Role of Finite Ion Temperature in the Generation
of Field Swelling Instability

O. A. Pokhotelov^a and O. G. Onishchenko^{a, b}

^a Schmidt Institute of Earth Physics, Russian Academy of Sciences, ul. Bol’shaya Gruzinskaya 10, Moscow, 123995 Russia

^b Space Research Institute, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117997 Russia

e-mail: pokh@ifz.ru, onish@ifz.ru

Received May 14, 2013; in final form, August 25, 2013

Abstract—Field swelling instability is one of the most important instabilities in plasmas in which electrons are
hotter than ions. In contrast to diamagnetic (mirror) instability belonging to the branch of slow magnetosonic
waves, field swelling instability corresponds to the branch of fast magnetosonic waves. The theory of this insta-
bility was developed by (Basu and Coppi, 1982, 1984) in the early 1980s in the idealized zero ion temperature
limit in the context of the magnetohydrodynamic model. To make the model more realistic, it is necessary to
complete it with finite ion temperature effects. In addition, we consider the field swelling theory in the context
of a more instructive quasi-hydrodynamic approach which showed a good performance on examination of the
mirror instability. Here, it appears to be necessary to use only the transverse plasma pressure balance condition
and Liouville theorem for calculating the transverse pressure variation. This consideration is simpler and clearer
and makes it possible to understand in more detail the physical nature of the instability and to prepare the nec-
essary basis for interpreting observational data.

DOI: 10.1134/S0016793214010137

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