Effect of anisotropic Cairns distribution on drift magnetosonic wave

Abstract.

Non-monotonic shoulder like velocity distributions and high-energy tails are often observed in space plasmas, e.g., in solar wind. In this work, these effects are studied for obliquely propagating drift mode in an anisotropic and spatially inhomogeneous environment of solar wind at about 1 AU, using the Cairns distribution. Different cases are studied to see the interrelationship between Cairns parameter $\Lambda$, density inhomogeneity factor $\eta$, and the temperature anisotropy $T_{\Vert \alpha}/T_{\perp \alpha} > 1$. It is observed that while the temperature anisotropy alone gives only damping on kinetic scale for drift magnetosonic mode, but in conjunction with $\Lambda$ (showing the extent of non-thermality), it can generate instability. The three interesting effects together automatically satisfy the firehose instability condition. Further, when we consider reactive-type instability, the electron temperature anisotropy $T_{\Vert e}/T_{\perp e} > 1$ can independently generate resonant firehose instability for $R(\omega ) = 0$, which develops at oblique propagation of the wave at comparatively high $\beta_{\Vert e}$. These results are quite important for all non-thermal environments where the plasma is inhomogeneous and temperature anisotropic, such as in space and astrophysical plasmas. The results might be helpful in understanding the phenomena of heating and acceleration of particles in solar corona and solar wind via Landau damping and in explaining the physical nature of coronal Extreme-ultraviolet Imaging Telescope (EIT) waves.