Publication Date:
2016-03-10
Description:
We used the inferred equatorial mass density ρ m,eq based on measurements of Alfven wave frequencies measured by the GOES satellites during 1980–1991 in order to construct a number of different models of varying complexity for the equatorial mass density at geostationary orbit. The most complicated models are able to account for 66% of the variance with a typical variation from actual values of a factor of 1.56. The factors that influenced ρ m,eq in the models were, in order of decreasing importance, the F10.7 EUV index, magnetic local time, MLT, the solar wind dynamic pressure P dyn , the phase of the year, and the solar wind B Z (GSM Z direction). During some intervals, some of which were especially geomagnetically quiet, ρ m,eq rose to values that were significantly higher than those predicted by our models. For 10 especially quiet intervals, we examined long-term (〉 1 day) apparent refilling, the increase in ρ m,eq at a fixed location. We found that the behavior of ρ m,eq varies for different events. In some cases, there is significant apparent refilling, whereas in other cases ρ m,eq stays the same or even decreases slightly. Nevertheless, we showed that on average ρ m,eq increases exponentially during quiet intervals. There is variation of apparent refilling with respect to the phase of the solar cycle. On the third day of apparent refilling, ρ m,eq has on average a similar value at solar maximum or solar minimum, but at solar maximum, ρ m,eq begins with a larger value and rises relatively less than at solar minimum.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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