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Resonant diffusion of energetic electrons by narrowband Z mode waves in Saturn's inner magnetosphere
Author(s) -
Gu Xudong,
Thorne Richard M.,
Ni Binbin,
Ye ShengYi
Publication year - 2013
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 - 10.1029/2012gl054330
Subject(s) - physics , electron , pitch angle , van allen radiation belt , saturn , magnetosphere , momentum diffusion , atomic physics , diffusion , computational physics , waves in plasmas , scattering , plasma , optics , astrophysics , geophysics , nuclear physics , planet , turbulence , thermodynamics
Banded emissions near 5 and 20 kHz are observed by the Cassini Radio and Plasma Wave Science (RPWS) instrument and are identified as Z mode waves in the regions where the plasma frequency is below the electron gyrofrequency. Using wave parameters derived from Gaussian fits to the measured power spectral density for narrow‐band Z mode waves and the ambient density and magnetic field information at L = ~4, we compute the bounce‐averaged diffusion coefficients for the Saturnian radiation belt electrons. Our results indicate that 5 kHz Z mode emissions can cause resonant scattering of electrons from ~2 MeV to tens of megaelectron volts, while 20 kHz waves can interact with electrons from hundreds of kiloelectron volts to ~2 MeV. In principle, the rate of momentum diffusion can be an order of magnitude larger than that of pitch angle diffusion and cross diffusion for electrons at equatorial pitch angles > ~10°, suggesting that Z mode waves on Saturn are responsible for local acceleration of radiation belt energetic electrons at intermediate pitch angles.