Evolution of the ring current ion population, as observed by the CRRES/MICS instrument
- Rutherford Appleton Lab (United Kingdom)
Using the MICS instrument on CRRES, we have examined high charge state magnetospheric ions in the energy range 20-400 keV/Q, believed to be originally solar wind material, as well as singly charged Oxygen and helium. We will present survey plots of MICS data from the whole CRRES mission. These show a number of interesting features. In particular, it can be seen that the generic feature of storm bulk ring current composition changes is the emergence of a concentration of ionospheric material at low (L=3) altitude, and its rise to higher L-shells during the recovery. By contrast, solar wind material remains preponderantly at higher L-shells, and a belt of ring current alphas forms around L=4. The altitude of the peak in ionospheric material is a strong function of Dst. Substorms are seen to reflect the background composition at energization, with onset properties apparently unrelated to injection composition, but may contribute to the upflow of oxygen subsequent to onset. During the solar storm of March 1991 we see a considerable increase in the numbers of alpha particles, Fe, Si and other species. Simultaneous changes in their charge states are seen. For example, in the case of iron, we can recognize charge peaks around 9 and 16, and swings between the dominant charge state. The swings in other species charge states are consistent with a change in source temperature from 1.1 to 2.5 million degrees, as expected for different streams of coronal origin. It is clear that this material is locally trapped within the magnetosphere, which suggests that not only has there been an abrupt change between fast and slow stream material, but also that this signature has penetrated promptly to geostationary altitude. This hypothesis is to some extent confirmed by data from the GOES 7 satellite, which shows evidence of a sudden compression of the magnetosphere coincident with the start of the main period of high charge state material. The signature of a change from low to high temperature seems to fit well the suggestions of Tsurutani and Gonzales (ref /5/) of a fast stream tamped by a slower one as a generator of great storms.
- OSTI ID:
- 21163528
- Journal Information:
- AIP Conference Proceedings, Vol. 383, Issue 1; Conference: Workshop on the Earth's trapped particle environment, Taos, NM (United States), 15-19 Aug 1994; Other Information: DOI: 10.1063/1.51525; (c) 1996 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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