Injection of a bubble into the inner magnetosphere

Zhang, J.-C.; Wolf, R. A.; Sazykin, S.; Toffoletto, F.

doi:10.1029/2007gl032048

Cited by 32 publications

(51 citation statements)

References 20 publications

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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%

“…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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Section: 1002/2015ja021398mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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“…V ⊥ ) measured by C3 points at TC-2, increasing confidence that the feature observed by Cluster is the same as that detected by TC-2. Simulations have studied the features of a depleted flux tube that might be expected close to the Earth (Birn et al, 2004), and the effect the presence of a depleted flux tube might have on the inner magnetosphere (Zhang et al, 2008), although to date no plasma bubbles have been detected at X GSM >−8 R E . Birn et al (2004) predicted that, close to the Earth, after sufficient time had passed since the creation of a depleted flux tube, the plasma depletion and commensurate increase in magnetic pressure that characterise a plasma bubble actually reverse -field-aligned flows from further downtail transport plasma to the higher latitude, near-Earth region, increasing the local plasma pressure.…”

Section: Tc-2 Datamentioning

confidence: 99%

Cluster and Double Star multipoint observations of a plasma bubble

et al. 2009

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Abstract. Depleted flux tubes, or plasma bubbles, are one possible explanation of bursty bulk flows, which are transient high speed flows thought to be responsible for a large proportion of flux transport in the magnetotail. Here we report observations of one such plasma bubble, made by the four Cluster spacecraft and Double Star TC-2 around 14:00 UT on 21 September 2005, during a period of southward, but B Y -dominated IMF. In particular the first direct observations of return flows around the edges of a plasma bubble, and the first observations of plasma bubble features within 8 R E of the Earth, consistent with MHD simulations (Birn et al., 2004) are presented. The implications of the presence of a strong B Y in the IMF and magnetotail on the propagation of the plasma bubble and development of the associated current systems in the magnetotail and ionosphere are discussed. It is suggested that a strong B Y can rotate the field aligned current systems at the edges of the plasma bubble away from its duskward and dawnward flanks.

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“…[4] Here, we describe the setup of a more sophisticated substorm-associated bubble simulation that extends the work of Zhang et al [2008]. We focus on an observed substorm instead of an idealized one, and tailor RCM inputs for consistency with Geotail measurements on 22 July 1998.…”

Section: Introductionmentioning

confidence: 99%

“…Lemon et al [2004] showed that even strong convection could not force loaded flux tubes characterized by growth-phase plasma sheet values of the entropy parameter PV 5/3 to drift onto quasi-dipolar inner magnetosphere flux tubes, while flux tubes with reduced values of PV 5/3 could do so. Zhang et al [2008] used the Rice Convection Model (RCM) to examine the process by which reduced content plasma-sheet bubbles could result in a pressure increase in the ring current region.…”

Section: Introductionmentioning

confidence: 99%

Rice Convection Model simulation of the substorm‐associated injection of an observed bubble into the inner magnetosphere: 1. Magnetic field and other inputs

et al. 2009

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[1] The objective of this work is a realistic Rice Convection Model (RCM) simulation of a modest substorm that occurred on 22 July 1998 and was observed by the Geotail spacecraft in the inner plasma sheet. It represents the first time the RCM has been used for detailed modeling of an inner magnetospheric event using data from a spacecraft in the inner plasma sheet beyond geosynchronous orbit to drive the model's time-dependent boundary conditions. Since this represents a substantial departure from past practice, we present, in this paper, a detailed account of how model inputs are determined. An accompanying paper presents results and interpretations. Model inputs are adjusted to achieve approximate consistency between RCM-computed values and measurements by Geotail, which was within the RCM modeling region near X GSM = À9 R E , Y GSM = 0. To represent the magnetic field in the growth phase, we utilize a Tsyganenko (1989) statistical magnetic field model, adjusted to agree with Geotail-measured pressure and magnetic field in a new way using analytic solutions to the linear Grad-Shafranov equation. The magnetic field during the expansion phase is represented by adding a substorm current wedge using formulas developed by Tsyganenko. Induction electric fields play a central role in these simulations, because they are large in the vicinity of the substorm injection region. We provide a detailed description of how induction electric fields are included in the RCM as well as a prescription of the electromagnetic gauge condition used in the code.

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Injection of a bubble into the inner magnetosphere

Cited by 32 publications

References 20 publications

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

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

Cluster and Double Star multipoint observations of a plasma bubble

Rice Convection Model simulation of the substorm‐associated injection of an observed bubble into the inner magnetosphere: 1. Magnetic field and other inputs

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