TY - JOUR
T1 - The ionosphere of Ganymede
AU - Eviatar, Aharon
AU - Vasyliunas, Vytenis M.
AU - Gurnett, Donald A.
N1 - Funding Information:
We gratefully acknowledge helpful discussions with W.S. Kurth, M.A. McGrath, R.E. Johnson, P.D. Feldman, D.F. Strobel, L.J. Paxton and M.E. Brown. We are grateful to M.G. Kivelson for her gracious permission to use the magnetometer data upon which Fig. 4 is based. The work at Tel Aviv University and at the Max-Planck-Institut für Aeronomie was sponsored in part by the German–Israel Foundation for Basic Research (GIF) under grant I-562-242.07/97. The research at the University of Iowa was supported by NASA through JPL contract 958779. The final revision of this paper was carried out while A. Eviatar was a visitor at the Hubble Space Telescope Science Institute in Baltimore MD, USA. Their hospitality is gratefully acknowledged.
PY - 2001/3
Y1 - 2001/3
N2 - We consider the distribution of plasma density in the atmosphere of Ganymede and present electron density profiles inferred from data of the Plasma Wave instrument of Galileo. To study the question of ionospheric plasma, we present a zero-dimensional local rate equation model of the source and loss functions and the atomic and molecular processes we assume to be taking place. We conclude from the model that Ganymede has a bound ionosphere composed mainly of molecular oxygen ions in the polar regions and of atomic oxygen ions at low latitudes and that protons are absent everywhere. This implies that the plasma observed to be flowing out along the open flux tubes connected to the polar cap is composed of ions of atomic oxygen. We predict that Ganymede is surrounded by a corona of hot oxygen atoms. The model neutral atmosphere has a composition similar to that of the ionosphere and is exospheric everywhere. Our calculated neutral column density is consistent with values of Ganymede ultraviolet auroral brightness observed by means of the Hubble Space Telescope.
AB - We consider the distribution of plasma density in the atmosphere of Ganymede and present electron density profiles inferred from data of the Plasma Wave instrument of Galileo. To study the question of ionospheric plasma, we present a zero-dimensional local rate equation model of the source and loss functions and the atomic and molecular processes we assume to be taking place. We conclude from the model that Ganymede has a bound ionosphere composed mainly of molecular oxygen ions in the polar regions and of atomic oxygen ions at low latitudes and that protons are absent everywhere. This implies that the plasma observed to be flowing out along the open flux tubes connected to the polar cap is composed of ions of atomic oxygen. We predict that Ganymede is surrounded by a corona of hot oxygen atoms. The model neutral atmosphere has a composition similar to that of the ionosphere and is exospheric everywhere. Our calculated neutral column density is consistent with values of Ganymede ultraviolet auroral brightness observed by means of the Hubble Space Telescope.
UR - http://www.scopus.com/inward/record.url?scp=0347037832&partnerID=8YFLogxK
U2 - 10.1016/S0032-0633(00)00154-9
DO - 10.1016/S0032-0633(00)00154-9
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AN - SCOPUS:0347037832
SN - 0032-0633
VL - 49
SP - 327
EP - 336
JO - Planetary and Space Science
JF - Planetary and Space Science
IS - 3-4
ER -