Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

Yang, Jian; Toffoletto, F.; Wolf, R. A.; Sazykin, S.; Spiro, R. W.; Brandt, P. C.; Henderson, M. G.; Frey, H. U.

doi:10.1029/2008ja013635

Cited by 21 publications

(21 citation statements)

References 44 publications

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“…Although the present study does not give in situ observations in the magnetosphere of a flow channel or onset instability, the temporal evolution of the pre‐onset auroral form can be regarded as motion of magnetospheric plasma, based on the known association of PBIs and N‐S arcs with flow bursts in the magnetotail. First, new plasma, presumably with lower entropy than the surrounding plasma [ Yang et al , 2008; Wolf et al , 2009], is supplied across the open‐closed field line boundary. This plasma is then transported earthward along an azimuthally narrow flow channel, with upward field‐aligned currents and the N‐S aurora measured by ASIs along its westward edge.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, the high probability of diffuse‐appearing aurora near the onset latitude indicates the existence of high plasma pressure along these inner plasma sheet field lines, which would drive large region 2 currents. High pressure in the near‐Earth plasma sheet will also provide a favorable condition for interchange instability following an injection of low entropy plasma to this region [ Yang et al , 2008]. Note also that the evidence indicating that the equatorward portion of the growth phase arc may be the region of proton aurora and SAPS [ Lyons et al , 2009; Zou et al , 2009a, 2009b] also implies connection with the region 2 system.…”

Section: Resultsmentioning

confidence: 99%

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Substorm triggering by new plasma intrusion: THEMIS all‐sky imager observations

et al. 2010

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[1] A critical, long-standing problem in substorm research is identification of the sequence of events leading to substorm auroral onset. Based on event and statistical analysis of THEMIS all-sky imager data, we show that there is a distinct and repeatable sequence of events leading to onset, the sequence having similarities to and important differences from previous ideas. The sequence is initiated by a poleward boundary intensification (PBI) and followed by a north-south (N-S) arc moving equatorward toward the onset latitude. Because of the linkage of fast magnetotail flows to PBIs and to N-S auroras, the results indicate that onset is preceded by enhanced earthward plasma flows associated with enhanced reconnection near the pre-existing open-closed field line boundary. The flows carry new plasma from the open field line region to the plasma sheet. The auroral observations indicate that Earthward-transport of the new plasma leads to a near-Earth instability and auroral breakup ∼5.5 min after PBI formation. Our observations also indicate the importance of region 2 magnetosphere-ionosphere electrodynamic coupling, which may play an important role in the motion of pre-onset auroral forms and determining the local times of onsets. Furthermore, we find motion of the pre-onset auroral forms around the Harang reversal and along the growth phase arc, reflecting a well-developed region 2 current system within the duskside convection cell, and also a high probability of diffuse-appearing aurora occurrence near the onset latitude, indicating high plasma pressure along these inner plasma sheet field lines, which would drive large region 2 currents.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Substorm triggering by new plasma intrusion: THEMIS all‐sky imager observations

et al. 2010

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“…In order to quantitatively calculate substorm time particle injections, more realistic representations of the magnetic field collapse (and therefore the associated induction electric field) were designed and then applied to calculate particle trajectories. These efforts include (1) ad hoc analytic representations of magnetic field collapse superimposed to a background model [e.g., Li et al , 1998; Ganushkina et al , 2001; Li et al , 2003; Zaharia et al , 2004], (2) gradual transition from stretched configuration to a less stretched configuration using empirical magnetic field models with different inputs [e.g., Delcourt , 2002; Jones et al , 2006; Yang et al , 2008], (3) time‐varying magnetic field derived from tail MHD simulations with neutral sheet formation and magnetic field dipolarization [e.g., Birn et al , 1997b], and (4) time‐varying magnetic field derived from 3‐D global MHD simulations [e.g., Fok et al , 2006]. Each of the different approaches treats some physics/processes well and others poorly.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2011

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[1] In this paper, we investigate the role of plasma sheet bubbles in the ion flux variations at geosynchronous orbit during substorm injections by using the Rice Convection Model with an equilibrated magnetic field model (RCM-E). The bubble is initiated in the near-Earth plasma sheet with a localized reduction in entropy parameter PV 5/3 following a substorm growth phase. In the expansion phase, characteristic features of substorm injections are reproduced; that is, there is a prominent dispersionless flux increase for energetic protons (>40 keV) and a flux decrease for lower-energy protons near midnight geosynchronous orbit while there is dispersive flux enhancement near the dusk sector. We find that the injection boundary is well coincident with the earthward boundary of the bubble, inside which the depletion of plasma content causes the magnetic field dipolarization, and in return, the magnetic field collapse energizes particles and alters the drift paths dramatically. Our results also show that a high-PV 5/3 island is pushed ahead of the fast earthward propagating bubble, and a dipolarization front forms between them. Within the high-PV 5/3 island, the diamagnetic effect makes the plasma pressure increase and the strength of the magnetic field decrease to a local minimum. We suggest that plasma sheet bubbles are elementary vehicles of substorm time particle injections from the main plasma sheet to the inner magnetosphere.Citation: Yang, J., F. R. Toffoletto, R. A. Wolf, and S. Sazykin (2011), RCM-E simulation of ion acceleration during an idealized plasma sheet bubble injection,

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“…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%

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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Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

Cited by 21 publications

References 44 publications

Substorm triggering by new plasma intrusion: THEMIS all‐sky imager observations

Substorm triggering by new plasma intrusion: THEMIS all‐sky imager observations

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

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

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