Volume 82, Number 1, April 2008
Article Number 19001
Number of page(s) 6
Section Geophysics, Astronomy and Astrophysics
Published online 12 March 2008
EPL, 82 (2008) 19001
DOI: 10.1209/0295-5075/82/19001

Thermo-rotational instability in plasma disks around compact objects

B. Coppi

Massachusetts Institute of Technology, Cambridge, MA, USA

received 18 October 2007; accepted in final form 12 February 2008; published April 2008
published online 12 March 2008

Differentially rotating plasma disks, around compact objects, that are imbedded in a "seed" magnetic field are shown to develop vertically localized ballooning modes that are driven by the combined radial gradient of the rotation frequency and vertical gradients of the plasma density and temperature. When the electron mean free path is shorter than the disk height and the relevant thermal conductivity can be neglected, the vertical particle flows produced by these modes have the effect to drive the density and temperature profiles toward the "adiabatic condition" where $\eta_{T}\equiv\left({\rm d}\ln T/{\rm d}z\right)/\left({\rm d}\ln n/{\rm d}z\right)$= 2/3 . Here T is the plasma temperature and n the particle density. The faster growth rates correspond to steeper temperature profiles ($\eta_{T}$ > 2/3) such as those produced by an internal (e.g., viscous) heating process. In the end, ballooning modes excited for various values of $\eta_{T}$ can lead to the evolution of the disk into a different current carrying configuration such as a sequence of plasma rings.

98.62.Mw - Infall, accretion, and accretion disks.
52.35.Py - Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.).
47.65.Md - Plasma dynamos.

© EPLA 2008