A statistical study of field-aligned currents in the Earth's inner magnetosphere

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6306328

Chun, F K

Field-aligned currents (FAC's) play a major role in the solar wind-magnetospheric interaction by electrodynamically coupling magnetospheric and ionospheric plasmas, so that stresses applied to the outer magnetospheric plasma are transmitted to the ionosphere and ultimately to the upper atmosphere. FAC's have been studied extensively since 1967 and all of our knowledge and understanding of this coupling mechanism is based on data from low altitude polar orbiting satellites. The purpose of this dissertation is to address some of the questions related to the persistence of magnetospheric FAC's during low levels of geomagnetic activity, their motion throughout the magnetosphere and their possible source mechanisms. ISEE-1 and 2 magnetometer data was detrended and rotated into a field-aligned coordinate system using the Tsyganenko magnetic field model in order to identify current sheet crossings. The properties of the FAC's were computed to include their current intensity, density, velocity and thickness. The location and orientation of the FAC's was determined, as well as a measure of how closely they resemble sheets of current. Two types of FAC's were identified in the magnetosphere; one that is quasi-stationary and another that is moving quickly so that it is observed simultaneously by the spacecraft. The quasi-stationary FAC's are magnetospheric extensions of the low altitude region 1 and 2 currents while the fast moving FAC's are possibly current carrying waves and/or transient phenomena. Both currents are highly responsive to geomagnetic activity with the fast moving currents responding strongly to high activity. During periods of quiet activity, magnetospheric FAC's are infrequently observed except for a region on the dusk night side from mid to high L-values suggesting that global convection does drive the dusk FAC's but that the three dimensional current system is non existent on the dawn side.

• Research Organization: California Univ., Los Angeles, CA (United States)
• OSTI ID: 6306328
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COUPLING
CURRENT DENSITY
CURRENTS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
IONOSPHERE
MAGNETIC FIELDS
PLANETARY IONOSPHERES
PLASMA
SOLAR ACTIVITY
SOLAR WIND
STRESSES