Energy transport and dissipation within Earth's supercritical bow shock: The role of intense whistler waves

We present detailed analysis of whistler wave observations from the Magnetospheric Multiscale (MMS) mission within Earth's bow shock. Particular attention is focused on the role of whistler waves in energy transport and dissipation within the layer. The multipoint observations from MMS are used to quantify the currents, Poynting fluxes, and dissipation rates J·E associated with these waves and to assess their spatial and temporal properties. Characteristic of the multiscale structure of the whistler wave packets, we show that the currents, Poynting fluxes and J·E are bursty and patchy within the layer with values that increase in intensity with increasing penetration into the layer. How these quantities vary as a function of scales within the layer will be discussed. We show that these whistlers support the most intense currents in the layer with values reaching the order of μAmp/m² and down to sub-ion inertial length scales. These waves carry Poynting fluxes that range from tens to few hundreds of μW/m². Energy dissipation J·E from intense whistlers range from a few thousandths to few hundredths of μW/m³. These values were shown to yield net energy exchanged from the plasma to whistlers in the foot, whereas the waves are dissipated into the plasma in the ramp. This observations suggests a scenario whereby the waves are generated in the foot and subsequently get blown into the ramp, where their energy accumulates due to the slowing flow and is dissipated into plasma heating.