Plasma density and magnetic field fluctuations in the ion gyro-frequency range near the diamagnetic cavity of comet 67P

Elias Odelstad , Anders Eriksson , Mats André , Daniel Graham , Hugo Breuillard (1) , Charlotte Goetz , Erik Vigren , Kei Masunaga , Hans Nilsson , Pierre Henri (1) , Tomas Karlsson

1 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

We report the detection of large-amplitude, quasi-harmonic density-fluctuations with associated magnetic field oscillations in the region surrounding the diamagnetic cavity of comet 67P. Typical frequencies are ∼0.1 Hz, corresponding to ∼10 times the water and ≲0.5 times the proton gyro-frequencies, respectively. Magnetic field oscillations are not always clearly observed in association to these density fluctuations, but when they are, they consistently have wave vectors perpendicular to the background magnetic field, with the principal axis of polarization close to field-aligned and with a ∼90∘ phase lag w.r.t. the density fluctuations. The fluctuations are observed in association with asymmetric plasma and magnetic field enhancements previously found in the region surrounding the diamagnetic cavity, occurring predominantly on their descending slopes. We speculate that they are Ion Bernstein waves (IBWs) excited by the drift-cyclotron instability resulting from strong plasma inhomogeneities in the region surrounding the diamagnetic cavity.

Domains: Sciences of the Universe [physics]

Elias Odelstad, Anders Eriksson, Mats André, Daniel Graham, Hugo Breuillard, et al.. Plasma density and magnetic field fluctuations in the ion gyro-frequency range near the diamagnetic cavity of comet 67P. 21st EGU General Assembly, Apr 2019, Vienne, Austria. ⟨insu-03563842⟩