| Автор | Mahajan, K. K. |
| Автор | Upadhyay, H. O. |
| Автор | Ghosh, Suchita |
| Дата выпуска | 1996 |
| dc.description | When the solar wind dynamic pressure (P<sub>sw</sub>) is high, the “top” of the Venus ionosphere (defined by the altitude where the steep density gradient begins) moves down to altitudes between 200 and 300 km. Thick ionopauses are formed in the region between 200 and 400 km and here the electron density decreases with a scale height of about 20 km. Further, these regions get permeated by strong horizontal magnetic fields. However, during conditions of low P<sub>sw</sub>, the “top” of the ionosphere moves to higher altitudes and the region between 200 and 400 km is nearly free of magnetic fields. This region then forms a part of the “main” ionosphere, where electron density decreases with a scale height of about 200 km. In this paper, we study the electron cooling processes and their rates in the region between 200 and 400 km for these two conditions, namely, (1) when this region is fully magnetized and (2) when this region is unmagnetized. We use Langmuir probe measurements of electron density and electron temperature from the Pioneer Venus Orbiter for these studies. We find that the dominant electron cooling process in the ionopause region is due to electronic excitation of the ground state of O to the O(<sup>1</sup>D) level. In the main ionosphere, the major processes are cooling due to the fine structure of O, and electron ion Coulomb collisions. Further, the cooling rates are lower in the ionopause region than in the ionospheric region. Only if thermal conduction is assumed to be inhibited in the presence of a horizontal magnetic field, the magnetized orbits can then be used to estimate heating rates by equating these to cooling rates (i.e., local equilibrium). Under this assumption, we find that heating rates so estimated are far smaller than those used by several workers in the heat balance models. However, these rates are closer to model values which include inhibition of photoelectron transport in the presence of a horizontal magnetic field. |
| Формат | application.pdf |
| Копирайт | Copyright 1996 by the American Geophysical Union. |
| Тема | IONOSPHERE |
| Тема | Planetary ionospheres |
| Тема | MAGNETOSPHERIC PHYSICS |
| Тема | Solar wind interactions with unmagnetized bodies |
| Тема | PLANETARY SCIENCES: SOLID SURFACE PLANETS |
| Тема | Planetology: Solid Surface Planets: Ionospheres |
| Тема | Ionospheres |
| Тема | PLANETARY SCIENCES: FLUID PLANETS |
| Тема | Ionospheres |
| Тема | PLANETARY SCIENCES: COMETS AND SMALL BODIES |
| Тема | Ionospheres |
| Название | A comparative study of electron cooling rates in the Venus ionosphere during magnetized and unmagnetized conditions |
| Тип | article |
| DOI | 10.1029/95JE03757 |
| Electronic ISSN | 2156-2202 |
| Print ISSN | 0148-0227 |
| Журнал | Journal of Geophysical Research: Planets |
| Том | 101 |
| Первая страница | 9253 |
| Последняя страница | 9259 |
| Выпуск | E4 |
| Библиографическая ссылка | Banks, P. M., G.Kockarts, Aeronomy, Academic, San Diego, Calif., 1973. |
| Библиографическая ссылка | Brace, L. H., R. F.Theis, W. R.Hoegy, J. H.Wolfe, J. D.Mihalov, C. T.Russell, E. C.Elphic, A. F.Nagy, The dynamic behavior of the Venus ionosphere in response to solar wind interactions, J. Geophys. Res., 85, 7663–7678, 1980. |
| Библиографическая ссылка | Butler, D. M., R. S.Stolarski, Photoelectrons and electron temperature in the Venus ionosphere, J. Geophys. Res., 83, 2057–2065, 1978. |
| Библиографическая ссылка | Cravens, T. E., T. I.Gombosi, J.Kozyra, A. F.Nagy, L. H.Brace, W. C.Knudsen, Model calculations of the dayside ionosphere of Venus: Energetics, J. Geophys. Res., 85, 7778–7786, 1980. |
| Библиографическая ссылка | Dalgarno, A., T. P.Degges, Electron cooling in the upper atmosphere, Planet Space Sci., 16, 125–127, 1968. |
| Библиографическая ссылка | Gan, L., T. E.Cravens, M.Horanyi, Electrons in the ionopause boundary layer of Venus, J. Geophys. Res., 95, 19023–19035, 1990. |
| Библиографическая ссылка | Hedin, A. E., H. B.Niemann, W. T.Kasprzak, A.Seiff, Global empirical model of the Venus thermosphere, J. Geophys. Res., 88, 73–83, 1983. |
| Библиографическая ссылка | Hoegy, W. R., New fine structure cooling rate, Geophys. Res. Lett., 3, 541–544, 1976. |
| Библиографическая ссылка | Kar, J., K. K.Mahajan, On the response of ionospheric magnetization to solar wind dynamic pressure from Pioneer Venus measurements, Geophys. Res. Lett., 14, 507–510, 1987. |
| Библиографическая ссылка | Keating, G. M., et al., Models of the Venus neutral upper atmosphere: Structure and composition, Adv. Space Res., 511, 117–171, 1985. |
| Библиографическая ссылка | Krehbiel, J. P., L. H.Brace, R. F.Thies, J. R.Cutler, W. H.Pinkus, R. B.Kaplan, Pioneer Venus Orbiter electron temperature probe, IEEE Trans. Geosci. Remote Sens., GE 18, 49–54, 1980. |
| Библиографическая ссылка | Luhmann, J. G., R. C.Elphic, C. T.Russell, J. D.Mihalov, J. H.Wolfe, Observations of large scale magnetic fields in the dayside Venus ionosphere, Geophys. Res. Lett., 7, 917–920, 1980. |
| Библиографическая ссылка | Mahajan, K. K., H. G.Mayr, L. H.Brace, P. A.Cloutier, On the lower altitude limit of the Venusian ionopause, Geophys. Res. Lett., 16, 759–762, 1989. |
| Библиографическая ссылка | Mahajan, K. K., S.Ghosh, N. K.Sethi, R.Kohli, Ionospheric evidence of hot oxygen in the upper atmosphere of Venus, Geophys. Res. Lett., 19, 1627–1629, 1992. |
| Библиографическая ссылка | Mahajan, K. K., S.Ghosh, R.Paul, W. R.Hoegy, Variability of dayside electron temperature at Venus, Geophys. Res. Lett., 21, 77–88, 1994. |
| Библиографическая ссылка | Rees, M. H., J. C. G.Walker, A.Dalgarno, Auroral excitation of the forbidden lines of atomic oxygen, Planet. Space Sci., 15, 1097–1110, 1967. |
| Библиографическая ссылка | Russell, C. T., R. C.Snare, J. D.Means, R. C.Elphic, Pioneer Venus Orbiter fluxgate magnetometer, IEEE Trans. Geosci. Remote Sensing, GE‐18, 32–35, 1980. |
| Библиографическая ссылка | Schunk, R. W., A. F.Nagy, Electron temperature in the F region of the ionosphere: Theory and observations, Rev. Geophys., 16, 355–399, 1978. |
| Библиографическая ссылка | Shinagawa, H., J.Kim, A. F.Nagy, T. E.Cravens, A comprehensive magnetohydrodynamic model of the Venus ionosphere, J. Geophys. Res., 96, 11,083–11,095, 1991. |
| Библиографическая ссылка | Stubbe, P., Energy exchange and thermal balance problems, J. Sci. Ind. Res., 30, 379–387, 1971. |
