文章基本信息

标题：Properties and magnetic origins of solar S-bursts
本地全文：下载
作者：Brendan P. Clarke ; Diana E. Morosan ; Peter T. Gallagher 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：622
DOI：10.1051/0004-6361/201833939
语种：English
出版社：EDP Sciences
摘要：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 17.4–83.1 MHz 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 ≡ 104Jy). The source particle velocities of S-bursts were found to be ∼0.07 c. S-burst source heights were found to range from 1.3R⊙to 2R⊙. 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.
关键词：enSun: coronaSun: radio radiationSun: magnetic fieldsSun: particle emissionradiation mechanisms: non-thermal