On the Origin of Alfven Waves Required for Heating in Solar Coronal Holes

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The Earth is situated in a solar wind, whose origins are unclear. The source of this is "coronal holes". This study deals with this plasma source. The fact that Alfven waves may play a significant role in the energy balance in solar coronal holes has been known for many years. The traditional view has been that these waves are generated in the convectively unstable subphotospheric layers. Just very recently Parker (1991, Astrophys. J., 372, 719) and Moore et al. (1991, Astrophys. J., 376, in press) have suggested that these waves can be generated by small-scale magnetic fields assoicated with the network and presented some qualitative arguments to support this idea. Because there are also other mechanisms of Alfven wave generation operating in the solar atmosphere, more detailed calculations are needed to estimate which mechanism dominates in the excitation of these waves. The PI propose to calculate the wave energy spectra and energy fluxes for three different mechanisms of Alfven wave generation: (1) excitation of transverse waves on magnetic flux tubes by the subphotospheric convection, (2) generation of transverse tube waves by the photospheric granulation, and (3) excitation of Alfven waves by the network microflaring. To find out which mechanism is dominant in supplying the wave energy into solar coronal holes, the PI will compare all three obtained wave energy fluxes with total heat input required by observations. This study will be important in ongoing efforts to understand the principal energy sources for solar coronal holes and the basic physical processes responsible for creating the heliosphere, in which the Earth resides.