Synthetic Radio Maps of CMEs up to 24 Solar Radii Heliocentric Distance

Details Synthetic Radio Maps of CMEs up to 24 Solar Radii Heliocentric Distance Synthetic Radio Maps of CMEs up to 24 Solar Radii Heliocentric Distance

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsh23b..01s&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #SH23B-01

Physics

6982 Tomography And Imaging (7270, 8180), 7513 Coronal Mass Ejections (2101), 7827 Kinetic And Mhd Theory, 7847 Radiation Processes, 7851 Shock Waves (4455)

Scientific paper

We present numerical MagnetoHydroDynamic (MHD) simulations of coronal mass ejections (CMEs) and plasma simulations of radio emission from the CME-driven shocks. The simulations correspond to an idealized system, where rotational symmetry around the rotation axis of the Sun is assumed. So the CME has a flux rope structure that extends like a torus around the symmetry axis, i.e. no geometrical effects due to a connection of footpoints of the flux rope with the solar surface are considered. The CME-driven shock extends to an almost spherical shape during the temporal evolution of the CME. We find that our simulations can reproduce the dynamic spectra of coronal radio type II bursts, where the frequency drift rates correspond to the CME-driven shock speeds. We find further, that the CME-driven shock is an effective radio emitter at metric wavelengths, when the CME has reached a heliocentric distance of about two solar radii (R\odot). Towards the center of the CME, where the plasma emission frequency drops significantly due to an over expansion of the core of the CME, the emission is eclipsed for a fixed frequency radio receiver. We apply our simulation results to explain the radio images of type II bursts obtained by radio heliographs, in particular to the banana-shaped images of radio sources associated with fast CMEs. The shock at the rear part of the CME can become an effective radio emitter, where reconnection of magnetic field lines leads to enhanced gradients of magnetic fields. Yet, this emission is usually at lower frequencies than that at the shock front. We apply our kinetic and analytic model of plasma radiation further to MHD simulations of CMEs in 3D. The differences between the 3D and 2D cases are discussed.

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