共查询到19条相似文献，搜索用时 171 毫秒
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太阳大气中磁重联的MHD数值模拟 总被引：1，自引：0，他引：1
回顾了近３０年太阳大气中磁重联过程的ＭＨＤ数值模拟工作取得的进展。着重描述了在验证理论模型,解释观测现象,以及研究各种因素对重联的影响三个方面的成果,如快速磁重联,太阳耀斑机制及色球,日冕中的各种爆发现象等。指出了在数值模拟中应注意的几个问题,并对该领域今后的发展作了简要的展望。 相似文献
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本文研究了磁流体力学与高频等离子体波（ 包括纵横模式） 之间的精巧的相互作用。研究表明,这些等离激元会在电流片内诱发一种阻抗不稳定,并最终导至磁重联,出现爆发性不稳定。在高涨的离声湍动情况下,高温电流片模型必须采用反常电导率,而非库仑电导率。理论估算的结果与观测相一致。因此这种计及等离激元有质动力作用的新磁重联理论,基本上能解释耀斑现象。 相似文献
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胡友秋 《中国天文和天体物理学报》1999,(2)
采用二维三分量磁流体力学模型,对日冕三重无力场电流片的磁场重联进行了数值研究,揭示了重联过程的基本物理特征．这类重联过程将加热和加速日冕等离子体,并导致多个高温、高密度、高磁螺度的磁岛的形成和向上喷发．这表明,多重无力场电流片的重联可能在日冕磁能释放、上行等离子体团的形成和太阳磁场螺度向行星际空间的逃逸方面起重要的作用． 相似文献
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采用二维三分量磁流体力学模型,对日冕三重无力场电流片的磁场重磁联进行了数值研究,揭示了重联过程的基本物理特征,这类重联过程将加热和加速日冕等离子体,并导致多个高温、高密度、高磁螺度的磁岛的形成和向上喷发,这表明,多重无力场电流片的重联可能在日冕磁能释放、上行等离子体的形成和太阳磁场螺度向行星际空间的逃逸方面起重要的作用。 相似文献
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讨论了磁环（电流环）在耀斑的贮能和释能过程中的重要作用，贮存于环中的磁能可能通过两种方式经由磁重联而散逸，即磁环的相互作用和环的扭转，并给出一些观测证据和理论分析结果。 相似文献
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《天文学报》2015,(6)
日冕物质抛射(Coronal Mass Ejection,CME)通常会将其后面区域中的磁场急剧拉伸,使得极性相反的磁力线相互靠近而形成磁重联电流片.磁重联电流片在爆发过程中,既是磁自由能迅速转化为热能、等离子动能和高能粒子束流的重要区域,又起着连接日冕物质抛射和耀斑的作用.2003年1月3日和11月4日的两次CME事件,在CME离开太阳表面附近之后,均有电流片被观测到.结合搭载在SOHO(Solar and Heliospheric Observatory)上的LASCO(Large Angle and Spectrometric Coronagraph)、UVCS(Ultraviolet Coronagraph Spectrometer)数据,以及大熊湖天文台和云南天文台的Hα资料,研究两次爆发事件的动力学特征,以及电流片的物理特性.电流片中高电离度粒子的存在,如Fe~(+17)、Si~(+11),表明电流片区域中温度高达3×10~6～5×10~6K.直接测量发现电流片的厚度在1.3×10~4～1.1×10~5km范围之间,并随时间先增大后逐渐减小.利用CHIANTI(ver 7.1)光谱代码,进一步计算得到2003年1月3日电流片中的电子温度和相应辐射量(Emission Measure,EM)的均值分别为3.86×10~6K和6.1×10~(24)cm~(-5).另一方面,利用SOHO/UVCS观测数据对2003年11月4日的CME爆发事件中的电流片进行分析,发现电流片呈现准周期性扭转运动. 相似文献
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《天文学进展》2016,(4)
作为汪景琇院士主持的中国科学院数理学部"天体辐射磁流体力学"战略研究项目组成部分~([1]),从等离子体的动力学属性出发,介绍了用于研究等离子体与周围磁场结构相互作用的粒子云网格方法,及其在研究具有复杂等离子体和磁场结构的磁重联过程中的应用。这里提到的磁场与等离子体的复杂性包括变化的等离子体β值,磁重联电流片中包含有多种尺度的结构,以及这些结构之间的相互作用,而且这些结构的尺度变化范围很大(从105km变化到102km)。进一步探讨了该方法在太阳物理领域,特别是在太阳爆发磁重联过程方面的可能应用以及未来的发展;并为项目研究中其他部分在数值方法~([2–5])和太阳物理~([6,7])方面提供借鉴和补充。 相似文献
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We analyze the relationship between the dynamics of the coronal mass ejection (CME) of 15 May 2001 and the energy release in the associated flare. The flare took place behind the east limb and was disclosed by a growing system of hot soft X-ray (SXR) loops that appeared from behind the limb around the onset of the rapid acceleration of the CME. The highly correlated behavior of the SXR light-curve derivative and the time profile of the CME acceleration reveals an intrinsic relationship between the CME dynamics and the flare energy release. Furthermore, we found that the CME acceleration peak occurs simultaneously with the fastest growth (100 km s-1) of X-ray loops, indicating that the reconnection plays an essential role in the eruption. Inspecting the CME/flare morphology we recognized in the Yohkoh-SXT images an oval feature that formed within the rising structure at the onset of the rapid acceleration phase, simultaneously with the appearance of the X-ray loops. The eruptive prominence was imbedded within the lower half of the oval, suggestive of a flux-rope/prominence magnetic configuration. We interpret the observed morphological evolution in terms of a reconnection process in the current sheet that presumably formed below the erupting flux-rope at the onset of the CME acceleration. Measurements of the tip-height of the cusped X-ray loop system and the height of the lower edge of the oval, enable us to trace the stretching of the current sheet. The initial distance between the oval and the loops amounted to 35 – 40 Mm. In about 1 h the inferred length of the current sheet increased to 150 – 200 Mm, which corresponds to a mean elongation speed of 35 – 45 km s-1. The results are discussed in the framework of CME models that include the magnetic reconnection below the erupting flux-rope. 相似文献
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We describe the evolution of morphological features of the magnetic configuration of CME according to the catastrophe model developed previously. For the parameters chosen for the present work, roughly half of the total mass is nominally contained in the initial flux rope, while the remaining plasma is brought by magnetic reconnection from the corona into the current sheet and from there into the CME bubble. The physical attributes of the difference in the observable features between CME bubble and flare loop system were studied. We tentatively identified distinguishable evolutionary features like the outer shell, the expanding bubble and the flux rope with the leading edge, void and core of the 3-component CME structure. The role of magnetic reconnection is discussed as a possible mechanism for the heating of the prominence material during eruptions. Several aspects of this explanation that need improvement are outlined. 相似文献
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Alexei A. Pevtsov 《Journal of Astrophysics and Astronomy》2008,29(1-2):49-56
Concept of magnetic/current helicity was introduced to solar physics about 15 years ago. Earlier studies led to discovery of such fundamental properties as hemispheric helicity rule, and role of helicity in magnetic reconnection and solar eruptions. Later, the concept was successfully applied in studies of different solar processes from solar dynamo to flare and CME phenomena. Although no silver bullet, helicity has proven to be a very useful “tool” in answering many still-puzzling questions about origin and evolution of solar magnetic fields. I present an overview of some helicity studies and briefly analyze their findings. 相似文献
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We present a theory of filament eruption before the impulsive phase of solar flares. We show that the upward motion of the magnetic X-point tracing the filament eruption begins several minutes before the impulsive phase of the flare, where the explosive magnetic reconnection starts at the X-point magnetic field configuration located under the filament. No change occurs in the character of the motion of the X-point during the onset of the explosive magnetic reconnection. The upward speed of the X-point is about 110 km s-1 at the onset of the impulsive phase. We give an important condition leading to filament eruptions, which relate to the state of the current sheet under the filament, where the magnetic energy can be released. 相似文献
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Yohkoh observations strongly suggest that electron acceleration in solar flares occurs in magnetic reconnection regions in the corona above the soft X-ray flare loops. Unfortunately, models for particle acceleration in reconnecting current sheets predict electron energy gains in terms of the reconnection electric field and the thickness of the sheet, both of which are extremely difficult to measure. It can be shown, however, that application of Ohm's law in a turbulent current sheet, combined with energy and Maxwell's equations, leads to a formula for the electron energy gain in terms of the flare power output, the magnetic field strength, the plasma density and temperature in the sheet, and its area. Typical flare parameters correspond to electron energies between a few tens of keV and a few MeV. The calculation supports the viewpoint that electrons that generate the continuum gamma-ray and hard X-ray emissions in impulsive solar flares are accelerated in a large-scale turbulent current sheet above the soft X-ray flare loops. 相似文献
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Jun Lin 《Solar physics》2004,222(1):115-136
Kopp–Pneuman-type magnetic configurations, which include a vertical current sheet, with various background fields are investigated. Dissipation of the current sheet as a result of magnetic reconnection produces bright flare ribbons on the solar disk and a growing flare loop system in the corona. In principle, the growth of flare loop system is governed by a reconnection process only, and the behavior of flare ribbons is also controlled by the background field. The flare ribbons may appear either separate or attached to one another at the onset of the flare depending on the background field distribution on the boundary surface. We calculate the decrease in height that magnetic field lines undergo after they have reconnected to form closed loops. Following previous practice, we refer to this decrease as field line shrinkage. Unlike the motions of flare ribbons, the shrinkage of flare loops depends weakly on the background field. Individual loops always shrink fastest at the moment it is produced by reconnection and just starts to leave the current sheet. The earlier the loop forms, the more and faster it shrinks. The relevant observations are explained on the basis of our calculations, and the aspects of the explanation that need improvement are also discussed. 相似文献
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Understanding the onset of coronal mass ejections (CMEs) is surely one of the holy grails of solar physics today. Inspection of data from the Heliospheric Imagers (HI), which are part of the SECCHI instrument suite aboard the two NASA STEREO spacecraft, appears to have revealed pre-eruption signatures which may provide valuable evidence for identifying the CME onset mechanism. Specifically, an examination of the HI images has revealed narrow rays comprised of a series of outward-propagating plasma blobs apparently forming near the edge of the streamer belt prior to many CME eruptions. In this pilot study, we inspect a limited dataset to explore the significance of this phenomenon, which we have termed a pre-CME ‘fuse’. Although, the enhanced expulsion of blobs may be consistent with an increase in the release of outward-propagating blobs from the streamers themselves, it could also be interpreted as evidence for interchange reconnection in the period leading to a CME onset. Indeed, it is argued that the latter could even have implications for the end-of-life of CMEs. Thus, the presence of these pre-CME fuses provides evidence that the CME onset mechanism is either related to streamer reconnection processes or the reconnection between closed field lines in the streamer belt and adjacent, open field lines. We investigate the nature of these fuses, including their timing and location with respect to CME launch sites, as well as their speed and topology. 相似文献
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In this paper, we study multiwavelength observations of an M6.4 flare in Active Region NOAA 11045 on 7 February 2010. The space- and ground-based observations from STEREO, SoHO/MDI, EIT, and Nobeyama Radioheliograph were used for the study. This active region rapidly appeared at the north-eastern limb with an unusual emergence of a magnetic field. We find a unique observational signature of the magnetic field configuration at the flare site. Our observations show a change from dipolar to quadrapolar topology. This change in the magnetic field configuration results in its complexity and a build-up of the flare energy. We did not find any signature of magnetic flux cancellation during this process. We interpret the change in the magnetic field configuration as a consequence of the flux emergence and photospheric flows that have opposite vortices around the pair of opposite polarity spots. The negative-polarity spot rotating counterclockwise breaks the positive-polarity spot into two parts. The STEREO-A 195 Å and STEREO-B 171 Å coronal images during the flare reveal that a twisted flux tube expands and erupts resulting in a coronal mass ejection (CME). The formation of co-spatial bipolar radio contours at the same location also reveals the ongoing reconnection process above the flare site and thus the acceleration of non-thermal particles. The reconnection may also be responsible for the detachment of a ring-shaped twisted flux tube that further causes a CME eruption with a maximum speed of 446 km/s in the outer corona. 相似文献
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C. P. Goff L. van Driel-Gesztelyi P. Démoulin J. L. Culhane S. A. Matthews L. K. Harra C. H. Mandrini K. L. Klein H. Kurokawa 《Solar physics》2007,240(2):283-299
A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio
observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations
from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary
to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the
following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only
separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring
flux tubes. We conclude that “tether cutting” reconnection in the sheared arcade progressively transforms it to a twisted
flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination
of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure
and neighboring magnetic fields.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献