共查询到20条相似文献,搜索用时 0 毫秒
1.
E. Mitsakou G. Babasidis X. Moussas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We have used Omniweb data in order to identify the sheath and the ejecta boundaries of 67 shock-driving interplanetary coronal mass ejections during the time period 2003–2006. We examine and compare their statistical properties (speed, magnetic field strength, proton density and temperature, proton plasma beta), with those of the typical solar wind. We also calculate their passage time and radial width. We study the correlation between the ejecta and sheath characteristics. 相似文献
2.
Y. Chen Y.Q. Hu L.D. Xia 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1780-1786
It remains an open question how magnetic energy is rapidly released in the solar corona so as to create solar explosions such as solar flares and coronal mass ejections (CMEs). Recent studies have confirmed that a system consisting of a flux rope embedded in a background field exhibits a catastrophic behavior, and the energy threshold at the catastrophic point may exceed the associated open field energy. The accumulated free energy in the corona is abruptly released when the catastrophe takes place, and it probably serves as the main means of energy release for CMEs at least in the initial phase. Such a release proceeds via an ideal MHD process in contrast with nonideal ones such as magnetic reconnection. The catastrophe results in a sudden formation of electric current sheets, which naturally provide proper sites for fast magnetic reconnection. The reconnection may be identified with a solar flare associated with the CME on one hand, and produces a further acceleration of the CME on the other. On this basis, several preliminary suggestions are made for future observational investigations, especially with the proposed Kuafa satellites, on the roles of the MHD catastrophe and magnetic reconnection in the magnetic energy release associated with CMEs and flares. 相似文献
3.
M. Youssef R. Mawad Mosalam shaltout 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We present a statistical study of post-flare-associated CMEs (PFA-CMEs) during the period from 1996 to 2010. By investigating all CMEs and X-ray flares, respectively, in the LASCO and GOES archives, we found 15875 CMEs of which masses are well measured and 25112 X-ray flares of which positions are determined from their optical counterparts. Under certain temporal and spatial criteria of these CMEs and solar flare events, 291PFA-CMEs events have been selected. Linking the flare fluxes with CME speeds of these paired events, we found that there is a reasonable positive linear relation between the CME linear speed and associated flare flux. The results show also the CME width increases as the flux of its associated solar flare increases. Besides we found that there is a fine positive linear relation between the CME mass and its width. Matching the flare fluxes with CME masses of these paired events, we find the CME mass increases as the flux of its associated solar flare increases. Finally we find the PFA-CME events are in regular more decelerated than the other CMEs. 相似文献
4.
C.Q. Xiang F.S. Wei X.S. Feng J.F. Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2308-2312
The evolution of coronal mass ejection/shock system is investigated by numerically solving the usual set of two-dimensional single-fluid polytropic magnetohydrodynamic equations from 1 Rs to 1 AU in the meridian plane. The simulation result reveals that the coronal mass ejection/shock system formed near the sun evolves into the magnetic cloud/shock system near the earth’s orbit through the following three phases: the initial formation, the dominant latitudinal expansion and the similar expansion. 相似文献
5.
R.A. Harrison C.J. Davis D. Bewsher J.A. Davies C.J. Eyles S.R. Crothers 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
With the advent of the NASA STEREO mission, we are in a position to perform unique investigations of the evolution of coronal mass ejections (CMEs) as they propagate through the heliosphere, and thus can investigate the relationship between CMEs and their interplanetary counterparts, so-called interplanetary CMEs (ICMEs). ICME studies have been principally limited to single-point, in-situ observations; interpretation of the in-situ characteristics of ICMEs has been used to derive a range of ICME properties which we can now confirm or refute using the STEREO imaging data. This paper is a review of early STEREO CME observations and how they relate to our currently understanding of ICMEs based on in-situ observations. In that sense, it is a first glance at the applications of the new data-sets to this topic and provides pointers to more detailed analyses. We find good agreement with in-situ-based interpretations, but this in turn leads to an anomaly regarding the final stages of a CME event that we investigate briefly to identify directions for future study. 相似文献
6.
P. Démoulin E. Pariat 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Mounting observational evidence of the emergence of twisted magnetic flux tubes through the photosphere have now been published. Such flux tubes, formed by the solar dynamo and transported through the convection zone, eventually reach the solar atmosphere. Their accumulation in the solar corona leads to flares and coronal mass ejections. Since reconnections occur during the evolution of the flux tubes, the concepts of twist and magnetic stress become inappropriate. Magnetic helicity, as a well preserved quantity, in particular in plasma with high magnetic Reynolds number, is a more suitable physical quantity to use, even if reconnection is involved. 相似文献
7.
Janusz Nicewicz Grzegorz Michalek 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Space weather is significantly controlled by halo coronal mass ejections (HCMEs) originating close to the central meridian and directing toward the Earth. Unfortunately, coronagraphic observations (especially for HCMEs) are subject to a projection effect which makes it impossible to determine the true radial velocity and width of CMEs. However, these parameters can be estimated by correcting for the projection effect using the asymmetric cone model (Michalek, 2006). A set of 20 CMEs, observed as halo events in the LASCO field of view and simultaneously as limb events in the STEREO/SECCHI field of view, are used to check the accuracy of the asymmetric cone model. For this purpose, characteristics of the considered CMEs (angular widths and radial speeds) measured in STEREO/SECCHI images are compared with those obtained by the asymmetric cone model. We demonstrate that the widths and speeds determined by both methods are very similar. Correlation coefficients for speeds and angular widths are 0.99 and 0.96, respectively. We have also shown that the projection effect is unpredictable and could sometimes be very significant (up to 100% of the velocity measured in the LASCO field of view). On average, the SOHO/LASCO projected speeds for the HCMEs are 23% smaller than the radial velocities obtained from the STEREO/SECCHI images. 相似文献
8.
Noé Lugaz Ilia I. Roussev Tamas I. Gombosi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Transients in the heliosphere, including coronal mass ejections (CMEs) and corotating interaction regions can be imaged to large heliocentric distances by heliospheric imagers (HIs), such as the HIs onboard STEREO and SMEI onboard Coriolis. These observations can be analyzed using different techniques to derive the CME speed and direction. In this paper, we use a three-dimensional (3-D) magneto-hydrodynamic (MHD) numerical simulation to investigate one of these methods, the fitting method of and . Because we use a 3-D simulation, we can determine with great accuracy the CME initial speed, its speed at 1 AU and its average transit speed as well as its size and direction of propagation. We are able to compare the results of the fitting method with the values from the simulation for different viewing angles between the CME direction of propagation and the Sun-spacecraft line. We focus on one simulation of a wide (120–140°) CME, whose initial speed is about 800 km s−1. For this case, we find that the best-fit speed is in good agreement with the speed of the CME at 1 AU, and this, independently of the viewing angle. The fitted direction of propagation is not in good agreement with the viewing angle in the simulation, although smaller viewing angles result in smaller fitted directions. This is due to the extremely wide nature of the ejection. A new fitting method, proposed to take into account the CME width, results in better agreement between fitted and actual directions for directions close to the Sun–Earth line. For other directions, it gives results comparable to the fitting method of Sheeley et al. (1999). The CME deceleration has only a small effect on the fitted direction, resulting in fitted values about 1–4° higher than the actual values. 相似文献
9.
Xingming Bao Hongqi Zhang Jun Lin Yunchun Jiang Leping Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,39(12):1847-1852
This work reports the investigation of two coronal mass ejections (CME) observed in white light, H, EUV and X-ray by various instruments both in space and on ground on February 18, 2003 and January 19, 2005, respectively. The white light coronal images show that the first CME began with the rarefaction of a region above the solar limb and was followed by the formation of its leading edge at the boundary of the rarefying region at altitude of 0.46 R from the solar surface. The rarefaction coincided the slow rising phase of the filament eruption, and the CME leading edge was observed to form as the filament eruption started to accelerate apparently. In the early stage of the second CME, a bright loop was first observed above the solar limb with height of 0.37 R in EUV images. We found that the more gradual CMEs initial process, the larger the timing difference between CMEs and their associated flares. The lower part of the filament brightened in H images as the filament rose to a certain height. These brightenings imply that the filament may be heated by magnetic reconnection below the filament in the early stage of the eruption. We suggest that the possible mechanism which led to the formation of the CME leading edge and cavity is magnetic reconnection which occurred under the filament when it reached a certain height. 相似文献
10.
SMESE: A SMall Explorer for Solar Eruptions 总被引:1,自引:0,他引:1
J.-C. Vial F. Auchre J. Chang C. Fang W.Q. Gan K.-L. Klein J.-Y. Prado G. Trottet C. Wang Y.H. Yan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1787-1801
The SMall Explorer for Solar Eruptions (SMESE) mission is a microsatellite proposed by France and China. The payload of SMESE consists of three packages: LYOT (a Lyman imager and a Lyman coronagraph), DESIR (an Infra-Red Telescope working at 35–80 and 100–250 μm), and HEBS (a High-Energy Burst Spectrometer working in X- and γ-rays).
The status of research on flares and coronal mass ejections is briefly reviewed in the context of on-going missions such as SOHO, TRACE and RHESSI. The scientific objectives and the profile of the mission are described. With a launch around 2012–2013, SMESE will provide a unique tool for detecting and understanding eruptions (flares and coronal mass ejections) close to the maximum phase of activity. 相似文献
11.
Yayuan Wen Jingxiu Wang Hui Zhao Dalmiro Jorge Filipe Maia 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
A statistical study of acceleration and its error of coronal mass ejections (CMEs) observed by the Large Angle Spectrometric Coronagraph (LASCO) is performed. A total of 5594 CMEs events have been analyzed by using a least-square method and using the error in the height measures. We verify that slower CMEs (velocities in the interval from 200 to 500 km s−1) tend to have a positive acceleration (about 1 m s−2) at heights above 5 solar radii, while less than 10% CMEs show an average negative acceleration (about −2.2 m s−2) as they propagate from 5 to 30 solar radii. For most individual CMEs one can not say if they are accelerated or decelerated, only for 8% of all observed CMEs events one can extract the sign of the acceleration in the 5–30 solar radii. 相似文献
12.
H. Gutiérrez L. Taliashvili Z. Mouradian 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We study the short-term topological changes of equatorial and polar coronal hole (CH) boundaries, such as a variation of their area and disintegration, associated to reconnection with nearby (within 15° distance) quiescent prominence magnetic fields leading to eruptions and subsequent Coronal Mass Ejections (CMEs). The examples presented here correspond to the recent solar minimum years 2008 and 2009. We consider a temporal window of one day between the CH topological changes and the start and end times of prominence eruptions and onset of CMEs. To establish this association we took into account observational conditions related to the instability of prominence/filaments, the occurrence of a CME, as well as the subsequent evolution after the CME. We found an association between short-term local topological changes in CH boundaries and the formation/disappearance of bright points near them, as well as, between short-term topological changes within the whole CH and eruptions of nearby quiescent prominences followed by the appearance of one or more CMEs. 相似文献
13.
Carlos Roberto Braga Alisson Dal Lago Guillermo Stenborg 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The white light coronagraphs onboard SOHO (LASCO-C2 and -C3) and most recently STEREO (SECCHI -COR1 and -COR2) have detected a myriad of coronal mass ejections (CME). They are a key component of space weather and under certain conditions they can become geo-effective, hence the importance of their kinematic characterization to help predict their effects. However, there is still a lot of debate on how to define the event boundaries for space weather purposes, which in turn makes it difficult to agree on their kinematic properties. That lack of agreement is reflected in both the manual and automated CME catalogs in existence. To contribute to a more objective definition and characterization of white-light coronagraph events, Goussies et al. (2010) introduced recently the concept of “texture of the event”. Based on that property, they developed a supervised segmentation algorithm to allow the automatic tracking of dynamic events observed in the coronagraphs field of view, which is called CORonal SEgmentation Technique (CORSET). In this work, we have enhanced the capabilities of the algorithm by adding several new functionalities, namely the automatic computation of different morphological and kinematic parameters. We tested its performance on 57 well-studied limb CME events observed with the LASCO coronagraphs between 1997 and 2001, and compared the parameters obtained with those from three existent CME lists: two of them obtained from an observer-based detection and tracking method (i.e., two manual catalogs), and the other one based on the automated detection and characterization of the CME events (i.e., a fully automated catalog). We found that 51 events could be tracked and quantified in agreement with the CME definition. In general terms, the position angle, and the radial and expansion speeds are in agreement with the manual catalogs used for comparison. On the other hand, some discrepancies between CORSET and the automated catalog were found, which can be explained by the different delimitation of the CME angular extent. 相似文献
14.
L.K. Harra 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(1):138-143
It is common to use imaging instruments such as EUV and X-ray imagers and coronagraphs to study large-scale phenomena such as coronal mass ejections and coronal waves. Although high resolution spectroscopy is generally limited to a small field of view, its importance in understanding global phenomena should not be under-estimated. I will review current spectroscopic observations of large-scale dynamic phenomena such as global coronal waves and coronal mass ejections. The aim is to determine plasma parameters such as flows, temperatures and densities to obtain a physical understanding of these phenomena. 相似文献
15.
结合STEREO卫星的观测和三维磁流体力学数值模拟方法, 采用WSO (Wilcox Solar Observatory)磁场数据和势场源表面模型建立日冕初始磁场, 并在日面活动区加上时变的压强扰动, 对2009年2月13日05:35UT爆发的CME-EUV波(Coronal Mass Ejections-Extreme Ultraviolet wave, 日冕物质抛射-远紫外波)事件进行研究. 从COR1/STEREO-A图像判断, 此次CME前沿速度约340km·s-1, 角宽度约60°; 分析EUVI/STEREO-B 195 Å的差分图像, 可以看到, 环形亮环波前从活动区向四周传播, 亮环波前后面是日冕暗化区, 取四个方向的波前位置进行线性拟合可知, 该EUV波速度为247km·s-1, 数值模拟得到的EUV波速度为245km·s-1, 将计算结果采用IDL可视化后可以看到明显的亮环和暗区结构, 数值模拟结果与卫星观测相一致, 表明该EUV波现象是快磁声波. 相似文献
16.
Bimal Pande Seema Pande Ramesh Chandra Mahesh Chandra Mathpal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(2):777-785
We present here a study of Solar Energetic Particle Events (SEPs) associated with solar flares during 2010–2014 in solar cycle 24. We have selected the flare events (≥GOES M-class), which produced SEPs. The SEPs are classified into three categories i.e. weak (proton intensity?≤?1?pfu), minor (1?pfu?<?proton intensity?<?10?pfu) and major (proton intensity?≥?10?pfu). We used the GOES data for the SEP events which have intensity greater than one pfu and SOHO/ERNE data for the SEP event less than one pfu intensity. In addition to the flare and SEP properties, we have also discussed different properties of associated CMEs. 相似文献
17.
A. Mahrous M. Shaltout M.M. Beheary R. Mawad M. Youssef 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The relation between coronal mass ejections (CMEs) and solar flares are statistically studied. More than 10,000 CME events observed by SOHO/LASCO during the period 1996–2005 have been analyzed. The soft X-ray flux measurements provided by the Geostationary Operational Environmental Satellite (GOES), recorded more than 20,000 flares in the same time period. The data is filtered under certain temporal and spatial conditions to select the CME–flare associated events. The results show that CME–flare associated events are triggered with a lift-off time within the range 0.4–1.0 h. We list a set of 41 CME–flare associated events satisfying the temporal and spatial conditions. The listed events show a good correlation between the CME energy and the X-ray flux of the CME–flare associated events with correlation coefficient of 0.76. 相似文献
18.
E. Romashets M. Vandas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2268-2272
It is generally assumed that magnetic fields inside interplanetary magnetic clouds and flux ropes in the solar photosphere are force-free. In order to model such fields, the solution of rot B = B is commonly used where = const. But comparisons of this solutions with observations show significant difference. To treat this problem,we examine the solutions with . 相似文献
19.
日冕冲浪形成的磁流体动力学模拟 总被引:2,自引:0,他引:2
应用二维时变可压缩磁流体动力学模拟,数值研究了双极-单极磁场中电阻撕裂模不稳定性引起的磁场重联过程,用于模拟日冕冲浪的形成.结果表明,在包含有三区——双极场、电流片和单极场的磁静力平衡初态下,双极场和单极场中的磁力线将会直接重联,磁场演变成鞭状(whip)结构.由弯曲磁力线支撑的等离子体团向上运动到最高位置后,逐渐下落和弥散.等离子体团上升速度可达到0.10vA(vA为双极场中的Alfv'én速度).模拟结果证实日冕冲浪的形成可能与双极-单极场中的磁场重联密切相关. 相似文献
20.
E. Valtonen T. Laitinen K. Huttunen-Heikinmaa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2295-2302
We have studied statistically associations of moderate and intense geomagnetic storms with coronal mass ejections (CMEs) and energetic particle events. The goal was to identify specific energetic particle signatures, which could be used to improve the predictions of the geoeffectiveness of full and partial halo CMEs. Protons in the range 1–110 MeV from the ERNE experiment onboard SOHO are used in the analysis. The study covers the time period from August 1996 to July 2000. We demonstrate the feasibility of energetic particle observations as an additional source of information in evaluating the geoeffectiveness of full and partial halo CMEs. Based on the observed onset times of solar energetic particle (SEP) events and energetic storm particle (ESP) events, we derive a proxy for the transit times of shocks driven by the interplanetary counterparts of coronal mass ejections from the Sun to the Earth. For a limited number of geomagnetic storms which can be associated to both SEP and ESP signatures, we found that this transit time correlates with the strength of geomagnetic storms. 相似文献