On the auroral currentvoltage relationship
Abstract
A simple model of collisionless plasma kinetic theory [Knight, 1973] has been 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 the high altitude plasma parameters without contamination from auroral heating. The fieldalighed current density from Knight's formula is almost linear in the ratio of j_{∥}/eΦ_{∥} for values of eΦ_{∥}/kT between 1 and 10. We find, using measured values of J_{∥} (mapped to the surface) and Φ_{∥} (inferred from measurements either at high altitudes or low altitudes), the ratio of J_{∥}/eΦ_{∥} varies considerably but with a mean value about 0.5~2.2×10^{}^{9} mho/m^{2}. Using either the full Knight's formula or the linear simplification, we can predict the parallel potential drop (given the highaltitude density, temperature, current, and magnetic mirror factor) to test against the measured potential drop, or we can predict the current given the potential drop and the highaltitude plasma parameters. The agreement is generally quite good and the linear simplification is reasonable; however, the Knight current, since it does not include upward ionospheric electrons, is not valid in the downward return current region. We also show that suprathermal electron bursts are 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.
 Publication:

Journal of Geophysical Research
 Pub Date:
 March 1991
 DOI:
 10.1029/90JA02462
 Bibcode:
 1991JGR....96.3523L
 Keywords:

 Auroras;
 Collisionless Plasmas;
 Ionospheric Currents;
 MagnetosphereIonosphere Coupling;
 Satellite Sounding;
 Dynamics Explorer 1 Satellite;
 Dynamics Explorer 2 Satellite;
 Field Aligned Currents;
 Kinetics;
 Geophysics;
 Magnetospheric Physics: Auroral phenomena;
 Ionosphere: Electric fields;
 Magnetospheric Physics: Electric fields;
 Magnetospheric Physics: Magnetosphere/ionosphere interactions