Langmuir instabilities in the solar wind plasma

The development of the anisotropy of the electron distribution function in the lower solar corona has been studied through a test-particle model, revealing that particles with v(parallel to) > 5r(e) will eventually run away owing to the magnetic pumping effect. The scaling with v(parallel to) of the parallel distribution function and of the perpendicular temperature is also derived. The theory shows a suprathermal tail originated near the coronal base that dominates the energy flux at distances r similar or equal to 4 R(.). We analyze the high-frequency instability produced by the small anisotropy in perpendicular energy of the runaway electron distribution in the magnetized plasma of the solar wind. A phenomenological description of this instability is obtained. It is also reported that the stability behavior is uncorrelated with the perpendicular temperature profile. The efficiency of Langmuir oscillations as a heating mechanism for the solar wind is discussed.