On Relationship Between CMEs' Speed and Magnetic Field Structure in the Corona and Inner Heliosphere
Abstract
In this study, we search for correlation between the speed of active region-related haloCMEs and the configuration of the ambient magnetic fields. Having studied 99 halo CMEsin the period from 2000 to 2004, we find that CMEs under the heliospheric currentsheet (streamer) are significantly slower than CMEs situated under unidirectional openfield structures (pseudo-streamer or coronal hole). The average speed of the former is883 km s^(-1), while the latter is 1388 km s^(-1). The effect is not biased by the flareimportance. This implies that the ambient magnetic field structure plays a role indetermining the speed of the halo CMEs. We further test this hypothesis by searching forasymmetry in distribution of CMEs' speed in the North- and South-hemisphere, becausethe features of the corona and inner heliosphere, such as streamers, pseudo-streamers andcoronal holes, are primarily determined by the polar field and distribution of solar active regions. Both are asymmetric. Consequently, configuration of large-scale magnetic field (streamer and pseudo-streamer) should have North-South asymmetry. It is found, based on the data in the NASA CMEs catalog (http://cdaw.gsfc.nasa.gov/CME_list/) in 1996-2009, that the (yearly-averaged) CMEs speed is faster in South hemisphere before the polar field reversal (years 2002-2003) and slower after the reversal. A test from our 3D MHD simulation also confirms it.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2012)
- Pub Date:
- June 2012
- Bibcode:
- 2012shin.confE..79L