A study of anisotropy in electron pressure in the tail current sheet
- Rice Univ., Houston, TX (United States)
The authors adopt a magnetotail model with stretched field lines where ion motions are generally nonadiabatic and where it is assumed that the pressure anisotropy resides only in the electron pressure tensor. They show that the magnetic field lines with p{sub {perpendicular}}>p{sub {parallel}} are less stretched than the corresponding field lines in the isotropic model. For p{sub {parallel}}> p{sub {perpendicular}}, the magnetic field lines become more and more stretched as the anisotropy approaches the marginal firehose limit, p{sub {parallel}}=p{sub {perpendicular}}+B{sup 2}/{mu}{sub 0}. The authors also show that the tail current density is highly enhanced at the firehose limit, a situation that might be subject to a microscopic instability. However, they emphasize that the enhancement in the current density is notable only near the center of the tail current sheet (z=0). Thus it remains unclear whether any microscopic instability can significantly alter the global magnetic field configuration of the tail. By comparing the radius of the field-line curvature at z=0 with the particle`s gyroradius, the authors suspect that even the conventional adiabatic description of electrons may become questionable very close to the marginal firehose limit. 22 refs., 9 figs.
- OSTI ID:
- 207159
- Journal Information:
- Journal of Geophysical Research, Vol. 100, Issue A3; Other Information: PBD: 1 Mar 1995
- Country of Publication:
- United States
- Language:
- English
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