Diagnosis of Auroral Dynamics Using Global Auroral Imaging with Emphasis on Large-Scale Evolutions
Abstract
The spatial extent of the auroral oval and polar cap for typical auroral conditions covers an area of about Mkm2, for which a minimum of more than 20 well-placed ground stations is required for full spatial coverage, even if significant difficulties such as sunlight, moonlight, geography, and meteorology are neglected. As shown here, auroral imaging with high-altitude spacecraft provides substantial advantages relative to ground-based techniques. Variations in the dimensions of the auroral oval with changes in the sign of the Z component of the interplanetary magnetic field (IMP) are easily observed. Auroral luminosities all along the auroral oval increase within minutes following arrival at the magnetosphere of a shock in the interplanetary medium. It appears that the dawn-dusk motion of the large-scale transpolar arc of a theta aurora observed in the northern (southern) polar cap is in the same (opposite) direction as the By component of the IMF. It is shown that the onsets of auroral substorms occur within a range of less than 3.5 hours of magnetic local time centered at 2250 MLT. This is nearly identical to the statistically determined location for the initial response to substorm onset at the orbits of geosynchronous spacecraft. The auroral bulge does not always expand symmetrically in the east-west direction from the position of substorm onset, but can progress preferentially into either the evening or morning sector. (sdw)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1989
- Accession Number
- ADA219668
Entities
People
- John D. Craven
- Louis A. Frank
Organizations
- University of Iowa