  New unstable temperature gradient driven modes in an inhomogeneous plasma are
identified. These modes represent transient $\omega \simeq k_{\Vert
}v_{th}^{(e,i)}$ sound oscillations in magnetized plasma that are kinetically
destabilized via Landau interactions. Electron and ion sound branches are
unstable for large values of the Larmor radius parameter $% k_{\bot}\rho
_{e,i}\gg 1,$ respectively. The instability occurs due to a specific plasma
response that significantly deviates from Boltzmann distribution in the region
$k_{\bot}\rho_{i,e}\gg 1$ . Pacs: 52.35 Kt, 52.35 Qz
