Consequences of violation of frozen-in-flux: Evidence from OpenGGCM simulations

Hu, Bei; Wolf, R. A.; Toffoletto, F.; Yang, Jian; Raeder, J.

doi:10.1029/2011ja016667

Cited by 21 publications

(31 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At 7:37 UT, immediately before reconnection, the entropy in the ballooning/interchange fingers at P3 reached the same values as observed by P2. Figure 17 provides a possible interpretation of the observations in Figure 16 that is consistent with the results of Yang et al [2011] and Hu et al [2011]. The bottom of Figure 17 shows the radial profile of B Z ; a minimum is the point with ∂ B Z /∂ X = 0.…”

Section: Summary and Discussionsupporting

confidence: 77%

See 1 more Smart Citation

Kinetic ballooning/interchange instability in a bent plasma sheet

Panov¹,

Nakamura²,

Baumjohann³

et al. 2012

J. Geophys. Res.

View full text Add to dashboard Cite

[1] We use Time History of Events and Macroscale Interactions during Substorms (THEMIS) and GOES observations to investigate the plasma sheet evolution on 28 February 2008 between 6:50 and 7:50 UT, when there developed strong magnetic field oscillations with periods of 100 s. Using multispacecraft analysis of the plasma sheet observations and an empirical plasma sheet model, we determine both the large-scale evolution of the plasma sheet and the properties of the oscillations. We found that the oscillations exhibited signatures of kinetic ballooning/interchange instability fingers that developed in a bent current sheet. The interchange oscillations had a sausage structure, propagated duskward at a velocity of about 100 km/s, and were associated with fast radial electron flows. We suggest that the observed negative gradient of the Z GSM magnetic field component (∂B Z /∂X) was a free energy source for the kinetic ballooning/interchange instability. Tens of minutes later a fast elongation of ballooning/interchange fingers was detected between 6 and 16 R E downtail with the length-to-width ratio exceeding 20. The finger elongation ended with signatures of reconnection in an embedded current sheet near the bending point. These observations suggest a complex interplay between the midtail and near-Earth plasma sheet dynamics, involving localized fluctuations in both cross-tail and radial directions before current sheet reconnection.

show abstract

Section: Summary and Discussionsupporting

confidence: 77%

“… Pritchett and Coroniti [2011] demonstrated that a kinetic ballooning/interchange instability can lead to near‐Earth reconnection in the plasma sheet. And, indeed, Yang et al [2011] and Hu et al [2011] found that an interchange mechanism would accelerate plasma sheet thinning, which may facilitate reconnection.…”

Section: Introductionmentioning

confidence: 97%

Kinetic ballooning/interchange instability in a bent plasma sheet

Panov¹,

Nakamura²,

Baumjohann³

et al. 2012

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…The magnetospheric and the ionospheric dynamics are summarized in the cartoon of Figure 14. From the inner magnetospheric point of view, the driver of the reconfiguration is the fast earthward propagation of a bubble as represented by the depletion of plasma content through the tail boundary, which is created by either magnetic reconnection further down tail or other instabilities that can violate the frozen‐in‐flux condition [e.g., Birn et al , 2009; Yang et al , 2011b; Hu et al , 2011]. In the magnetosphere (Figure 14, bottom), the bubble (pink), consisting of low entropy flux tubes, is injected earthward, as it partially disrupts the cross‐tail current in the plasma sheet.…”

Section: Discussionmentioning

confidence: 99%

Large‐scale current systems and ground magnetic disturbance during deep substorm injections

et al. 2012

Self Cite

View full text Add to dashboard Cite

[1] We present a detailed analysis of the large-scale current systems and their effects on the ground magnetic field disturbance for an idealized substorm event simulated with the equilibrium version of the Rice Convection Model. The objective of this study is to evaluate how well the bubble-injection picture can account for some classic features of the substorm expansion phase. The entropy depletion inside the bubble is intentionally designed to be so severe that it can penetrate deep into geosynchronous orbit. The results are summarized as follows: (1) Both the region-1-sense and region-2-sense field-aligned currents (FACs) intensify substantially. The former resembles the substorm current wedge and flows along the eastern and western edges of the bubble. The latter is connected to the enhanced partial ring current in the magnetosphere associated with a dipolarization front earthward of the bubble. In the ionosphere, these two pairs of FACs are mostly interconnected via Pedersen currents. (2) The horizontal ionospheric currents show a significant westward electrojet peaked at the equatorward edge of the footprint of the bubble. The estimated ground magnetic disturbance is consistent with the typical features at various locations relative to the center of the westward electrojet. (3) A prominent Harang-reversal-like boundary is seen in both ground DH disturbance and plasma flow pattern, appearing in the westward portion of the equatorward edge of the bubble footprint, with a latitudinal extent of $5and a longitudinal extent of the half width of the bubble. (4) The dramatic dipolarization inside the bubble causes the ionospheric map of the inner plasma sheet to exhibit a bulge-like structure, which may be related to auroral poleward expansion. (5) The remarkable appearance of the westward electrojet, Harang-reversal-like boundary and poleward expansion starts when the bubble reaches the magnetic transition region from tail-like to dipole-like configuration. We also estimate the horizontal and vertical currents using magnetograms at tens of ground stations for a deep injection substorm event occurred on April 9, 2008, resulting in a picture that is qualitatively consistent with the simulation. Based on the simulations and the observations, an overall picture of the ionospheric dynamics and its magnetospheric drivers during deep bubble injections is obtained.Citation: Yang, J., F. R. Toffoletto, R. A. Wolf, S. Sazykin, P. A. Ontiveros, and J. M. Weygand (2012), Large-scale current systems and ground magnetic disturbance during deep substorm injections,

show abstract

“…4. Global MHD models attempt to model the plasma sheet and often exhibit features that look like substorms and bursty bulk flows [e.g., Wiltberger et al , 2000; Pembroke et al , 2012], but they do not include transport by gradient/curvature drift; furthermore, numerical diffusion often prevents conservation of the entropy parameter (∫ P 3/5 ds / B ) 5/3 under circumstances when it should be conserved in ideal MHD [ Hu et al , 2011; Pembroke et al , 2012]. Furthermore, the grid spacing on the earthward boundary of the MHD grid is often too coarse to allow accurate treatment of magnetosphere‐ionosphere coupling [ Hu et al , 2010b].…”

Section: Introductionmentioning

confidence: 99%

Thin filament simulations for Earth's plasma sheet: Tests of validity of the quasi‐static convection approximation

2012

Self Cite

View full text Add to dashboard Cite

[1] The main goal of this paper is to estimate the errors involved in applying a quasi-static convection model such as the Rice Convection Model (RCM) or its equilibrium version (RCM-E), which neglect inertial currents, to treat the injection of fresh particles into the inner magnetosphere in a substorm expansion phase. The approach is based on the idea that the dipolarization process involves earthward motion of a bubble that consists of flux tubes that have lower values of the entropy parameter than the surrounding medium. Our tests center on comparing MHD simulations with RCM-and RCM-E-like quasi-static approximations, for cases where the bubble is considered to be a thin ideal-MHD filament. Those quasi-static solutions miss the interchange oscillations that are often a feature of the MHD results. RCM and, to a lesser extent, RCM-E calculations tend to overestimate the westward electric field at the ionospheric footprint of the bubble and underestimate its duration. However, both get the time integral of the E Â B drift velocity right as well as the net energization of the particles in the filament. The quasi-static approximation is most accurate if its computed value of the braking time of the bubble's earthward motion is long compared to the period of the relevant interchange oscillation. Comparison of MHD filament simulations of interchange instability with corresponding RCM calculations suggests a similar validity criterion. For plasma sheet conditions, the quasi-static approximation is typically best if the background medium has low b, worst if it consists of highly stretched field lines.Citation: Wolf, R. A., C. X. Chen, and F. R. Toffoletto (2012), Thin filament simulations for Earth's plasma sheet: Tests of validity of the quasi-static convection approximation,

show abstract

Consequences of violation of frozen-in-flux: Evidence from OpenGGCM simulations

Cited by 21 publications

References 22 publications

Kinetic ballooning/interchange instability in a bent plasma sheet

Kinetic ballooning/interchange instability in a bent plasma sheet

Large‐scale current systems and ground magnetic disturbance during deep substorm injections

Thin filament simulations for Earth's plasma sheet: Tests of validity of the quasi‐static convection approximation

Contact Info

Product

Resources

About