Impulsive Magnetic Perturbations of the High Latitude, Dayside Ionosphere
Abstract
Recently interest has grown in the study of dayside magnetic impulse events observed at high latitude ground stations. These signals may be signatures of dayside magnetopause processes in the ionosphere. Successful identification of the ground signature of any process means that its contribution to the magnetospheric environment can be monitored with ground stations. Recent work has focused on signals that are expected to accompany mesoscale field-aligned currents moving through the ionosphere. The actual source of these currents remains controversial, with Flux Transfer Events (FTEs) and solar wind pressure enhancements being the primary candidates. We use a data set from the Ninth Coordinated Data Analysis Workshop which includes observations of the type that have been associated with dayside magnetic impulse events. We focus on the morphology and dynamics of this event which appear unique. For example, the inferred velocity across a chain of station near 1400 local time is two to ten times faster than reported near the terminator. We compare solar wind plasma and magnetic field parameters with models that relate the impulsive events to solar wind pressure perturbations of FTEs. There is an increase of the dynamic pressure prior to the event and the solar wind magnetic field is southward throughout the entire interval. The event is well correlated to the dynamic pressure change, but the theories reviewed do not satisfactorily explain all of the observed features, possibly because a pressure increase and an FTE are both present, or because of incomplete station coverage.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1991
- Accession Number
- ADA249872
Entities
People
- Michael D. Krajnak
Organizations
- University of California, Los Angeles