Polarization, temporal, and spectral parameters of solar flare hard X-rays as measured by the SPR-N instrument onboard the CORONAS-F satellite

Zhitnik, I. A.; Logachev, Yu. I.; Bogomolov, A. V.; Denisov, Yu. I.; Kavanosyan, S. S.; Kuznetsov, S. N.; Morozov, O. V.; Myagkova, I. N.; Свертилов, С. И.; Ignat'ev, A. P.; Oparin, S. N.; Pertsov, A. A.; Tindo, I. P.

doi:10.1134/s003809460602002x

Cited by 36 publications

(22 citation statements)

References 4 publications

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“…A large polarization was observed during the bursts of emission associated with the flare of October 20, 2003 (Zhitnik et al, 2006), the harder radiation being stronger polarized. Then, a smooth transition to the background values took place by the end of the flare.…”

Section: Solar X-ray Spectropolarimeter Spr-nmentioning

confidence: 93%

Results of solar observations by the CORONAS-F payload

Кузнецов

Sobelman

Zhitnik

et al. 2011

Advances in Space Research

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Section: Solar X-ray Spectropolarimeter Spr-nmentioning

confidence: 93%

Results of solar observations by the CORONAS-F payload

Кузнецов

Sobelman

Zhitnik

et al. 2011

Advances in Space Research

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“…Further, the orientation of th e polarization plane, detennined within a claimed uncertainty of 30 0 , was parallel to the solar equator, representing a near-azimuthal polarization vecto r. Both the magnitude and oricntaImaging X-ray Polarimeter for Solar Flares (t XPS) , tion of such a polarization vector imply a highl y non-vertical guiding magnetic fi eld. Even more remarkable is Ihat out 0[90 flarcs studied, only 25 had a sufficicmly high polarization 10 be de tctted, and only three had polarization values as high as those exhibited by the October 29 event (61]. Nevertheless, a continuation of this very high polari:l'.ation signal would be a powerful constraint on flare models.…”

Section: Scientific Motivationmentioning

confidence: 99%

“…Extremely large polarization magnitudes of 50-70% for the X I 0 flare of2003 Oclober 29 have been re ported using 20-100 keY data from the CORONAS-F SPR-N hard X-ray polarimeter (10,61]. This instrument records photons scattered from a series of beryllium plates into a SCI of six scintillation detectors.…”

Section: Scientific Motivationmentioning

confidence: 99%

Imaging X-ray Polarimeter for Solar Flares (IXPS)

Hosack

Black²,

Deines‐Jones

et al. 2011

Exp Astron

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We describe the design ora balloon-borne Imaging X-ray Polarimeter for Solar flares (IX PS). This novel instrument, a Time Projection Cham ber (TPq fo r photoelectric polarimetry, will be capable of measuring polarization at the few percent level in the 20-50 keY energy range during an M-or X·class flare , and will provide imaging information at the ~JO arcscc level. The primary objective of such observations is to determine the direct ivity of nonthennal high-energy electrons producing solar hard X-rays, and hence to learn about the partic le acceleration and energy release processes in solar Rares. Secondary objectives include the separation of the thermal and nonthermal components of the flare X-ray em issions and the separation of photospheric albedo fluxes from direct emissions.

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“…The polarimetric observations are indicative of the high variability of the HXR polarization degrees in different events: from a few percent (Tramiel et al 1984) up to 40% (Tindo et al 1976;Suarez-Garcia et al 2006), or even above 50% as observed for the flare of 23 July 2002(McConnell et al 2003 or 75% as observed by the CORONAS payload (Zhitnik et al 2006). The bulk of observations also detect a noticeable increase of the HXR polarization and directivity in flares located closer to the limb, although some deviations from this trend have been recently observed by RHESSI (Suarez-Garcia et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Diagnostics of energetic electrons with anisotropic distributions in solar flares

Zharkova

Kuznetsov²,

Siversky

2010

A&A

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Aims. The paper aims are to simulate steady-state distributions of electrons beams precipitating in collisional and Ohmic losses with pitch angle anisotropy into a flaring atmosphere with converging magnetic field and to apply these to the interpretation of HXR photon spectra, directivity and polarization observed for different photon energies and flare positions on the solar disk. Methods. Summary approximation method is applied to a time-dependent Fokker-Planck equation by splitting the temporal derivative equally between the derivatives in depth, energy and pitch angles and finding the solutions in forward and backward directions for each variable. Results. For softer beams, there is a noticeable flattening of the photon spectra at lower energies caused by the self-induced electric field that increases for larger viewing angles. For the models with an electric field, the HXR emission with lower energies (30 keV) becomes directed mainly upwards at upper atmospheric levels owing to the increased number of particles moving upwards, while in deeper layers it again becomes directed downwards. The polarization maximum shifts to higher energies with every precipitation depth approaching 25 keV for the models with pure collisions and 100 keV for the models with return currents. At deeper layers, the polarization decreases because of the isotropization of electrons by collisions. The maximum polarization is observed at the viewing angle of 90 • , becoming shifted to lower angles for softer beams. The integrated polarization and directivity shows a dependence on a magnetic field convergence for harder beams, while for softer beams the directivity is strongly affected by the self-induced electric field changing from a downward motion to an upward one at upper atmospheric depths. Conclusions. The proposed precipitation model for an electron beam with wider pitch angle dispersion of 0.2 taking into account collisional and Ohmic losses allowed us to fit the double power law HXR photon spectra with a spectrum flattening at lower energies observed in the flares of 20 and 23 July 2002. The observed directivity of HXR photons of 20 keV derived for a large number of flares located from the disk center to limb is also reproduced well by the theoretical directivity calculated for an electron beam with a very narrow pitch angle dispersion of 0.02. The simulated polarization of this narrowly-directed electron beam fits up to 90% of all the available polarimetric observations carried out at various locations across the solar disk.

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Polarization, temporal, and spectral parameters of solar flare hard X-rays as measured by the SPR-N instrument onboard the CORONAS-F satellite

Cited by 36 publications

References 4 publications

Results of solar observations by the CORONAS-F payload

Results of solar observations by the CORONAS-F payload

Imaging X-ray Polarimeter for Solar Flares (IXPS)

Diagnostics of energetic electrons with anisotropic distributions in solar flares

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