M. Hattori et K. Umetsu, A possible route to spontaneous reduction of the heat conductivity by a temperature gradient-driven instability in electron-ion plasmas, ASTROPHYS J, 533(1), 2000, pp. 84-94
We have shown that there exist low-frequency growing modes driven by a glob
al temperature gradient in electron and ion plasmas by linear perturbation
analysis within the framework of plasma kinetic theory. The driving force o
f the instability is the local deviation of the distribution function from
the Maxwell-Boltzmann distribution due to a global temperature gradient. Ap
plication of the results to the intracluster medium is being reduced to 5-7
orders of magnitude less than the mean free paths due to Coulomb collision
s. This may provide a hint in explaining why hot and cool gas can coexist i
n the intracluster medium in spite of the very short evaporation timescale
due to thermal conduction if the conductivity is the classical Spitzer valu
e. Our results suggest that the realization of the global thermal equilibri
um is postponed by the local instability, which is induced for a quicker re
alization of the local thermal equilibrium state in plasmas. The instabilit
y provides a new possibility to create and grow cosmic magnetic fields with
out any seed magnetic field.