我们报告了1997年至2006年在1天文单位的Wind和ACE测量的49个在日冕物质抛射（CME）内传播的快模前向激波。与典型的日冕物质抛射驱动的冲击相比，这些冲击在不同的上游条件下传播，其中上游Alfv{é}n速度的中值为85 km s $^{-1}$，质子$β= 0.08$和磁场强度为8 nT。这些激波速度很快，平均速度为590 km/s $^{-1}$，但强度较弱，平均阿尔夫{é}尼克马赫数为1.9。它们通常将磁场和密度压缩2-3倍。发现的最极端的上游条件是230 km/s $^{-1}$的快磁音速、0.02的等离子体$β$、740 km/s $^{-1}$的上游太阳风速度和0.5 cm $^{-3}$的密度。在这些复杂事件中，有19个与在Wind探测到地震后12小时内的强烈地磁暴（峰值Dst低于$-100$ nT）有关，15个与地震探测后3至9小时内的风暴时间Dst指数下降超过50 nT有关。我们还将它们与在更典型的上游条件下传播的45个冲击样本进行了比较。我们通过叠加历元分析显示了这些地震的平均性质，并对低$β$区的地震压缩比提出了一些分析考虑。由于大多数这些冲击是在后半部分的日冕物质抛射测量，我们得出结论，大约一半的冲击可能不会保持快速模式的冲击，因为它们通过整个日冕物质抛射传播，由于大的上游和磁音速。
英文摘要：
We report on 49 fast-mode forward shocks propagating inside coronal mass ejections (CMEs) as measured by Wind and ACE at 1 AU from 1997 to 2006. Compared to typical CME-driven shocks, these shocks propagate in different upstream conditions, where the median upstream Alfv{é}n speed is 85 km s$^{-1}$, the proton $β= 0.08$ and the magnetic field strength is 8 nT. These shocks are fast with a median speed of 590 km s$^{-1}$ but weak with a median Alfv{é}nic Mach number of 1.9. They typically compress the magnetic field and density by a factor of 2-3. The most extreme upstream conditions found were a fast magnetosonic speed of 230 km s$^{-1}$, a plasma $β$ of 0.02, upstream solar wind speed of 740 km s$^{-1}$ and density of 0.5 cm$^{-3}$. Nineteen of these complex events were associated with an intense geomagnetic storm (peak Dst under $-100$ nT) within 12 hours of the shock detection at Wind, and fifteen were associated with a drop of the storm-time Dst index of more than 50 nT between 3 and 9 hours after shock detection. We also compare them to a sample of 45 shocks propagating in more typical upstream conditions. We show the average property of these shocks through a superposed epoch analysis, and we present some analytical considerations regarding the compression ratios of shocks in low $β$ regimes. As most of these shocks are measured in the back half of a CME, we conclude that about half the shocks may not remain fast-mode shocks as they propagate through an entire CME due to the large upstream and magnetosonic speeds.
Coronal mass ejections (CMEs) may disturb the solar wind either by overtaking it, or by expanding into it, or both. CMEs whose front moves faster in the solar wind frame than the fast magnetosonic speed, drive shocks. Such shocks are important contributors to space weather, by triggering substorms, compressing the magnetosphere and accelerating particles. In general, near 1 AU, CMEs with speed greater than about 500 km s$^{-1}$ drive shocks, whereas slower CMEs do not. However, CMEs as slow as 350 km s$^{-1}$ may sometimes, although rarely, drive shocks. Here, we study these slow CMEs with sho…
We present a review of the different aspects associated with the interaction of successive CMEs in the corona and inner heliosphere, focusing on the initiation of series of CMEs, their interaction in the heliosphere, the particle acceleration associated with successive CMEs, and the effect of compound events on Earth's magnetosphere. The two main mechanisms resulting in the eruption of series of CMEs are sympathetic eruptions and homologous eruptions. The interaction of successive CMEs has been observed remotely in coronagraphs and heliospheric imagers, and inferred from in situ measurements. …
From data by LASCO C2 and C3 coronagraphs, depending on time (distance), we have determined positions and velocities of the front for fast limb CMEs' body with their sources near the limb, and for the body of halo-type CME with the sources near the solar disk center. These characteristics of CME body are compared to similar kinematic characteristics obtained for CME body-associated shock waves (shocks). For the body of halo-type CME with the sources near the solar disk center and associated shocks, we determined and compared their kinematic characteristics in 3D space. It has been shown that f…
In the early days of 2017 September, an exceptionally energetic solar active region AR12673 aroused great interest in the solar physics community. It produced four X class flares, more than 20 CMEs and an intense geomagnetic storm, for which the peak value of the Dst index reached up to -142nT at 2017 September 8 02:00 UT. In this work, we check the interplanetary and solar source of this intense geomagnetic storm. We find that this geomagnetic storm was mainly caused by a shock-ICME complex structure, which was formed by a shock driven by the 2017 September 6 CME propagating into a previous I…
The prediction of the arrival time for fast coronal mass ejections (CMEs) and their associated shocks is highly desirable in space weather studies. In this paper, we use two shock propagation models, i.e. Data Guided Shock Time Of Arrival (DGSTOA) and Data Guided Shock Propagation Model (DGSPM), to predict the kinematical evolution of interplanetary shocks associated with fast CMEs. DGSTOA is based on the similarity theory of shock waves in the solar wind reference frame, and DGSPM on the non-similarity theory in the stationary reference frame. The inputs are the kinematics of the CME front at…
We examine the propagation and interaction properties of three successive coronal mass ejections (CMEs) from 2001 November 21-22, with a focus on their connection with the behaviors of the associated long-duration complex type II radio burst. In combination with coronagraph and multi-point in situ observations, the long-duration type II burst provides key features for resolving the propagation and interaction complexities of the three CMEs. The two CMEs from November 22 interacted first and then overtook the November 21 CME at a distance of about 0.85 AU from the Sun. The time scale for the sh…
The Sun is an active star that can launch large eruptions of magnetised plasma into the heliosphere, called coronal mass ejections (CMEs). These ejections can drive shocks that accelerate particles to high energies, often resulting in radio emission at low frequencies (<200 MHz). To date, the relationship between the expansion of CMEs, shocks and particle acceleration is not well understood, partly due to the lack of radio imaging at low frequencies during the onset of shock-producing CMEs. Here, we report multi-instrument radio, white-light and ultraviolet imaging of the second largest flare …
On 2017-09-10, solar energetic particles (SEPs) originating from the active region 12673 were registered as a ground level enhancement (GLE) at Earth and the biggest GLE on the surface of Mars as observed by the Radiation Assessment Detector (RAD) since the landing of the Curiosity rover in August 2012. Based on multi-point coronagraph images, we identify the initial 3D kinematics of an extremely fast CME and its shock front as well as another 2 CMEs launched hours earlier (with moderate speeds) using the Graduated Cylindrical Shell (GCS) model. These three CMEs interacted as they propagated o…
We investigate the evolution of both normal and inverse CMEs ejected at different initial velocities, and observe the effect of the background wind density and their magnetic polarity on their evolution up to 1 AU. We performed 2.5D simulations by solving the magnetohydrodynamic equations on a radially stretched grid, employing a block-based adaptive mesh refinement scheme based on a density threshold to achieve high resolution following the evolution of the magnetic clouds and the leading bow shocks. All the simulations discussed in the present paper were performed using the same initial grid…
Propagation of the 2012 March Coronal Mass Ejections from the Sun to Heliopause
2012年3月，太阳展示了非凡的活动。特别是，活动区NOAA AR 11429发射了一系列大的日冕物质抛射（CME），当它随太阳从东向西旋转时，STEREO成像。这些持续的喷发预计将产生一个席卷日光层的扰动物质的全球外壳。在地球附近观测到一组激波和行星际日冕物质抛射（ICME），并使用MHD模型从1 AU向外传播。瞬态流相互作用，这擦除源的记忆，并导致一个大的合并的相互作用区域（MIR）与前一个冲击。MHD模型预测，激波和和平号将在2013年4月22日左右达到120 AU，这与旅行者1号探测到的射电辐射周期和银河系宇宙射线的瞬态扰动时间吻合得很好。这些结果对于了解日冕物质抛射在外层日光层中的“命运”是很重要的，并提供了太阳风层顶位于距离太阳约120天文单位的信心。
An outstanding problem in heliospheric physics is understanding the acceleration of solar energetic particles (SEP) in coronal mass ejections (CMEs) and flares. A fundamental question is whether the acceleration occurs in interplanetary space, or near the Sun. Recent work has shown that CME-driven shocks may produce SEPs while still below 5 solar radii. In this work we explore SEP acceleration during the onset of CMEs and shocks even lower in the corona, using realistic suprathermal spectra, for a selection of events. We have calculated quiet-time, pre-event suprathermal particle spectra from …
Solar type II radio bursts are the signature of particle acceleration by shock waves in the solar corona and interplanetary medium. The shocks originate in solar eruptions involving coronal mass ejections (CMEs) moving at super-Alfvenic speeds. Type II bursts occur at frequencies ranging from hundreds of MHz to tens of kHz, which correspond to plasma frequencies prevailing in the inner heliosphere from the base of the solar corona to the vicinity of Earth. Type II radio bursts occurring at frequencies below the ionospheric cutoff are of particular importance, because they are due to very energ…
Taking the 32 storm sudden commencements (SSCs) listed by ISGI during 2002 as a starting point, we performed a multi-criterion analysis based on observations (propagation time, velocity comparisons, sense of the magnetic field rotation, radio waves) to associate them with solar sources. We identified their effects in the interplanetary medium, and looked at the response of the terrestrial ionized and neutral environment. We find that 28 SSCs can be related to 44 coronal mass ejections (CMEs), 15 with a unique CME and 13 with a series of multiple CMEs, among which 19 involved halo CMEs; 12 of t…
Sun-to-Earth Characteristics of Two Coronal Mass Ejections Interacting near 1 AU: Formation of a Complex Ejecta and Generation of a Two-Step Geomagnetic Storm
Using Coordinated Observations in Polarised White Light and Faraday Rotation to Probe the Spatial Position and Magnetic Field of an Interplanetary Sheath
Recently it has been suggested that the "twin-CME" scenario Li.etal2012 may be a very effective mechanism in causing extreme Solar Energetic Particle (SEP) events and in particular Ground Level Enhancement (GLE) events. Ding.etal2013 performed a statistical examination of the twin-CME scenario with a total of $126$ fast and wide western Coronal Mass Ejections (CMEs). They found that CMEs having a preceding CME with a speed $>$ 300 $km/s$ within $9$ hours from the same active region have larger probability of leading to large SEP events than CMEs that do not have preceding CMEs. The choice of $…
We investigate the kinetic properties of a typical fast-mode shock inside an interplanetary coronal mass ejection (ICME) observed on 1998 August 6 at 1 AU, including particle distributions and wave analysis with the in situ measurements from Wind. Key results are obtained concerning the shock and the shock-ICME interaction at kinetic scales: (1) gyrating ions, which may provide energy dissipation at the shock in addition to wave-particle interactions, are observed around the shock ramp; (2) despite the enhanced proton temperature anisotropy of the shocked plasma, the low plasma beta inside the…
Coronal mass ejections (CMEs) are the primary sources of intense disturbances at Earth, where their geo-effectiveness is largely determined by their dynamic pressure and internal magnetic field, which can be significantly altered during interactions with other CMEs in interplanetary space. We analyse three successive CMEs that erupted from the Sun during September 4-6, 2017, investigating the role of CME-CME interactions as source of the associated intense geomagnetic storm (Dst_min=-142 nT on September 7). To quantify the impact of interactions on the (geo-)effectiveness of individual CMEs, w…
In order to have a comprehensive view of the propagation and evolution of coronal mass ejections (CMEs) from the Sun to deep interplanetary space beyond 1 au, we carry out a kinematic analysis of 7 CMEs in solar cycle 23. The events are required to have coordinated coronagraph observations, interplanetary type II radio bursts, and multi-point in-situ measurements at the Earth and Ulysses. A graduated cylindrical shell model, an analytical model without free parameters and a magnetohydrodynamic model are used to derive CME kinematics near the Sun, to quantify the CME/shock propagation in the Su…
Coronal mass ejections (CMEs) are the most dynamic phenomena in our solar system. They abruptly disrupt the continuous outflow of solar wind by expelling huge clouds of magnetized plasma into interplanetary space with velocities enabling to cross the Sun-Earth distance within a few days. Earth-directed CMEs may cause severe geomagnetic storms when their embedded magnetic fields and the shocks ahead compress and reconnect with the Earth's magnetic field. The transit times and impacts in detail depend on the initial CME velocity, size, and mass, as well as on the conditions and coupling processe…
The study of the acceleration of particles is an essential element of research in the heliospheric science. Here, we discuss the predisposition to the particle acceleration around coronal mass ejections (CMEs)-driven shocks with corrugated wave-like features. We adopt these attributes on shocks formed from disturbances due to the bimodal solar wind, CME deflection, irregular CME expansion, and the ubiquitous fluctuations in the solar corona. In order to understand the role of a wavy shock in particle acceleration, we define three initial smooth shock morphologies each one associated with a fas…
We examine 188 coronal mass ejections (CMEs) measured by the twin STEREO spacecraft during 2007-2016 to investigate the generic features of the CME sheath and the magnetic ejecta (ME) and dependencies of average physical parameters of the sheath on the ME. We classify the MEs into three categories, focusing on whether a ME drives both a shock and sheath, or only a sheath, or neither, near 1 AU. We also reevaluate our initial classification through an automated algorithm and visual inspection. We observe that even for leading edge speeds greater than 500 km/s, 1 out of 4 MEs do not drive shocks…
We investigate the source eruption, propagation and expansion characteristics, and heliospheric impacts of the 2020 November 29 coronal mass ejection (CME) and associated shock, using remote sensing and in situ observations from multiple spacecraft. A potential--field source--surface model is employed to examine the coronal magnetic fields surrounding the source region. The CME and associated shock are tracked from the early stage to the outer corona using extreme ultraviolet and white light observations. Forward models are applied to determine the structures and kinematics of the CME and the …
Aims. Our goal is to thoroughly analyse the dynamics of single and multiple solar eruptions, as well as a stealth ejecta. The data were obtained through self-consistent numerical simulations performed in a previous study. We also assess the effect of a different background solar wind on the propagation of these ejecta to Earth. Methods. We calculated all the components of the forces contributing to the evolution of the numerically modelled consecutive coronal mass ejections (CMEs) obtained with the 2.5D magnetohydrodynamics (MHD) module of the code MPI-AMRVAC. We analysed the thermal and magne…
A powerful coronal mass ejection (CME) occurred on 2017 September 10 near the end of the declining phase of the historically weak solar cycle 24. We obtain new insights concerning the geometry and kinematics of CME-driven shocks in relation to their heliospheric impacts from the optimal, multi-spacecraft observations of the eruption. The shock, which together with the CME driver can be tracked from the early stage to the outer corona, shows a large oblate structure produced by the vast expansion of the ejecta. The expansion speeds of the shock along the radial and lateral directions are much l…
The electromotive force (EMF) describes how the evolution and generation of a large-scale magnetic field is influenced by small-scale turbulence. Recent studies of in-situ measurements have shown a significant peak in the EMF while a coronal mass ejection (CME) shock front passes by the spacecraft. The goal of this study is to use the EMF as an indicator for the arrival of CME shock fronts. With Helios spacecraft measurements we carry out a statistical study on the EMF during CMEs in the inner heliosphere. We develop an automated shock front detection algorithm using the EMF as the main detect…
