共查询到20条相似文献，搜索用时 15 毫秒
1.
Tuan-Hui Zhou Hai-Sheng Ji 《中国天文和天体物理学报》2009,9(3)
We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our empha-sis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse mag-netic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena. 相似文献
2.
We study the magnetic structure of five well-known active regions that produced great flares (X5 or larger). The six flares under investigation are the X12 flare on 1991 June 9 in AR 6659, the X5.7 flare on 2000 July 14 in AR 9077, the X5.6 flare on 2001 April 6 in AR 9415, the X5.3 flare on 2001 August 25 in AR 9591, the X17 flare on 2003 October 28 and the X10 flare on 2003 October 29, both in AR 10486. The last five events had corresponding LASCO observations and were all associated with Halo CMEs. We analyzed vector magne-tograms from Big Bear Solar Observatory, Huairou Solar Observing Station, Marshall Space Right Center and Mees Solar Observatory. In particular, we studied the magnetic gradient derived from line-of-sight magnetograms and magnetic shear derived from vector magne-tograms, and found an apparent correlation between these two parameters at a level of about 90%. We found that the magnetic gradient could be a better proxy than the shear for predicting where a major flare might occur: all six flares occurred in neutral lines with maximum gradient. The mean gradient of the flaring neutral lines ranges from 0.14 to 0.50 G km-1, 2.3 to 8 times the average value for all the neutral lines in the active regions. If we use magnetic shear as the proxy, the flaring neutral line in at least one, possibly two, of the six events would be mis-identified. 相似文献
3.
P. Kotr
《Astronomische Nachrichten》2003,324(4):324-326
Large solar telescopes built at places with a quite excellent seeing, equipped with a sophisticated optics and control system are too expensive and unique to be used currently in hunting of sudden and short‐lasting activity events, e.g. flares and eruptive prominences. For a systematic observation of selected kinds of active phenomena it is still necessary to use smaller or medium‐sized telescopes equipped with a special setup of devices. Detection of linear polarization in the Hα line emitted in a flare seems to be just a right task and delicate matter for such a systematic observation. This kind of polarization is supposed to be generated by particle beams accelerated in thke corona and directed towards denser chromospheric layers where the particle beams deposit their kinetic energy. As the accelerated particle beams possess a preferred direction of velocity they can produce a linearly polarized light. However, the occurrence of the accelerated particle beams and the related linear polarization in the Hα line may have a tendency to appear: 1) at the early beginning of a flare 2) in pulses lasting just a few seconds or even less. To measure the linear polarization in flares regularly we have built an additional branch in the Ondřejov multichannel flare spectrograph. In this paper we describe the optical system, the detectors, the method used for data recording and reduction and we also briefly discuss the first results. 相似文献
4.
K. Iwasawa A. C. Fabian A. J. Young H. Inoue C. Matsumoto 《Monthly notices of the Royal Astronomical Society》1999,306(1):L19-L24
We report results on the broad iron emission line of the Seyfert galaxy MCG–6-30-15, obtained from the second long ASCA observation in 1997. The time-averaged profile of the broad line is very similar to that seen with ASCA in 1994, so confirming the detailed model fit then obtained. A bright flare is seen in the light curve, during which the continuum was soft. At that time the emission line peaks around 5 keV and most of its emission is shifted below 6 keV with no component detected at 6.4 keV ( This can be interpreted as the result of an extraordinarily large gravitational redshift owing to a dominant flare occurring very close to the black hole at a radius of ≲5 . 相似文献
5.
1986年2月4日太阳耀斑的演化研究 总被引：1，自引：0，他引：1
本文根据乌鲁木齐天文站的H_α耀斑及3.2cm射电流量观侧资料、云南天文台的黑子精细结构照相和Marshall Space Flight Center的向量磁场图,对1986年2月4日的六个耀斑的形态相关及演化联系,特别是0736UT 4B/3X大耀斑的发展过程进行了综合分析。主要结果是: 1.4日大耀斑的初始亮点和闪光相的主要形态演化,与活动区中沿中性线新浮现的强大电流/磁环系密切相关。后者的主要标志是沿中性线的长的剪切半影纤维及它两端的偶极旋涡黑子群(1_3F_3)。 2.上述大耀斑与1972年8月4日0624 UT大耀斑爆发的磁场背景及主要形态特征相似,表明两者的储能和触发机制可能相同。 3.大耀斑爆发的H_α初始亮点,双带出现,环系形成,亮物质抛射和吸收冕珥等现象同3.2cm射电流量的变化在时间上有较好的对应关系。 4.重复性的前期小耀斑爆发位置和发展趋势与大耀斑的主要形态及演化特征相似。它们相对于剪切的纵场中性线两侧的位置相近或相同。因而,可以看作上述强大电流/磁环系不稳性发展过程中的前置小爆发。 相似文献
6.
YingLiu Ming－DeDing 《中国天文和天体物理学报》2002,2(3):277-286
The line profiles of Hα 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 Hα and from CaⅡ 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 Hα. Possible origins of the large scale motions are discussed. 相似文献
7.
8.
Horizontal proper motions were measured with local correlation tracking (LCT) techniques in active region NOAA 11158 on 2011 February 15 at a time when a major (X2.2) solar flare occurred. The measurements are based on continuum images and magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The observed shear flows along the polarity inversion line were rather weak (a few 100 m s–1). The counter‐streaming region shifted toward the north after the flare. A small circular area with flow speeds of up to 1.2 km s–1 appeared after the flare near a region of rapid penumbral decay. The LCT signal in this region was provided by small‐scale photospheric brigthenings, which were associated with fast traveling moving magnetic features. Umbral strengthening and rapid penumbral decay was observed after the flare. Both phenomena were closely tied to kernels of white‐light flare emission. The white‐light flare only lasted for about 15 min and peaked 4 min earlier than the X‐ray flux. In comparison to other major flares, the X2.2 flare in active region NOAA 11158 only produced diminutive photospheric signatures (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
本文主要根据Ｈａ线心和不同偏带的观测资料，结合紫外ＣＩＶ１５４８谱线的测量结果，分析研究了１９８０年６月２５日ＡＲ２５２２活动区中一段暗条在耀斑爆发前１５分钟所经历的三次逐渐增强的间歇式扭绞，最终导致暗条破裂和耀斑爆发的物理过程，并且用无力场磁绳近似模拟时间条的扭绞运动，估算了暗条扭绞引直怕无力因子ａ的变化，轴向电流增大和守能，讨论了暗条的稳定性，试图对暗条的瓦解和耀斑爆发予以理论解释。 相似文献
10.
Dramatic extensions of experimental possibilities (spacecraft RHESSI, CORONAS-F and others) in solar gamma-ray astronomy call for urgent, detailed theoretical consideration of a set of physical problems of solar activity and solar-terrestrial relationships that earlier may have only been outlined. Here we undertake a theoretical analysis of issues related to the production of gamma-radiation in the processes of interactions of energetic (accelerated) heavy and middle nuclei with the nuclei of the solar atmosphere (the so-called i-j interactions). We also make an estimate of the contribution of these interactions to the formation of nuclear and isotopic abundances of the solar atmosphere in the range of light and rare elements. The analysis is carried out for solar flares in the wide range of their intensities. We compare our theoretical estimates with RHESSI observations for the flare of 2002 July 23. It was shown that the 24Mg gamma-ray emission in this event was produced by the newly generated Mg nucle 相似文献
11.
We present the results of studying the proton flare 2B/X4.8 on 23 July 2002, observed with the Large Solar Vacuum Telescope (LSVT) at the Baikal Astrophysical Observatory in spectropolarimetric mode with high spatial and spectral resolution. We have found some evidence for H?? line impact linear polarization, predominantly during the initial moments of the flare. For the H?? line 606 cuts were made along the dispersion in 53 spectrograms, and a polarization signal was found more or less confidently in 60 cuts (13 spectrograms). Polarization was mainly observed in one of the kernels of the flare. A particular feature of this kernel was that the H?? line was observed to show a reversal in the central part of this kernel, which created a dip in the kernel center in the photometric cut. The size of these dips and the size of the sites with the linear polarization coincide and are equal to 3??C?6?arcsec. The maximum polarization degree in this kernel reached 15?%. The direction of the polarization in the kernel is radial, except for the first two frames, where the direction of the polarization was both radial and tangential. Furthermore, we found an analogy between the effects observed at the chromospheric level in this kernel (polarization and depression in H?? line) and the temporal variation of the HXR sources. 相似文献
12.
Alaa I. Ibrahim Hisham Anwer Mohamed H. Soliman Nicholas Mackie-Jones Kalvir S. Dhuga William C. Parke Jean H. Swank Tilan Ukwatta M. T. Hussein T. El-Sherbini 《Astrophysics and Space Science》2007,308(1-4):535-539
A 6.4 keV emission line was discovered in an unusual burst from the soft gamma repeater SGR 1900+14 with the Rossi X-ray Timing
Explorer (RXTE). The line was detected in part of a complex multipeak precursor that preceded the unusual burst of 1998 August
29, i.e. two days after the giant flare of August 27 from the source. The origin of the line was not firmly identified and
two possible interpretations were equally plausible including (a) Kα fluorescence from a small iron rich material that was ejected to the magnetosphere during the August 27 flare, and (b) proton
or α-particle cyclotron resonance. If the iron scenario was correct, we expect to find evidence for the line during the intervening
interval between the flare and the August 29 burst, i.e. on August 28. Here we present the results of the August 28 burst
observation, taken with RXTE. We detect a total of seven bursts whose individual and joint spectra do not show evidence for
spectral lines. We also investigated a sample of nine bursts before and after the August 29 burst (from 1998 June to December)
that do not reveal evidence for a spectral line near 6.4 keV or elsewhere. These results disfavor the iron scenario and make
the proton/α-particle cyclotron resonance interpretation more plausible. The appearance of the emission line in part of a complex burst
and its absence from the studied sample indicate that the line is likely due to a transient phenomenon that may depend on
the burst morphology, energetics and the properties of the emission region.
相似文献
13.
Flare-induced signals in polarization measurements which were manifested as apparent polarity reversal in magnetograms have been reported since 1981. We are motivated to further quantify the phenomenon by asking two questions: can we distinguish the flare-induced signals from real magnetic changes during flares, and what we can learn about flare energy release from the flare-induced signals? We select the X2.6 flare that occurred on 2005 January 15, for further study. The flare took place in NOAA active re-gion (AR) 10720 at approximately the central meridian, which makes the interpretation of the vector magnetograms less ambiguous. We have identified that flare-induced signals during this flare appeared in six zones. The zones are located within an average distance of 5 Mm from their weight center to the main magnetic neutral line, have an average size of (0.6±0.4)×1017 cm2, duration of 13±4 min, and flux density change of 181±125 G in the area of reversed polarity. The following new facts have been revealed by this study: (1) the flare-induced signal is also seen in the transverse magnetograms but with smaller magnitude, e.g., about 50 G; (2) the flare-induced signal mainly manifests itself as apparent polarity reversal, but the signal starts and ends as a weakening of flux density; (3) The flare-induced signals appear in phase with the peaks of hard X-ray emission as observed by the Ramaty High Energy Solar Spectroscopic lmager (RHESSI), and mostly trace the position of RHESSI hard X-ray footpoint sources. (4) in four zones, it takes place cotemporally with real magnetic changes which persist after the flare. Only for the other two zones does the flux density recover to the pre-flare level immediately after the flare.The physical implications of the flare-induced signal are discussed in view of its relevance to the non-thermal electron precipitation and primary energy release in the flare. 相似文献
14.
In a search for linear polarization effects, 37 profiles of the H
line emitted in the 16 May 1991 flare have been analyzed. Linear polarization is clearly present in the central part of line. On average, the degree of polarization is 7 %, but it reaches 20 % in regions with lower H
ga
emission. Generally the orientation of the plane of polarization coincides with the flare to disk center direction, except for sections where the H
ga
line has the characteristic form observed in moustaches. We believe that the linear polarization observed in the 16 May 1991 flare was caused by bombardment of the chromosphere by beams of accelerated particles, protons in the main part of the flare and electrons at locations where the H
ga
line has the characteristic moustache structure. 相似文献
15.
Joseph D. Gelfand 《Astrophysics and Space Science》2007,308(1-4):39-42
On 27 December 2004, just the third giant flare was observed from a magnetar, in this case SGR 1806-20. This giant flare was
the most energetic of the three, and analysis of a Very Large Array observation of SGR 1806-20 after the giant flare revealed
the existence of a new, bright, transient radio source at its position. Follow-up radio observations of this source determined
that initially, this source underwent a mildly relativistic one-sided expansion which ceased at the same time as a temporary
rebrightening of the radio source. These observational results imply that the radio emission is powered by ∼1024 g of baryonic material which was ejected off the surface on the neutron star during the giant flare.
相似文献
16.
17.
We developed a polarimeter with ferroelectric liquid crystals (FLCs) to observe polarization of flare kernels in the H line. Polarization is one of the important diagnostics of the high-energy particles in solar flares, and high-cadence imaging polarimetry with the precision of the order of 0.1% is required to observe the polarization of flare kernels. However, to achieve such high precision is difficult mainly due to the seeing-induced polarization error, which particularly appears around the flare kernels, because the brightness gradient is steep there. To reduce the seeing-induced error, a high modulation frequency is required, and our new polarimeter based on the combination of a high-speed CCD camera and FLCs realized high-frequency polarization modulation nearly 250 Hz. We evaluated the polarization error, and confirmed that the error was significantly reduced with the new polarimeter. We concluded that the polarimeter with FLCs meets the requirement of solar flare polarimetry. 相似文献
18.
Xing-Ming Bao Hong-Qi Zhang Jun Lin National Astronomical Observatories Chinese Academy of Sciences Beijing National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming Harvard-Smithsonian Center for Astrophysics Garden Street Cambridge MA USA 《中国天文和天体物理学报》2006,6(6):741-750
This work investigates a typical coronal mass ejection (CME) observed on 2003 February 18, by various space and ground instruments, in white light, Ha, EUV and X-ray. The Ha and EUV images indicate that the CME started with the eruption of a long filament located near the solar northwest limb. The white light coronal images show that the CME initiated with the rarefaction of a region above the solar limb and followed by the formation of a bright arcade at the boundary of the rarefying region at height 0.46 R(?) above the solar surface. The rarefying process synchronized with the slow rising phase of the eruptive filament, and the CME leading edge was observed to form as the latter started to accelerate. The lower part of the filament brightened in Ha as the filament rose to a certain height and parts of the filament was visible in the GOES X-ray images during the rise. These brightenings imply that the filament may be heated by the magnetic reconnection below the filament in the early stage of the eruption. We suggest that a possible mechanism which leads to the formation of the CME leading edge and cavity is the magnetic reconnection which takes place below the filament after the filament has reached a certain height. 相似文献
19.
Min Wang Rui-Xiang Xie Chun Xu Shuo-Biao Shi Yi-Hua Yan National Astronomical Observatories Yunnan Observatory Chinese Academy of Sciences Kunming National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2005,5(5):508-518
We present a, large complex radio burst and its associated fast tune structures observed on 2001 April 10 in the frequency range of 0.65-7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a bipolar, a tripolar (a 'bipolar + remote unipolar'), and a quadrupolar structure. This suggests that the radio burst is generated from a very complicated loop structure. According to the spectral and image observations, we assume that the beginning of this flare was caused by a single bipolar loop configuration with a 'Y-type' re-connection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type III bursts, and slowly drifting and no-drift structures. The tripolar configurations may form a double-loop with a 'three-legged' structure, which is an important source of the various types of fast time structures. The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively. Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the 'inverted Y-type' (bipolar) and the 'three-legged' structures (tripolar or quadrupolar). 相似文献
20.
Shan-Jie Qian Xi-Zhen ZhangNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2004,4(1):37-50
The rapid polarization position angle swing of ~ 180?observed in QSO 1150+812 at 2cm by Kochenov and Gabuzda is quite a regular event. One interesting property of the event is that, during the time of the swing the polarized flux density remained almost constant. We suggest that such an event can be explained in terms of a relativistic thin shock propagating through a uniform helical magnetic field, giving rise to relativistic aberration effects as the transverse field component rotates. The model may also be applicable to other similar events in which variations in polarization are not accompanied by variations in total flux density. 相似文献