Context. Impulsive solar energetic particle events in the inner heliosphere show the long-lasting enrichment of 3 He. Aims. We study the source regions of long-lasting 3 He-rich solar energetic particle (SEP) events Methods. We located the responsible open magnetic field regions, we combined potential field source surface extrapolations with the Parker spiral, and compared the magnetic field of the identified source regions with in situ magnetic fields. The candidate open field regions are active region plages. The activity was examined by using extreme ultraviolet images from the Solar Dynamics Observatory (SDO) and STEREO together with radio observations from STEREO and WIND. Results. Multi-day periods of 3 He-rich SEP events are associated with ion production in single active region. Small flares or coronal jets are their responsible solar sources. We also find that the 3 He enrichment may depend on the occurrence rate of coronal jets.
26We present a detailed description of the interrelation between the Type III radio 27 bursts and energetic phenomena associated with the flare activities in Active region 28 AR 11158 at 07:58 UT on 2011, Feb. 15. The timing of the Type-III radio burst 29 measured by the radio wave experiment on the Wind/WAVE and an array of 30 ground-based radio telescopes, coincided with an EUV jet and hard X-ray emission 31 observed by SDO/AIA and RHESSI., respectively. There is clear evidence that the 32 EUV jet shares the same source region as the hard X-ray emission. The temperature of 33 the jet, as determined by multiwavelength measurements of AIA, suggests that type 34 III emission is associated with hot, 7 MK, plasma at the jet's footpoint. 35 Subject heading: Sun: flares ---Sun: X-rays ---Sun: type-III radio bursts 36 37 38 39 40 41 42 43 44 45
One of the most important products of solar flares is nonthermal energetic particles, which may carry up to 50% of the energy released in the flaring processes. In radio observations, nonthermal particles generally manifest as spectral fine structures with fast frequency-drifting rates, named as solar fast-drifting radio bursts (FDRBs). This work demonstrated three types of FDRBs, including type III pair bursts, narrowband stochastic spike bursts following the type III bursts, and spike-like bursts superimposed on a type II burst in an X1.3 flare on 2014 April 25. We find that although all of them have fast frequency-drifting rates, they are intrinsically different from each other in frequency bandwidth, drifting rate, and statistical distribution. We suggest that they are possibly generated from different accelerating mechanisms. The type III pair bursts may be triggered by high-energy electron beams accelerated by the flaring magnetic reconnection, spike bursts are produced by the energetic electrons accelerated by a termination shock wave triggered by the fast reconnecting plasma outflows impacting the flaring loop top, and spike-like bursts are possibly generated by nonthermal electrons accelerated by moving magnetic reconnection triggered by interaction between coronal mass ejection and the background magnetized plasma. These results may help us to understand the generation mechanism of nonthermal particles and energy release in solar flares.
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