Stability of the solar wind against the whistler mode

The stability of the solar wind against the whistler mode is analyzed. It is shown that the solar wind can become unstable owing to this mode after a distance of 100 R from the sun. The minimum value of the relative velocity (U_r) between -particles and protons for the excitation of this instability is the proton thermal velocity αi. The maximum growth rate at 200 R occurs for the values of the parameters kρ_i = 0·3,(T┤/T)_i = 0·3 and U_r/α_i = 0·5.