Magnetic storm ring current injection modeled with the Rice Convection Model and a self‐consistent magnetic field

Lemon, C.; Wolf, R. A.; Hill, T. W.; Sazykin, S.; Spiro, R. W.; Toffoletto, F.; Birn, J.; Hesse, Michael

doi:10.1029/2004gl020914

Cited by 96 publications

(132 citation statements)

References 19 publications

(14 reference statements)

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“…Earthward convection penetrates deeper into the inner magnetosphere if the nearEarth X-line (NEXL) forms closer to Earth to produce closed flux tubes with lower values of specific entropy for injection of ring cur rent [Lemon et al, 2004].This is consistent with the ring current injection conjecture proposed by this article's co-author Joe Kan (University of Alaska Fairbanks) that the ring current intensity increases with X-line formed closer to Earth. Unfortunately there was no time for meaningful discussion of the conjecture.…”

Section: Smc Events Without Substormssupporting

confidence: 82%

Storm‐substorm relations workshop

Kan

2006

EoS Transactions

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Magnetic storms in the magnetosphere can cause damage to communication satellites and large‐scale power outages.The concept that a magnetic storm is a compilation of a series of substorms was proposed by Akasofu [1968]. However, Kamide [1992] showed that substorms are not a necessary condition for the occurrence of a magnetic storm. This controversy initiated a new era of research on the storm‐substorm relation, which was the subject of a recent workshop in Banff, Alberta, Canada. The main topics discussed during the meeting included a brief overview of what a substorm is, how quasiperiodic substorm events and steady magnetospheric convection (SMC) events without substorms contribute to storms, and how plasma flows enhanced by magnetic reconnection in the plasma sheet contribute to substorms and storms.

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Section: Smc Events Without Substormssupporting

confidence: 82%

Storm‐substorm relations workshop

Kan

2006

EoS Transactions

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“…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]. On the other hand, numerical simulations of Lemon et al [2004] suggested that it was difficult for lossless adiabatic convection to transport a fully populated flux tube from the middle plasma sheet into the ring current region even when the cross polar cap potential (CPCP) drop is 100 kV. This is because the inflation of the magnetic field induces a dusk-to-dawn induction electric field on the nightside that partially counterbalances the convection electric field.…”

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%

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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“…[25] The simulations of Lemon et al [2004] suggested that strong sunward convection is capable of injecting plasma sheet flux tubes with PV 5/3 < $0.08 nPa(R E /nT) 5/3 deep into the inner magnetosphere. Higher entropy flux tubes moved around the flanks without entering the inner magnetosphere.…”

Section: Ring Current Intensity Increases If the X-line Forms Closer mentioning

confidence: 99%

Intensity of geomagnetic storms depends on the X‐line location in the plasma sheet

2007

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[1] Magnetic reconnection in the plasma sheet, known as the near-Earth X-line (NEXL), is observed within $30 R E from Earth during substorms. In the absence of substorms, the reconnection X-line is observed beyond $30 R E , denoted as mid-distant-tail X-line (MDXL). During quasi-periodic substorms, convection is enhanced by the NEXL to intensify the ring current of major storms with Dst < $ À100 nT. During extended periods without substorms, convection is driven by the MDXL to intensify the ring current of minor storms with Dst > $ À100 nT. Motivated by observations, we propose a ring current injection conjecture to order the storm intensity: Ring current intensity increases if the X-line forms closer to Earth. We carry out a rough entropy analysis as a first step toward theoretical investigation of the ring current injection conjecture. We show that substorm-associated near-Earth reconnection of closed plasma sheet field lines cannot provide the ring current particles for a major magnetic storm. However, we find that near-Earth reconnection of tail lobe field lines in a few strong substorm events could provide the particles for the storm-time ring current, if the X-line is located earthward of $15 R E with an uncertainty up to $25 R E .

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Magnetic storm ring current injection modeled with the Rice Convection Model and a self‐consistent magnetic field

Cited by 96 publications

References 19 publications

Storm‐substorm relations workshop

Storm‐substorm relations workshop

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

Intensity of geomagnetic storms depends on the X‐line location in the plasma sheet

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