THE SOLAR CORONA AS PROBED BY COMET LOVEJOY (C/2011 W3)

Abstract

EUV images of Comet Lovejoy (C/2011 W3) from the AIA show striations related\nto the magnetic field structure in both open and closed magnetic regions. The\nbrightness contrast implies coronal density contrasts of at least a factor of 6\nbetween neighboring flux tubes over scales of a few thousand km. These density\nstructures imply variations in the Alfven speed on a similar scale. They will\ndrastically affect the propagation and dissipation of Alfven waves, and that\nshould be taken into account in models of coronal heating and solar wind\nacceleration. In each striation, the cometary emission moves along the magnetic\nfield and broadens with time. The speed and the rate of broadening are related\nto the parallel and perpendicular components of the velocities of the cometary\nneutrals when they become ionized. We use an MHD model of the coronal magnetic\nfield and the theory of pickup ions to compare the measurements with\ntheoretical predictions, in particular with the energy lost to Alfven waves as\nthe cometary ions isotropize.\n