NPG Nonlinear Processes in Geophysics NPG Nonlin. Processes Geophys. 1607-7946 Copernicus Publications Göttingen, Germany 10.5194/npg-10-27-2003 Magnetic field turbulence, electron heating, magnetic holes, proton cyclotron waves, and the onsets of bipolar pulse (electron hole) events: a possible unifying scenario Tsurutani B. T. 1 Dasgupta B. 1 Arballo J. K. 1 Lakhina G. S. 2 Pickett J. S. 3 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA Indian Institute of Geomagnetism, Mumbai/Bombay 400 005, India Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA 30 04 2003 10 1/2 27 35 Copyright: © 2003 B. T. Tsurutani et al. 2003 This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/ This article is available from https://npg.copernicus.org/articles/10/27/2003/npg-10-27-2003.html The full text article is available as a PDF file from https://npg.copernicus.org/articles/10/27/2003/npg-10-27-2003.pdf

Two electron heating events have been identified on 20 May 1996 when Polar was in the polar cap/polar cusp boundary layer. The electron heating events were located within magnetic holes/cavities/bubbles and were accompanied by nonlinear ± 14 nT peak-to-peak (f ~ 0.6 to 0.7 f<sub>cp</sub>) obliquely propagating proton cyclotron waves. The electrons appear to be heated isotropically. Electric bipolar pulse (electron hole) onset events were also detected within the heating events. We propose a scenario which can link the above phenomena. Nonlinear Alfvén waves, generated through cusp magnetic reconnection, propagate down magnetic field lines and locally heat electrons through the ponderomotive force. The magnetic cavity is created through the diamagnetic effect of the heated electrons. Ion heating also occurs through ponderomotive acceleration (but much less than the electrons) and the protons generate the electromagnetic proton cyclotron waves through the loss cone instability. The obliquely propagating electromagnetic proton cyclotron waves accelerate bi-streaming electrons, which are the source of free energy for the electron holes.