Investigation of CME-driven shocks with coronagraphic white light and UV data
Abstract
Recent studies of shocks driven by Coronal Mass Ejections have shown that unique information on coronal plasma are provided by a combination of white light (WL) and UV data analyses. On one hand, coronagraphic WL images (like those provided by SOHO/LASCO) can be used to infer the pre-shock coronal density and shock compression ratio, together with other kinematical properties like shock projected speed and inclination of the shock surface. On the other hand, UV intensities (like those provided by SOHO/UVCS) provide the pre-shock plasma temperature and outflow velocity. Then, by applying the Rankine-Hugoniot equations for the general case of an oblique shock it is possible to infer the pre- and post-shock magnetic field strengths and rotations of field vector induced by the shock transit on the plane of the sky, together with post-shock plasma temperatures and outflow velocities. The compression ratio turns out to maximize at the shock nose, where the shock is also supercritical, suggesting that this could be the location for more efficient particle acceleration. The transit of the shock surface corresponds to very strong plasma heating (factors 8 - 12), much weaker at the shock flanks: this likely represents heating of coronal protons (whose kinetic energy is dissipated at the shock), while electrons could be heated by adiabatic compression alone, leading to a decoupling of temperatures across the shock. This technique seems also very promising for applications to UV (H I Lyman-alpha) and WL coronagraphic images that will be provided by the METIS coronagraph onboard the future ESA-Solar Orbiter mission.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E.272B