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1.
对于足点被日面边缘遮挡住的耀斑的观测研究是诊断日冕硬X射线辐射的一个重要方法.通过统计分析RHESSI (Reuven Ramaty High-Energy Solar Spectroscopic Imager)卫星观测到的71个此类耀斑硬X射线源发现,前人提出的两类源,即日冕X射线辐射中热辐射与非热辐射源区空间分离较小的源和分离较大的源,在能谱、成像、光变曲线以及GOES持续时间等方面都没有显著的区别,其中辐射区的面积、耀斑总热能以及GOES持续时间与分离距离之间有很好的相关性.这些结果支持近年来提出的一些耀斑统一模型.同时也表明Masuda耀斑只是一类非常特殊的事件,不具有日冕硬X射线辐射的一般特征. 相似文献
2.
先进天基太阳天文台(ASO-S)卫星的3大载荷之一硬X射线成像仪(Hard X-ray Imager, HXI)是一套基于傅立叶变换调制成像技术的望远镜.它利用91组不同摆放角和节距的光栅子准直器排列摆布,获得45个基于空间调制的傅立叶变换对,重建太阳耀斑源30–200 keV的硬X射线像,最高分辨率可达3.1′′.在光栅节距已经确定的前提下,它的摆放角分布仍会影响成像质量.通过对HXI仪器傅立叶分量μν分布与点扩散函数(PSF)的空间演化关系分析研究,寻求HXI光栅摆放角的最优分布.其结果将作为改进HXI仪器设计和开发相应科学分析软件的依据. 相似文献
3.
耀斑软X射线流量的统计性质 总被引：1，自引：0，他引：1
为了更定量地研究太阳耀斑软X射线辐射的统计性质,发展了一套对于给定峰值流量区间的耀斑的自动识别程序,并用它分析了从1980年到2013年GOES(Geostationary Operational Environmental Satellite)在两个软X射线波段上对太阳耀斑的观测.研究发现耀斑软X射线流量在峰值附近变化的统计特征和耀斑流量峰值的绝对大小无关:平均而言耀斑流量的上升时间约是下降时间的一半,而且高能量通道的上升和下降时间比相应的低能量通道时间要短,但是这些时间还是会随着耀斑流量变化幅度的增加而增加. 相似文献
4.
先进天基太阳天文台卫星(Advanced Space-based Solar Observatory, ASO-S)是中国科学院第2批空间科学先导专项之一,其主要目标是同时观测太阳磁场、耀斑和日冕物质抛射,并对3者之间的相互关系和内在联系进行研究.硬X射线成像仪(HXI)是ASOS卫星的3大载荷之一,它通过对太阳活动发射的硬X射线进行傅里叶调制成像,实现高空间分辨率和高时间分辨率的太阳能谱成像观测.量能器单机是HXI的关键单机之一,其主要任务是精准测量通过每对光栅后太阳硬X射线的能量和通量.主要介绍了量能器单机的工作原理及其关键指标要求、标定设备及标定方案,最后给出了标定结果,从而验证了量能器单机方案设计的合理性. 相似文献
5.
太阳耀斑中硬X射线(HXR)光子谱的低能变平过去一般认为是由于耀斑中非热电子的低能截止造成的,但现在也有作者认为耀斑光子与下层大气的逆康普顿散射(albedo效应)或者其他作用也能够使得HXR光子谱出现低能变平的情形.采用Gan etal.(2001,2002)中提出的求非热电子低能截止的方法,统计分析了Ramaty High EnergySolar Spectroscopy Imager(RHESSI)卫星在2002--2005年间观测的100个耀斑,发现经albedo校正,有18个耀斑的HXR光子谱可以利用单幂律谱来拟合,在80个可以用双幂律谱来拟合HXR光子谱的耀斑中,有21个耀斑可以直接用单幂律电子谱加一个低能截止来解释.低能截止范围为20-50keV,平均值约为30keV.同时也分析了耀斑光子谱特征的其他可能解释. 相似文献
6.
伽马暴偏振探测仪(POLAR)是天宫2号实验室上搭载的一个γ射线偏振仪,于2016年9月15日搭载在天宫2号进入低轨运行,主要用于探测在50-500 keV能区的硬X射线辐射的线偏振.POLAR由25个模块组成,每个模块有64个塑料闪烁体棒,总计有1600个塑料闪烁体棒,具有较大的有效探测面积和视场.在轨运行期间探测到多个小耀斑,它们的硬X射线光子能量通常小于50 keV,无法直接使用在轨和地面的高能定标结果来进行能谱分析.结合拉马第太阳高能光谱成像探测器(RHESSI)对耀斑SOL2016112907能谱的观测和蒙特卡洛模拟,对耀斑期间被激活的闪烁体棒进行能量低于50 keV的低能相对定标.虽然定标得到的能量阈值(～10 keV)和转换因子相对稳定,但是和高能定标给出的结果相比有显著差异,并且不同闪烁体棒显示出的差异没有明显的规律性. 相似文献
7.
近年来对太阳耀斑的研究取得了重要的进展。一些新的发现主要来自高分辨率的观测，特别是来自"阳光"卫星的结果。综述的范围包括太阳耀斑中磁重联的新证据、硬X射线源（包括所谓的超热源）的分类、X射线喷流的发现、环－环相互作用的证据以及对耀斑大气动力学过程的新认识等。基于这些新的知识，讨论了有关耀斑模型的一些问题。 相似文献
8.
利用SDO (Solar Dynamics Observatory)/HMI (Helioseismic and Magnetic Imager)观测到的矢量磁图,研究了与活动区AR12673上爆发的一个X9.3级耀斑(2017年9月6日)的相关电流分布和演化.结果显示,在该活动区的磁中性线两边存在一对方向相反的电流密度约为0.4 A/m~2的长电流带,可称其为一对共轭电流带.这对共轭电流带在耀斑发生之前、期间以及之后一直存在;并且观测到,该耀斑的两个亮带的位置几乎刚好与两个电流带重叠,它们的形状也极其相似. 9月6日电流总强度演化曲线表明,电流强度在X9.3级强耀斑爆发期间出现快速增加的现象,这种现象持续了几个小时.这一研究结果有力支持了磁准分界面(Quasi-Separatrix Layer, QSL) 3维重联模型. 相似文献
9.
分析了2个耀斑事件,这2个事件分别是2002年3月14日M5.7级和2003年10月29日X10级耀斑。这两个耀斑在紫外(Ultroviolet or UV,160.0 nm)或远紫外(Extremeultraviolet or EUV,17.1 nm)都具有双带结构,在硬X射线(Hard X-ray or HXR)能段有明显的共轭足点。通过"重心法",可以得到EUV双带以及硬X射线足点的位置。通过对这2个耀斑事件的初步分析,得到下面的结论:(1)耀斑脉冲期,这两个耀斑的共轭亮核和双带都具有明显的会聚运动,会聚运动延续了3～10 min。亮核或双带的分离运动发生在会聚运动后;(2)耀斑的硬X射线足点具有很强的剪切运动,并且在耀斑过程中,剪切角的变化持续减小。这些结果表明磁重联通常发生在剪切程度高的磁场区域。这些结果支持Ji(2007)的磁场模型,这个模型认为耀斑环的收缩运动是剪切磁场松弛引起的。 相似文献
10.
太阳耀斑脉冲相的X射线光变曲线的复杂性表明此阶段有多种物理过程参与其中.基于某些显著的观测特征对耀斑分类可以用来探索这些特征的物理起源.对GOES (Geostationary Operational Environmental Satellite)卫星观测数据的分析表明有一类X射线发射度在脉冲相呈显著指数增长的耀斑.指数增长阶段的平均温度为正态分布.在此温度分布1σ之内的大多数耀斑属于B级或C级耀斑,其GOES低通道流量的峰值分布为对数正态分布.指数增长相的增长率和持续时间也遵循对数正态分布.持续时间分布范围大概为几十秒到几千秒.正如所预期的,增长时标同软X射线的衰减时标具有相关性.此外,指数增长相的增长率与持续时间呈强烈的反相关,而且随增长率的增大,对应的平均温度也有缓慢增大的趋势. 相似文献
11.
Zongjun Ning 《Solar physics》2008,248(1):99-111
Previous observations show that in many solar flares there is a causal correlation between the hard X-ray flux and the derivative
of the soft X-ray flux. This so-called Neupert effect is indicative of a strong link between the primary energy release to
accelerate particles and plasma heating. It suggests a flare model in which the hard X-rays are electron – ion bremsstrahlung
produced by energetic electrons as they lose their energy in the lower corona and chromosphere and the soft X-rays are thermal
bremsstrahlung from the “chromospheric evaporation” plasma heated by those same electrons. Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes in a broad energy band and its high spectral resolution and coverage of the low-energy range allow us to
separate the thermal continuum from the nonthermal component, which gives us an opportunity to investigate the Neupert effect.
In this paper, we use the parameters derived from RHESSI observations to trace the primary energy release and the plasma response:
The hard X-ray flux or spectral hardness is compared with the derivative of plasma thermal energy in three impulsive flares
on 10 November 2002 and on 3 and 25 August 2005. High correlations show that the Neupert effect does hold for the two hard
X-ray peaks of the 10 November 2002 flare, for the first peaks of the 3 August 2005 flare, and for the beginning period of
the 25 August 2005 flare. 相似文献
12.
We analyze the observations of the hard (ACS SPI, > 150 keV) and soft (GOES, 1–8 Å) X-ray emissions and the microwave (15.5 GHz) emission in the solar flares on September 7, 2005 and December 6 and 13, 2006. The time profiles of the nonthermal emission from these flares had a complex structure, suggesting that active processes in the flare region continued for a long time (more than an hour). We have verified the linear relationship between the nonthermal flux and the time derivative of the soft X-ray flux (the Neupert effect) in the events under consideration. In the first two cases, the Neupert effect held at the time of the most intense nonthermal emission peak, but not at the decay phase of the soft X-ray emission, when the intensity of the nonthermal emission was much higher than the background values. At the same time, the hard X-ray emission was suppressed compared to the main peak, while the microwave emission remained approximately at the same level. In the December 13, 2006 event, the prolonged hard X-ray emission was difficult to observe due to the fast arrival of solar protons, but the Neupert effect did not hold for its main peak either. At comparable intensities of the microwave emission on December 6 and 13, the intensity of the hard X-ray emission on December 13 at the time of the main peak was suppressed approximately by an order of magnitude. These observational facts are indicative of several particle acceleration and interaction episodes under various physical conditions during one flare. When the Neupert effect did not hold, the interaction of electrons took place mainly in a low-density medium. An effective escape of accelerated particles into interplanetary space rather than their precipitation into dense layers of the solar atmosphere may take place precisely at this time. 相似文献
13.
We present H CCD observations of three small-to-medium-size two-ribbon flares observed in the giant AR 9433 on 24 April 2001. Flare observations at other associated wavelengths (e.g., soft X-rays (SXR), hard X-rays (HXR), microwaves (MW)) obtained from archives are also presented and compared. We have tested the Neupert effect for the most energetic third flare. The flare observations are in agreement with the thick-target model. In the case of this flare the HXR emitting electrons appears to be the heating source of SXR and H emissions. The flares are also studied in EUV and UV emissions using TRACE data. We discuss the complexity of the magnetic field using SOHO/MDI magnetograms. The flares are observed to occur in both (f/p) polarity regions in highly sheared magnetic field with emerging flux regions and MMFs. 相似文献
14.
The flattening at the low energy end of the hard X-ray (HXR) photon spectrum of solar flares was generally thought to be due to a cutoff of nonthermal electrons in flares. However, some authors have suggested that inverse Compton scattering (i.e., the albedo effect) or certain other reaction of flare photons with the lower atmosphere can also lead to the flattening. This paper adopts the method of deriving the cutoff proposed by Gan et al. [12–14], and makes a statistical analysis on 100 flares observed by the satellite Ramaty High Energy Solar Spectroscopy Imager (RHESSI) in 2002–2005. We found that after the albedo correction, the HXR photon spectra of 18 flares can be fitted with single powerlaw spectra, and those of 80 flares, with double power-law spectra. Besides, 21 flares can be directly interpreted with a single power-law electron spectrum plus a low energy cutoff. The range of the low energy cutoff is 20–50 keV and the mean value is approximately 30 keV. Some other possible interpretations are also investigated. 相似文献
15.
The acceleration of charged particles in the solar corona during flares is investigated in terms of a model in which the electrons and ions preaccelerated in the magnetic reconnection region are injected into a collapsing magnetic trap. Here, the particle energy increases rapidly simultaneously through the Fermi and betatron mechanisms. Comparison of the efficiencies of the two mechanisms shows that the accelerated electrons in such a trap produce more intense hard X-ray (HXR) bursts than those in a trap where only the Fermi acceleration mechanism would be at work. This effect explains the Yohkoh and RHESSI satellite observations in which HXR sources more intense than the HXR emission from the chromosphere were detected in the corona. 相似文献
16.
The Neupert effect is the name given to the correlation observed in many flares between the time-integrated microwave and hard X-ray emissions and the soft X-ray emission light curve. We have used hard X-ray data from the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM) and soft X-ray data from the detector on GOES to determine what fraction of all events show this correlation and how the correlation changes from the impulsive to the gradual phase. We have found that of 66 HXRBS events observed in 1980 with a peak rate of > 1000 counts s-1, 58 (80%) showed good correlations with peaks in the GOES time derivative plot corresponding to peaks in the hard X-ray (HXR) plots to within ±20 s. In 20 of these good-correlation cases (30%), the soft X-ray (SXR) time derivative stays high after the HXR emission has decreased suggesting that the later emissions result from energy release in a loop already affected by the initial energy release. In 8 of the 13 flares that showed poor correlation, the SXR time derivative shows no peak corresponding to the initial HXR impulsive peak that has structure on a time scale of 1 s. This suggests that in these events the initial impulsive energy release results primarily in electron acceleration, and that the secondary plasma heating from the accelerated electrons contributes relatively little compared to the more gradual plasma heating already taking place at the same time. The more gradually varying events, commonly referred to as type C flares, tend to show poorer correlation between the SXR time derivative and the HXR time profile. Of 26 GOES X1 or greater flares recorded between 1980 and 1989 with HXR peaks lasting over 10 rain, 13 (50%) showed poor correlation with the gradual HXR peaks either not registering at all in the SXR time derivative plots or showing up as very broad peaks. In one case, on 1981 April 26, the SXR time derivative peak was delayed by 13 rain. Only 17 (65%) of the 26 X-flares had an earlier, impulsive component and of those, 12 (71%) showed good correlation between the impulsive peaks. 相似文献
17.
We investigate the M1.8 solar flare of 20 October 2002. The flare was accompanied by quasi-periodic pulsations (QPP) of both thermal and nonthermal hard X-ray emissions (HXR) observed by RHESSI in the 3?–?50 keV energy range. Analysis of the HXR time profiles in different energy channels made with the Lomb periodogram has indicated two statistically significant time periods of about 16 and 36 s. The 36 s QPP were observed only in the nonthermal HXR emission in the impulsive phase of the flare. The 16 s QPP were found in thermal and nonthermal HXR emission both in the impulsive and in the decay phases of the flare. Imaging analysis of the flare region, the determined time periods of the QPP, and the estimated physical parameters of the flare loops allowed us to interpret the observed QPP in terms of MHD oscillations excited in two spatially separated, but interacting systems of flaring loops. 相似文献
18.
B. V. Somov 《Solar physics》1975,42(1):235-246
Part of the proper X-ray emission of a flare is absorbed in the chromosphere and heats the region which creates an optical (in particular Hα) flare emission. The heating of chromosphere by X-ray emission may be responsible for the diffuse halo around the flare kernels. The optical emission of flare kernels, whose main sources of heating are energetic particles and/or thermal fluxes, may be also increased. By simple model calculations the present paper discusses the possibility of such effects for the large flare of 1972 August 7. 相似文献
19.
Using RHESSI and some auxiliary observations we examine possible connections between the spatial and temporal structure of
nonthermal hard X-ray (HXR) emission sources from the two-ribbon flares of 29 May 2003 and 19 January 2005. In each of these
events quasi-periodic pulsations (QPP) with time period of 1 – 3 minutes are evident in both hard X rays and microwaves. The
sources of nonthermal HXR emission are situated mainly at the footpoints of the flare arcade loops observed by TRACE and the
SOHO/EIT instrument in the EUV range. At least one of the sources moves systematically during and after the QPP phase in each
flare. The sources move predominantly parallel to the magnetic inversion line during the 29 May flare and along flare ribbons
during the QPP phase of both flares. By contrast, the sources start to show movement perpendicular to the flare ribbons with
velocity comparable to that along the ribbons’ movement after the QPP phase. The sources of each pulse are localized in distinct
parts of the ribbon during the QPP phase. The measured velocity of the sources and the estimated energy release rate do not
correlate well with the flux of the HXR emission calculated from these sources. The sources of microwaves and thermal HXRs
are situated near the apex of the flare loop arcade and are not stationary either. Almost all of the QPP as well as some pulses
of nonthermal HXR emission during the post-QPP phase reveal soft – hard – soft spectral behavior, indicating separate acts
of electron acceleration and injection. In our opinion at least two different flare scenarios based on the Nakariakov et al. (2006, Astron. Astrophys.
452, 343) model and on the idea of current-carrying loop coalescence are suitable for interpreting the observations. However,
it is currently not possible to choose between them owing to observational limitations. 相似文献
20.
Heating and acceleration of electrons in solar impulsive hard X-ray (HXR) flares are studied according to the two-stage acceleration model developed by Zhang for solar 3He-rich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons (up to 40 MK) through Landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flare-produced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements. 相似文献