A new mechanism of coronal heating

The interaction between network magnetic fields and emerging intranetwork f ields may lead to magnetic reconnection and microflares, which generate fas t shocks with an Alfven Mach number M-A<2. Protons and less abundant ions i n the solar corona are then heated and accelerated by fast shocks. Our stud y of shock heating shows that (a) the nearly nondeflection of ion motion ac ross the shock ramp leads to a large perpendicular thermal velocity (v(th p erpendicular to)), which is an increasing function of the mass/charge ratio ; (b) the heating by subcritical shocks with 1.1 less than or equal to M-A less than or equal to 1.5 leads to a large temperature anisotropy with T-pe rpendicular to/T-parallel to approximate to 50 for O5+ ions and a mild anis otropy with T-perpendicular to/T-parallel to approximate to 1.2 for protons ; (c) the large perpendicular thermal velocity of He++ and O5+ ions can be converted to the radial outflow velocity (u) in the divergent coronal field lines; and (d) the heating and acceleration by shocks with 1.1 less than o r equal to M-A less than or equal to 1.5 can lead to u(O5+) approximate tov (th perpendicular to)(O5+) approximate to 460 km s(-) (1) for O5+ ions, u(H e++) approximate tov(th perpendicular to)(He++) approximate to 360 km s(-1) for He++ ions, and u(H+) approximate tov(th perpendicular to)(H+) approxim ate to 240 km s(-1) for protons at r=3-4 R-.. Our results can explain recen t SOHO observations of the heating and acceleration of protons and heavier ions in the solar corona.