Model of solar wind flow near an equatorial coronal streamers

VÁSQUEZ, ALBERTO M.; VAN BALLEGOOIJEN, ADRIAAN A.; RAYMOND, JOHN C.

Congreso; Solar Wind 9; 1998

In a previous work (1) we developed a semiempirical axisymmetric and magnetostatic model of the minimum activity corona, accounting for the gas pressure gradient effects on the magnetic structure. The model is able to reproduce the streamer belt closed region and the streamer surrounding open field lines, predicting high plasma beta values (> 1) in the closed region, low values in the surrounding open-field regions (streamer legs) and even lower values for the polar hole region. In this work we add to that model a solar wind solution under the assumption of mass and momentum flux conservation. For open field lines arising from the polar hole region we find a fast wind solution that reaches values of about 600 km/s at 10 Rsun. For open field lines arising from the surroundings of the closed region (streamer legs), the morphology of the field lines is fast diverging, we find that this results in the existence of two possible sonic points. The first sonic point, located below the streamer cusp, gives a relatively fast solar wind solution, reaching values of about 400 km/s at 10 Rsun. The second sonic point, located above the streamer cusp, gives a slow solution, reaching values of up to 200 km/s for lines close to the streamer core, becoming supersonic only well above the streamer cusp.