The altitude structure of the coronal magnetic field of AR 10933

Kaltman, T. I.; Bogod, V. M.; Stupishin, A. G.; Yasnov, L. V.

doi:10.1134/s1063772912100022

Cited by 24 publications

(12 citation statements)

References 21 publications

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“…The expected properties of gyroresonance sources discussed above, have been confirmed by both high spatial resolution observations at a few frequencies (e.g., Kundu et al, 1977;Alissandrakis et al, 1980;Alissandrakis andKundu, 1982, 1984;Lang and Wilson, 1982;Kundu and Alissandrakis, 1984;Gopalswamy et al, 1996b;Nindos et al, 1996Nindos et al, , 2002Vourlidas and Bastian, 1996;Zlotnik et al, 1996;Vourlidas et al, 1997;Lee et al, 1998Lee et al, , 1999White, 2004, 2006;Tun et al, 2011;Nita et al, 2018) as well as multi-frequency spectral observations (e.g., Akhmedov et al, 1982;Alissandrakis et al, 1993aAlissandrakis et al, , 2019Lee et al, 1993;Gary and Hurford, 1994;Tun et al, 2011;Kaltman et al, 2012;Stupishin et al, 2018).…”

Section: Observations Of Gyroresonance Emissionmentioning

confidence: 62%

“…Below 10 5 K and down to 2 × 10 4 K, the temperature is determined by the model of Cheng and Moe (1977), while above 2.6 × 10 6 K it is taken as constant. Models of gyroresonance emission can be found in several other publications (e.g., Zlotnik, 1968a,b;Gelfreikh and Lubyshev, 1979;Alissandrakis et al, 1980;Alissandrakis and Kundu, 1984;Holman and Kundu, 1985;Krüger et al, 1985;Hurford, 1986;Brosius and Holman, 1989;Lee et al, 1993Lee et al, , 1998Lee et al, , 1999Gopalswamy et al, 1996b;Nindos et al, 1996Nindos et al, , 2002Vourlidas et al, 1997;Tun et al, 2011;Kaltman et al, 2012;Wang et al, 2015;Nita et al, 2018). Figure 7 shows the x-and o-mode brightness temperature as a function of distance from the center of the model sunspot that results from the dipole field.…”

Section: Structure Of Gyroresonance Sourcesmentioning

confidence: 87%

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Incoherent Solar Radio Emission

Nindos

2020

Front. Astron. Space Sci.

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Incoherent solar radio radiation comes from the free-free, gyroresonance, and gyrosynchrotron emission mechanisms. Free-free is primarily produced from Coulomb collisions between thermal electrons and ions. Gyroresonance and gyrosynchrotron result from the acceleration of low-energy electrons and mildly relativistic electrons, respectively, in the presence of a magnetic field. In the non-flaring Sun, free-free is the dominant emission mechanism with the exception of regions of strong magnetic fields which emit gyroresonance at microwaves. Due to its ubiquitous presence, free-free emission can be used to probe the non-flaring solar atmosphere above temperature minimum. Gyroresonance opacity depends strongly on the magnetic field strength and orientation; hence it provides a unique tool for the estimation of coronal magnetic fields. Gyrosynchrotron is the primary emission mechanism in flares at frequencies higher than 1-2 GHz and depends on the properties of both the magnetic field and the accelerated electrons, as well as the properties of the ambient plasma. In this paper we discuss in detail the above mechanisms and their diagnostic potential.

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Section: Observations Of Gyroresonance Emissionmentioning

confidence: 62%

Section: Structure Of Gyroresonance Sourcesmentioning

confidence: 87%

Incoherent Solar Radio Emission

Nindos

2020

Front. Astron. Space Sci.

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“…Indeed, the gyro emission from a truly homogeneous thermal source (with a unique single magnetic field value), called gyroresonance (GR) emission, would represent a number of distinct narrow peaks occurring around a few small integer multiples of the gyrofrequency (gyroharmonics), Figure 1, although a realistic variation of the magnetic field along the line of sight smooths these peaks out to form a continuum spectrum. Formation of such a continuous spectrum is accounted for by the theory of GR emission, which properly takes into account the magnetic field variation along the line of sight (e.g., Zheleznyakov 1970) and has been widely applied to the solar active regions (Alissandrakis & Kundu 1984;Akhmedov et al 1986;Gary & Hurford 1994Peterova et al 2006;Lee 2007;Bogod & Yasnov 2009;Tun et al 2011;Nita et al 2011;Kaltman et al 2012). For the purpose of the practical forward fit there is no need to include the magnetic field nonuniformity explicitly.…”

Section: Fit To Maxwellian Plasmamentioning

confidence: 99%

Energy Partitions and Evolution in a Purely Thermal Solar Flare

Fleishman¹,

Nita²,

Gary³

2015

ApJ

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This paper presents a solely thermal flare, which we detected in the microwave range from the thermal gyro-and free-free emission it produced. An advantage of analyzing thermal gyro emission is its unique ability to precisely yield the magnetic field in the radiating volume. When combined with observationally-deduced plasma density and temperature, these magnetic field measurements offer a straightforward way of tracking evolution of the magnetic and thermal energies in the flare. For the event described here, the magnetic energy density in the radioemitting volume declines over the flare rise phase, then stays roughly constant during the extended peak phase, but recovers to the original level over the decay phase. At the stage where the magnetic energy density decreases, the thermal energy density increases; however, this increase is insufficient, by roughly an order of magnitude, to compensate for the magnetic energy decrease. When the magnetic energy release is over, the source parameters come back to nearly their original values. We discuss possible scenarios to explain this behavior.

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“…During non-flaring times in the lower corona above active regions, where magnetic fields are strong (typically in the range 100 to 2000 G), gyroresonance emission dominates in the 1-20 GHz range of microwave frequencies. The polarization and the spectra of gyroresonance emission provide the diagnostic information needed to derive coronal magnetic fields, which has a long history (Lantos 1968;Zlotnik 1968a,b;Gelfreikh & Lubyshev 1979;Alissandrakis et al 1980;Akhmedov et al 1982;Alissandrakis & Kun 1984;Akhmedov et al 1986;Peterova et al 2006;Bogod & Yasnov 2009;Kaltman et al 2012). See also reviews by White & Kundu (1997); Gary & Keller (2004); Lee (2007).…”

Section: Introductionmentioning

confidence: 99%

Coronal Magnetography of a Simulated Solar Active Region From Microwave Imaging Spectropolarimetry

Wang

Gary

Fleishman

et al. 2015

ApJ

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We have simulated the Expanded Owens Valley Solar Array (EOVSA) radio images generated at multiple frequencies from a model solar active region, embedded in a realistic solar disk model, and explored the resulting datacube for different spectral analysis schemes to evaluate the potential for realizing one of EOVSA's most important scientific goals-coronal magnetography. In this paper, we focus on modeling the gyroresonance and free-free emission from an on-disk solar active region model with realistic complexities in electron density, temperature and magnetic field distribution. We compare the magnetic field parameters extrapolated from the image datacube along each line of sight after folding through the EOVSA instrumental profile with the original (unfolded) parameters used in the model. We find that even the most easily automated, image-based analysis approach (Level 0) provides reasonable quantitative results, although they are affected by systematic effects due to finite sampling in the Fourier (uv) plane. Finally, we note the potential for errors due to misidentified harmonics of the gyrofrequency, and discuss the prospects for applying a more sophisticated spectrally-based analysis scheme (Level 1) to resolve the issue in cases where improved uv coverage and spatial resolution are available.

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The altitude structure of the coronal magnetic field of AR 10933

Cited by 24 publications

References 21 publications

Incoherent Solar Radio Emission

Incoherent Solar Radio Emission

Energy Partitions and Evolution in a Purely Thermal Solar Flare

Coronal Magnetography of a Simulated Solar Active Region From Microwave Imaging Spectropolarimetry

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