RHESSI microflares with quiet microwave emission

CORC > 紫金山天文台 > 中国科学院紫金山天文台 > 太阳活动的多波段观测研究团组

	RHESSI microflares with quiet microwave emission
	Ning, Zongjun
刊名	ASTROPHYSICAL JOURNAL
	2008-10-10
卷号	686 期号:1 页码:674-685
关键词	Sun : flares Sun : radio radiation Sun : X-rays gamma rays
ISSN号	0004-637X
英文摘要	We statistically study RHESSI microflares, or "weak events,'' from the first month of 2003. In total, 94 events are selected from the RHESSI flare catalog in the 3-6 and 12-25 keV energy ranges. The sample differs from those of previous studies in that the events are characterized by having quiet microwave emission, based on observations from the Nobeyama Radio Polarimeters. These microflares cluster around GOES class C1.1 and are associated with active regions. Consistent with previous findings, the thermal plasma observed by RHESSI is found to be hot, 10 MK less than or similar to T less than or similar to 15 less than or similar to MK, with low emission measure (10(46) cm(-3) less than or similar to EM less than or similar to 10(47) cm(-3)) and density (1.0; 10(9) cm(-3) less than or similar to n(e) less than or similar to 12; 10(9) cm(-3)). The spectral fitting requires a steep nonthermal power-law component, with median index of 8.1. Further evidence for the presence of nonthermal electrons is that the estimated nonthermal energy is comparable to the thermal energy, having a median value of similar to 4.0; 10(28) ergs for the events studied here. Using the correlation between the time derivative of the light curve at 3-6 keV and the 12-25 keV hard X-ray flux, we investigate the Neupert effect in these microflares. Similar to findings for large flares, roughly half of these microflares (46 of 94) display the Neupert effect. RHESSI imaging shows that each event has a single source at 3-12 keV. Such characteristics indicate that some in situ heating mechanism is at work in the local corona surrounding microflares, with the low microwave emission resulting from a lack of nonthermal electron propagation to the chromosphere.
学科主题	Astronomy & Astrophysics
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Astronomy & Astrophysics
研究领域[WOS]	Astronomy & Astrophysics
关键词[WOS]	HARD X-RAY ; WAITING-TIME DISTRIBUTION ; SOLAR-FLARES ; FREQUENCY-DISTRIBUTIONS ; CHROMOSPHERIC EVAPORATION ; NONTHERMAL ELECTRONS ; ENERGY-DISTRIBUTION ; ACTIVE REGIONS ; TEMPERATURE ; BURSTS
收录类别	SCI
语种	英语
WOS记录号	WOS:000259822200055
公开日期	2011-12-30
内容类型	期刊论文
源URL	[http://159.226.72.40/handle/332002/2019]
专题	紫金山天文台_太阳活动的多波段观测研究团组
作者单位	Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Peoples R China
推荐引用方式 GB/T 7714	Ning, Zongjun. RHESSI microflares with quiet microwave emission[J]. ASTROPHYSICAL JOURNAL,2008,686(1):674-685.
APA	Ning, Zongjun.(2008).RHESSI microflares with quiet microwave emission.ASTROPHYSICAL JOURNAL,686(1),674-685.
MLA	Ning, Zongjun."RHESSI microflares with quiet microwave emission".ASTROPHYSICAL JOURNAL 686.1(2008):674-685.