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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 114,
A00D03,
11 PP., 2009
doi:10.1029/2008JA014015
Role of entropy in magnetotail dynamics
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Institut für Theoretische Physik, Ruhr‐Universität, Bochum, Germany
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
The role of entropy conservation and loss in magnetotail dynamics, particularly in relation to substorm phases, is discussed on the basis of MHD theory and simulations, using comparisons with particle‐in‐cell (PIC) simulations for validation. Entropy conservation appears to be a crucial element leading to the formation of thin embedded current sheets in the late substorm growth phase and the potential loss of equilibrium. Entropy conservation also governs the accessibility of final states of evolution and the amount of energy that may be released. Entropy loss (in the form of plasmoids) is essential in the earthward transport of flux tubes (bubbles, bursty bulk flows). Entropy loss also changes the tail stability properties and may render ballooning modes unstable and thus contribute to cross‐tail variability. We illustrate these effects through results from theory and simulations.
Received 22 December 2008; accepted 18 February 2009; published 18 April 2009.
Citation: (2009), Role of entropy in magnetotail dynamics, J. Geophys. Res., 114, A00D03, doi:10.1029/2008JA014015.
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