Khaled Darwish

We use a 2.5D model to investigate the propagation of Alfven waves and their interaction with the solar wind. In the absence of waves, the dipole field is stretched into a helmet streamer by the solar wind. The wind speeds near the equator are lower than those near the poles. We next inject monochromatic Alfven waves with a period of 1000 s at the coronal base and investigate their propagation at different azimuthal angles. The result is a moderate acceleration and heating of the background plasma. Enhanced wave amplitudes are seen in the region between 1.4 Rsun and 14 Rsun. This region remains fixed in time and it shows features of forward and backward propagating modes. The width of the region increases with an increase in the period of the Alfven waves.
When the period equals 4000 s, we find enhanced acceleration and heating of the solar wind plasma. The amplitudes of the Alfv\'en waves remain large up to 20 Rsun. However, the width of this region changes with time. Beyond the threshold radii, the wave amplitudes are small. Possible scenarios of wave energy conversion are studied to understand the mechanisms of solar wind acceleration by the long period Alfven waves.