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Observation of Electron Conics by Juno: Implications for Radio Generation and Acceleration Processes
Author(s) -
Louarn P.,
Allegrini F.,
McComas D. J.,
Valek P. W.,
Kurth W. S.,
André N.,
Bagenal F.,
Bolton S.,
Ebert R. W.,
Imai M.,
Levin S.,
Szalay J. R.,
Wilson R. J.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl078973
Subject(s) - physics , maser , particle acceleration , electric field , ionosphere , acceleration , electron , jovian , plasma , cyclotron , magnetic field , instability , computational physics , turbulence , geophysics , astrophysics , mechanics , classical mechanics , quantum mechanics , planet , saturn
Using Juno plasma, electric and magnetic field observations (from JADE, Waves, and MAG instruments), we show that electron conic distributions are commonly observed in Jovian radio sources. The conics are characterized by maximum fluxes at oblique pitch angles, ~20°–30° from the B field, both in the upward and downward directions. They constitute an efficient source of free energy for the cyclotron maser instability. Growth rates of ~3 to 7 × 10 4 s −1 are obtained for hectometric waves, leading to amplification by e 10 with propagation paths of 50–100 km. We show that stochastic acceleration due to interactions with a low‐frequency electric field turbulence located a few 10 4 km above the ionosphere may form the observed conics. A possible source of turbulence could be inertial Alfvén waves, suggesting a connection between the auroral acceleration and generation of coherent radio emissions.