Science projects related to solar radio observations
The project Action 1 GLOBAL WAVES AND SHOCKS IN THE CORONA: ORIGIN, NATURE, INVERSE & FORWARD MODELING was dedicated to the study of global coronal waves and shocks associated with solar eruptive events. It's based on an extensive study of well-observed events, following a multiwavelength approach (optic, EUV, radio...), to retrieve physical parameters linked to the shock or wave propagation.
Type II radio bursts are the longest-known signatures of MHD shock waves (Wild 1950, Nelson & Melrose 1985). Type II bursts appear in dynamic radio spectra as slowly drifting lanes of enhanced radio emission, generated at the local plasma frequency and/or its harmonics. The metric-wavelength type II bursts appear typically at or below 100 MHz, and they are caused by shocks traveling through the lower solar corona. The type II bursts recorded in the dekameter-to-kilometer wavelength range are excited by shocks traveling through the upper corona and interplanetary space. While most of the interplanetary shocks are CME-driven, coronal shock waves can be attributed to solar flares, CMEs, or some combination of these two phenomena (see e.g. Reiner et al. 2001, Magdalenic et al. 2008, Vrsnak & Cliver 2008, Liu et al. 2009). Since the acceleration phase of the CME and the flare impulsive phase are usually closely synchronized (Maricic et al. 2007; Temmer et al. 2008, Temmer et al. 2010), it is hard to distinguish between the flare energy-release effects and the CME expansion. Due to this problem the origin of the coronal shocks, i.e. metric type II bursts, still remains unresolved.
In the framwork of the Action 1 project, a detailed multiwavelength study of several coronal mass ejection/flare events (CME/flare) and associated coronal shock waves manifested as type II radio bursts was performed. The study was focused on the events in which the flare energy release, and not the associated CME, is the most probable source of the shock wave. Therefore, events associated with rather slow CMEs (reported mean velocity below 500 km/s), were selected. The studied events are presented below. For more details, see Magdalenic et. al, 2008 and Magdalenic et. al, 2010.
Characteristics of the studied events
Radio spectral observations
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Contact: Jasmina Magdalenic