Open AccessWave activity in Europa's wake: Implications for ion pickup
Author(s) -
Volwerk M.,
Kivelson M. G.,
Khurana K. K.
Publication year - 2001
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 - 10.1029/2000ja000347
Subject(s) - physics , jovian , wake , pickup , cyclotron , ion , magnetic field , polarization (electrochemistry) , current sheet , wave power , magnetosphere , magnetohydrodynamics , atomic physics , computational physics , geophysics , astrophysics , saturn , power (physics) , mechanics , planet , chemistry , quantum mechanics , artificial intelligence , computer science , image (mathematics)
Intense wave power at low frequencies (near and below the cyclotron frequencies of heavy ions) was present in Europa's wake during the E11 and E15 flybys. The fluctuations are mainly transverse to the background magnetic field, and wave characteristics indicate that they are ion cyclotron waves driven by positively charged pickup ions. In both flybys there is evidence, from the wave polarization, for pickup of negatively charged chlorine ions. The pickup rate inferred for the E15 flyby, when the moon is near the center of the Jovian current sheet, is larger than that for the E11 flyby, when the moon is outside the Jovian current sheet. The wave power does not provide absolute pickup density values, because the waves are observed in regions where their growth has not yet saturated. Low‐frequency (< K + gyrofrequency) magnetohydrodynamic waves are also present at the edges of the wake region. We identify signatures in the magnetic field that are reminiscent of interchange/ballooning of mass‐loaded flux tubes from the wake/pickup region expanding into less dense ambient medium.