Shear flow instabilities in the earth's plasma sheet region

1994 ◽  
Vol 12 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Sunayna Kalra ◽  
G. S. Lakhina
Keyword(s):  
Shear Flow ◽  
Plasma Sheet ◽  
Flow Instability ◽  
Velocity Shear ◽  
Mhd Equations ◽  
Data Sets ◽  
Neutral Sheet ◽  
Data Set ◽  
Central Plasma ◽  
Central Plasma Sheet

Abstract. Shear flow instability arising from the velocity shear between the inner and the outer central plasma sheet regions is studied by treating the plasma as compressible. Based on the linearized MHD equations, dispersion relations for the surface wave modes occurring at the boundary of the inner central plasma sheet (ICPS) and the outer central plasma sheet (OCPS) are derived. The growth rates and the eigenmode frequencies are obtained numerically. Three data sets consisting of parameters relevant to the earth's magnetotail are considered. The plasma sheet region is found to be stable for constant plasma flows unless MA>9.6, where MA is the Alfvén Mach number in the ICPS. However, for a continuously varying flow velocity profile in the ICPS, the instability is excited for MA\\geq1.4. The excited modes have oscillation periods of 2-10 min and 1.5-6 s, and typical transverse wavelengths of 30-100 RE and 0.5-6 RE for data sets 1 and 2 (i.e., case of no neutral sheet) respectively. For the data set 3, which corresponds to a neutral sheet at the center of the plasma sheet, the excited oscillations have periods of 2 s-1 min with transverse wavelengths of 0.02-1 RE.

scholarly journals Shear flow instabilities in the Earth's magnetotail

1996 ◽  
Vol 14 (8) ◽  
pp. 786-793
Author(s):  
R. V. Reddy ◽  
G. S. Lakhina
Keyword(s):  
Shear Flow ◽  
Plasma Sheet ◽  
Flow Instability ◽  
Mhd Equations ◽  
Surface Mode ◽  
Quiet Time ◽  
Central Plasma ◽  
Oscillating Boundary ◽  
Central Plasma Sheet ◽  
Shear Flow Instability

Abstract. Shear flow instability is studied in the Earth's magnetotail by treating plasma as compressible. A dispersion relation is derived from the linearized MHD equations using the oscillating boundary conditions at the inner central plasma sheet/outer central plasma sheet (OCPS) interface and OCPS/plasma-sheet boundary layer (PSBL) interface, whereas the surface-mode boundary condition is used at the PSBL/lobe interface. The growth rates and the real frequencies are obtained numerically for near-Earth (∣X∣~10–15 RE) and far-Earth (∣X∣~100 RE) magnetotail parameters. The periods and wavelengths of excited modes depend sensitively on the value of plasma-sheet half thickness, L, which is taken as L=5 RE for quiet time and L=1 RE for disturbed time. The plasma-sheet region is found to be stable for constant plasma flows unless MA3>1.25, where MA3 is the Alfvén Mach number in PSBL. For near-Earth magnetotail, the excited oscillations have periods of 2–20 min (quiet time) and 0.5–4 min (disturbed time) with typical transverse wavelengths of 2–30 RE and 0.5–6.5 RE, respectively; whereas for distant magnetotail, the analysis predicts the oscillation periods of ~8–80 min for quiet periods and 2–16 min for disturbed periods.

scholarly journals On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling

2011 ◽  
Vol 116 (A9) ◽  
pp. n/a-n/a ◽  
Author(s):  
Bingxian Luo ◽  
Weichao Tu ◽  
Xinlin Li ◽  
Jiancun Gong ◽  
Siqing Liu ◽  
...  
Keyword(s):  
Data Analysis ◽  
Plasma Sheet ◽  
Energetic Electrons ◽  
Central Plasma ◽  
Central Plasma Sheet

scholarly journals Plasma convection in the magnetotail lobes: statistical results from Cluster EDI measurements

2008 ◽  
Vol 26 (8) ◽  
pp. 2371-2382 ◽  
Author(s):  
S. Haaland ◽  
G. Paschmann ◽  
M. Förster ◽  
J. Quinn ◽  
R. Torbert ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Disturbance ◽  
Plasma Convection ◽  
Data Set ◽  
Central Plasma ◽  
Strong Convection ◽  
Central Plasma Sheet ◽  
Field Lines ◽  
Convection Patterns

Abstract. A major part of the plasma in the Earth's magnetotail is populated through transport of plasma from the solar wind via the magnetotail lobes. In this paper, we present a statistical study of plasma convection in the lobes for different directions of the interplanetary magnetic field and for different geomagnetic disturbance levels. The data set used in this study consists of roughly 340 000 one-minute vector measurements of the plasma convection from the Cluster Electron Drift Instrument (EDI) obtained during the period February 2001 to June 2007. The results show that both convection magnitude and direction are largely controlled by the interplanetary magnetic field (IMF). For a southward IMF, there is a strong convection towards the central plasma sheet with convection velocities around 10 km s−1. During periods of northward IMF, the lobe convection is almost stagnant. A By dominated IMF causes a rotation of the convection patterns in the tail with an oppositely directed dawn-dusk component of the convection for the northern and southern lobe. Our results also show that there is an overall persistent duskward component, which is most likely a result of conductivity gradients in the footpoints of the magnetic field lines in the ionosphere.

The quasi-adiabatic ion distribution in the central plasma sheet and its boundary layer

1991 ◽  
Vol 96 (A2) ◽  
pp. 1601-1609 ◽  
Author(s):  
Maha Ashour-Abdalla ◽  
Jorg Büchner ◽  
Lev M. Zelenyi
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Ion Distribution ◽  
Central Plasma ◽  
Central Plasma Sheet

Nonadiabatic heating of the central plasma sheet at substorm onset

1992 ◽  
Vol 97 (A2) ◽  
pp. 1481 ◽  
Author(s):  
C. Y. Huang ◽  
L. A. Frank ◽  
G. Rostoker ◽  
J. Fennell ◽  
D. G. Mitchell
Keyword(s):  
Plasma Sheet ◽  
Substorm Onset ◽  
Central Plasma ◽  
Central Plasma Sheet

scholarly journals Bi-directional electrons in the near-Earth plasma sheet

2003 ◽  
Vol 21 (7) ◽  
pp. 1497-1507 ◽  
Author(s):  
K. Shiokawa ◽  
W. Baumjohann ◽  
G. Paschmann
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
High Speed ◽  
Elevation Angle ◽  
Occurrence Rate ◽  
Neutral Sheet ◽  
Magnetospheric Configuration And Dynamics ◽  
Central Plasma ◽  
Occurrence Characteristics ◽  
The Magnetic Field

Abstract. We have studied the occurrence characteristics of bi-directional electron pitch angle anisotropy (enhanced flux in field-aligned directions, F^ /F|| > 1.5) at energies of 0.1–30 keV using plasma and magnetic field data from the AMPTE/IRM satellite in the near-Earth plasma sheet. The occurrence rate increases in the tailward direction from XGSM = - 9 RE to - 19 RE . The occurrence rate is also enhanced in the midnight sector, and furthermore, whenever the elevation angle of the magnetic field is large while the magnetic field intensity is small, B ~ 15 nT. From these facts, we conclude that the bi-directional electrons in the central plasma sheet are produced mainly in the vicinity of the neutral sheet and that the contribution from ionospheric electrons is minor. A high occurrence is also found after earthward high-speed ion flows, suggesting Fermi-type field-aligned electron acceleration in the neutral sheet. Occurrence characteristics of bi-directional electrons in the plasma sheet boundary layer are also discussed.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheet)

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