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We have compared the KOrea Multi-Purpose SATellite-1 (KOMPSAT-1) drag derived density with the MSISE model (NRLMSISE-00 and MSISE-90) density during strong solar and/or geomagnetic activities. It is well known that there are two major mechanisms to induce satellite drag caused by atmospheric density enhancement: the heating by solar EUV radiation and joule heating associated with local geomagnetic current enhancements during geomagnetic storms. For this work we select five events dominated by the radiation effect and/or the geomagnetic effect. For these events we compared the satellite drag derived density with the MSISE model density. The major results can be summarized as follows. (1) The density predicted from the MSISE models during radiation dominated periods are comparable to the drag derived density but the MSISE model density during strong geomagnetic storms is significantly underestimated when the MSISE model density is compared to the drag derived density, by about two times for the NRLMSISE-00 model. (2) The ratios of the KOMPSAT-1 (around 685 km) drag derived density to the MSISE model density during a strong geomagnetic storm are abruptly enhanced (up to a factor of about 8 for the MSISE-90 model and about 3 for the NRLMSISE-00 model), which are much larger than previous estimates from low altitude (around 400 km) satellites. (3) There is a possible correlation between daily drag enhancement and daily Dst variation. We note that there is a remarkable difference in daily drag enhancement although solar and geomagnetic activities are quite similar to each other. We suggest that such a difference should be explained by the accumulation of solar radiation effect depending on solar activity cycle.

Comparison between the KOMPSAT-1 drag derived density and the MSISE model density during strong solar and/or geomagnetic activities