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C T Russell - One of the best experts on this subject based on the ideXlab platform.
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magnetospheric multiscale observations of energetic oxygen ions at the duskside Magnetopause during intense substorms
Annales Geophysicae, 2020Co-Authors: Chen Zeng, Roy B. Torbert, S. A. Fuselier, Suping Duan, Chi Wang, James L Burch, B L Giles, C T RussellAbstract:Abstract. Energetic oxygen ions (1–40 keV) observed by the Magnetospheric Multiscale (MMS) satellites at the duskside Magnetopause boundary layer during phase 1 are investigated. There are 57 duskside Magnetopause crossing events identified during intense substorms ( AE>500 nT). These 57 events of energetic O+ at the duskside Magnetopause include 26 events during the expansion phase and 31 events during the recovery phase of intense substorms. It is found that the O+ density in the duskside Magnetopause boundary layer during the recovery phase (0.081 cm −3 ) is larger than that during the expansion phase (0.069 cm −3 ). The 26 events of energetic O+ ions at the duskside Magnetopause during intense substorm expansion phase are all under the southward interplanetary magnetic field (IMF). There are only seven events under northward IMF, and they all occurred during the intense substorm recovery phase. The density of energetic O+ at the duskside Magnetopause ranges from 0.007 to 0.599 cm −3 . The maximum density of O+ occurred during the intense substorm recovery phase and under southward IMF. When the IMF is southward, the O+ density shows an exponential increase with the IMF Bz absolute value. Meanwhile, the O + / H + density ratio shows an exponential growth with the IMF By . These results agree with previous studies in the near-Earth magnetosphere during intense substorm. It is suggested that O+ abundance in the duskside Magnetopause boundary layer has a close relation to O+ variations in the near-Earth magnetosphere during intense substorms.
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mms observations of energetic oxygen ions at the low latitude duskside Magnetopause during intense substorms
Annales Geophysicae, 2019Co-Authors: Chen Zeng, Roy B. Torbert, S. A. Fuselier, Suping Duan, Chi Wang, James L Burch, B L Giles, C T RussellAbstract:Abstract. Energetic oxygen ions O+ (> 1 keV) observed by the Magnetospheric Multiscale (MMS) satellites at the dusk flank Magnetopause during the phase 1a and 1b are investigated. There are 31 dusk flank Magnetopause crossing events during intense substorms (AE > 500 nT) are identified. These 31 events of energetic O+ at the dusk flank Magnetopause include 9 events during the expansion phase and 22 events during the recovery phase of intense substorms. It is noted that 9 events of energetic O+ ion at the dusk flank Magnetopause during intense substorms expansion phase are all under the southward IMF conditions. The number density of energetic O+ at the dusk flank Magnetopause ranges from 0.01 cm−3 to 0.2 cm−3. The maximum number density ratio of O+/H+ is ~ 0.055 during intense substorm recovery phase with AE index about 610 nT and under the northward interplanetary magnetic field (IMF). The number density ratio of O+/H+ also shows an exponential increase with the IMF By. While IMF Bz seems play a minor role in O+ abundance at the dusk flank Magnetopause during intense substrom. Our observations suggest that energetic oxygen ions play a key role in the mass and energy transferring from the tail to the dayside in the magnetosphere during intense substorms.
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electrodynamic context of Magnetopause dynamics observed by magnetospheric multiscale
Geophysical Research Letters, 2016Co-Authors: B J Anderson, F. Plaschke, C T Russell, R J Strangeway, W Magnes, D Fischer, H Korth, V G Merkin, R J Barnes, C L WatersAbstract:Magnetopause observations by Magnetospheric Multiscale (MMS) and Birkeland currents observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment are used to relate Magnetopause encounters to ionospheric electrodynamics. MMS Magnetopause crossings on 15 August and 19 September 2015 occurred earthward of expectations due to solar wind ram pressure alone and coincided with equatorward expansion of the Birkeland currents. Magnetopause erosion, consistent with expansion of the polar cap, contributed to the Magnetopause crossings. The ionospheric projections of MMS during the events and at times of the Magnetopause crossings indicate that MMS observations are related to the main path of flux transport in one case but not in a second. The analysis provides a way to routinely relate in situ observations to the context of in situ convection and flux transport.
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Magnetopause erosion during the 17 march 2015 magnetic storm combined field aligned currents auroral oval and Magnetopause observations
Geophysical Research Letters, 2016Co-Authors: G. Le, H Luhr, B J Anderson, C T Russell, R J Strangeway, J A Slavin, H J Singer, Y Zhang, T Huang, K R BromundAbstract:We present multimission observations of field-aligned currents, auroral oval, and Magnetopause crossings during the 17 March 2015 magnetic storm. Dayside reconnection is expected to transport magnetic flux, strengthen field-aligned currents, lead to polar cap expansion and Magnetopause erosion. Our multimission observations assemble evidence for all these manifestations. After a prolonged period of strongly southward interplanetary magnetic field, Swarm and AMPERE observe significant intensification of field-aligned currents .The dayside auroral oval, as seen by DMSP, appears as a thin arc associated with ongoing dayside reconnection. Both the field-aligned currents and the auroral arc move equatorward reaching as low as approx. 60 deg. magnetic latitude. Strong Magnetopause erosion is evident in the in situ measurements of the Magnetopause crossings by GOES 13/15 and MMS. The coordinated Swarm, AMPERE, DMSP, MMS and GOES observations, with both global and in situ coverage of the key regions, provide a clear demonstration of the effects of dayside reconnection on the entire magnetosphere.
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the importance of plasma β conditions for magnetic reconnection at saturn s Magnetopause
Geophysical Research Letters, 2012Co-Authors: M. K. Dougherty, C T Russell, A Masters, J P Eastwood, M Swisdak, M F Thomsen, N Sergis, F J Crary, A J CoatesAbstract:[1] Magnetic reconnection is an important process that occurs at the Magnetopause boundary of Earth's magnetosphere because it leads to transport of solar wind energy into the system, driving magnetospheric dynamics. However, the nature of Magnetopause reconnection in the case of Saturn's magnetosphere is unclear. Based on a combination of Cassini spacecraft observations and simulations we propose that plasma βconditions adjacent to Saturn's Magnetopause largely restrict reconnection to regions of the boundary where the adjacent magnetic fields are close to anti-parallel, severely limiting the fraction of the Magnetopause surface that can become open. Under relatively low magnetosheathβconditions we suggest that this restriction becomes less severe. Our results imply that the nature of solar wind-magnetosphere coupling via reconnection can vary between planets, and we should not assume that the nature of this coupling is always Earth-like. Studies of reconnection signatures at Saturn's Magnetopause will test this hypothesis.
J. H. Shue - One of the best experts on this subject based on the ideXlab platform.
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Magnetopause expansions for quasi radial interplanetary magnetic field themis and geotail observations
arXiv: Space Physics, 2013Co-Authors: J. H. Shue, H Hasegawa, D G Sibeck, A. V. Dmitriev, A. V. Suvorova, J. P. Mcfadden, K L Ackerson, K JelinekAbstract:We report THEMIS and Geotail observations of prolonged Magnetopause (MP) expansions during long-lasting intervals of quasi-radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: the Magnetopause was located more than 3 RE and ~7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi-radial IMF conditions, indicating steady-state situations. For an observed solar wind pressure of ~1.1-1.3 nPa, the new equilibrium subsolar MP position lay at ~14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The Magnetopause expansions result from significant decreases in the total pressure of the high-beta magnetosheath, which we term the low-pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20 ~ 25 grad, high Mach numbers and proton plasma beta<1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the Magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the Magnetopause was therefore 0.2, extremely small. The equilibrium location of the Magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
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Magnetopause expansions for quasi radial interplanetary magnetic field themis and geotail observations
Journal of Geophysical Research, 2010Co-Authors: J. H. Shue, H Hasegawa, D G Sibeck, A. V. Dmitriev, A. V. Suvorova, J. P. Mcfadden, K L Ackerson, K JelinekAbstract:[1] We report Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geotail observations of prolonged Magnetopause (MP) expansions during long-lasting intervals of quasi-radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: The Magnetopause was located more than 3 RE and ∼7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi-radial IMF conditions, indicating steady state situations. For an observed solar wind pressure of ∼1.1–1.3 nPa, the new equilibrium subsolar MP position lay at ∼14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The Magnetopause expansions result from significant decreases in the total pressure of the high-β magnetosheath, which we term the low-pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20°–25°, high Mach numbers and proton plasma β ≤ 1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the Magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the Magnetopause was therefore 0.2, extremely small. The equilibrium location of the Magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
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Anomalous magnetosheath flows and distorted subsolar Magnetopause for radial interplanetary magnetic fields
Geophysical Research Letters, 2009Co-Authors: J. H. Shue, J. K. Chao, James P. Mcfadden, Alexandra Suvorova, Vassilis Angelopoulos, P Song, Karl-heinz Glassmeier, F. PlaschkeAbstract:On 12 August 2007 from 1436 to 1441 UT, when the five THEMIS probes (THA, THB, THC, THD, and THE) were located near the subsolar Magnetopause, a sunward flow was observed in the magnetosheath. A fast antisunward flow (-280 km/s) was observed in the magnetosheath before the sunward flow. Although THA observed this fast anti-sunward flow, THC and THD, which were also in the magnetosheath, instead observed a slow flow, indicating that the fast flow was small in scale. With the observed flow vectors and the Magnetopause normal directions estimated from tangential discontinuity analysis, we conclude that this fast flow creates an indentation on the Magnetopause, 1 R < inf > E < /inf > deep and 2 R < inf > E < /inf > wide. The Magnetopause subsequently rebounds, rotating the flow direction sunward along the surface of the Magnetopause. The fast flow is likely related to the radial interplanetary magnetic field. Copyright 2009 by the American Geophysical Union.
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The location and shape of the Magnetopause
Planetary and Space Science, 2002Co-Authors: J. H. Shue, Paul SongAbstract:Abstract In this paper, we provide a comprehensive review on the development of Magnetopause location research over the past four decades, starting from John R. Spreiter's early fundamental work on the shape of the Magnetopause as a function of dipole tilt angle. Several 2-D empirical Magnetopause location models were developed later using in situ Magnetopause crossings mainly from low-latitude satellites under an assumption of axisymmetry of the Magnetopause shape to the Sun-Earth line. As more Magnetopause crossings at higher latitudes and in the distant tail were obtained from space missions, interest in the 3-D shape of the Magnetopause, including the high-latitude Magnetopause and magnetotail cross section, is growing. Increasing computer power has made 3-D numerical modeling and artificial neutral network technique more efficient to derive the global Magnetopause shape and its dependence on solar wind conditions. Presently, the Magnetopause location has been modeled as functions of the solar wind dynamic pressure and interplanetary magnetic field (IMF) B z . Some evidence has shown that Magnetopause erosion saturates when the southward IMF is extremely strong.
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The normal directions and shape of the Magnetopause
Science in China Series D: Earth Sciences, 1998Co-Authors: Jianyong Lü, J. H. Shue, J. K. Chao, H. C. Fu, P SongAbstract:The minimum variance and tangential discontinuity analyses are used to find the normal directions of the Magnetopause using 550 crossings from ISEE 1 and 2, AMPTE/IRM, and IMP 8 satellites. Then, the average shape of the Magnetopause is studied by using two-region fit procedure. These studies show: (i) most of the crossings are reasonably characterized as tangential discontinuity; (ii) there does appear to be east-west and north-south asymmetry in the shape of the Magnetopause; (iii) the Magnetopause in the equatorial region is swept back from the vacuum location for both northward and southward IMF, which means that the simple single conic section used in previous fits may not be appropriate to the entire shape of the Magnetopause, especially at the nightside.
S. A. Fuselier - One of the best experts on this subject based on the ideXlab platform.
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magnetospheric multiscale observations of energetic oxygen ions at the duskside Magnetopause during intense substorms
Annales Geophysicae, 2020Co-Authors: Chen Zeng, Roy B. Torbert, S. A. Fuselier, Suping Duan, Chi Wang, James L Burch, B L Giles, C T RussellAbstract:Abstract. Energetic oxygen ions (1–40 keV) observed by the Magnetospheric Multiscale (MMS) satellites at the duskside Magnetopause boundary layer during phase 1 are investigated. There are 57 duskside Magnetopause crossing events identified during intense substorms ( AE>500 nT). These 57 events of energetic O+ at the duskside Magnetopause include 26 events during the expansion phase and 31 events during the recovery phase of intense substorms. It is found that the O+ density in the duskside Magnetopause boundary layer during the recovery phase (0.081 cm −3 ) is larger than that during the expansion phase (0.069 cm −3 ). The 26 events of energetic O+ ions at the duskside Magnetopause during intense substorm expansion phase are all under the southward interplanetary magnetic field (IMF). There are only seven events under northward IMF, and they all occurred during the intense substorm recovery phase. The density of energetic O+ at the duskside Magnetopause ranges from 0.007 to 0.599 cm −3 . The maximum density of O+ occurred during the intense substorm recovery phase and under southward IMF. When the IMF is southward, the O+ density shows an exponential increase with the IMF Bz absolute value. Meanwhile, the O + / H + density ratio shows an exponential growth with the IMF By . These results agree with previous studies in the near-Earth magnetosphere during intense substorm. It is suggested that O+ abundance in the duskside Magnetopause boundary layer has a close relation to O+ variations in the near-Earth magnetosphere during intense substorms.
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mms observations of energetic oxygen ions at the low latitude duskside Magnetopause during intense substorms
Annales Geophysicae, 2019Co-Authors: Chen Zeng, Roy B. Torbert, S. A. Fuselier, Suping Duan, Chi Wang, James L Burch, B L Giles, C T RussellAbstract:Abstract. Energetic oxygen ions O+ (> 1 keV) observed by the Magnetospheric Multiscale (MMS) satellites at the dusk flank Magnetopause during the phase 1a and 1b are investigated. There are 31 dusk flank Magnetopause crossing events during intense substorms (AE > 500 nT) are identified. These 31 events of energetic O+ at the dusk flank Magnetopause include 9 events during the expansion phase and 22 events during the recovery phase of intense substorms. It is noted that 9 events of energetic O+ ion at the dusk flank Magnetopause during intense substorms expansion phase are all under the southward IMF conditions. The number density of energetic O+ at the dusk flank Magnetopause ranges from 0.01 cm−3 to 0.2 cm−3. The maximum number density ratio of O+/H+ is ~ 0.055 during intense substorm recovery phase with AE index about 610 nT and under the northward interplanetary magnetic field (IMF). The number density ratio of O+/H+ also shows an exponential increase with the IMF By. While IMF Bz seems play a minor role in O+ abundance at the dusk flank Magnetopause during intense substrom. Our observations suggest that energetic oxygen ions play a key role in the mass and energy transferring from the tail to the dayside in the magnetosphere during intense substorms.
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mass loading the earth s dayside Magnetopause boundary layer and its effect on magnetic reconnection
Geophysical Research Letters, 2019Co-Authors: S. A. Fuselier, K. J. Trattner, S. M. Petrinec, S Toledoredondo, N Aunai, M H Denton, M Andre, C R Chappell, A GlocerAbstract:When the interplanetary magnetic field is northward for a period of time, O + from the high-latitude ionosphere escapes along reconnected magnetic field lines into the dayside Magnetopause boundary layer. Dual-lobe reconnection closes these field lines, which traps O + and mass loads the boundary layer. This O + is an additional source of magnetospheric plasma that interacts with magnetosheath plasma through magnetic reconnection. This mass loading and interaction is illustrated through analysis of a Magnetopause crossing by the Magnetospheric Multiscale spacecraft. While in the O +-rich boundary layer, the interplanetary magnetic field turns southward. As the Magnetospheric Multiscale spacecraft cross the high-shear Magnetopause, reconnection signatures are observed. While the reconnection rate is likely reduced by the mass loading, reconnection is not suppressed at the Magnetopause. The high-latitude dayside ionosphere is therefore a source of magnetospheric ions that contributes often to transient reduction in the reconnection rate at the dayside Magnetopause.
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Magnetospheric ion influence at the dayside Magnetopause
Journal of Geophysical Research, 2017Co-Authors: S. A. Fuselier, K. J. Trattner, S. M. Petrinec, J. L. Burch, R G Gomez, J. Mukherjee, Kevin Genestreti, S. K. Vines, Jerry Goldstein, Benoit LavraudAbstract:Magnetospheric ions have the potential to affect magnetic reconnection at the Magnetopause. The results of a survey of magnetospheric ions near the Magnetopause are reported here. Composition measurements from the Magnetospheric Multiscale (MMS) mission are used to determine the total mass density of all magnetospheric ions and distinguish two populations of magnetospheric ions: the warm plasma cloak and the plasmaspheric drainage plume. The warm plasma cloak can contain substantial O+ and the plasmaspheric plume can contain substantial He+. The results of the survey show that, for nominal magnetospheric activity, the warm plasma cloak and plasmaspheric plume will reduce the normalized reconnection rate at the Magnetopause by greater than 20% only a few percent of the time.
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comparison of magnetospheric multiscale ion jet signatures with predicted reconnection site locations at the Magnetopause
Geophysical Research Letters, 2016Co-Authors: S. M. Petrinec, S. A. Fuselier, K. J. Trattner, J. L. Burch, R G Gomez, W S Lewis, R E Ergun, B H Mauk, C J PollockAbstract:Magnetic reconnection at the Earths Magnetopause is the primary process by which solar wind plasma and energy gains access to the magnetosphere. One indication that magnetic reconnection is occurring is the observation of accelerated plasma as a jet tangential to the Magnetopause. The direction of ion jets along the Magnetopause surface as observed by the Fast Plasma Instrument (FPI) and the Hot Plasma Composition Analyzer (HPCA) instrument on board the recently launched Magnetospheric Multiscale (MMS) set of spacecraft is examined. For those cases where ion jets are clearly discerned, the direction of origin compares well statistically with the predicted location of magnetic reconnection using convected solar wind observations in conjunction with the Maximum Magnetic Shear model.
D G Sibeck - One of the best experts on this subject based on the ideXlab platform.
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statistical analysis of the plasmaspheric plume at the Magnetopause
Journal of Geophysical Research, 2013Co-Authors: B M Walsh, D G Sibeck, Y Nishimura, Vassilis AngelopoulosAbstract:[1] During times of enhanced magnetospheric convection, cold dense plasma from the plasmasphere can form a plume extending sunward toward the dayside Magnetopause. A statistical study is presented of cold high-density plasmaspheric plasma at the Magnetopause. Observations from the Time History of Events and Macroscale Interactions (THEMIS) spacecraft show the plume to be present at the dayside Magnetopause during 12.5% (148 of 1184) of the crossings. Its most common location in magnetic local time when contacting the Magnetopause is at 13.6 h. The Magnetopause crossings show evidence for reconnection in 68% of events with the plume while only 47% of events without plume. Although the plume is more likely to be observed at the Magnetopause when reconnection is occurring, the typical reconnection jet velocity is lower for plume events than nonplume events, indicating the presence of the plume may be slowing the efficiency of the reconnection process.
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Magnetopause expansions for quasi radial interplanetary magnetic field themis and geotail observations
arXiv: Space Physics, 2013Co-Authors: J. H. Shue, H Hasegawa, D G Sibeck, A. V. Dmitriev, A. V. Suvorova, J. P. Mcfadden, K L Ackerson, K JelinekAbstract:We report THEMIS and Geotail observations of prolonged Magnetopause (MP) expansions during long-lasting intervals of quasi-radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: the Magnetopause was located more than 3 RE and ~7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi-radial IMF conditions, indicating steady-state situations. For an observed solar wind pressure of ~1.1-1.3 nPa, the new equilibrium subsolar MP position lay at ~14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The Magnetopause expansions result from significant decreases in the total pressure of the high-beta magnetosheath, which we term the low-pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20 ~ 25 grad, high Mach numbers and proton plasma beta<1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the Magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the Magnetopause was therefore 0.2, extremely small. The equilibrium location of the Magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
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Magnetopause expansions for quasi radial interplanetary magnetic field themis and geotail observations
Journal of Geophysical Research, 2010Co-Authors: J. H. Shue, H Hasegawa, D G Sibeck, A. V. Dmitriev, A. V. Suvorova, J. P. Mcfadden, K L Ackerson, K JelinekAbstract:[1] We report Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geotail observations of prolonged Magnetopause (MP) expansions during long-lasting intervals of quasi-radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: The Magnetopause was located more than 3 RE and ∼7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi-radial IMF conditions, indicating steady state situations. For an observed solar wind pressure of ∼1.1–1.3 nPa, the new equilibrium subsolar MP position lay at ∼14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The Magnetopause expansions result from significant decreases in the total pressure of the high-β magnetosheath, which we term the low-pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20°–25°, high Mach numbers and proton plasma β ≤ 1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the Magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the Magnetopause was therefore 0.2, extremely small. The equilibrium location of the Magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
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solar wind control of the Magnetopause shape location and motion
Journal of Geophysical Research, 1991Co-Authors: D G Sibeck, Ramon Lopez, E C RoelofAbstract:We have assembled a data set of 1821 Magnetopause crossings. Separate fits to subsets of this data set determine the Magnetopause location as a function of solar wind dynamic pressure and interplanetary magnetic field orientation. Solar wind dynamic pressure variations produce self-similar Magnetopause motion on time scales of one hour or longer. We verify the pressure balance relationship between the solar wind dynamic pressure and the location of the subsolar Magnetopause. We quantify the relationship between the IMF Bz, region l Birkeland current strength, the position of the subsolar Magnetopause, and the shape of the dayside magnetosphere. Cross sections of the dayside Magnetopause in planes perpendicular to the Earth-Sun line are oblate.
A. V. Suvorova - One of the best experts on this subject based on the ideXlab platform.
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The Shape of Strongly Disturbed Dayside Magnetopause
Terrestrial Atmospheric and Oceanic Sciences, 2013Co-Authors: A. V. Dmitriev, A. V. SuvorovaAbstract:During strong geomagnetic disturbances, the Earth’s magnetosphere exhibits unusual and nonlinear interaction with the incident flow of magnetized solar wind plasma. Global Magneto-hydro-dynamic (MHD) modeling of the magnetosphere predicts that the storm-time effects at the Magnetopause result from the abnormal plasma transport and/or extremely strong field aligned currents. In-situ observations of the magnetospheric boundary, Magnetopause, by Geosynchronous Operational Environmental Satellite (GOES) allowed us to find experimentally such effects as a saturation of the dayside reconnection, unusual bluntness and prominent duskward skewing of the nose Magnetopause. The saturation and duskward skewing were attributed to the storm-time Magnetopause formation under strong southward interplanetary magnetic field (IMF). The unusual bluntness was observed during both high solar wind pressure and strong southward IMF. We suggest that these phenomena are caused by a substantial contribution of the cross-tail current magnetic field and the hot magnetospheric plasma from the asymmetrical ring current into the pressure balance at the dayside Magnetopause.
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Magnetopause expansions for quasi radial interplanetary magnetic field themis and geotail observations
arXiv: Space Physics, 2013Co-Authors: J. H. Shue, H Hasegawa, D G Sibeck, A. V. Dmitriev, A. V. Suvorova, J. P. Mcfadden, K L Ackerson, K JelinekAbstract:We report THEMIS and Geotail observations of prolonged Magnetopause (MP) expansions during long-lasting intervals of quasi-radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: the Magnetopause was located more than 3 RE and ~7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi-radial IMF conditions, indicating steady-state situations. For an observed solar wind pressure of ~1.1-1.3 nPa, the new equilibrium subsolar MP position lay at ~14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The Magnetopause expansions result from significant decreases in the total pressure of the high-beta magnetosheath, which we term the low-pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20 ~ 25 grad, high Mach numbers and proton plasma beta<1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the Magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the Magnetopause was therefore 0.2, extremely small. The equilibrium location of the Magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
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Equatorial trench at the Magnetopause under saturation
arXiv: Space Physics, 2012Co-Authors: A. V. Dmitriev, A. V. SuvorovaAbstract:Magnetic data from GOES geosynchronous satellites were applied for statistical study of the low-latitude dayside Magnetopause under a strong interplanetary magnetic field of southward orientation when the reconnection at the Magnetopause was saturated. From minimum variance analysis, we determined the Magnetopause orientation and compared it with predictions of a reference model. The Magnetopause shape was found to be substantially distorted by a duskward shifting such that the nose region appeared in the postnoon sector. At equatorial latitudes, the shape of Magnetopause was characterized by a prominent bluntness and by a trench formed in the postnoon sector. The origin of distortions was regarded in the context of the storm-time magnetospheric currents and the large-scale quasi-state reconnection at the dayside Magnetopause.
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Magnetopause expansions for quasi radial interplanetary magnetic field themis and geotail observations
Journal of Geophysical Research, 2010Co-Authors: J. H. Shue, H Hasegawa, D G Sibeck, A. V. Dmitriev, A. V. Suvorova, J. P. Mcfadden, K L Ackerson, K JelinekAbstract:[1] We report Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geotail observations of prolonged Magnetopause (MP) expansions during long-lasting intervals of quasi-radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: The Magnetopause was located more than 3 RE and ∼7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi-radial IMF conditions, indicating steady state situations. For an observed solar wind pressure of ∼1.1–1.3 nPa, the new equilibrium subsolar MP position lay at ∼14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The Magnetopause expansions result from significant decreases in the total pressure of the high-β magnetosheath, which we term the low-pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20°–25°, high Mach numbers and proton plasma β ≤ 1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the Magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the Magnetopause was therefore 0.2, extremely small. The equilibrium location of the Magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
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Dayside Magnetopause models
Radiation Measurements, 1999Co-Authors: A. V. Suvorova, A. V. Dmitriev, S. N. KuznetsovAbstract:Abstract A review of empirical data-based models of the Magnetopause and a comparative analysis are given with special attention to the dynamics of the dayside boundary. Recently different research groups have presented new Magnetopause models as an alternative to the model of Roelof and Sibeck (1993, J. Geophys. Res. 94, 15, 125). All models have a greater parametric extent than the model of Roelof and Sibeck and allow prediction of the Magnetopause location during extreme solar wind and IMF conditions. The models of Shue et al. (1997, J. Geophys. Res. 102, 9497–9511) and Kuznetsov et al. (1998) , developed using classic multi-factor regression analysis are two-dimensional and bivariate. The model of Dmitriev et al. (1999) created using artificial neural networks (ANNs) is three-dimensional and contains multiple parameters. A statistical study of Kuznetsov et al. confirmed by the ANN modeling of Dmitriev et al. has shown that the shape of dayside Magnetopause has dawn–dusk asymmetry. The uncertainty in the determination of the dayside Magnetopause position is practically the same for these models in spite of some discrepancies of the model results caused by different data sets, different assumptions and functional forms, different treatment methods of the models.