Suprathermal corrections on galactic cosmic rays driven magnetohydrodynamic waves and gravitational instability in astrophysical plasmas.

This article investigates the influence of suprathermal corrections, modeled by the kappa (κ) distribution function, on cosmic ray (CR)–driven low-frequency magnetohydrodynamic (MHD) waves and gravitational (Jeans) instability in astrophysical plasmas. Using a hydrodynamic fluid–fluid approach, the study derives modified dispersion relations for fast, slow, and Alfvén MHD waves and analyzes how suprathermal particles and CR pressure affect wave phase speeds and gravitational collapse criteria. Key findings include that suprathermal corrections enhance the phase speed of fast MHD waves in plasmas with κ > 3/2, modify the Jeans instability criterion—especially in the absence of CR diffusion—and stabilize the growth rate of gravitational instability, thereby supporting the collapse of non-thermal interstellar gas. The results have implications for understanding wave propagation in the solar atmosphere and star formation processes in molecular clouds and other astrophysical environments.