Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation
Abstract
We present the first quantified measure of the energy dissipation rates, due to waveparticle interactions, in the transition region of the Earth's collisionless bow shock using data from the Time History of Events and Macroscale Interactions during Substorms spacecraft. Our results show that waveparticle interactions can regulate the global structure and dominate the energy dissipation of collisionless shocks. In every bow shock crossing examined, we observed both lowfrequency (<10 Hz) and highfrequency (≳10 Hz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The lowfrequency waves were consistent with magnetosonicwhistler waves. The highfrequency waves were combinations of ionacoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The highfrequency waves had the following: (1) peak amplitudes exceeding δB∼ 10 nT and δE∼ 300 mV/m, though more typical values were δB∼ 0.11.0 nT and δE∼ 1050 mV/m; (2) Poynting fluxes in excess of 2000 μW m^{2} (typical values were ∼110 μW m^{2}); (3) resistivities > 9000 Ω m; and (4) associated energy dissipation rates >10 μW m^{3}. The dissipation rates due to waveparticle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for ∼90% of the wave burst durations. For ∼22% of these times, the waveparticle interactions needed to only be ≤ 0.1% efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that waveparticle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collisionless shocks.
 Publication:

Journal of Geophysical Research (Space Physics)
 Pub Date:
 August 2014
 DOI:
 10.1002/2014JA019930
 Bibcode:
 2014JGRA..119.6475W
 Keywords:

 waveparticle interactions;
 collisionless shock waves;
 energy dissipation;
 ionacoustic waves;
 electron cyclotron drift instability;
 electrostatic solitary waves