Conversion of electromagnetic energy at plasma jet fronts

Tuesday, 15 December 2015: 11:20
2018 (Moscone West)
Yuri V Khotyaintsev1, Andrey V Divin2, Daniel Bruce Graham1, Andris Vaivads1, Mats Andre1, Per-Arne Lindqvist3, Alessandro Retino4, Olivier Le Contel5, Robert E Ergun6, Katherine Goodrich7, Roy B Torbert8, Christopher T Russell9, Werner Magnes10, Rumi Nakamura11, Craig J Pollock12, Barry Mauk13 and Stephen A Fuselier14, (1)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (2)Swedish Inst of Space Physics, Uppsala, Sweden, (3)KTH Royal Institute of Technology, Stockholm, Sweden, (4)CNRS, Paris Cedex 16, France, (5)Laboratoire de Physique des Plasmas (UMR7648), CNRS/Ecole Polytechnique/UPMC/Univ. Paris Sud/Obs. de Paris, Paris, France, (6)University of Colorado, Laboratory for Atmospheric and Space Research, Boulder, CO, United States, (7)University of Colorado at Boulder, Boulder, CO, United States, (8)University of New Hampshire Main Campus, Durham, NH, United States, (9)University of California Los Angeles, IGPP/EPSS, Los Angeles, CA, United States, (10)Space Research Institute, Austrian Academy of Sciences, Graz, Austria, (11)Austrian Academy of Sciences, Vienna, Austria, (12)NASA Goddard Space Flight Center, Heliophysics Sci. Div., Greenbelt, MD, United States, (13)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (14)Southwest Research Institute, San Antonio, TX, United States
We use multi-spacecraft observations by MMS and Cluster in the magnetotail and 3D PIC simulations to investigate conversion of electromagnetic energy at the front of a plasma jet. In PIC simulations the plasma jets (fast localized plasma flows) are produced by magnetic reconnection, while in observations we study bursty bulk flows (BBFs). Jet fronts are known to have a sharp increase of magnetic field (referred to as dipolarization fronts in the magnetospheric physics) as well as sharp gradients in plasma density and temperature. These sharp gradients at the front generate broadband turbulence in the lower-hybrid frequency range, which have amplitudes several times larger than the convective field, wave potential comparable to electron thermal energy, and perpendicular wavelength of the order of several electron gyro-scales. Despite the large wave amplitudes, we find only moderate dissipation due to these waves in the front reference frame, which goes into heating of electrons. We find that the major dissipation is happening in the Earth (laboratory) frame and it is related to reflection and acceleration of ions from the jet front. This dissipation operates at scales of the order several ion inertial lengths, and the primary contribution to E*J is coming from the convective electric field of the front (E=Vfront_x B) and the current flowing at the front.