共查询到20条相似文献，搜索用时 625 毫秒
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E. K. J. Kilpua M. Mierla A. N. Zhukov L. Rodriguez A. Vourlidas B. Wood 《Solar physics》2014,289(10):3773-3797
We examine solar sources for 20 interplanetary coronal mass ejections (ICMEs) observed in 2009 in the near-Earth solar wind. We performed a detailed analysis of coronagraph and extreme ultraviolet (EUV) observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory (SOHO). Our study shows that the coronagraph observations from viewpoints away from the Sun–Earth line are paramount to locate the solar sources of Earth-bound ICMEs during solar minimum. SOHO/LASCO detected only six CMEs in our sample, and only one of these CMEs was wider than 120°. This demonstrates that observing a full or partial halo CME is not necessary to observe the ICME arrival. Although the two STEREO spacecraft had the best possible configuration for observing Earth-bound CMEs in 2009, we failed to find the associated CME for four ICMEs, and identifying the correct CME was not straightforward even for some clear ICMEs. Ten out of 16 (63 %) of the associated CMEs in our study were “stealth” CMEs, i.e. no obvious EUV on-disk activity was associated with them. Most of our stealth CMEs also lacked on-limb EUV signatures. We found that stealth CMEs generally lack the leading bright front in coronagraph images. This is in accordance with previous studies that argued that stealth CMEs form more slowly and at higher coronal altitudes than non-stealth CMEs. We suggest that at solar minimum the slow-rising CMEs do not draw enough coronal plasma around them. These CMEs are hence difficult to discern in the coronagraphic data, even when viewed close to the plane of the sky. The weak ICMEs in our study were related to both intrinsically narrow CMEs and the non-central encounters of larger CMEs. We also demonstrate that narrow CMEs (angular widths ≤?20°) can arrive at Earth and that an unstructured CME may result in a flux rope-type ICME. 相似文献
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We summarize ERNE/SOHO observations of solar energetic particle events associated with impulsive soft X-ray flares and LASCO coronal mass ejections (CMEs). The new observational data support an idea that the >10 MeV proton acceleration may be initiated at different coronal sources, operating in the flaring active region and on the global coronal scale, in concert with CME development. However, the particle acceleration continues beyond the coronal scales and may culminate at the interplanetary CME well after the flare. We emphasize the importance of CME liftoff/aftermath processes in the solar corona and the possible role of seed particle re-acceleration, which may explain the existence of hybrid solar energetic particle events. 相似文献
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Klaus Wilhelm Ingolf E. Dammasch Donald M. Hassler 《Astrophysics and Space Science》2002,282(1):189-207
The plasma conditions in the solar atmosphere and, in particular, in coronal holes are summarized, before space-borne instrumentation
for observing these regions in vacuum-ultraviolet light is briefly introduced with the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) as example. Spectroscopic measurements of
small plasma jets are then analyzed in detail. Magnetic reconnection is thought to be responsible for heating the corona of
the Sun as well as accelerating the solar wind by converting magnetic energy into thermal and kinetic energies. The continuous
outflow of the fast solar wind from coronal holes on ‘open’ field lines, which reach out into interplanetary space, then requires
many reconnection events of very small scale sizes – most of them probably below the resolution capabilities of present-day
instruments. Our observations of such an event have been obtained with the Solar and Heliospheric Observatory (SOHO) providing
both high-resolution imaging and spectral information for structural and dynamical studies. We find whirling or rotating motions
as well as jets with acceleration along their propagation paths in close spatial and temporal vicinity to the coronal jet.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
We study the correlation between near-Earth observations of interplanetary coronal mass ejections (ICMEs) detected by the
Wind and ACE spacecrafts and their counterparts of coronal mass ejections (CMEs) observed near the Sun by the SOHO/LASCO coronagraph during
1996–2002. The results have been compared with an empirical model given by Gopalswamy, et al. (2000; 2001) to predict the
1-AU arrival time of CMEs. In this paper, we use an expected data set with a wider range with initial velocities than that
considered in previous models. To improve the accuracy of the predicted arrival time, we divided the CME events into two groups
according to their effective acceleration and deceleration. The results show that our model works well for events with a negative
acceleration in the initial velocity range between 500 and 2500 km/s, while the model described by Gopalswamy is better for
events with initial velocities near the solar wind velocity.
Published in Russian in Astronomicheskii Vestnik, 2009, Vol. 43, No. 2, pp. 137–144.
The text was translated by the authors. 相似文献
6.
We have analyzed five solar energetic particle (SEP) events observed aboard the SOHO spacecraft during 1996–1997. All events
were associated with impulsive soft X-ray flares, Type II radio bursts and coronal mass ejections (CMEs). Most attention is
concentrated on the SEP acceleration during the first 100 minutes after the flare impulsive phase, post-impulsive-phase acceleration,
being observed in eruptions centered at different solar longitudes. As a representative pattern of a (nearly) well-connected
event, we consider the west flare and CME of 9 July 1996 (S10 W30). Similarities and dissimilarities of the post-impulsive-phase
acceleration at large heliocentric-angle distance from the eruption center are illustrated with the 24 September 1997 event
(S31 E19). We conclude that the proton acceleration at intermediate scales, between flare acceleration and interplanetary
CME-driven shock acceleration, significantly contributes to the production of ≳10 MeV protons. This post-impulsive-phase acceleration
seems to be caused by the CME lift-off. 相似文献
7.
Ya-Yuan Wen Jing-Xiu Wang Yu-Zong Zhang National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):265-280
Using Nancay Radioheliograph (NRH) imaging observations, combined with SOHO/Michelson Doppler Imager (MDI) magnetogram observations and coronal magnetic field extrapolation, we studied the magnetic nature of metric noise storms that are associated with coronal mass ejections (CMEs). Four events are selected: the events of 2000 July 14, 2001 April 26, 2002 August 16 and 2001 March 28. The identified noise storm sources cover or partially cover the active regions (ARs), but the centers of storm sources are offset from the ARs. Using extrapolated magnetic field lines, we find that the noise storm sources trace the boundary between the open and closed field lines. We demonstrate that the disappearance of noise storm source is followed by the appearance of the burst source. The burst sources spread on the solar disk and their distributions correspond to the extent of the CME in LASCO C2 field of view. All the SOHO/Extreme Ultraviolet Imaging Telescope (EIT) dimmings associ- ated with noise storm sources are located at the periphery of noise storms where the magnetic lines of force were previously closed and low-lying. When the closed field becomes partially or fully open, the basic configurations of noise storm sources are changed, then the noise storm sources are no longer observed. These observations provide the information that the variations of noise storms manifest the restructuring or reconfiguring of the coronal magnetic field. 相似文献
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We review recent progress on our understanding of radio emission from solar flares and coronal mass ejections (CMEs) with emphasis on those aspects of the subject that help us address questions about energy release and its properties, the configuration of flare?–?CME source regions, coronal shocks, particle acceleration and transport, and the origin of solar energetic particle (SEP) events. Radio emission from electron beams can provide information about the electron acceleration process, the location of injection of electrons in the corona, and the properties of the ambient coronal structures. Mildly relativistic electrons gyrating in the magnetic fields of flaring loops produce radio emission via the gyrosynchrotron mechanism, which provides constraints on the magnetic field and the properties of energetic electrons. CME detection at radio wavelengths tracks the eruption from its early phase and reveals the participation of a multitude of loops of widely differing scale. Both flares and CMEs can ignite shock waves and radio observations offer the most robust tool to study them. The incorporation of radio data into the study of SEP events reveals that a clear-cut distinction between flare-related and CME-related SEP events is difficult to establish. 相似文献
10.
We present velocity estimates of bulk motions in the solar corona using data from the Large Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory spacecraft ( SOHO ). We describe a new technique which automatically provides a mass-weighted mean velocity profile in an entirely objective fashion without the need for individual event identification. A weighted velocity profile of this kind reflects the motion of the energetically dominant component of the coronal mass ejection (CME) mass spectrum and is of particular interest in consideration of the overall energy budget of the CME process. We consider the mean motion within three latitudinal bands centred at 0°, 20° and 40° over a one-year period around the time of solar minimum. We find terminal velocities within the LASCO field of around 300 km s−1 in all latitude bands but note a latitudinal dependence in CME evolution through the low corona prior to reaching these velocities. We find evidence that ejections in the equatorial zone undergo continuous acceleration whilst at higher latitudes a discrete burst of acceleration is seen to occur at around 4 R⊙ from the Sun's centre with relatively little acceleration thereafter. We also consider the energy deposition rates necessary to generate these profiles. 相似文献
11.
The observed CME (coronal mass ejection) is its projection on the sky plane, and this leads to certain discrepancies between the observational and true parameters of the CME. For example, the observed velocity is generally smaller than the true velocity. The method of making projection correction for the CME velocity based on the conical model is utilized to analyze the velocity distributions of the 1691 CMEs which are only correlated to flares (called the class FL CMEs for short) and the 610 CMEs which are only correlated to filament eruptions (called the class FE CMEs for short) before and after the projection correction. These CMEs were observed with the Large Angle and Spectrometric Coronograph on the Solar and Heliospheric Observatory from September 1996 to September 2007 (close to a solar cycle). The obtained results are as follows: (1) before and after the projection correction the velocity distribution of FL CMEs is quite similar to that of FE CMEs, and before and after the projection correction the mean velocities of the two classes of CMEs are almost the same; (2) before and after the projection correction, the natural logarithm distribution of the FL CME velocities is also very similar to that of the FE CME velocities. 相似文献
12.
Nishant Mittal Joginder Sharma Vivek Tomar Udit Narain 《Planetary and Space Science》2009,57(1):53-57
We have analyzed the data for more than 12900 coronal mass ejections (CMEs) which were obtained by SOHO/LASCO during the period of 1996-2007. The online CME catalogue contains all major CMEs detected by LASCO C2 and C3 coronagraphs. Basically we determine the CME speeds from the linear and quadratic fits to the height-time measurements. It is found that linear (constant speed) fit is preferable for 90% of the CMEs. The distribution of speeds of CMEs in solar cycle 23 is presented along with those obtained by others. As expected, the speeds decrease in the decay phase of the cycle 23. There is an unusual drop in speed in the year 2001 and an abnormal increase in speed in the year 2003 due to the high concentration of CMEs, X-class soft X-ray flares, solar energetic particle (SEP) events and interplanetary shocks observed during October-November period called Halloween events. 相似文献
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The characteristics of the magnetic field ubiquitously permeating the coronal plasma are still largely unknown. In this paper we analyze some aspects of coronal physics, related to the magnetic field behavior, which forthcoming SOHO UVCS observations can help better understand. To this end, three coronal structures will be examined: streamers, coronal mass ejections (CMEs), and coronal holes.As to streamers and CMEs, we show, via simulations of the Ly- and white-light emission from these objects, calculated on the basis of recent theoretical models (Wang et al., 1995), how new data from SOHO can help in advancing our knowledge of the streamer/CME magnetic configuration. Our discussion highlights also those observational signatures which might offer clues on reconnection processes in streamers' current sheets.Coronal holes (CHs) are discussed in the last section of the paper. Little is known about CH flux tube geometry, which is closely related to the behavior of the solar wind at small heliocentric distances.Indirect evidence for the flux tube spreading factors, within a few solar radii, is here examined. 相似文献
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Leonard Strachan 《Journal of Astrophysics and Astronomy》2008,29(1-2):167-170
Measurements made with the Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory can be used to determine physical parameters in the solar corona such as hydrogen and ion kinetic temperatures, electron densities, and absolute elemental abundances. Hydrogen and ion outflow velocities can be determined by combining the UV spectroscopic measurements with white light polarized brightness measurements. These combined measurements can be used to reveal physical characteristics of coronal streamers. To date we have studied plasma properties, such as the variation of plasma outflows in quiescent streamers, primarily in classic helmet streamers at solar minimum. Out-flows have not been observed in the centers of coronal streamers suggesting that these are closed magnetic field regions. We propose to study all of the coronal streamers in the UVCS synoptic dataset in order to investigate different types of streamers and their long-term evolution. 相似文献
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主要论述宁静日冕洞，以及日冕加热问题的研究现状。讨论了宁静日冕的理论模型、观测模型和混合模型，以及冕洞区大气模型和太阳风加热问题。最后对计划中的日冕空间探测作了简要介绍。 相似文献
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Peng-Xin Gao Ke-Jun Li Qi-Xiu Li 《Monthly notices of the Royal Astronomical Society》2009,394(2):1031-1036
Using Howard et al.'s method, we investigate, before and after the projection correction, the speed and acceleration distributions for 1747 coronal mass ejections (CMEs) associated solely with flares (FL CMEs) and 631 CMEs associated solely with filament eruptions (FE CMEs) observed by the Large Angle and Spectrometric Coronagraph on board the Solar and Heliographic Observatory ( SOHO /LASCO) from 1996 September to 2007 September, corresponding to almost an entire solar cycle. The results show the following. (1) Before the correction, the speed distributions for FL and FE CMEs are statistically different from each other; after the correction, the speed distributions for FL and FE CMEs should also be statistically different from each other. (2) Before the correction, the acceleration distributions for FL and FE CMEs are statistically different from each other. However, after the correction, FL and FE CMEs should have quite similar acceleration distributions. 相似文献
17.
日冕物质抛射(Coronal Mass Ejection, CME)是一种剧烈的太阳爆发现象, 它会对行星际空间造成严重扰动, 进而影响人类生产、生活. 基于CME的时空显著性, 将显著性检测方法引入到CME检测中, 利用结构化矩阵分解SOHO (Solar and Heliospheric Observatory)的大角度光谱日冕仪(Large Angle and Spectrometric Coronagraph Experiment, LASCO) C2的日冕图像对应的特征矩阵, 从中恢复出稀疏部分获得显著前景. 然后考虑CME运动时产生的时间显著性, 从而去除非CME结构(如冕流), 得到最终检测结果. 实验表明, 以人工目录协调数据分析中心(Coordinated Data Analysis Workshop, CDAW)检测结果为基准时, 所提方法不仅在检测CME数量上比计算机辅助跟踪软件包(Computer Aided CME Tracking Software package, CACTus)和太阳爆发事件检测系统(Solar Eruptive Event Detection System, SEEDS)有优势, 还在CME中心角度和张角宽度等特征物理参数测量上比CACTus和SEEDS更接近CDAW目录参考值. 相似文献
18.
M. Youssef 《Earth, Moon, and Planets》2012,109(1-4):13-27
We studied the relation between the near-Earth signatures of the interplanetary coronal mass ejections (ICMEs) shocks such as sudden storms commencement (SSC), and their counterparts of coronal mass ejections (CMEs) observed near-Sun by solar and heliospheric observatory (SOHO)/large angle and spectrometric coronagraph (LASCO) coronagraph during 1996?C2008. Our result showed that there is a good correlation between the travel time of the ICMEs shocks and their associated radial speeds. Also we have separated the ICME shocks into two groups according to their effective acceleration and deceleration. The results showed that the faster ICME shocks (with negative accelerations which decelerated by solar wind plasma) are more correlated to their associated travel time than those with positive accelerations. 相似文献
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《Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science》1999,24(4):415-419
Using the high-resolution mass spectrometer MTOF on board SOHO we have measured the solar wind isotopic abundance ratios of Ne, Mg, and Si in different solar wind regimes with bulk velocities ranging from 350 km/s to 650 km/s. Data indicate a systematic depletion of the heavier isotopes in the slow solar wind compared to their abundances in the fast solar wind from coronal holes. These variations in the solar wind isotopic composition represent a pure mass-dependent effect because the different isotopes of an element pass the inner corona with the same charge state distribution. The influence of particle mass on the acceleration of minor solar wind ions is discussed in the context of theoretical models and recent optical observations with other SOHO instruments. 相似文献
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Yoichiro Hanaoka Jun Nakazawa Osamu Ohgoe Yoshiaki Sakai Kazuo Shiota 《Solar physics》2014,289(7):2587-2599
White-light observations of the total solar eclipse on 13 November 2012 were made at two sites, where the totality occurred 35 min apart. The structure of the corona from the solar limb to a couple of solar radii was observed with a wide dynamic range and a high signal-to-noise ratio. An ongoing coronal mass ejection (CME) and a pre-CME loop structure just before the eruption were observed in the height range between 1?–?2 R⊙. The source region of CMEs was revealed to be in this height range, where the material and the magnetic field of CMEs were located before the eruption. This height range includes the gap between the extreme ultraviolet observations of the low corona and the spaceborne white-light observations of the high corona, but the eclipse observation shows that this height range is essential for the study of CME initiation. The eclipse observation is basically just a snapshot of CMEs, but it indicates the importance of a continuous coverage of CME observations in this height range in the future. 相似文献