Magnetohydrodynamic flows and waves in the Earth`s magnetotail. Ph.D. Thesis

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:237314

Chen, S H

Several questions in the Earth`s magnetotail have been raised and studied. The outline is: (1) The dependence of the magnetosheath flows on the orientation of interplanetary magnetic field; (2) The surface waves at the tail magnetopause are nonsinusoidal in shape and steepened toward the Sun while moving away from the Sun. This may indicate an anomalous momentum transport process in the low-latitude boundary layer; (3) The wave power in the lobe is not large enough to supply the energy to heat the plasma sheet and to initiate a substorm as proposed by the thermal catastrophe model of Goertz and Smith; and (4) Some characteristics of global MHD wave modes in the magnetotail are studied by using simultaneous measurements of waves in the solar wind, in the lobes, and on the ground. Using multiple spacecraft observations, the author shows that the magnetosheath flow speed on the shanks of the magnetotail steadily exceeded the solar wind speed by 20%. The author proposes that the acceleration of the magnetosheath flow is achieved by magnetic tension in the draped field configuration for northward IMF. Results of a 3-D MHD simulation support the model. The author examins two intervals of multiple magnetopause crossings along the flanks of the tail on January 22 and February 15, 1978. In the presence of northward IMF, the surface waves on the magnetopause were nonsinusoidal with steepened sunward facing surfaces. It is proposed that the magnetic field in the magnetosheath modulates the wave form in a way that may result in an anomalous transport of momentum across the magnetopause. The author examines ULF waves (0.26 to 5 mHz) in the Earth`s magnetotail lobe region. It is found that the wave power in the lobe is less than 1 nT for most of the time. The power of the wave is much less than the requirement of the thermal catastrophe model of Goertz and Smith.

• Research Organization: California Univ., Los Angeles, CA (United States). Dept. of Mechanical, Aerospace and Nuclear Engineering
• OSTI ID: 237314
• Report Number(s): N--96-23040; NIPS--96-07426
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
FLOW RATE
HYDROMAGNETIC WAVES
INTERPLANETARY MAGNETIC FIELDS
MAGNETOSHEATH
MAGNETOTAIL
MOMENTUM TRANSFER
PLASMA DRIFT
PLASMA HEATING
SOLAR WIND
WAVE FORMS
WAVE PROPAGATION