Calibration of Siberian Radioheliograph Images

Fedotova, Anastasiya; Altyntsev, A. T.; Kochanov, A. A.; Lesovoi, Sergey; Meshalkina, N. S.

doi:10.12737/stp-54201904

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…The solar disk imaging was performed with the 48-antenna prototype of the Siberian Radio Heliograph at five frequencies: 4.5, 5.2, 6.0, 6.8, and 7.5 GHz with 8.4 s time cadence (Lesovoi et al 2012(Lesovoi et al , 2017. The interferometer maximum base was 107.4 m, and the SRH beamwidth was up to 100 arcsec and varied inversely with frequency.…”

Section: Instrumentationmentioning

confidence: 99%

Temporal and spatial association between microwaves and type III bursts in the upper corona

Altyntsev

Reid²,

Meshalkina

et al. 2023

A&A

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One of the most important tasks in solar physics is the study of particles and energy transfer from the lower corona to the outer layers of the solar atmosphere. The most sensitive methods for detecting fluxes of non-thermal electrons in the solar atmosphere is observing their radio emission using modern large radioheliographs. We analyzed joint observations from the 13 April 2019 event observed by LOw-Frequency ARray (LOFAR) at meter wavelengths, and the Siberian Radio Heliograph (SRH) and the Badary Broadband Microwave Spectropolarimeter (BBMS) spectropolarimeter in microwaves performed at the time of the second PSP perihelion. During a period without signatures of non-thermal energy release in X-ray emission, numerous type III and/or type J bursts were observed. During the same two hours we observed soft X-ray brightenings and the appearance of weak microwave emission in an abnormally narrow band around 6 GHz. At these frequencies the increasing flux is well above the noise level, reaching 9 sfu. In the LOFAR dynamic spectrum of 53−80 MHz a region is found that lasts about an hour whose emission is highly correlated with 6 GHz temporal profile. The flux peaks in the meter waves are well correlated with extreme UV (EUV) emission variations caused by repeated surges from the bright X-point. We argue that there is a common source of non-thermal electrons located in the tail of the active region, where two loop systems of very different sizes interacted. The frequencies of type III and/or type J bursts are in accordance with large loop heights around 400 Mm, obtained by the magnetic field reconstruction. The microwave coherent emission was generated in the low loops identified as bright X-ray points seen in soft X-ray and EUV images, produced by electrons with energies several tens of keV at about twice the plasma frequency.

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Section: Instrumentationmentioning

confidence: 99%

Temporal and spatial association between microwaves and type III bursts in the upper corona

Altyntsev

Reid²,

Meshalkina

et al. 2023

A&A

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Background Microwave Emission and Microflares in Young Active Region 12635

Altyntsev

Meshalkina

Fedotova

et al. 2020

ApJ

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The goal of this work is to study the atmospheric heating above isolated AR 12635 during a period in which a quasistationary increase in microwave and soft X-ray emission is combined with a series of B- and C-class microflares. Analysis of photospheric vector magnetograms showed that an increase in the SXR brightness lasting 14 hours was observed during the simplification of the magnetic structure and the growth of vertical currents in the head part of the active region. A long-term increase of SXR and microwave emission occurred when the total unsigned vertical current exceeded the critical value and coincided in time with the increased level of the emission measure calculated from the GOES X-ray data. Against the background of quasistationary emission, microflares lasting 6–10 minutes occurred. In the hard X-ray range, bursts are recorded with RHESSI channels up to 25 keV. In microwave emission, pulsed and smooth components are distinguished during microflares. The first component was recorded in the 4.5–7.5 GHz range at the beginning of microflares and it is generated by a small population of relativistic electrons by the gyrosychrotron mechanism. The smooth component of the bursts dominated at 17 GHz and was emitted by bremsstrahlung. It is shown that the sources of quasistationary emission and microflares coincide with each other and with the bremsstrahlung source calculated from the differential emission measure obtained from the EUV maps. Coronal magnetic field reconstruction shows that the release of energy on both timescales occurs in a stably existing bundle of magnetic field lines.

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Calibration of Siberian Radioheliograph Images

Cited by 2 publications

References 6 publications

Temporal and spatial association between microwaves and type III bursts in the upper corona

Temporal and spatial association between microwaves and type III bursts in the upper corona

Background Microwave Emission and Microflares in Young Active Region 12635

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