On the origin of solar wind. Alfvén waves induced jump of coronal temperature
Department of Theoretical Physics, Faculty of Physics, University of Sofia St. Clement of Ohrid, 5 J. Bourchier Boulevard, 1164 Sofia, Bulgaria
Revised: 13 April 2007
Published online: 29 June 2007
Absorption of Alfvén waves is considered to be the main mechanism of heating in the solar corona. It is concluded that the sharp increase of the plasma temperature by two orders of magnitude is related to a self-induced opacity with respect to Alfvén waves. The maximal frequency for propagation of Alfvén waves is determined by the strongly temperature dependent kinematic viscosity. In such a way the temperature jump is due to absorption of high frequency Alfvén waves in a narrow layer above the solar surface. It is calculated the power per unit area dissipated in this layer due to damping of Alfvén waves that blows up the plasma and gives birth to the solar wind. A model short wave-length (WKB) evaluation takes into account the 1/f2 frequency dependence of the transversal magnetic field and velocity spectral densities. Such spectral densities agree with old magnetometric data taken by Voyager 1 and recent theoretical calculations in the framework of Langevin-Burgers MHD. The presented theory predicts existence of intensive high frequency MHD Alfvén waves in the cold layer beneath the corona. It is briefly discussed how this statement can be checked experimentally. It is demonstrated that the magnitude of the Alfvén waves generating random noise and the solar wind velocity can be expressed only in terms of satellite experimental data. It is advocated that investigation of properties of the solar surface as a random driver by optical methods is an important task for future solar physics.
PACS: 52.35.Bj – Magnetohydrodynamic waves (e.g., Alfven waves) / 52.50.Sw – Plasma heating by microwaves; ECR, LH, collisional heating / 96.60.P- – Corona / 94.30.cq – MHD waves, plasma waves, and instabilities
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2007