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Three-dimensional Forward-fit Modeling of the Hard X-Ray and Microwave Emissions of the 2015 June 22 M6.5 Flare  

Natsuha Kuroda   Submitted: 2018-01-08 11:58

The well-established notion of a "common population" of the accelerated electrons simultaneously producing the hard X-ray (HXR) and microwave (MW) emission during the flare impulsive phase has been challenged by some studies reporting the discrepancies between the HXR-inferred and MW-inferred electron energy spectra. The traditional methods of spectral inversion have some problems that can be mainly attributed to the unrealistic and oversimplified treatment of the flare emission. To properly address this problem, we use a nonlinear force-free field (NLFFF) model extrapolated from an observed photospheric magnetogram as input to the three-dimensional, multiwavelength modeling platform GX Simulator and create a unified electron population model that can simultaneously reproduce the observed HXR and MW observations. We model the end of the impulsive phase of the 2015 June 22 M6.5 flare and constrain the modeled electron spatial and energy parameters using observations made by the highest-resolving instruments currently available in two wavelengths, the Reuven Ramaty High Energy Solar Spectroscopic Imager for HXR and the Expanded Owens Valley Solar Array for MW. Our results suggest that the HXR-emitting electron population model fits the standard flare model with a broken power-law spectrum (E_break ∼ 200 keV) that simultaneously produces the HXR footpoint emission and the MW high-frequency emission. The model also includes an "HXR invisible" population of nonthermal electrons that are trapped in a large volume of magnetic field above the HXR-emitting loops, which is observable by its gyrosynchrotron radiation emitting mainly in the MW low-frequency range.

Authors: Natsuha Kuroda, Dale E. Gary, Haimin Wang, Gregory D. Fleishman, Gelu M. Nita, Ju Jing
Projects: GOES X-rays,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI

Publication Status: Published on The Astrophysical Journal, Volume 852, Issue 1, article id. 32, 16 pp. (2018)
Last Modified: 2018-01-09 11:30
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Observation of 2011-02-15 X2.2 flare in Hard X-ray and Microwave  

Natsuha Kuroda   Submitted: 2015-06-04 22:48

Previous studies have shown that the energy release mechanism of some solar flares follow the Standard magnetic-reconnection model, but the detailed properties of high-energy electrons produced in the flare are still not well understood. We conducted a unique, multi-wavelength study that discloses the spatial, temporal and energy distributions of the accelerated electrons in the X2.2 solar flare on 2011, Feb. 15. We studied the source locations of seven distinct temporal peaks observed in hard X-ray (HXR) and microwave (MW) lightcurves using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in 50 to 75 keV channels and Nobeyama Radioheliograph (NoRH) in 34 GHz, respectively. We found that the seven emission peaks did not come from seven spatially distinct sites in HXR and MW, but rather in HXR we observed a sudden change in location only between the second and the third peak, with the same pattern occurring, but evolving more slowly in MW. Comparison between the HXR lightcurve and the temporal variations in intensity in the two MW source kernels also confirmed that the seven peaks came predominantly from two sources, each with multiple temporal peaks. In addition, we studied the polarization properties of MW sources, and time delay between HXR and MW. We discuss our results in the context of the tether-cutting model.

Authors: Natsuha Kuroda, Haimin Wang, Dale E. Gary
Projects: Nobeyama Radioheliograph,RHESSI,SDO-AIA,SDO-HMI

Publication Status: ApJ (in press)
Last Modified: 2015-06-05 05:59
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Three-dimensional Forward-fit Modeling of the Hard X-Ray and Microwave Emissions of the 2015 June 22 M6.5 Flare
Observation of 2011-02-15 X2.2 flare in Hard X-ray and Microwave

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