Three-Dimensional Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity

Abstract

Many problems in solar physics require analysis of imaging data obtained in multiple wavelength domains with differing spatial resolution in a framework supplied by advanced three-dimensional (3D) physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The enhanced software architecture allows the user to (1) import photospheric magnetic field maps and perform magnetic field extrapolations to generate 3D magnetic field models; (2) investigate the magnetic topology by interactively creating field lines and associated flux tubes; (3) populate the flux tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform, nonthermal electron distributions; (4) investigate the spatial and spectral properties of radio and X-ray emission calculated from the model; and (5) compare the model-derived images and spectra with observational data. The package integrates shared-object libraries containing fast gyrosynchrotron emission codes, IDL-based soft and hard X-ray codes, and potential and linear force-free field extrapolation routines. The package accepts user-defined radiation and magnetic field extrapolation plug-ins. We use this tool to analyze a relatively simple single-loop flare and use the model to constrain the magnetic 3D structure and spatial distribution of the fast electrons inside this loop. We iteratively compute multi-frequency microwave and multi-energy X-ray images from realistic magnetic flux tubes obtained from pre-flare extrapolations, and compare them with imaging data obtained by SDO, NoRH, and RHESSI. We use this event to illustrate the tool's use for the general interpretation of solar flares to address disparate problems in solar physics.

Validation of the Coronal Thick Target Source Model

“…Comparison of the RHESSI and OVSA images shows that they have comparable apparent source sizes, but are clearly displaced relative to each other as often seen in observations and modeling (see, e.g., Nita et al 2015). The reason for this displacement is generally understood: even though the energy-independent spatial distribution of accelerated electrons producing both HXR and microwave emissions is the same, the HXR emission is weighted with the ambient plasma density, while the microwave emission is weighted by magnetic field strength.…”

“…The context GOES-10data and the line-of-sight magnetogram from the Solar and Heliospheric Observatory (SOHO)/MDI (Domingo et al 1995) are used as well. In particular, the lineof-sight magnetogram is utilized to perform a linear force-free field extrapolation needed for the 3D modeling with the GX Simulator (Nita et al 2015).…”

“…According to Nita et al (2015) the first step of this modeling is to select the photospheric magnetogram to perform the extrapolation of the magnetic field to the coronal volume. In our case no vector magnetogram is available, so a nonlinear force-free field ( B r B ( )  á = , NLFFF) extrapolation could not be performed.…”

“…Instead, we used the SOHO/MDI line-of-sight magnetogram, which allows either potential or linear forcefree field ( B B  á = with a constant α, LFFF) extrapolation. Although LFFF is known to be globally incorrect (e.g., Fleishman & Toptygin 2013), it can nevertheless offer an approximately valid local solution needed to approximate a given coronal loop (e.g., Nita et al 2015), if the constant α parameter is selected in such a way that the implied magnetic connectivity can be established. In particular, we use the microwave and X-ray images as guides to the flaring flux tube location and orientation and look for a corresponding field line in a magnetic data cube obtained for a given α.…”

Broadband microwave sub-second pulsations in an expanding coronal loop of the 2011 August 10 flare

“…These SDO/HMI data were processed using the GX Simulator tool (Nita et al 2015) to recon- We used the magnetic field extrapolation in the potential approach in our study because the limb effects are strong in the reconstructed region. This is not a fully correct description of the magnetic field characteristics during the flare.…”