RCM-E simulation of ion acceleration during an idealized plasma sheet bubble injection

Yang, Jian; Toffoletto, F.; Wolf, R. A.; Sazykin, S.

doi:10.1029/2010ja016346

Cited by 118 publications

(187 citation statements)

References 56 publications

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“…Thus our case study suggests that a preonset azimuthal pressure gradient buildup is common near the onset location within the inner plasma sheet, and this condition may be easily disturbed when the reduced entropy plasma is transported into the inner plasma sheet region. It is also possible that the preonset pressure gradient enhancement near the inner plasma sheet region that we have observed could be related to the pressure enhancement ahead of an earthward moving low‐entropy flow channel [ Yang et al , 2011]. This transient azimuthal pressure gradient change before substorm onset should be further investigated using more detailed observations and instability analysis to determine the role it plays in leading to substorm onsets.…”

Section: Summary and Discussionmentioning

confidence: 94%

Near-Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

et al. 2011

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[1] The azimuthal plasma pressure gradient in the near-Earth plasma sheet makes crucial contributions to field-aligned current (FAC) formation. Numerical simulations and statistical observations have shown that a plasma pressure peak tends to build up in the premidnight region of the near-Earth plasma sheet during the substorm growth phase owing to enhanced magnetic drift. This leads to azimuthal pressure gradients in this region. The temporal variation of the azimuthal pressure gradient may provide an indication for the FAC variations associated with the substorm growth phase and may set up a plasma sheet precondition for the substorm onset being triggered near this region. We take advantage of two of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft separated azimuthally near the orbit apogee and investigate the azimuthal plasma pressure gradient before substorm onset in the R ∼10-12 R E region. Equatorial plasma pressure is estimated by removing the curvature force effect. Five events with the spacecraft footprints mapped very close to the aurora onset region were selected. These events show substantial duskward pressure gradient enhancement 1-5 min before onset. The onset arc, which results from enhanced energetic electron precipitation, was found to intensify simultaneously with the pressure gradient enhancement before onset breakup occurs. Since the energy and energy flux of precipitating electrons reflect the upward FAC strength, these results indicate that the duskward azimuthal pressure gradient enhancement is associated with enhanced upward FAC during the late growth phase and leads to the intensification of the onset auroral arc soon before it breaks up. It is possible that this pressure gradient enhancement may lead to ballooning mode instability and thus substorm onset along the intensifying arc.Citation: Xing, X

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Section: Summary and Discussionmentioning

confidence: 94%

Near-Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

et al. 2011

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“…This signifies magnetotail relaxation from its stretched configuration to its previous configuration (i.e., from Figures 3b to 3a) [see also Fairfield, 1973]. A dipolarization is usually believed to be associated with SCW formation [e.g., Yang et al, 2011]. Region-2-type FACs do not appear, however.…”

Section: Event 1 Inmentioning

confidence: 99%

Distribution of Region 1 and 2 currents in the quiet and substorm time plasma sheet from THEMIS observations

Liu

Angelopoulos

Chu

et al. 2016

Geophysical Research Letters

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Although Earth's Region 1 and 2 currents are related to activities such as substorm initiation, their magnetospheric origin remains unclear. Utilizing the triangular configuration of THEMIS probes at 8–12 RE downtail, we seek the origin of nightside Region 1 and 2 currents. Our statistical study reveals that both kinds of currents exist in the plasma sheet during quiet and active times. Region 2 currents are deep inside the plasma sheet; Region 1 currents, which are farther away from the neutral sheet, extend to the plasma sheet boundary layer. At geomagnetic quiet times, the separation between the two currents is located ~2.5 RE from the neutral sheet. During substorms, the separation migrates toward (away from) the neutral sheet as the plasma sheet thins (thickens). These findings suggest that the plasma sheet is a source of Region 1 and 2 currents and its deformation is associated with redistribution of FAC sources in the magnetotail.

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“…The flux tubes immediately earthward of the bubbles are pushed inward by the bubbles. They are the other element that also plays an important role in the pressure buildup [Zhang et al, 2008;Yang et al, 2011]. The electric field that is concentrated inside a bubble channel leaks out at the head of the bubble, which yields strong earthward E × B drift velocity there.…”

Section: 1002/2015ja021398mentioning

confidence: 99%

“…Bubbles accelerate to a high speed due to the earthward tension force inside their depleted flux tubes. Those BBFs/bubbles are believed to account for the majority of transport in the plasma sheet [e.g., Angelopoulos et al, 1994], serving as an important mechanism for particle acceleration and transport from the magnetotail to the inner magnetosphere [e.g., Lyons et al, 2003;Birn et al, 2011;Yang et al, 2011]. They can penetrate deep into the inner magnetosphere through interchange instability [e.g., Wolf et al, 2009], which often leads to magnetic field dipolarization and particle energization during storm times [Ohtani et al, 2007;Gkioulidou et al, 2014;Turner et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, the Rice Convection Model (RCM) and the Rice Convection Model-Equilibrium (RCM-E) have been extensively used to investigate how the plasma inside depleted flux tubes is transported in the nearEarth region [Lemon et al, 2004;Zhang et al, 2008;Zhang et al, 2009aZhang et al, , 2009bYang et al, 2008Yang et al, , 2011Yang et al, , 2012Yang et al, , 2014aYang et al, , 2014b. The model uses the slow-flow approximation and assumes an isotropic pressure distribution along magnetic field lines.…”

Section: Introductionmentioning

confidence: 99%

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On the contribution of plasma sheet bubbles to the storm time ring current

et al. 2015

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Particle injections occur frequently inside 10 Re during geomagnetic storms. They are commonly associated with bursty bulk flows or plasma sheet bubbles transported from the tail to the inner magnetosphere. Although observations and theoretical arguments have suggested that they may have an important role in storm time dynamics, this assertion has not been addressed quantitatively. In this paper, we investigate which process is dominant for the storm time ring current buildup: large‐scale enhanced convection or localized bubble injections. We use the Rice Convection Model‐Equilibrium (RCM‐E) to model a series of idealized storm main phases. The boundary conditions at 14–15 Re on the nightside are adjusted to randomly inject bubbles to a degree roughly consistent with observed statistical properties. A test particle tracing technique is then used to identify the source of the ring current plasma. We find that the contribution of plasma sheet bubbles to the ring current energy increases from ~20% for weak storms to ~50% for moderate storms and levels off at ~61% for intense storms, while the contribution of trapped particles decreases from ~60% for weak storms to ~30% for moderate and ~21% for intense storms. The contribution of nonbubble plasma sheet flux tubes remains ~20% on average regardless of the storm intensity. Consistent with previous RCM and RCM‐E simulations, our results show that the mechanisms for plasma sheet bubbles enhancing the ring current energy are (1) the deep penetration of bubbles and (2) the bulk plasma pushed ahead of bubbles. Both the bubbles and the plasma pushed ahead typically contain larger distribution functions than those in the inner magnetosphere at quiet times. An integrated effect of those individual bubble injections is the gradual enhancement of the storm time ring current. We also make two predictions testable against observations. First, fluctuations over a time scale of 5–20 min in the plasma distributions and electric field can be seen in the central ring current region for the storm main phase. We find that the plasma pressure and the electric field EY there vary over about 10%–30% and 50%–300% of the background values, respectively. Second, the maximum plasma pressure and magnetic field depression in the central ring current region during the main phase are well correlated with the Dst index.

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RCM-E simulation of ion acceleration during an idealized plasma sheet bubble injection

Cited by 118 publications

References 56 publications

Near-Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

Near-Earth plasma sheet azimuthal pressure gradient and associated auroral development soon before substorm onset

Distribution of Region 1 and 2 currents in the quiet and substorm time plasma sheet from THEMIS observations

On the contribution of plasma sheet bubbles to the storm time ring current

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