

Author(s):

Vladimir V. Safargaleev ◽

Alexander E. Kozlovsky ◽

Valery M. Mitrofanov

Keyword(s):

Large Scale ◽

Auroral Oval ◽

Auroral Zone ◽

Substorm Onset ◽

Optical Observations ◽

Time Interval ◽

Polar Cap ◽

Local Maxima ◽

Current Disruption ◽

Auroral Breakup

Abstract. Comprehensive analysis of a moderate 600 nT substorm was performed using simultaneous optical observations inside the auroral oval and in the polar cap, combined with data from satellites, radars, and ground magnetometers. The onset took place near the poleward boundary of the auroral oval that is not typical for classical substorms. The substorm onset was preceded by two negative excursions of the interplanetary magnetic field (IMF) Bz component, with a 1 min interval between them, two enhancements of the antisunward convection in the polar cap with the same time interval, and 15 min oscillations in the geomagnetic H component in the auroral zone. The distribution of the pulsation intensity along meridian has two local maxima, namely at the equatorial and poleward boundaries of the auroral oval, where pulsations occurred in the out-of-phase mode resembling the field line resonance. At the initial stage, the auroral breakup developed as the auroral torch stretched and expanded poleward along the meridian. Later it took the form of the large-scale coiling structure that also distinguishes the considered substorm from the classical one. Magnetic, radar, and the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite data show that, before the collapse, the coiling structure was located between two field-aligned currents, namely downward at the poleward boundary of structure and upward at the equatorial boundary. The set of GEOTAIL satellites and ground data fit to the near-tail current disruption scenario of the substorm onset. We suggest that the 15 min oscillations might play a role in the substorm initiation.

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Plasma patches inside the polar cap and auroral oval: the impact on the spaceborne GPS receiver

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2019028 ◽

2019 ◽

Vol 9 ◽

pp. A25 ◽

Cited By ~ 2

Author(s):

Chao Xiong ◽

Fan Yin ◽

Xiaomin Luo ◽

Yaqi Jin ◽

Xin Wan

Keyword(s):

Large Scale ◽

Magnetic Measurements ◽

Auroral Oval ◽

Lower Latitude ◽

Small Scale ◽

Gps Receiver ◽

Polar Cap ◽

Cusp Region ◽

Swarm Satellites ◽

The Impact

In this study, we focus on plasma patches with very dense plasma in the southern hemisphere during the main phase of 2015 St. Patrick’s Day storm. With in situ electron densities exceeding 1.5 × 1012 m−3 at 450–500 km altitude, the patches cause strong signal outages of the global positioning system (GPS) receivers on board Swarm satellites. By using the field-aligned currents derived from the Swarm magnetic measurements, we determined whether the satellites fly inside the auroral oval or not. Different influences on the spaceborne GPS receiver are seen when these patches are located at different latitude regions, e.g., inside the polar cap or auroral oval. The simultaneously measurements of 2 Hz electron density as well as 50 Hz magnetic signatures from Swarm show that when large-scale polar cap patches transported from dayside lower latitude entering the cusp region, irregularities with much finer scale-size are generated; associated with various instabilities inside the cusp region, the small-scale irregularities cause much more severe influence on the GPS signals. This is the first direct evidence to show that when plasma patches are located inside the cusp region, the spaceborne receiver experiences stronger outage of GPS signals.

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Astrid-2 and ground-based observations of the auroral bulge in the middle of the nightside convection throat

Annales Geophysicae ◽

10.5194/angeo-19-633-2001 ◽

2001 ◽

Vol 19 (6) ◽

pp. 633-641 ◽

Cited By ~ 5

Author(s):

G. T. Marklund ◽

T. Karlsson ◽

P. Eglitis ◽

H. Opgenoorth

Keyword(s):

Electric Field ◽

Electric Fields ◽

Large Scale ◽

Current Model ◽

Energetic Electron ◽

Auroral Oval ◽

Plasma Convection ◽

Magnetometer Data ◽

Electric Fields And Currents ◽

Good Agreement

Abstract. Results concerning the electrodynamics of the nightside auroral bulge are presented based on simultaneous satellite and ground-based observations. The satellite data include Astrid-2 measurements of electric fields, currents and particles from a midnight auroral oval crossing and Polar UVI images of the large-scale auroral distribution. The ground-based observations include STARE and SuperDARN electric fields and magnetic records from the Greenland and MIRACLE magnetometer network, the latter including stations from northern Scandinavia north to Svalbard. At the time of the Astrid-2 crossing the ground-based data reveal intense electrojet activity, both to the east and west of the Astrid-2 trajectory, related to the Polar observations of the auroral bulge but not necessarily to a typical substorm. The energetic electron fluxes measured by Astrid-2 across the auroral oval were generally weak being consistent with a gap observed in the auroral luminosity distribution. The electric field across the oval was directed westward, intensifying close to the poleward boundary followed by a decrease in the polar cap. The combined observations suggests that Astrid-2 was moving close to the separatrix between the dusk and dawn convection cells in a region of low conductivity. The constant westward direction of the electric field across the oval indicates that current continuity was maintained, not by polarisation electric fields (as in a Cowling channel), but solely by localized up- and downward field-aligned currents in good agreement with the Astrid-2 magnetometer data. The absence of a polarisation electric field and thus of an intense westward closure current between the dawn and dusk convection cells is consistent with the relatively weak precipitation and low conductivity in the convection throat. Thus, the Cowling current model is not adequate for describing the electrodynamics of the nightside auroral bulge treated here.Key words. Ionosphere (auroral ionosphere; electric fields and currents; plasma convection)

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Polar substorm on 7 December 2015: pre-onset phenomena and features of auroral breakup

10.5194/angeo-2019-118 ◽

2019 ◽

Author(s):

Vladimir V. Safargaleev ◽

Alexander E. Kozlovsky ◽

Valery M. Mitrofanov

Keyword(s):

Large Scale ◽

Auroral Oval ◽

Auroral Zone ◽

Substorm Onset ◽

Optical Observations ◽

Polar Cap ◽

Local Maxima ◽

Current Disruption ◽

Initial Stage ◽

Auroral Breakup

Abstract. Comprehensive analysis of a moderate 600-nT substorm was performed with using simultaneous optical observations inside the auroral oval and in the polar cap, combined with data from satellites, radars, and ground magnetometers. The onset took place near the poleward boundary of the auroral oval that is not typical for classical substorms. The substorm onset was preceded by two negative excursions of the IMF Bz component with 15-min interval between them, two enhancements of the antisunward convection in the polar cap with the same repetition period, and 15-minute oscillations in geomagnetic H-component in the auroral zone. The distribution of the pulsation intensity along meridian has two local maxima – at equatorial and poleward boundaries of the auroral oval where pulsations occurred in the out-of-phase mode resembling the field-line resonance. At initial stage, the auroral breakup developed as auroral torch stretching and expanding poleward along the meridian. Some later it took a form of the large-scale coiling structure that also distinguishes the considered substorm from classical one. Magnetic, radar and AMPERE satellite data show that before the collapse the coiling structure was located between two field-aligned currents: downward at poleward boundary of structure and upward at equatorial boundary. The set of GEOTAIL satellite and ground data fits to the near-tail current disruption scenario of the substorm onset. We suggest that the 15-min oscillations might play a role in the substorm initiation.

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Monopolar and bipolar auroral electric fields and their effects

Annales Geophysicae ◽

10.5194/angeo-28-2027-2010 ◽

2010 ◽

Vol 28 (11) ◽

pp. 2027-2046 ◽

Cited By ~ 11

Author(s):

J. De Keyser ◽

R. Maggiolo ◽

M. Echim

Keyword(s):

High Altitude ◽

Electric Fields ◽

Current System ◽

Analytic Solutions ◽

Auroral Oval ◽

Electrostatic Model ◽

Polar Cap ◽

Magnetospheric Convection ◽

Field Aligned Current ◽

Auroral Current

Abstract. Most of the high-altitude auroral electric fields observed by CLUSTER can be classified into monopolar and bipolar structures. The observations associate monopolar electric fields with polar cap boundary arcs, while bipolar fields tend to be linked to discrete arcs within the auroral oval and to polar cap arcs. The present paper proposes an explanation for this association based on a simple model of the magnetotail configuration and kinetic model computations. The paper introduces a quasi-electrostatic model to describe the auroral current system associated with monopolar and bipolar high-altitude fields. Analytic solutions are presented. The model gives indications about the location of the up- and downward field-aligned current regions, the ionospheric and magnetospheric convection along the arc, the acceleration or deceleration of precipitating particles, and the behaviour of escaping ionospheric ions.

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Ionospheric F-region response to the 26 September 2011 geomagnetic storm in the Antarctica American and Australian sectors

Annales Geophysicae ◽

10.5194/angeo-35-1113-2017 ◽

2017 ◽

Vol 35 (5) ◽

pp. 1113-1129 ◽

Cited By ~ 4

Author(s):

Emilia Correia ◽

Luca Spogli ◽

Lucilla Alfonsi ◽

Claudio Cesaroni ◽

Adriana M. Gulisano ◽

...

Keyword(s):

Southern Hemisphere ◽

Geomagnetic Storm ◽

Electric Fields ◽

Main Phase ◽

First Episode ◽

High Latitudes ◽

Polar Cap ◽

Middle Latitudes ◽

F Region ◽

Gnss Receivers

Abstract. The ionospheric response at middle and high latitudes in the Antarctica American and Australian sectors to the 26–27 September 2011 moderately intense geomagnetic storm was investigated using instruments including an ionosonde, riometer, and GNSS receivers. The multi-instrument observations permitted us to characterize the ionospheric storm-enhanced density (SED) and tongues of ionization (TOIs) as a function of storm time and location, considering the effect of prompt penetration electric fields (PPEFs). During the main phase of the geomagnetic storm, dayside SEDs were observed at middle latitudes, and in the nightside only density depletions were observed from middle to high latitudes. Both the increase and decrease in ionospheric density at middle latitudes can be attributed to a combination of processes, including the PPEF effect just after the storm onset, dominated by disturbance dynamo processes during the evolution of the main phase. Two SEDs–TOIs were identified in the Southern Hemisphere, but only the first episode had a counterpart in the Northern Hemisphere. This difference can be explained by the interhemispheric asymmetry caused by the high-latitude coupling between solar wind and the magnetosphere, which drives the dawn-to-dusk component of the interplanetary magnetic field. The formation of polar TOI is a function of the SED plume location that might be near the dayside cusp from which it can enter the polar cap, which was the case in the Southern Hemisphere. Strong GNSS scintillations were observed at stations collocated with SED plumes at middle latitudes and cusp on the dayside and at polar cap TOIs on the nightside.

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