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Title: MHD Ballooning Instability in the Plasma Sheet

Abstract

Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheetmore » region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.« less

Authors:
;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
820113
Report Number(s):
PPPL-3890
TRN: US0305689
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 20 Oct 2003
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; BALLOONING INSTABILITY; COMPRESSIBILITY; FREE ENERGY; INSTABILITY; IONOSPHERE; KINETICS; MAGNETIC FIELDS; PLASMA; PLASMA PRESSURE; PLASMA SHEET; STABILITY; TRAPPED ELECTRONS; BALLOONING INSTABILITIES; MAGNETOHYDRODYNAMICS (MHD); SPACE PLASMA PHYSICS; SUBSTORM

Citation Formats

C.Z. Cheng, and S. Zaharia. MHD Ballooning Instability in the Plasma Sheet. United States: N. p., 2003. Web. doi:10.2172/820113.
C.Z. Cheng, & S. Zaharia. MHD Ballooning Instability in the Plasma Sheet. United States. doi:10.2172/820113.
C.Z. Cheng, and S. Zaharia. Mon . "MHD Ballooning Instability in the Plasma Sheet". United States. doi:10.2172/820113. https://www.osti.gov/servlets/purl/820113.
@article{osti_820113,
title = {MHD Ballooning Instability in the Plasma Sheet},
author = {C.Z. Cheng and S. Zaharia},
abstractNote = {Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.},
doi = {10.2172/820113},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {10}
}