Relationship between solar radio type-I noise storm and Coronal Mass Ejection

Details Relationship between solar radio type-I noise storm and Coronal Mass Ejection Relationship between solar radio type-I noise storm and Coronal Mass Ejection

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh54c..06i&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SH54C-06

Astronomy and Astrophysics

Astronomy

[0654] Electromagnetics / Plasmas, [2101] Interplanetary Physics / Coronal Mass Ejections, [6954] Radio Science / Radio Astronomy, [6984] Radio Science / Waves In Plasma

Scientific paper

Type-I noise storm is one of the solar radio phenomena observed in a meter wavelength. While type-I is the most frequently observed solar radio burst, it has little relation to solar flare or other coronal phenomena. So the generation processes of type-I have not been understood well. Sharp decreases of type-I noise storms were observed in some previous studies (Chertok et al., 2001). Decreases of type-I noise storms appear to be associated with coronal mass ejections (CMEs) and post-CME phenomena. Therefore, identifying the ambient magnetic field structure modulated by CME when the type-I noise storms decrease is important to understand the generation mechanisms of type-I, thoughobservational results have not been enough to identify them. In this study, we have investigated an active region which was located around the solar disk center using ground based radio burst observation and coronal imaging observations of the STEREO satellites that located around 65 to 70 degree from the Sun - Earth line. Such coordinated observations at different angles from the active regions are essential for studying the type-I noise burst. The observation of the disc center is best to identify radio bursts because of the emission directivity, whilethe limb observation can capture easily the coronal loop structures and their dynamics. A decrease of type-I noise storm was observed around 100 - 200 MHz on Feb. 7, 2010. In this event, radio flux of the type-I noise storm decreased for about 1 hour and then finally disappeared after emitted at least for 3 hours. A CME eruption was observed at several hours before the type-I dissipation. The STEREO observations suggest that the CME moved above the active region and pre-existing coronal loop structures disappeared during the type-I dissipation. Another CME was observed 1 hour after the type-I dissipation. A potential-field source-surface simulation using SOHO/MDI magnetogram also suggest that there were trans-equatorial magnetic loops extended from the source region of the CME. We have tried to explain the observation results using the CME break out model. In the CME break out model, CMEs emerge inside pre-existing coronal loops and interact with them. After the eruption of the first CME, a current sheet is made in the post CME loop, which is usually much less sheared and their reconnections proceed slowly. Therefore, this current sheet reconnection region can provide energetic particles weakly for a long time and it can explain the long duration of the type-I emission. There is a possibility that flux emergence which lead to this second CME might cause deformation or destruction of the current sheet of the radio source region, and suppressed the radio burst emission. This explanation is consistent with the fact that the type-I dissipation occurred when the first CME front had reached at a height of several solar radius, which is so distant from the height of expected radio source region that the first CME could not modulate the radio source region by itself.

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