共查询到8条相似文献，搜索用时 15 毫秒
1.
The evolution of the soft X-ray and EUV coronal loops related to the April 15, 1998 solar flare–CME event is studied with multiwavelength observations including hard X-rays (BATSE), microwaves (NoRP, CNAO) and magnetograms (SOHO/MDI), as well as images from Yohkoh/SXT and SOHO/EIT at 195 Å. It is shown that: (1) two soft X-ray and EUV loops rose, crossed and turned bright, (2) near one footpoint of these loops, the background magnetic field decreased, (3) there were similar quasi periodic oscillations in the time profiles of hard X-ray and microwave emissions, which characterized the loop–loop coalescence instability, (4) after the loop–loop reconnection, two new loops formed, the small one stayed at the original place, and the large one ejected out as part of the constructed prominence cloud. Based upon these observations, we argue that the decrease of the background magnetic field near these loops caused them to rise and approach each other, and in turn, the fast loop–loop coalescence instability took place and triggered the flare and the CME. 相似文献
2.
The Soft X-ray Telescope (SXT) onboard Yohkoh often observed large-scale coronal loops connecting two active regions situated in opposite hemispheres. These are the trans-equatorial
loop systems (TLSs). The formation mechanism of TLSs is not yet known. We analyzed a TLS observed simultaneously with Yohkoh/SXT and a coronagraph (SOHO/LASCO-C1). SOHO/LASCO-C1 observed loop expansion and eruption at the west solar limb. Yohkoh/SXT observed a rising motion (chromospheric evaporation) of hot and dense plasmas from the active regions located at the
footpoints of the loop. Important results of our analyses are that (1) the loop eruption and the rising motion of the plasmas
were simultaneous, (2) the TLS had a cusp-like appearance, and (3) the highest temperature region of the TLS was located above
the bright loop seen in soft X rays. These observational results (loop expansion, eruption, and chromospheric evaporation)
suggest that this bright (high-density) TLS was created by the same mechanism by which a solar flare occurs, namely, magnetic
reconnection. In this paper, we propose a formation mechanism of the TLS that forms between two independent active regions. 相似文献
3.
1 ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｍａｇｎｅｔｉｃｆｉｅｌｄａｎｄｍａｔｅｒｉａｌｍｏｔｉｏｎｈａｖｅａｌｗａｙｓｂｅｅｎｔｈｅｐｏｉｎｔｓｔｏｗｈｉｃｈｃｌｏｓｅａｔｔｅｎｅｉｏｎｉｓｐａｉｄｉｎｔｈｅｓｔｕｄｙｏｆｓｏｌａｒｆｌａｒｅｐｒｏｃｅｓｓ.Ｅｓｐｅｃｉａｌｌｙｔｈｅｔｗｉｓｔｉｎｇｅｎｅｒｇｙｓｔｏｒｇｅｐｒｏｃｅｓｓｉｓａｐｒｏｂ ｌｅｍｔｈａｔａｕｔｈｏｒｓｏｆｍａｎｙｆｌａｒｅｔｈｅｏｒｉｅｓａｎｄｍｏｄｅｌｓｈｏｐｅｔｏｒｅｓｏｌｖｅ .Ｇｏｌｄ＆Ｈｏｌｙｅ ( 1 96 0 ) ｐｒｅｓ… 相似文献
4.
At the onset of a solar flare, initiated by magnetic reconnection high in the corona, reconnection outflow sets up warm proton beams (PBs), streaming down along just-reconnected field lines through steady underlying plasma. Incorporating this scenario, we study excitation of kinetic Alfvén waves (KAWs) by PBs, keeping the effects of a beam-induced electric field and thermal effects. Taking into account the high growth rate (105 s–1), short relaxation distance (106 cm), and energy flux partition between the waves and the beam after relaxation (PKAW/PPB1), we conclude that PB-driven KAW instability is an efficient energy conversion mechanism in flaring loops. The quasilinear spectral energy concentration at the largest wavenumbers indicates the possibility of nonlinear spectral modification. We suggest that the resulting turbulence of KAWs plays an important role in the flare plasma energization. 相似文献
5.
We develop a simple method to deduce the temperature and density in the loop of a limb flare from the spectral observations of two lines, H and Caii 8542 Å. We first build a grid of homogeneous slab models with various temperature and density values and compute the emergent line intensities, and then find the relevant model that can match the observed intensities. This is an approximate method because there are several other factors which can influence the line intensities. We apply this method to the limb flare of 11 November 1998 and deduce the values of temperature and hydrogen number density at different spatial points in the flaring loop, as well as their temporal variations. The loop contains relatively high density and possibly the loop top is slightly hotter and more condensed than the legs of the loop at the flare maximum time. A favorable scenario to produce this result is that magnetic reconnection occurs above the loop, and the reconnection outflow may heat and condense the plasma near the loop top. 相似文献
6.
《天文研究与技术》1999,(Z1)
1 ＩｎｔｒｏｄｕｃｔｉｏｎＡｎｅｘｔｒａｌａｒｇｅＴｙｐｅⅣｍｉｃｒｏｗａｖｅｂｕｒｓｔｗａｓｏｂｓｅｒｖｅｄｗｉｔｈＰｈｏｅｎｉｘⅡＭｉｃｒｏｗａｖｅＳｐｅｃ ｔｒｏｍｅｔｅｒ ( 4 0 0ＧＨｚ ,2 84ＧＨｚａｎｄ 1 42ＧＨｚ)ａｔＹｕｎｎａｎＯｂｓｅｒｖａｔｏｒｙｆｒｏｍ 0 8ｈ31 ｍｔｏ 0 9ｈ41 ｍＵＴｏｎＤｅｃｅｍｂｅｒ 1 6 ,1 988.Ｉｎｔｈｅｍｏｒｅｔｈａｎ 70ｍｉｎｕｔｅｓ ,ｆｉｖｅｉｎｔｅｎｓｉｖｅｍａｉｎｐｅａｋｓｗｅｒｅｇｅｎｅｒ ａｔｅｄｏｎｔｈｅＴｙｐｅ Ⅳμｂｕｒｓｔｏｎｔｈｒｅｅｗａ… 相似文献
7.
Coronal holes (CH) emit significantly less at coronal temperatures than quiet-Sun regions (QS), but can hardly be distinguished in most chromospheric and lower transition region lines. A key quantity for the understanding of this phenomenon is the magnetic field. We use data from SOHO/MDI to reconstruct the magnetic field in coronal holes and the quiet Sun with the help of a potential magnetic model. Starting from a regular grid on the solar surface we then trace field lines, which provide the overall geometry of the 3D magnetic field structure. We distinguish between open and closed field lines, with the closed field lines being assumed to represent magnetic loops. We then try to compute some properties of coronal loops. The loops in the coronal holes (CH) are found to be on average flatter than in the QS. High and long closed loops are extremely rare, whereas short and low-lying loops are almost as abundant in coronal holes as in the quiet Sun. When interpreted in the light of loop scaling laws this result suggests an explanation for the relatively strong chromospheric and transition region emission (many low-lying, short loops), but the weak coronal emission (few high and long loops) in coronal holes. In spite of this contrast our calculations also suggest that a significant fraction of the cool emission in CHs comes from the open flux regions. Despite these insights provided by the magnetic field line statistics further work is needed to obtain a definite answer to the question if loop statistics explain the differences between coronal holes and the quiet Sun. 相似文献
8.
Until recently, most of the information on particle acceleration processes in solar flares has been obtained from hard X-ray and cm-microwave observations. As a rule they provide information on electrons with energies below 300 keV. During recent years it became possible to measure the gamma-ray and millimeter radio emission with improved sensitivities. These spectral ranges carry information on much higher energy electrons. We studied the temporal and spectral behaviour of the radio burst emission at centimeter-millimeter wavelengths (8–50 GHz) by using the data from the patrol instruments of IAP (Bern University). We have analyzed more than 20 impulsive and long duration radio bursts (of 10 s to several 100 s duration).The main finding of the data analysis is the presence of spectral flattening throughout the bursts, which occurs always during the decay phase of flux peaks, at frequencies well above the spectral peak frequency and independently of burst duration. Furthermore, for some of the bursts, the flux maxima at higher frequencies are delayed. These findings can serve as evidence of the hardening of the electron spectrum at energies above some hundreds of keV during the decay phase of cm–mm flux peaks. As a most likely reason for such a hardening we consider Coulomb collisions of energetic electrons continuously injected and trapped in a flaring loop. 相似文献