MHD simulation of the magnetotail during the December 10, 1996, substorm

Wiltberger, M. J.; Pulkkinen, Tuija; Lyon, J. G.; Goodrich, C. C.

doi:10.1029/1999ja000251

Cited by 95 publications

(94 citation statements)

References 34 publications

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“…Birn et al (1996) used resistive MHD simulations to investigate the current disruption and diversion properties. By using a global MHD magnetosphere model, Wiltberger et al (2000) unveiled many fast flow channels in the magnetotail with plasma and magnetic field properties that are consistent with observations conducted by Angelopoulos et al (1992). On the other hand, Lui and Najmi (1997) showed that during the current disruption, the spectrum of accompanied magnetic fluctuations becomes intermittently broad, covering timescales from below to above the ion gyroperiod.…”

Section: Introductionsupporting

confidence: 59%

Statistical analysis of severe magnetic fluctuations in the near-Earth plasma sheet observed by THEMIS-E

Shiokawa

Frühauff

2017

Ann. Geophys.

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Abstract. We statistically analyzed severe magnetic fluctuations in the nightside near-Earth plasma sheet at 6-12 R E (Earth radii; 1 R E = 6371 km), because they are important for non-magnetohydrodynamics (non-MHD) effects in the magnetotail and are considered to be necessary for current disruption in the inside-out substorm model. We used magnetic field data from 2013 and 2014 obtained by the Time History of Events and Macroscale Interactions during Substorms E (THEMIS-E) satellite (sampling rate: 4 Hz). A total of 1283 severe magnetic fluctuation events were identified that satisfied the criteria σ B /B > 0.5, where σ B and B are the standard deviation and the average value of magnetic field intensity during the time interval of the local proton gyroperiod, respectively. We found that the occurrence rates of severe fluctuation events are 0.00118, 0.00899, and 0.0238 % at 6-8, 8-10, and 10-12 R E , respectively, and most events last for no more than 15 s. From these occurrence rates, we estimated the possible scale sizes of current disruption by severe magnetic fluctuations as 3.83 R E 3 by assuming that four substorms with 5 min intervals of current disruption occur every day. The fluctuation events occurred most frequently at the Z GSM (Z distance in the geocentric solar magnetospheric coordinate system) close to the model neutral sheet within 0.2 R E . Most events occur in association with sudden decreases in the auroral electrojet lower (AL) index and magnetic field dipolarization, indicating that they are related to substorms. Sixty-two percent of magnetic fluctuation events were accompanied by ion flow with velocity V > 100 km s −1 , indicating that the violation of ion gyromotion tends to occur during high-speed flow in the near-Earth plasma sheet. The superposed epoch analysis also indicated that the flow speed increases before the severe magnetic fluctuations. We discuss how both the inside-out and outside-in substorm models can explain this increase in flow speeds before magnetic fluctuation events.

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Section: Introductionsupporting

confidence: 59%

Statistical analysis of severe magnetic fluctuations in the near-Earth plasma sheet observed by THEMIS-E

Shiokawa

Frühauff

2017

Ann. Geophys.

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“…The other two substorms were run at a higher resolution (50×48×64). These events have been previously studied to explore issues such as substorm onset Lyon et al, 1998) and the occurrence of fast magnetotail flows (Wiltberger et al, 2000). Here we significantly extend the analysis of these events to determine a common pattern in the evolution of energy storage and release during substorms.…”

Section: Methodsmentioning

confidence: 84%

“…To achieve that global picture of the energy distribution and dynamics in the magnetosphere, the Lyon-Fedder-Mobarry magneto-hydrodynamic code was used to simulate three substorms and calculate the energy in the plasma sheet and lobes during these events. In this paper we present calculations for the substorms of 9 March 1995 Lopez et al, 1998), 10 December 1996 (Wiltberger et al, 2000;Pulkkinen et al, 1999) and 27 August 2001 (Wiltberger et al, 2005a). Our analysis includes calculations of the polar cap flux, lobe energy and plasma sheet energy during growth and expansion phase of the substorms.…”

Section: Introductionmentioning

confidence: 99%

Studies of magnetotail dynamics and energy evolution during substorms using MHD simulations

Brogl¹,

López

Wiltberger³

et al. 2009

Ann. Geophys.

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Abstract. We examine the distribution and propagation of energy in the plasma sheet and lobes using observations and simulations for three substorms. The substorms occurred on 9 March 1995, 10 December 1996, and 27 August 2001 and have been simulated using the Lyon-Fedder-Mobarry magneto-hydrodynamic code. All three events occur over North America and show a clear substorm current wedge over the ground magnetometer chains of Alaska, Canada, and Greenland. The three simulations show the thinning of the plasma sheet during the growth phase of the event and an increase in the relative amount of thermal energy due to the compression of the plasma sheet. Generally, the total lobe energy, polar cap flux, and lobe magnetic field strength simultaneously increase during the growth phase, and polar cap flux and total lobe energy only start dropping at substorm onset, as measured by the CANOPUS magnetometer chain. Starting at time of onset and continuing throughout the expansion phase a transfer of magnetic energy from the lobes into the plasma sheet occurs, with the increase in the plasma sheet energy ranging from 30-40% of the energy that is released from the lobes.

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“…Ohtani et al (2009) suggest that the sources of tailward flows could be the balloon instability and rebound of fast sunward flows near the Earth. The latter mechanism is supported by the fact that tailward flows are normally preceded by fast sunward flows and also by global Magnetohydrodynamics (MHD) simulations (Wiltberger et al, 2000).…”

Section: Introductionmentioning

confidence: 77%

Solar-wind control of plasma sheet dynamics

2015

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Abstract. The purpose of this study is to quantify how solarwind conditions affect the energy and plasma transport in the geomagnetic tail and its large-scale configuration. To identify the role of various effects, the magnetospheric data were sorted according to different solar-wind plasma and interplanetary magnetic field (IMF) parameters: speed, dynamic pressure, IMF north-south component, epsilon parameter, Auroral Electrojet (AE) index and IMF ultra low-frequency (ULF) fluctuation power. We study variations in the average flow speed pattern and the occurrence rate of fast flow bursts in the magnetotail during different solar-wind conditions using magnetospheric data from five Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission spacecraft and solar-wind data from NASA's OMNIWeb. The time interval covers the years from 2008 to 2011 during the deep solar minimum between cycles 23 and 24 and the relatively quiet rising phase of cycle 24. Hence, we investigate magnetospheric processes and solar-windmagnetospheric coupling during a relatively quiet state of the magnetosphere. We show that the occurrence rate of the fast (|V tail | > 100 km s −1 ) sunward flows varies under different solar-wind conditions more than the occurrence of the fast tailward flows. The occurrence frequency of the fast tailward flows does not change much with the solar-wind conditions. We also note that the sign of the IMF B Z has the most visible effect on the occurrence rate and pattern of the fast sunward flows. High-speed flow bursts are more common during the slow than fast solar-wind conditions.

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MHD simulation of the magnetotail during the December 10, 1996, substorm

Cited by 95 publications

References 34 publications

Statistical analysis of severe magnetic fluctuations in the near-Earth plasma sheet observed by THEMIS-E

Statistical analysis of severe magnetic fluctuations in the near-Earth plasma sheet observed by THEMIS-E

Studies of magnetotail dynamics and energy evolution during substorms using MHD simulations

Solar-wind control of plasma sheet dynamics

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