CSP Seminar Speaker: Jeffrey J. Love (USGS)
Speaker: Jeffrey J. Love
Affiliation: USGS Geomagnetism Program
Title: Movie-Maps of Low-Latitude Storm-Time Magnetic Disturbance
Date: Thursday, March 24, 2011
Time: 3:30 PM Refreshments in CAS 500, 4:00 PM Talk
Place: 725 Commonwealth Ave. CAS 502
Using data from a numerous magnetic observatories around the world, we examine movie-maps of low-latitude magnetic disturbance for several large magnetic storms. The principle disturbance pattern seen in the movie-maps, and also in statistical analyses of long time series, is the well-known (but seemingly insufficiently recognized!) dawn-dusk asymmetry. The disturbance at dawn (dusk) is about 20% higher (lower) than Dst, and this is often interpreted in terms of partial ring currents. However, an examination of magnetic-field data from mid-latitudes shows, very clearly, that the dawn-dusk asymmetry is more consistent with field-aligned currents (Birkeland) directed inwards at noon and outwards at midnight (Crooker and Siscoe 1981). Partial ring current might contribute to the ground magnetic disturbance, but its contribution to local-time disturbance morphology is very small.