On the Heating of the Solar Corona and the Acceleration of the Low-Speed Solar Wind by Acoustic Waves Generated in Corona

摘要

We investigate possibilities of solar coronal heating by acoustic wavesgenerated not at the photosphere but in the corona, aiming at heating in themid- to low-latitude corona where the low-speed wind is expected to come from.Acoustic waves of period tau ~ 100s are triggered by chromosphericreconnection, one model of small scale magnetic reconnection events recentlyproposed by Sturrock. These waves having a finite amplitude eventually formshocks to shape sawtooth waves (N-waves), and directly heat the surroundingcorona by dissipation of their wave energy. Outward propagation of the N-wavesis treated based on the weak shock theory, so that the heating rate can beevaluated consistently with physical properties of the background coronalplasma without setting a dissipation length in an ad hoc manner. We constructcoronal structures from the upper chromosphere to the outside of 1AU forvarious inputs of the acoustic waves having a range of energy flux of F_{w,0} =(1-20) times 10^5 erg cm^{-2} s^{-1} and a period of tau = 60-300s. The heatingby the N-wave dissipation effectively works in the inner corona and we findthat the waves of F_{w,0} >= 2 times 10^5 erg cm^{-2} s^{-1} and tau >= 60scould maintain peak coronal temperature, T_{max} > 10^6 K. The model could alsoreproduce the density profile observed in the streamer region. However, due toits short dissipation length, the location of T_{max} is closer to the surfacethan the observation, and the resultant flow velocity of the solar wind islower than the observed profile of the low-speed wind. The cooperations withother heating and acceleration sources with the larger dissipation length areinevitable to reproduce the real solar corona.