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1.
A type IV radio burst accompanied by several normal- and reverse-drifting type III bursts, multiple long-term quasi-periodic pulsations and spikes was observed with the radio spectrometers (1.0–2.0 and 2.6–3.8 GHz) at National Astronomical Observatories of China (NAOC) on 23 September 1998. In combination with the images of Siberian Solar Radio Telescope (SSRT) of Russia, the complex and multiple magnetic structures inferred from the radio bursts reveal the existence of both large-scale and small-scale magnetic structures. This event suggests that the geometries of coronal magnetic fields contain multiple discrete electron acceleration/injection sites at different heights, and extended open and closed magnetic field lines. It can be shown that the energetic electrons gain access to open, diverging and closed field lines thus producing different types of radio bursts. From the characteristics of position, polarization, dispersion and displacement of the sources, the model of the type IV event is supported, which involves synchrotron emission from the electrons confined by the rapid scattering through the interaction of hydromagnetic wave with particles. 相似文献
2.
The so-called zebra structures in radio dynamic spectra, specifically their frequencies and frequency drifts of emission stripes,
contain information on the plasma parameters in the coronal part of flare loops. This paper presents observations of zebra
structures in a microwave range. Dynamic spectra were recorded by Chinese spectro-polarimeters in the frequency band close
to the working frequencies of the Siberian Solar Radio Telescope. The emission sources are localized in the flare regions,
and we are able to estimate the plasma parameters in the generation sites using X-ray data. The interpretation of the zebra
structures in terms of existing theories is discussed. The conclusion has been arrived at that the preferred generation mechanism
of zebra structures in the microwave range is the conversion of plasma waves to electromagnetic emission on the double plasma
resonance surfaces distributed across a flare loop. 相似文献
3.
We have analyzed the properties of oscillations in a sunspot based on SDO observations with a duration of 6 h. The 3-min oscillation spectrum has turned out to consist of dozens of spectral lines. The line widths are at the spectral resolution limit. The oscillations in a sunspot have been broken down into individual areas with a size of a few arcseconds, each having its own oscillation spectrum. These oscillation properties cannot be explained in terms of the existing models based on the assumption that the sunspot oscillates as a whole. We propose a model of local oscillations that explains the complex spectrum of the oscillations and their locality. We show that in addition to the chromospheric resonator, there exists a subphotospheric resonator for slow MHD waves. The existence of this resonance layer allows the locality of the oscillations and their complex spectrum to be explained in terms of Parker’s model. 相似文献
4.
R. B. Teplitskaya O. A. Ozhogina I. P. Turova R. A. Sych 《Geomagnetism and Aeronomy》2010,50(7):831-842
The dynamic regime of eight regions in the quiet solar chromosphere was analyzed. Observations in CaII lines were performed
with a moderate spatial resolution of around 2″. The purpose of this study was to compare the diagnostic capabilities of these
observations with high-precision measurements conducted in recent years by different authors with new-generation instruments.
Being probably of importance in the chromospheric heating, the recently revealed structural formations (magnetoacoustic portals,
magnetic aureoles, and magnetic shadows) were found to manifest themselves at moderate resolutions too. These findings are
important in the context of investigations of coronal hole bases conducted by the authors with the same observational data. 相似文献
5.
G. P. Chernov R. A. Sych Yihua Yan Qijun Fu Chengming Tan Guangli Huang De-Yu Wang Hongao Wu 《Solar physics》2006,237(2):397-418
We present results of the first simultaneous observations of zebra patterns (ZPs) with super-fine spiky structure in the microwave range made at two observatories ～1000 km apart (Beijing and Nanjing, China). The fine structure was recorded by a spectra polarimeter in the 5.2 – 7.6 and 2.8 – 3.6 GHz ranges at the Huairou station and by the spectrometer in the 4.5 – 7.5 GHz range at the Purple Mountain Observatory. Simultaneously, the locations of radio sources were observed by the Siberian Solar Radio Telescope (SSRT) at 5.7 GHz. For a general analysis of the April 10, 2001 event, the Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) data and Transition Region and Coronal Explorer (TRACE) images in EUV 171 Å line were used. The circular polarization degree was very weak for the burst background radio emission and moderate to strong for the fine structure. The polarization sign in all the cases probably corresponds to the extraordinary wave mode. Estimations of the magnetic field values in the whistler model for fine structure agree well with the extrapolated values from magnetic maps. Given the possibility of wave transformation in the perpendicular magnetic field and the spiky structure of the ZP, the whistler wave model appears to be the most appropriate explanation for the zebra stripe phenomenon. 相似文献
6.
A group of centimetric spikes was detected during the burst of 10 March 2002 with the spectrometer of NAOC (National Astronomical Observatories of China). These centimetric spikes are resolved clearly in the time and frequency panels. A statistical analysis shows that these spikes have very short durations (5–10 ms), narrow bandwidths (20–40 MHz), very high polarization degrees (≥90%), and relatively weak flux densities (10–40 sfu). The simultaneous 2D image observations of NoRH (Nobeyama Radioheliograph) and SSRT (Siberian Solar Radio Telescope) imply that the spikes should come from a small source region, which was located in an area with a complex magnetic field. It is also found that the spikes are polarized in the X-mode. These observations suggest that the electron cyclotron maser (ECM) is the most likely mechanism of these centimetric spikes. 相似文献
7.
利用国家天文台微波(1.0-2.0 GHz和2.6-3.8GHz)射电频谱仪于1998年9月23日观测到了一个稀少事件,它是一个伴生多重周期脉动、Ⅲ型爆发和类I型噪暴的复杂射电Ⅳ型爆发,着重介绍该爆发所具有的多重长周期(约7.3、4.9、3.7、1.2和0.4分钟)脉动成分。这个长周期脉动可能是归因于在封闭环中的驻波模式,由于光球层速度场驱动的MHD的Alfven驻波横穿磁场,导致了对射电辐射的调制。此外,由于这些脉动存在向下的运动,也不排除在一个封闭环或开放场结构中传播的扰动引起振荡的可能性。因为Alfven波的共振与光球层5分钟振荡模式相联系,所以甚长周期的脉动可能来自光球层驱动源的假设,可以说明日冕磁环和光球层之间存在一个互相耦合的可能性。 相似文献
8.
A group of centimetric spikes was detected during the burst of 10 March 2002 with the spectrometer of NAOC (National Astronomical Observatories of China). These centimetric spikes are resolved clearly in the time and frequency panels. A statistical analysis shows that these spikes have very short durations (5–10 ms), narrow bandwidths (20–40 MHz), very high polarization degrees (≥90%), and relatively weak flux densities (10–40 sfu). The simultaneous 2D image observations of NoRH (Nobeyama Radioheliograph) and SSRT (Siberian Solar Radio Telescope) imply that the spikes should come from a small source region, which was located in an area with a complex magnetic field. It is also found that the spikes are polarized in the X-mode. These observations suggest that the electron cyclotron maser (ECM) is the most likely mechanism of these centimetric spikes. 相似文献
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