THE POWER-DENSITY SPECTRUM BREAK IN A ALFVEN WAVE-DRIVEN SOLAR-WIND

The in situ observations of the solar wind in the interplanetary medium show a spectral break in the power density spectra. Bavassano (1990) showed that near the Sun most of the fluctuations are propagating outward with respect to the Sun, indicating that the fluctuations observed originate from the Sun. Jatenco-Pereira & Opher (1989c, hereafter JPO) used nonthermal mechanisms, such as Alfven waves, to explain coronal heating and the origin of the solar wind. A single average frequency for the Alfven waves was used. On the other hand, Tu (1987) tried to explain the spectral break in the power density in the interplanetary medium in the solar wind but did not treat coronal heating or the origin of the solar wind. No previous attempt has been made to explain the spectral break in the power density spectra. We here obtain the coronal heating, wind velocity, and power density of Alfven waves with a spectral break compatible with observations, using the JPO model for the Sun with a frequency- dependent flux of Alfven waves.