Loop-Top Nonthermal Microwave Source in Extended Solar Flaring Loops

Melnikov, V. F.; Shibasaki, Κ.; Reznikova, Veronika

doi:10.1086/345587

Cited by 118 publications

(87 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The fast electrons are concentrated at or near the looptop as often seen in flares (e.g., Melnikov et al 2002). Both longitudinal and transverse distributions are well described by Gaussian functions with the parameters listed in Table 1; see also Figure 6, right column.…”

Section: Discussionmentioning

confidence: 73%

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

Nita

Fleishman

Kuznetsov

et al. 2015

ApJ

109

104

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 73%

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

Nita

Fleishman

Kuznetsov

et al. 2015

ApJ

109

104

View full text Add to dashboard Cite

show abstract

“…Also, the isotropic injection implies strong scattering in the acceleration process. Although the electron accumulation at the looptop can be explained by a trapplus-precipitation model with modest mirror ratios σ < 2, we concluded that the pitch-angle distribution must be wide enough to be divided by the losscone, or else it will result in either a fully trapped (as proposed by Melnikov et al (2002) due to an anisotropic pitch-angle distribution orthogonal do the magnetic field, the so-called pancake distribution) or fully precipitated scenario (as in the classical thick-target model). This requirement can be fulfilled by moderate/strong pitch-angle scattering processes.…”

Section: Pitch-angle Scatteringmentioning

confidence: 77%

Implications for electron acceleration and transport from non-thermal electron rates at looptop and footpoint sources in solar flares

Simões¹,

Kontar²

2013

A&A

View full text Add to dashboard Cite

The interrelation of hard X-ray (HXR) emitting sources and the underlying physics of electron acceleration and transport presents one of the major questions in high-energy solar flare physics. Spatially resolved observations of solar flares often demonstrate the presence of well-separated sources of bremsstrahlung emission, so-called coronal and footpoint sources. Using spatially resolved X-ray observations by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and recently improved imaging techniques, we investigate in detail the spatially resolved electron distributions in a few well-observed solar flares. The selected flares can be interpreted as having a standard geometry with chromospheric HXR footpoint sources related to thick-target X-ray emission and the coronal sources characterised by a combination of thermal and thin-target bremsstrahlung. Using imaging spectroscopy techniques, we deduce the characteristic electron rates and spectral indices required to explain the coronal and footpoint X-ray sources. We found that, during the impulsive phase, the electron rate at the looptop is several times (a factor of 1.7−8) higher than at the footpoints. The results suggest that a sufficient number of electrons accelerated in the looptop explain the precipitation into the footpoints and imply that electrons accumulate in the looptop. We discuss these results in terms of magnetic trapping, pitch-angle scattering, and injection properties. Our conclusion is that the accelerated electrons must be subject to magnetic trapping and/or pitch-angle scattering, keeping a fraction of the population trapped inside the coronal loops. These findings put strong constraints on the particle transport in the coronal source and provide quantitative limits on deka-keV electron trapping/scattering in the coronal source.

show abstract

“…We suggest that this spatial QPP distribution is not the pulsation mode property, but is connected with the properties of the acceleration and transport of energetic electrons. It was found from the model simulations (Melnikov et al 2002;Gorbikov & Melnikov 2007;Reznikova et al 2009) that the absence of the emission peaks in the LT can be a natural consequence of anisotropic injection of accelerated electrons near to the loop apex predominantly along magnetic field lines. In this case the injected electrons pass quickly though the upper part of the loop with almost zero pitch-angle and, therefore, effectiveness of their gyrosynchrotron emission there is very low.…”

Section: Spatial Distribution Of Qpp and Modulation Depthmentioning

confidence: 99%

Flare quasi-periodic pulsations with growing periodicity

Reznikova

Shibasaki

2010

A&A

Self Cite

View full text Add to dashboard Cite

We conducted a wavelet analysis of the flare intensity variations for the long duration flare on 2005 August 22 observed with the Nobeyama Radioheliograph at frequencies 17 and 34 GHz and with the Ramaty High Energy Solar Spectroscopic Imager at 25-50 keV. We found that the signals contain a well-pronounced periodicity in which the oscillation period grows from 2.5 to 5 min. An analysis of the loop length and plasma temperature evolution during the flare allowed us to interpret the quasi-periodic pulsations in terms of the second standing harmonics of the slow magnetoacoustic mode. This mode can be generated by the initial impulsive energy release and work as a trigger for the repeated energy releases.

show abstract

Loop-Top Nonthermal Microwave Source in Extended Solar Flaring Loops

Cited by 118 publications

References 15 publications

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

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

Implications for electron acceleration and transport from non-thermal electron rates at looptop and footpoint sources in solar flares

Flare quasi-periodic pulsations with growing periodicity

Contact Info

Product

Resources

About