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Kinetic theory of Jeans instability
S A Trigger1, A I Ershkovich, G J F van Heijst
1Joint Institute for High Temperatures, Russian Academy of Sciences, 127412 Moscow, Russia. strig@gmx.net
Summary
Collisions do not alter the Jeans instability criterion but modify oscillation spectra and introduce new damped modes. The Jeans instability persists despite collisions, though its growth rate is reduced.
Area of Science:
- Plasma physics
- Astrophysics
- Gravitational dynamics
Background:
- The Jeans instability is a fundamental concept in astrophysics describing the gravitational collapse of matter.
- Previous studies primarily focused on collisionless systems, neglecting particle interactions.
Purpose of the Study:
- To kinetically analyze the Jeans gravitational instability including particle collisions.
- To investigate the impact of collisions on instability criteria, growth rates, and oscillation modes.
Main Methods:
- Solving the initial-value problem for the kinetic equation with a particle-conserving collision integral.
- Deriving and analyzing the dispersion relation for the system.
- Identifying and characterizing new wave modes.
Main Results:
- Collisions do not change the Jeans instability criterion.
- Instability growth rates are diminished by collisions but not eliminated.
- New propagating modes are discovered, though they are heavily damped.
- Oscillation spectra are significantly altered, showing strong dependence on collision frequency near the stability threshold.
Conclusions:
- Particle collisions do not prevent Jeans gravitational instability.
- Collisions introduce new damped modes and significantly modify the oscillation spectrum.
- Kinetic effects, including collisions, are crucial for a complete understanding of gravitational instability in astrophysical systems.