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Statistical study of Euv and X-ray transient brightenings

Research in Astronomy and Astrophysics 2010年第7期10卷 696-706页

作者： Jing-Wei Li Hui Li Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

Using the visual inspection and base difference method and data from the X-ray Telescope （XRT） onboard Hinode and TRACE with improved spatial and temporal resolution, we selected 48 X-ray transient brightenings （XTBs） and 237 Euv transient brightenings （ETBs） to study the connection between these two types of transient brightenings （TBs）. These ETBs and XTBs have smaller areas （8.42 Mm^2 and 36.3 Mm^2, respectively, on average） and shorter durations （9.0 min and 6.9 min, respectively, on average） than previous studies. These XTBs show three types of morphological structure： point-like, single-loop and multiple-loop. We find only 20% of the ETBs have corresponding XTBs while the other 80% have no X-ray signatures at all. This is presumably due to the small amount of released energy, which is not enough to heat the plasma to coronal temperatures which produce X-ray emission rather than being due to the limitation of spatial resolution and temperature sensitivity of the X-ray instrument. These small ETBs may significantly contribute to the coronal heating.

关键词： sun X-rays, gamma rays -- sun uv radiation -- sun corona

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Signature of high-order azimuthal MHD body modes in sunspot's low atmosphere

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Research in Astronomy and Astrophysics 2015年第9期15卷 1449-1454页

作者： Ding Yuan Centre for mathematical Plasma Astrophysics Department of Mathematics

The five-minute oscillations inside sunspots appear to be the absorption of the solar p-mode. It is a potential tool to probe a sunspot＇s sub-structure. We studied the collective properties of five-minute oscillations in the power and phase distribution at the sunspot＇s umbra-penumbra boundary. The azimuthal distributions of the power and phase of five-minute oscillations enclosing a sunspot＇s umbra were obtained with images taken with the Solar Dynamics Observatory/Atmospheric Imaging Assembly （SDO/AIA）. The azimuthal modes were quantified with periodogram analysis and justified with significance tests. The azimuthal nodal structures in an approximately ax- ially symmetric sunspot AR 11131 （2010 Dec 08） were investigated. Mode numbers ra = 2, 3, 4, 7, 10 were obtained in both 1700 A and 1600A bandpasses. The 1600A channel also revealed an extra mode at m = 9. In the upper atmosphere （304 A）, fewer modes were detected at m = 3, 4, 7. The azimuthal modes in the sunspot＇s low atmo- sphere could be interpreted as high-order azimuthal MHD body modes. They were detected in the power and phase of the five-minute oscillations in sunspot AR 11131 with SDO/AIA data. Fewer modes were detected in the sunspot＇s upper atmosphere.

关键词： sun atmosphere - sun uv radiation -- sun sunspots

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维普期刊数据库

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Observations of Euv and soft X-ray recurring jets in an active region

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Research in Astronomy and Astrophysics 2011年第10期11卷 1229-1242页

作者： Li-Heng Yang Yun-Chun Jiang Jia-Yan Yang Yi Bi Rui-Sheng Zheng National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China

We present simultaneous observations of three recurring jets in Euv and soft X-ray （SXR）, which occurred in an active region on 2007 June 5. By comparing their morphological and kinematic characteristics in these two different wavelengths, we found that Euv and SXR jets had similar locations, directions, sizes and velocities. We also analyzed their spectral properties by using six spectral lines from the Euv Imaging Spectrometer （EIS） onboard Hinode and found that these jets had temperatures from 0.05 to 2.0MK and maximum electron densities from 6.6× 10^9 to 3.4× 10^10cm^-3. For each jet, an elongated blue-shifted component and a red- shifted component at the jet base were simultaneously observed in the Fe XII A195 and the He II A256 lines. The three jets had maximum Doppler velocities from 25 to 121 km s-1 in the FexII A195 line and from 115 to 232 km s -1 in the HeII A256 line. They had maximum non-thermal velocities from 98 to 181 km s-1 in the Fe xII A195 line and from 196 to 399 km s-1 in the He II A256 line. We also examined the relationship between averaged Doppler velocities and maximum ionization temperatures of these three jets and found that averaged Doppler velocities decreased with the increase of maximum ionization temperatures. In the photosphere, magnetic flux emergences and cancelations continuously took place at the jet base. These observa- tional results were consistent with the magnetic reconnection jet model, implying that magnetic reconnection between emerging magnetic flux and ambient magnetic field occurred in the lower atmosphere.

关键词： sun activity -- sun corona -- sun uv radiation -- sun magnetic fields

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