Ion cyclotron instability at Io: Hybrid simulation results compared to in situ observations. Issue 8 (9th August 2016)

• Record Type: Journal Article
• Authors: Šebek, Ondřej; Trávníček, Pavel M.; Walker, Raymond J.; Hellinger, Petr
• Is Part Of: Journal of geophysical research. Volume 121:Issue 8(2016:Aug.)
• Page Start: 7514
• Page End: 7534
• Publication Date: 2016-08-09
• Subjects: Io -- ionization processes -- ion cyclotron waves; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022477
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We present analysis of global three‐dimensional hybrid simulations of Io's interaction with Jovian magnetospheric plasma. We apply a single‐species model with simplified neutral‐plasma chemistry and downscale Io in order to resolve the ion kinetic scales. We consider charge exchange, electron impact ionization, and photoionization by using variable rates of these processes to investigate their impact. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo flybys around Io. The hybrid model describes ion kinetics self‐consistently. This allows us to assess the distribution of temperature anisotropies around Io and thereby determine the possible triggering mechanism for waves observed near Io. We compare simulated dynamic spectra of magnetic fluctuations with in situ observations made by Galileo. Our results are consistent with both the spatial distribution and local amplitude of magnetic fluctuations found in the observations. Cyclotron waves, triggered probably by the growth of ion cyclotron instability, are observed mainly downstream of Io and on the flanks in regions farther from Io where the ion pickup rate is relatively low. Growth of the ion cyclotron instability is governed mainly by the charge exchange rate. Key Points: Ion cyclotron waves are triggered in regions of weak pickup farther from Io and outside its wake in agreement with Galileo observations Ion cyclotron wave growth at Io is controlled by the charge exchange rate Simulation results indicate latitudinal and/or longitudinal asymmetries of Io's atmosphere but no significant upstream/downstream asymmetry