Masters Thesis defense by Tina Ibsen – Niels Bohr Institute - University of Copenhagen

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Masters Thesis defense by Tina Ibsen

HELIOSPHERIC PROPAGATION OF CMEs- A study of the Radial Propagation of ICMEs from the SUN to 1.78 AU.

The Sun is not a quiet place, and large explosive events eject thousands of tons of mass into interplanetary space every day during solar maximum. The most violent of these events are called Coronal Mass Ejections (CMEs), and when these encounter the Earth they can cause severe damage. In the most extreme cases CMEs can cause power grid blackouts, completely set out navigation systems (GPS) and strongly interfere with or even block radio signals.

This thesis investigates the radial propagation of six Interplanetary Coronal Mass Ejections (ICMEs), in July and August 2000 where the Earth was closely aligned with the NEAR spacecraft which was situated at 1.78 AU. An ICME can have a magnetic cloud (MC) part, which is believed to have a force-free flux rope structure. A minimum variance analysis has been applied to the magnetic field data of the MCs in order to determine the orientation, as well as the size, magnetic field strength and speed of the ICMEs.

Some of the overall properties of the ICMEs can already be seen as they erupt from the Sun as CMEs, if the correct solar source can be linked with the event seen at Earth.

The solar source for most of these events has been found, and if the CME was associated with a solar flare the helicity of the ensuing post-flare loop has been found. The same helicity should later be present in the subsequent MC observed at Earth and NEAR and the helicities found here, have been compared to the helicity found at the solar source.

Supervisors: Susanne Vennerstrøm DTU-Space and Morten Bo Madsen NBI