Open AccessCassini plasma spectrometer measurements of Jovian bow shock structure
Author(s) -
Szego Karoly,
Young David T.,
Barraclough Bruce,
Berthelier JeanJacques,
Coates Andrew J.,
McComas David J.,
Crary Frank J.,
Dougherty Michele K.,
Erdos Geza,
Gurnett Donald A.,
Kurth William S.,
Thomsen Michelle F.
Publication year - 2003
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002ja009517
Subject(s) - jovian , physics , bow shock (aerodynamics) , solar wind , jupiter (rocket family) , magnetosheath , bow wave , shock (circulatory) , astronomy , magnetopause , shock wave , magnetosphere of jupiter , plasma , astrophysics , geophysics , planet , saturn , spacecraft , mechanics , medicine , quantum mechanics
The Cassini spacecraft on its way to Saturn flew by Jupiter and crossed its bow shock more than forty times on the dusk‐side of the planet, whereas the early missions targeting Jupiter explored the dawnside. Here we report the first results concerning these bow shock crossings, based on the measurements of the Cassini Plasma Spectrometer (CAPS), the magnetometer, and the radio and plasma wave science (RPWS) instrument. We present data for five bow shock crossings, one at about 1920 local time (LT), the other four between 2100 and 2130 LT, 47.5°–50° beyond terminator. During the flyby the solar activity was high and variable. The measurements confirm that the Jovian bow shock is huge, extending over 700 R J down the flank; Cassini was the first to observe such distant shock features. The bow shock was turbulent and very dynamic and magnetic fluctuations were superimposed on the shock; the downstream ion distributions exhibited bimodal structure time to time. For all bow shock crossings the onset of ion thermalization was a clear shock signature supported by an electrostatic wave signal; thermalization can be used as a signature of the shock location even in those cases when the field data are rather smeared. The strength of the shock potential weakened toward more distant regions even if the local Mach number did not decrease. Reflected protons were not detected upstream above our current sensitivity limit, but the incoming solar wind fluctuated in the foot region. We argue that the Jovian bow shock is not always in a steady state, and some of the observations might be connected with this fact.