After surveying the spectra of 39 prominences observed by the Multi-channel Infrared Solar Spectrograph at Purple Mountain Observatory and the 25 cm coronagraph at the Norikura Solar Observatory, we found that about 2...After surveying the spectra of 39 prominences observed by the Multi-channel Infrared Solar Spectrograph at Purple Mountain Observatory and the 25 cm coronagraph at the Norikura Solar Observatory, we found that about 28% of them show small spatial scale (6''–8'') and short time scale (tens of seconds to a few minutes), unusual large broadening and large shift velocities in spectral lines including Hα, Hβ, H, Ca II H, Ca II K, Ca II 8542?, He I D3 and He I 10830?. We present in detail two typical events observed respectively on 2002 May 27 and 1981 August 2. The full-width at half maximum of the widest profile of the 2001 prominence is 1.8? for Hα and 2.9 ? for He I 10830?, while that of the 1981 prominence is 5.3 ? for Hβ, 3.6 ? for Ca II K, 4.0 ? for Ca II H and 2.8 ? for He I D3. Such broadenings generally occur at a level of several-thousand kilometres above the chromosphere. Further, most of these prominences manifest a rotation of (0.4–1.35)×10<SUP>-2</SUP> rads s<SUP>?1</SUP> pointing to the Sun and large line-of-sight velocities of 20–200 km s<SUP>?1</SUP>. Some of these events correspond in time to an enhancement or a small peak in the GOES X-ray flux, indicating the existence of high energy process at work. These prominences generally display discernible changes in the Hα morphology around the time of large broadening, but do not show Hα brightening or overall eruption except for a few small surge-like events, hence, they are hardly observed in daily Hα patrols. According to the characteristics of their Hα structures and spectral properties, we infer these events are small-scale eruptions similar to nano-flares, which may contribute to the mass and energy transported into the corona. Large turbulent velocities of 25–120 km s<SUP>?1</SUP> are responsible for the observed broadenings.展开更多
One of the common spectral features is asymmetry of spectral line profile for the solar activity phenomena, such as flare, erupted prominence and loop prominence system. The asymmetry is a spectral reflection of the c...One of the common spectral features is asymmetry of spectral line profile for the solar activity phenomena, such as flare, erupted prominence and loop prominence system. The asymmetry is a spectral reflection of the complex active phenomena. In general, a radial motion of matter and some special physical conditions are responsible for the asymmetry of a spectral line profile. So, it is an important aspect in researching the activity phenomena of the Sun to observe and study the asymmetry of the profile. Ye Shi-hui et al. studied the ef-展开更多
The line profiles of Ha in a limb flare on 1998 November 11 appear to be unusually broadened. It is considered that macro-turbulence (or macroscopic mass motions) may be one of the main causes. We use an inversion tec...The line profiles of Ha in a limb flare on 1998 November 11 appear to be unusually broadened. It is considered that macro-turbulence (or macroscopic mass motions) may be one of the main causes. We use an inversion technique to extract the probability distribution of the line-of-sight velocity in the flare. There exist some differences between the velocity distributions deduced from Ha and from Ca II λ8542, which may be because the two lines depend differently on the temperature and velocity. Since the loop density is high, we obtain a rather short cooling time (several tens of seconds) from the hot X-ray loops to the cool loops visible in Ha. Possible origins of the large scale motions are discussed.展开更多
We study the properties of the He I 10830 A line in nine selected solar flares, using spectral data obtained with the Multi-channel Infrared Solar Spectrograph （MISS） at Purple Mountain Observatory （PMO） and photo...We study the properties of the He I 10830 A line in nine selected solar flares, using spectral data obtained with the Multi-channel Infrared Solar Spectrograph （MISS） at Purple Mountain Observatory （PMO） and photospheric images from the Michelson Doppler Imager （MDI） onboard the Solar and Heliospheric Observatory （SOHO）. Our results indicate that, over an area of 3″- 8″, the He I 10830 A line shows emission exceeding the continuum in nearby quiet region when the Geostationary Operations Environmental Satellite （GOES） X- ray class of the flare reaches a threshold value （C4.5）. The He I 10830 A line emission is detected only in the kernels of the Ha brightenings, but is not associated with the size of the flare. It is found that, whenever the He I 10830 Aline shows excess emission over the nearby continuum both the Ha and the Ca Ⅱ 8542 A lines display enhanced intensities exceeding their preflare intensities. The He I 10830A line emission can occasionally extend into the umbra of the involved sunspot, which is inconsistent with previous studies. The weak com- ponent of He I 10830A line changes from emission to absorption earlier than does the main component. Our results favor the photoionization-reconnection mechanism for the excitation of the He I 10830fi, line.展开更多
We have measured the line widths and nonthermal velocities in 12 solar regions using high resolution EUV data taken by Hinode/EIS. We find that there exists a positive correlation between the intensity and nonthermal ...We have measured the line widths and nonthermal velocities in 12 solar regions using high resolution EUV data taken by Hinode/EIS. We find that there exists a positive correlation between the intensity and nonthermal velocity for the Fe xII emission line as well as some other lines. The correlation coefficients decrease from the disk center to the limb. However, the nonthermal velocities of a particular spectral line do not vary much in different regions, so they are considered isotropic. In particular, we find that for a coronal loop structure, the largest widths and nonthermal velocities occur at the footpoints, where outflows appear. Based on these observational results, we discuss several physical processes responsible for coronal heating.展开更多
On 2002 July 23, a 2B/X4.8 flare was observed in the Hα line spec-tropolarimetrically by the Large Solar Vacuum Telescope of Baikal AstrophysicalObservatory. Linear polarization of 3%-10% was detected in the Hα line...On 2002 July 23, a 2B/X4.8 flare was observed in the Hα line spec-tropolarimetrically by the Large Solar Vacuum Telescope of Baikal AstrophysicalObservatory. Linear polarization of 3%-10% was detected in the Hα line, particu-larly where the line showed central reversal. The linear polarization is mainly radialon the solar disk and appears at the impulsive phase of the hard X-ray and γ-raybursts. It is limited to some relatively small regions of the flare. The polarizationin a limited small region (～ 4″ - 5″) changed its direction within a short period oftime (～ 10s).展开更多
基金Support by the National Natural Science Foundation of China.
文摘After surveying the spectra of 39 prominences observed by the Multi-channel Infrared Solar Spectrograph at Purple Mountain Observatory and the 25 cm coronagraph at the Norikura Solar Observatory, we found that about 28% of them show small spatial scale (6''–8'') and short time scale (tens of seconds to a few minutes), unusual large broadening and large shift velocities in spectral lines including Hα, Hβ, H, Ca II H, Ca II K, Ca II 8542?, He I D3 and He I 10830?. We present in detail two typical events observed respectively on 2002 May 27 and 1981 August 2. The full-width at half maximum of the widest profile of the 2001 prominence is 1.8? for Hα and 2.9 ? for He I 10830?, while that of the 1981 prominence is 5.3 ? for Hβ, 3.6 ? for Ca II K, 4.0 ? for Ca II H and 2.8 ? for He I D3. Such broadenings generally occur at a level of several-thousand kilometres above the chromosphere. Further, most of these prominences manifest a rotation of (0.4–1.35)×10<SUP>-2</SUP> rads s<SUP>?1</SUP> pointing to the Sun and large line-of-sight velocities of 20–200 km s<SUP>?1</SUP>. Some of these events correspond in time to an enhancement or a small peak in the GOES X-ray flux, indicating the existence of high energy process at work. These prominences generally display discernible changes in the Hα morphology around the time of large broadening, but do not show Hα brightening or overall eruption except for a few small surge-like events, hence, they are hardly observed in daily Hα patrols. According to the characteristics of their Hα structures and spectral properties, we infer these events are small-scale eruptions similar to nano-flares, which may contribute to the mass and energy transported into the corona. Large turbulent velocities of 25–120 km s<SUP>?1</SUP> are responsible for the observed broadenings.
文摘One of the common spectral features is asymmetry of spectral line profile for the solar activity phenomena, such as flare, erupted prominence and loop prominence system. The asymmetry is a spectral reflection of the complex active phenomena. In general, a radial motion of matter and some special physical conditions are responsible for the asymmetry of a spectral line profile. So, it is an important aspect in researching the activity phenomena of the Sun to observe and study the asymmetry of the profile. Ye Shi-hui et al. studied the ef-
文摘The line profiles of Ha in a limb flare on 1998 November 11 appear to be unusually broadened. It is considered that macro-turbulence (or macroscopic mass motions) may be one of the main causes. We use an inversion technique to extract the probability distribution of the line-of-sight velocity in the flare. There exist some differences between the velocity distributions deduced from Ha and from Ca II λ8542, which may be because the two lines depend differently on the temperature and velocity. Since the loop density is high, we obtain a rather short cooling time (several tens of seconds) from the hot X-ray loops to the cool loops visible in Ha. Possible origins of the large scale motions are discussed.
基金supported by the National Natural Science Foundation of China (GrantNos. 10573038 and 10333040)the National Basic Research Program of China (2006CB806302)+1 种基金the CASProject (KJCX2-YW-T04)the China Meteorological Administration Grant (GYHY200706013).
文摘We study the properties of the He I 10830 A line in nine selected solar flares, using spectral data obtained with the Multi-channel Infrared Solar Spectrograph （MISS） at Purple Mountain Observatory （PMO） and photospheric images from the Michelson Doppler Imager （MDI） onboard the Solar and Heliospheric Observatory （SOHO）. Our results indicate that, over an area of 3″- 8″, the He I 10830 A line shows emission exceeding the continuum in nearby quiet region when the Geostationary Operations Environmental Satellite （GOES） X- ray class of the flare reaches a threshold value （C4.5）. The He I 10830 A line emission is detected only in the kernels of the Ha brightenings, but is not associated with the size of the flare. It is found that, whenever the He I 10830 Aline shows excess emission over the nearby continuum both the Ha and the Ca Ⅱ 8542 A lines display enhanced intensities exceeding their preflare intensities. The He I 10830A line emission can occasionally extend into the umbra of the involved sunspot, which is inconsistent with previous studies. The weak com- ponent of He I 10830A line changes from emission to absorption earlier than does the main component. Our results favor the photoionization-reconnection mechanism for the excitation of the He I 10830fi, line.
基金supported by the National Natural Science Foundation of China under grants 10673004 and 10878002by NKBRSF under grant 2006 CB806302
文摘We have measured the line widths and nonthermal velocities in 12 solar regions using high resolution EUV data taken by Hinode/EIS. We find that there exists a positive correlation between the intensity and nonthermal velocity for the Fe xII emission line as well as some other lines. The correlation coefficients decrease from the disk center to the limb. However, the nonthermal velocities of a particular spectral line do not vary much in different regions, so they are considered isotropic. In particular, we find that for a coronal loop structure, the largest widths and nonthermal velocities occur at the footpoints, where outflows appear. Based on these observational results, we discuss several physical processes responsible for coronal heating.
基金Supported by the National Natural Science Foundation of China.
文摘On 2002 July 23, a 2B/X4.8 flare was observed in the Hα line spec-tropolarimetrically by the Large Solar Vacuum Telescope of Baikal AstrophysicalObservatory. Linear polarization of 3%-10% was detected in the Hα line, particu-larly where the line showed central reversal. The linear polarization is mainly radialon the solar disk and appears at the impulsive phase of the hard X-ray and γ-raybursts. It is limited to some relatively small regions of the flare. The polarizationin a limited small region (～ 4″ - 5″) changed its direction within a short period oftime (～ 10s).
