Properties and magnetic origins of solar S-bursts

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Clarke , B P , Morosan , D E , Gallagher , P T , Dorovskyy , V V , Konovalenko , A A & Carley , E P 2019 , ' Properties and magnetic origins of solar S-bursts ' , Astronomy & Astrophysics , vol. 622 , A204 . https://doi.org/10.1051/0004-6361/201833939

Title: Properties and magnetic origins of solar S-bursts
Author: Clarke, Brendan P.; Morosan, Diana E.; Gallagher, Peter T.; Dorovskyy, Vladimir V.; Konovalenko, Alexander A.; Carley, Eoin P.
Contributor: University of Helsinki, Department of Physics
Date: 2019-02-19
Language: eng
Number of pages: 10
Belongs to series: Astronomy & Astrophysics
ISSN: 1432-0746
URI: http://hdl.handle.net/10138/307409
Abstract: Context. Solar activity is often accompanied by solar radio emission, consisting of numerous types of solar radio bursts. At low frequencies (<100 MHz) radio bursts with short durations of milliseconds, such as solar S-bursts, have been identified. To date, their origin and many of their characteristics remain unclear. Aims. We report observations from the Ukrainian T-shaped Radio telescope, (UTR-2), and the LOw Frequency ARray (LOFAR) which give us new insight into their nature. Methods. Over 3000 S-bursts were observed on 9 July 2013 at frequencies of 17.4-83.1MHz during a period of low solar activity. Leading models of S-burst generation were tested by analysing the spectral properties of S-bursts and estimating coronal magnetic field strengths. Results. S-bursts were found to have short durations of 0.5-0.9 s. Multiple instruments were used to measure the dependence of drift rate on frequency which is represented by a power law with an index of 1.57. For the first time, we show a linear relation between instantaneous bandwidth and frequency over a wide frequency band. The flux calibration and high sensitivity of UTR-2 enabled measurements of their fluxes, which yielded 11 +/- 3 solar flux units (1 SFU equivalent to 10(4) Jy). The source particle velocities of S-bursts were found to be similar to 0.07 c. S-burst source heights were found to range from 1.3 R-circle dot to 2 R-circle dot. Furthermore, a contemporary theoretical model of S-burst generation was used to conduct remote sensing of the coronal magnetic field at these heights which yielded values of 0.9-5.8 G. Within error, these values are comparable to those predicted by various relations between magnetic field strength and height in the corona.
Subject: Sun: corona
Sun: radio radiation
Sun: magnetic fields
Sun: particle emission
radiation mechanisms: non-thermal
ELECTRON-DENSITY
FINE-STRUCTURE
SPIKES
UTR-2
115 Astronomy, Space science
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