Temporal structure of the fast convective flow in the plasma sheet: Comparison between observations and two‐fluid simulations

Ohtani, S.; Shay, M. A.; Mukai, T.

doi:10.1029/2003ja010002

Cited by 262 publications

(449 citation statements)

References 55 publications

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“…We set M = 6, which yields effective widths of bubbles being 2-3 Re, with the tailward boundary set at~15 Re; we also set T = 900 s, which yields effective injection time of bubbles being 3-4 min. Those values in the simulations are consistent with observed spatial [Nakamura et al, 2004] and temporal characteristics [Ohtani et al, 2004] of BBFs. For example, Movie S1 in the supporting information shows PV 5/3 along the boundary for run #1, and Movie S3a shows the bubble injections in the equatorial plane.…”

Section: 1002/2015ja021398supporting

confidence: 80%

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: 1002/2015ja021398supporting

confidence: 80%

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

et al. 2015

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“…Since the spacecraft crossed an upper (northern) part of this structure only, we can not state that it is closed, forming a magnetic island. It also may be an NFTE-type (Sergeev et al, 1992) or CD-related (Ohtani et al, 2004) surge of the current sheet. The electric current deviated from the perpendicular direction to ∼150 • , and |j×B| has a local minimum during A1.…”

Section: Detailed Analysis Of Cluster Observationsmentioning

confidence: 99%

Structure of the near-Earth plasma sheet during tailward flows

et al. 2008

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Abstract.A detailed analysis of successive tailward flow bursts in the near-Earth magnetotail (X∼−19 R E ) plasma sheet is performed on the basis of in-situ multi-point observations by the Cluster spacecraft on 15 September 2001. The tailward flows were detected during a northward IMF interval, 2.5 h after a substorm expansion. Each flow burst (V x <300 km/s) was associated with local auroral activation. Enhancements of the parallel and anti-parallel ∼1 keV electron flux were detected during the flows. The spacecraft configuration enables to monitor the neutral sheet (B x ≈0) and the level of B x ≈10-15 nT simultaneously, giving a possibility to distinguish between closed plasmoid-like structures and open NFTE-like surges. The data analysis shows NFTElike structures and localized current filaments embedded into the tailward plasma flow. 3-D shapes of the structures were reconstructed using the four-point magnetic filed measurements and the particle data.

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“…The X line in the tail was reported to be observed in a wide region at the downtail distance of~15 R E [e.g., Ohtani, 2004;Ohtani et al, 2004;Runov et al, 2008aRunov et al, , 2008bMachida et al, 1999]. According to Nagai et al [2005] and Nagai [2006], the X line site depends highly on solar wind (SW) condition, i.e., the interplanetary electric field E y .…”

Section: Introductionmentioning

confidence: 99%

X lines in the magnetotail for southward and northward IMF conditions

et al. 2015

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Utilizing associated observations of Geotail and ACE satellites from the year of 1998 to 2005, we investigated the X lines in the near‐Earth tail under different interplanetary magnetic field (IMF) conditions. The X lines are recognized by the tailward fast flows with negative Bz. Statistically, the X lines in the tail can be observed for southward as well as northward IMF, but more frequently observed for southward IMF. A typical case on 26 April 2005 showed clear evidence that the X line can occur for northward IMF while the geomagnetic activity is particularly quiet. Further analysis showed that the X line‐related solar wind has stronger Ey and Bz components for southward than northward IMF. In addition, the X line‐related geomagnetic activities are stronger for southward than northward IMF.

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Temporal structure of the fast convective flow in the plasma sheet: Comparison between observations and two‐fluid simulations

Cited by 262 publications

References 55 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

Structure of the near-Earth plasma sheet during tailward flows

X lines in the magnetotail for southward and northward IMF conditions

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