Double Coronal Hard and Soft X-Ray Source Observed by RHESSI: Evidence for Magnetic Reconnection and Particle Acceleration in Solar Flares

By Wei Liu, V. Petrosian, Brian R. Dennis, Y. Jiang. 2007

144 citations recorded by the source corpus.

We present data analysis and interpretation of an M1.4 class flare observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on 2002 April 30. This event, with its footpoints occulted by the solar limb, exhibits a rarely observed, but theoretically expected, double-source structure in the corona. The two coronal sources, observed over the 6-30 keV range, appear at different altitudes and show energy-dependent structures with the higher energy emission being closer together. Spectral analysis implies that the emission at higher energies in the inner region between the two sources is mainly nonthermal, while the emission at lower energies in the outer region is primarily thermal. The two sources are both visible for about 12 minutes and have similar light curves and power-law spectra above about 20 keV. These observations suggest that the magnetic reconnection site lies between the two sources. Bidirectional outflows of the released energy in the form of turbulence and/or particles from the reconnection site could be the source of the observed radiation. The spatially resolved thermal emission below about 15 keV, on the other hand, indicates that the lower source has a larger emission measure but a lower temperature than the upper source. This is likely the result of the differences in the magnetic field and plasma density of the two sources.

Subfields: Artificial Intelligence, Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f21af506cb9410303bc2c74476c1b5dc6bf2ff0a

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Artificial Intelligence

1. V. Petrosian
2. Heng Ji
3. Michele Piana
4. M. Temmer
5. Markus J. Aschwanden
6. D. Longcope

In Astronomy and Astrophysics

1. M. Temmer
2. H. Hudson
3. V. Petrosian
4. Wei Liu
5. Astrid Veronig
6. S. Krucker
7. L. Fletcher
8. Brian R. Dennis

Citations in the corpus

• Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares (2011, background): “The centroid of the lower source is higher in altitude at higher X-ray energies, while the centroid of the upper source is lower in altitude at higher X-ray energies, indicating that energy release occurred between these coronal sources (Sui and Holman 2003; Sui et al. 2004; Liu et al. 2008, 2009b).”
• An Observational Overview of Solar Flares (2011, background): “…first glance quasi-2-D properties, there is a better correlation between the HXR intensity and the derived local magnetic reconnection rateand energy release rate when there are only a few isolated HXR footpoints, than when the ribbon-like HXR emission appears (Jing et al. 2007; Liu et al. 2008a).”
• Stochastic Acceleration by Turbulence (2012, background): “• In rare cases, when the FP sources are weak or occulted, one can see a double LT source (Figure 2 middle, from Liu et al. 2008; see also Sui & Holman, 2003) as expected in the model depicted on the left.”
• PLASMOID EJECTIONS AND LOOP CONTRACTIONS IN AN ERUPTIVE M7.7 SOLAR FLARE: EVIDENCE OF PARTICLE ACCELERATION AND HEATING IN MAGNETIC RECONNECTION OUTFLOWS (2013, methodology): “In previous observations (e.g., Figure 4 in Liu et al. 2008), more obvious reversals occurred at slightly higher energies of 15–20 keV and were interpreted as a transition from the low-energy thermal regime to the high-energy nonthermal regime, in which greater stopping distances of higher energy…”
• Hard X-ray emission from the solar corona (2008, methodology): “An occulted event of 30 April 2002 showed similar coronal structure (Liu et al 2008), again with the above-the-loop coronal source showing an inverted temperature/energy gradient.”
• Deducing Electron Properties from Hard X-ray Observations (2011, background): “…energies (e.g., Krucker and Lin 2002; Saint-Hilaire and Benz 2002; Sui et al. 2002; Emslie et al. 2003; Ji et al. 2004; Alexander and Coyner 2006; Jin and Ding 2007; Alexander and Daou 2007; Liu et al. 2008; Dennis and Pernak 2009; Prato et al. 2009; Shao and Huang 2009; Petrosian and Chen 2010).”
• RECONNECTION OUTFLOWS AND CURRENT SHEET OBSERVED WITH HINODE/XRT IN THE 2008 APRIL 9 “CARTWHEEL CME” FLARE (2010, methodology): “Reports of impulsive-phase RHESSI double coronal sources have been made by other authors (e.g. Liu et al. 2008; Sui, Holman, & Dennis 2004; Sui & Holman 2003) with the lower source corresponding to the top of the rising arcade and the upper source possibly corresponding to an ascending reconnection…”