Hot plasma heavy ion abundance in the inner Jovian magnetosphere (< 10R(j))

Knowledge of the hot plasma components of the Jovian environment is importa nt for several scientific problems, including the acceleration and transpor t of Jovian plasmas, the stability of the plasma sheet, and the bombardment , implantation, and sputtering of the surfaces of Jovian moons, especially Europa. The multiple flybys of the Jovian moon Europa during the Galileo mi ssion have provided the opportunity to study the time and spatial dependenc e of the abundance of the dominant hot plasma (similar to 0.2-10 MeV/nucleo n (n)) heavy ions in the innermost region of the Jovian magnetosphere (less than or equal to 10 R-J). Reported here are measurements made by the CMS D eltaE x E telescopes in the EPD instrument on the Galileo orbiter during th e first six encounters with the moon Europa, data taken over a period of ab out 1.5 years. We use these measurements to study the hot plasma oxygen, su lfur, and sodium abundances near and inside the Europa orbit. The values we determine for these species in the energy range of 0.5-1.0 MeV/n are 0.67 +/- 0.05 for the S/O abundance and 0.05 +/- 0.01 for the Na/O abundance, an d are similar to previous determinations made by instruments on the Voyager (measurements in 1979) and Ulysses (measurements in 1992) spacecraft. (C) 2001 Elsevier Science Ltd. All rights reserved.