Dynamics of field-aligned currents in two hemispheres during a magnetospheric storm from magnetogram inversion technique data

We continue to study the physical processes occurring during the August 17, 2001 magnetospheric storm by analyzing the dynamics of the intensity of field-aligned currents (FACs) in Iijima—Potemra Region 1 in the polar ionospheres of the two hemispheres, using the modernized magnetogram inversion technique. The results obtained on the dynamics of two types of FAC asymmetry (dawn-dusk and interhemispheric), as well as the previously obtained regularities in the behavior of Hall currents and the polar cap boundaries depending on the large azimuthal component of the interplanetary magnetic field (IMF), observed during the storm, and the seasonal behavior of the conductivity are consistent with the open magnetosphere model and with satellite observations of auroras in two hemispheres. We have shown that the weakening of the asymmetry of two types in the FAC distribution during substorms in the storm under study occurs almost completely in the winter hemisphere and is much weaker in the summer one. We associate this phenomenon with the predominance of the effect of long-term exposure to the azimuthal IMF component in the sunlit polar ionosphere of the summer hemisphere over the substorm symmetrization effect of the night magnetosphere. A symmetrization effect of the polar cap and FACs, created by the solar wind pressure pulse at the end of the storm, is observed. We propose a qualitative explanation of this effect.

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Dynamics of field-aligned currents in two hemispheres during a magnetospheric storm from magnetogram inversion technique data

Solar-Terrestrial Physics ◽

10.12737/stp-71202104 ◽

2021 ◽

Vol 7 (1) ◽

pp. 27-31

Author(s):

Vladimir Mishin ◽

Yuriy Karavaev ◽

Sergey Lunyushkin ◽

Yury Penskikh ◽

Vyacheslav Kapustin

Keyword(s):

Wind Pressure ◽

Physical Processes ◽

Polar Cap ◽

Azimuthal Component ◽

Seasonal Behavior ◽

Inversion Technique ◽

Summer Hemisphere ◽

Solar Wind Pressure ◽

Winter Hemisphere

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Dynamics of the field-aligned currents distribution asymmetry during substorms in the equinox season

Solnechno-Zemnaya Fizika ◽

10.12737/szf-71202105 ◽

2021 ◽

Vol 7 (1) ◽

pp. 40-50

Author(s):

Vladimir Mishin ◽

Vilen Mishin ◽

Marina Kurikalova

Keyword(s):

Pressure Pulse ◽

Wind Pressure ◽

Physical Processes ◽

Polar Cap ◽

Azimuthal Component ◽

Seasonal Behavior ◽

Summer Hemisphere ◽

Solar Wind Pressure ◽

Winter Hemisphere

We continue to study the physical processes occurring during the August 17, 2001 magnetospheric storm by analyzing the dynamics of the intensity of field-aligned currents (FACs) in Iijima—Potemra Region 1 in the polar ionospheres of two hemispheres, using the modernized magnetogram inversion technique. The results obtained on the dynamics of the FAC asymmetry of two types (dawn–dusk and interhemispheric), as well as the previously obtained regularities in the behavior of Hall currents and polar cap boundaries depending on the large azimuthal component of the interplanetary magnetic field (IMF), observed during the storm, and the seasonal behavior of the conductivity are consistent with the open magnetosphere model and with satellite observations of auroras in two hemispheres. We have shown that the weakening of the asymmetry of two types in the FAC distribution during substorms in the storm under study occurs almost completely in the winter hemisphere and is much weaker in the summer one. We associate this phenomenon with the predominance of the effect of long-term exposure to the azimuthal IMF component in the sunlit polar ionosphere of the summer hemisphere over the substorm symmetrization effect of the night magnetosphere. A symmetrization effect of the polar cap and FACs, created by the solar wind pressure pulse at the end of the storm, is observed. We propose a qualitative explanation of this effect.

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Dynamics of the field-aligned currents distribution asymmetry during substorms in the equinox season

Solar-Terrestrial Physics ◽

10.12737/stp-71202105 ◽

2021 ◽

Vol 7 (1) ◽

pp. 32-40

Author(s):

Vladimir Mishin ◽

Vilen Mishin ◽

Marina Kurikalova

Keyword(s):

Pressure Pulse ◽

Wind Pressure ◽

Physical Processes ◽

Polar Cap ◽

Azimuthal Component ◽

Seasonal Behavior ◽

Summer Hemisphere ◽

Solar Wind Pressure ◽

Winter Hemisphere

We continue to study the physical processes occurring during the August 17, 2001 magnetospheric storm by analyzing the dynamics of the intensity of field-aligned currents (FACs) in Iijima—Potemra Region 1 in the polar ionospheres of two hemispheres, using the modernized magnetogram inversion technique. The results obtained on the dynamics of the FAC asymmetry of two types (dawn–dusk and interhemispheric), as well as the previously obtained regularities in the behavior of Hall currents and polar cap boundaries depending on the large azimuthal component of the interplanetary magnetic field (IMF), observed during the storm, and the seasonal behavior of the conductivity are consistent with the open magnetosphere model and with satellite observations of auroras in two hemispheres. We have shown that the weakening of the asymmetry of two types in the FAC distribution during substorms in the storm under study occurs almost completely in the winter hemisphere and is much weaker in the summer one. We associate this phenomenon with the predominance of the effect of long-term exposure to the azimuthal IMF component in the sunlit polar ionosphere of the summer hemisphere over the substorm symmetrization effect of the night magnetosphere. A symmetrization effect of the polar cap and FACs, created by the solar wind pressure pulse at the end of the storm, is observed. We propose a qualitative explanation of this effect.

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Observations of solar wind pressure initiated fast mode waves at geostationary orbit and in the polar cap

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/0021-9169(91)90107-i ◽

1991 ◽

Vol 53 (3-4) ◽

pp. 231-239 ◽

Cited By ~ 22

Author(s):

R.E. Erlandson ◽

D.G. Sibeck ◽

R.E. Lopez ◽

L.J. Zanetti ◽

T.A. Potemra

Keyword(s):

Solar Wind ◽

Wind Pressure ◽

Geostationary Orbit ◽

Fast Mode ◽

Polar Cap ◽

Solar Wind Pressure

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SWMF simulation of field-aligned currents for a varying northward and duskward IMF with nonzero dipole tilt

Annales Geophysicae ◽

10.5194/angeo-26-1461-2008 ◽

2008 ◽

Vol 26 (6) ◽

pp. 1461-1477 ◽

Cited By ~ 9

Author(s):

H. Wang ◽

A. J. Ridley ◽

H. Lühr

Keyword(s):

Open Field ◽

Hemispheric Asymmetry ◽

Closed Field ◽

Polar Cap ◽

Counterclockwise Rotation ◽

Summer Hemisphere ◽

Field Lines ◽

Winter Hemisphere ◽

Dipole Tilt ◽

The Imf

Abstract. This study concentrates on the FACs distribution for the varying northward and duskward interplanetary magnetic field (IMF) conditions when the dipole tilt is nonzero. A global MHD simulation (the Space Weather Modeling Framework, SWMF) has been used to perform this study. Hemispheric asymmetry of the time evolution of northward IMF Bz (NBZ) FACs is found. As the IMF changes from strictly northward to duskward, NBZ FACs shift counterclockwise in both summer and winter hemispheres. However, in the winter hemisphere, the counterclockwise rotation prohibits the duskward NBZ FACs from evolving into the midday R1 FACs. The midday R1 FACs seem to be an intrusion of dawnside R1 FACs. In the summer hemisphere, the NBZ FACs can evolve into the DPY FACs, consisting of the midday R0 and R1 FACs, after the counterclockwise rotation. The hemispheric asymmetry is due to the fact that the dipole tilt favors more reconnection between the IMF and the summer magnetosphere. When mapping the NBZ and DPY FACs into the magnetosphere it is found that the NBZ currents are located on both open and closed field lines, irrespective of the IMF direction. For the DPY FACs the hemispheric asymmetry emerges: the midday R1 FACs and a small part of R0 FACs are on closed field lines in the winter hemisphere, while a small part of the midday R1 FACs and all the R0 FACs are on open field lines in the summer hemisphere. Both IMF By and dipole tilt cause the polar cap hemispheric and local time asymmetric. When the IMF is northward, the summer polar cap is closed on the nightside while the winter polar cap is open. The polar cap boundary tends to move equatorward as the IMF rotates from northward to duskward, except in the summer hemisphere, the polar cap on the dawnside shifts poleward when the clock angle is less than 10°. The further poleward displacement of the polar cap boundary on one oval side is caused by the twist of the tail plasma sheet, which is in accordance with the changing open field lines topology in the magnetotail.

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An unusual giant spiral arc in the polar cap region during the northward phase of a Coronal Mass Ejection

Annales Geophysicae ◽

10.5194/angeo-25-507-2007 ◽

2007 ◽

Vol 25 (2) ◽

pp. 507-517 ◽

Cited By ~ 9

Author(s):

L. Rosenqvist ◽

A. Kullen ◽

S. Buchert

Keyword(s):

Solar Wind ◽

Coronal Mass Ejection ◽

Spiral Structure ◽

Wind Pressure ◽

Polar Cap ◽

Sheath Region ◽

Interplanetary Coronal Mass Ejection ◽

Solar Wind Pressure ◽

Pressure Changes ◽

Mass Ejection

Abstract. The shock arrival of an Interplanetary Coronal Mass Ejection (ICME) at ~09:50 UT on 22 November 1997 resulted in the development of an intense (Dst<−100 nT) geomagnetic storm at Earth. In the early, quiet phase of the storm, in the sheath region of the ICME, an unusual large spiral structure (diameter of ~1000 km) was observed at very high latitudes by the Polar UVI instrument. The evolution of this structure started as a polewardly displaced auroral bulge which further developed into the spiral structure spreading across a large part of the polar cap. This study attempts to examine the cause of the chain of events that resulted in the giant auroral spiral. During this period the interplanetary magnetic field (IMF) was dominantly northward (Bz>25 nT) with a strong duskward component (By>15 nT) resulting in a highly twisted tail plasma sheet. Geotail was located at the equatorial dawnside magnetotail flank and observed accelerated plasma flows exceeding the solar wind bulk velocity by almost 60%. These flows are observed on the magnetosheath side of the magnetopause and the acceleration mechanism is proposed to be typical for strongly northward IMF. Identified candidates to the cause of the spiral structure include a By induced twisted magnetotail configuration, the development of magnetopause surface waves due to the enhanced pressure related to the accelerated magnetosheath flows aswell as the formation of additional magnetopause deformations due to external solar wind pressure changes. The uniqeness of the event indicate that most probably a combination of the above effects resulted in a very extreme tail topology. However, the data coverage is insufficient to fully investigate the physical mechanism behind the observations.

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Changes of dayside auroral distribution caused by a solar wind pressure pulse and associated interplanetary magnetic field disturbances

Annales Geophysicae ◽

10.5194/angeo-25-929-2007 ◽

2007 ◽

Vol 25 (4) ◽

pp. 929-940 ◽

Cited By ~ 3

Author(s):

A. Kozlovsky ◽

M. Meurant ◽

T. Turunen

Keyword(s):

Solar Wind ◽

Auroral Oval ◽

Wind Pressure ◽

Pressure Increase ◽

Polar Cap ◽

Related System ◽

Obvious Effect ◽

Image Satellite ◽

Solar Wind Pressure ◽

The Imf

Abstract. Global auroral images from the IMAGE satellite were used to study statistically changes of the dayside aurora spatial distribution after an abrupt solar wind pressure increase, or so-called "Sudden Impulse" (SI). Contributions from IMF changes associated with a SI were also investigated. The effects of the IMF and pressure variations were separated using a multi-factor correlation analysis. The first prominent effect due to pressure increase is the auroral intensification equatorward of the middle dayside oval within 6 min after a SI occurred. This is consistent with the midday sub-auroral patches. The second effect due to pressure increase is the auroral intensification at high latitudes in the vicinity of the polar cap boundary. For the first 6 min the auroral intensification is most prominent in the postnoon sector. Later on (6–20 min) the intensification occurs in the prenoon sector. The most obvious effect of IMF changes is the "IMF By" effect, an intensification (fading) of the most poleward auroral forms when IMF By becomes negative (positive). This effect occurs 6–20 min after changes in the interplanetary medium. Such an effect is consistent with the IMF By-related system of field-aligned currents. No significant motion of the dayside auroral oval was observed associated with IMF Bz variations. This can be explained by a response time to IMF Bz changes larger than 20 min.

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Magnetospheric reconnection driven by solar wind pressure fronts

Annales Geophysicae ◽

10.5194/angeo-22-1367-2004 ◽

2004 ◽

Vol 22 (4) ◽

pp. 1367-1378 ◽

Cited By ~ 47

Author(s):

A. Boudouridis ◽

E. Zesta ◽

L. R. Lyons ◽

P. C. Anderson ◽

D. Lummerzheim

Keyword(s):

Solar Wind ◽

Auroral Oval ◽

Wind Pressure ◽

Pressure Jump ◽

Polar Cap ◽

Particle Precipitation ◽

Magnetospheric Convection ◽

Solar Wind Pressure ◽

Poleward Expansion ◽

The Imf

Abstract. Recent work has shown that solar wind dynamic pressure changes can have a dramatic effect on the particle precipitation in the high-latitude ionosphere. It has also been noted that the preexisting interplanetary magnetic field (IMF) orientation can significantly affect the resulting changes in the size, location, and intensity of the auroral oval. Here we focus on the effect of pressure pulses on the size of the auroral oval. We use particle precipitation data from up to four Defense Meteorological Satellite Program (DMSP) spacecraft and simultaneous POLAR Ultra-Violet Imager (UVI) images to examine three events of solar wind pressure fronts impacting the magnetosphere under two IMF orientations, IMF strongly southward and IMF Bz nearly zero before the pressure jump. We show that the amount of change in the oval and polar cap sizes and the local time extent of the change depends strongly on IMF conditions prior to the pressure enhancement. Under steady southward IMF, a remarkable poleward widening of the oval at all magnetic local times and shrinking of the polar cap are observed after the increase in solar wind pressure. When the IMF Bz is nearly zero before the pressure pulse, a poleward widening of the oval is observed mostly on the nightside while the dayside remains unchanged. We interpret these differences in terms of enhanced magnetospheric reconnection and convection induced by the pressure change. When the IMF is southward for a long time before the pressure jump, open magnetic flux is accumulated in the tail and strong convection exists in the magnetosphere. The compression results in a great enhancement of reconnection across the tail which, coupled with an increase of magnetospheric convection, leads to a dramatic poleward expansion of the oval at all MLTs (dayside and nightside). For near-zero IMF Bz before the pulse the open flux in the tail, available for closing through reconnection, is smaller. This, in combination with the weaker magnetospheric convection, leads to a more limited poleward expansion of the oval, mostly on the nightside. Key words. Magnetospheric physics (solar windmagnetosphere interactions; magnetospheric configuration and dynamics; auroral phenomena)

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Solar wind and substorm excitation of the wavy current sheet

Annales Geophysicae ◽

10.5194/angeo-27-2457-2009 ◽

2009 ◽

Vol 27 (6) ◽

pp. 2457-2474 ◽

Cited By ~ 25

Author(s):

C. Forsyth ◽

M. Lester ◽

R. C. Fear ◽

E. Lucek ◽

I. Dandouras ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Current Sheet ◽

Pressure Pulse ◽

Wind Pressure ◽

Expansion Velocity ◽

Solar Wind Pressure ◽

Wave Models ◽

Best Fit ◽

The Magnetic Field

Abstract. Following a solar wind pressure pulse on 3 August 2001, GOES 8, GOES 10, Cluster and Polar observed dipolarizations of the magnetic field, accompanied by an eastward expansion of the aurora observed by IMAGE, indicating the occurrence of two substorms. Prior to the first substorm, the motion of the plasma sheet with respect to Cluster was in the ZGSM direction. Observations following the substorms show the occurrence of current sheet waves moving predominantly in the −YGSM direction. Following the second substorm, the current sheet waves caused multiple current sheet crossings of the Cluster spacecraft, previously studied by Zhang et al. (2002). We further this study to show that the velocity of the current sheet waves was similar to the expansion velocity of the substorm aurora and the expansion of the dipolarization regions in the magnetotail. Furthermore, we compare these results with the current sheet wave models of Golovchanskaya and Maltsev (2005) and Erkaev et al. (2008). We find that the Erkaev et al. (2008) model gives the best fit to the observations.

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Ocean resurge-induced impact melt dynamics on the peak-ring of the Chicxulub impact structure, Mexico

International Journal of Earth Sciences ◽

10.1007/s00531-021-02008-w ◽

2021 ◽

Author(s):

Felix M. Schulte ◽

◽

Axel Wittmann ◽

Stefan Jung ◽

Joanna V. Morgan ◽

...

Keyword(s):

Impact Structure ◽

Physical Processes ◽

Hydrothermal Conditions ◽

Chemical Examination ◽

Impact Melt ◽

Target Rock ◽

Single Process ◽

Chicxulub Impact ◽

The Impact

AbstractCore from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucatán shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water–rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water–rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin–Helmholtz and Rayleigh–Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring.

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