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533 results on '"Brace, L. H."'

269. Electron temperatures during rapid subauroral ion drift events

Author

Moffett, R. J., Ennis, A. E., Bailey, G. J., Heelis, R. A., and Brace, L. H.

Abstract

Examples of data from DE-2 satellite instruments are presented. These illustrate the behaviour of plasma parameters in the F-region and adjacent topside ionosphere during rapid sub-auroral ion drift (SAID) events. In particular, a variety of behaviours of the electron temperature (Te) is demonstrated, both within and equatorward of the SAID region. The Sheffield University plasmasphere-ionosphere model (SUPIM) is used to perform calculations in which a model SAID is applied to a plasma flux tube. The model results indicate that strongly elevated ion temperature (a recognised signature of SAID events) is on occasion sufficient to raise Te to observed values by ion-electron heat transfer. On other occasions, an additional heat source is required. It is suggested that such a source for the electron gas may be due to interaction between the ring current and the plasmasphere at high altitudes. The magnitude of the downward heat flux is consistent with that necessary to produce sub-auroral red arcs. The resulting strongly heated electron gas causes vibrational excitation of molecular nitrogen in the thermosphere.

Published
1998
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271. The structure of the Venus ionosphere

Author

Brace, L. H. and Kliore, A. J.

Abstract

Our current knowledge of the spatial structure of the Venus ionosphere and its temporal behavior is reviewed, with emphasis on the more recent Pioneer Venus measurements and analysis not covered in earlier reviews. We will stress the ionosphere structure, since other papers in this issue deal with its dynamics, and its magnetic properties. We also discuss some of the limitations that the orbit has placed on the spatial and temporal coverage of the ionosphere. For the benefit of future users of the data some of the factors which affect the measurement accuracies are discussed in an Appendix.

Published
1991
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272. Solar cycle variation in the subauroral electron temperature enhancement: Comparison of AE-C and DE 2 satellite observations

Author

Fok, M.-C., Kozyra, J. U., and Brace, L. H.

Abstract

The elevation of the subauroral electron temperature is one of the phenomena showing the energy transfer from the magnetosphere and the response of the ionosphere. The present study addresses solar cycle variations in the subauroral Tepeak by comparing observations of the subauroral peak by the Atmosphere Explorer C (AE-C) satellite near solar minimum (1974 and 1977) with similar observations by the Dynamics Explorer 2 (DE 2) satellite near solar maximum (1981–1982). Electron temperature peaks with magnitudes sufficient to produce observable stable auroral red (SAR) arc emissions occurred more frequently during solar maximum than in solar minimum but the variation in the magnitudes and positions of these peaks with magnetic activity did not change significantly with solar cycle. These results will be discussed in terms of the solar cycle changes in the ionosphere and the magnetospheric energy source.

Published
1991
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278. Thermospheric and ionospheric structure of the southern hemisphere polar cap on October 21, 1981, as determined from Dynamics Explorer 2 satellite data

Author

Emery, B. A., primary, Roble, R. G., additional, Ridley, E. C., additional, Killeen, T. L., additional, Rees, M. H., additional, Winningham, J. D., additional, Carignan, G. R., additional, Hays, P. B., additional, Heelis, R. A., additional, Hanson, W. B., additional, Spencer, N. W., additional, Brace, L. H., additional, and Sugiura, M., additional

Published
1985
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