Auroral electrodynamics from simultaneous measurements at high and low altitudes

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5194144

Lu, Gang

Two auroras sampled nearly simultaneously at high and low altitudes along a field line by the Dynamics Explorer (DE) spacecraft were used to study auroral electrodynamics. Electric fields plotted as a function of invariant latitude show that the large-scale features are essentially the same at high and low altitudes outside the auroral acceleration region. Parallel electric fields associated with parallel currents are such as to filter the small-scale structure in the high altitude electric field pattern. From the magnetic field measurements, we find that there is a return current region embedded between two auroral arc structures. The latitude shift between the high-altitude and low-altitude return current regions indicates that the auroral arcs are moving equatorward with a velocity of about 250 m/s. Collisionless plasma kinetic theory was used to predict the relationship between the upward parallel current and the parallel potential drop. The DE 1/DE 2 pair offers a unique opportunity to test this relationship because the DE 1 spacecraft can measure high altitude plasma parameters without contamination from auroral heating. Using measured values of J(parallel) (mapped to the surface) and phi(parallel), the ratio of J(parallel)/ e(phi)(parallel) varies considerably but with a mean value of about 0.5 to approximately 2.2 x 10(exp -9) mho/sq m. Suprathermal electron bursts are also observed in the diffuse aurora at the same invariant latitudes, both at high and at low altitudes. Thus, we suggest that these 'bursts' are more properly described as a spatial rather than temporal phenomenon. Observations of upflowing ionospheric ions are obtained by both DE 1 and DE 2 over the nightside auroral regions. At low altitudes, the mean value of the net upward ion number flux is of the order of 10(exp 9)/(cc x sec).

• Research Organization: Rice Univ., Houston, TX (United States)
• OSTI ID: 5194144
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
COLLISIONLESS PLASMA
CURRENTS
ELECTRIC CURRENTS
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTRODYNAMICS
ENERGY
GEOMAGNETIC FIELD
IONIC COMPOSITION
KINETIC ENERGY
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FIELDS
PLASMA