Multi-Loop Structure of Nonthermal Microwave Sources in a Major Long-Duration Flare by V. Grechnev et al.*23 May 2017, 11:06 UTC
Hard X-ray (HXR) and microwave observations of flares show only a few nonthermal sources. They are simple and compact, especially in impulsive flares, suggesting involvement of one to two loops. Hanaoka (1996) and Nishio et al. (1997) interpreted these observations in terms of double-loop flares. This view was later extended up to long-duration flares (Tzatzakis, Nindos, and Alissandrakis, 2008). A concept of a simple flare loop became dominant. However, observations in thermal emissions present complex structures, in agreement with the standard flare model. These observational differences led to different views on flare configurations.
The 26 December 2001 M7.1 long-duration flare sheds light on this issue. SSRT observations at 5.7 GHz (Grechnev and Kochanov, 2016) revealed two gyrosynchrotron sources located above opposite magnetic polarities like conjugate legs of a single loop, but they were not static. We analyze observations of this flare with NoRH at 17 GHz, SSRT at 5.7 GHz, and TRACE in 1600 Angstroms.
Similar Motions of Microwave Sources and Flare Ribbons
NoRH images mostly show two microwave sources. The structure of each source is unresolved. Two flare ribbons appear in UV with intermittent bright kernels indicating footpoints of small loops. Figure 1a presents the centroids of each 17 ...