CME-driven Shock Research Articles

Properties and drivers of fast interplanetary shocks near the orbit of the Earth (1995–2013)

AbstractWe present a comprehensive statistical analysis spanning over a solar cycle of the properties and drivers of traveling fast forward and fast reverse interplanetary shocks. We combine statistics of 679 shocks between 1995 and 2013 identified from the near‐Earth (Wind and ACE) and STEREO‐A observations. We find that fast forward shocks dominate over fast reverse shocks in all solar cycle phases except during solar minimum. Nearly all fast reverse shocks are driven by slow‐fast stream interaction regions (SIRs), while coronal mass ejections (CMEs) are the principal drivers of fast forward shocks in all phases except at solar minimum. The occurrence rate and median speeds of CME‐driven fast forward shocks follow the sunspot cycle, while SIR‐associated shocks do not show such correspondence. The strength of the shock (characterized by the magnetosonic Mach number and by the upstream to downstream magnetic field and density ratio) shows relatively little variations over solar cycle. However, the shocks were slightly stronger during the ascending phase of a relatively weak solar cycle 24 than during the previous ascending phase. The CME‐ and SIR‐driven fast forward shocks and fast reverse shocks have distinct upstream solar wind conditions, which reflect to their relative strengths. We found that CME‐driven shocks are on average stronger and faster, and they show broader distributions of shock parameters than the shocks driven by SIRs.

Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars.

The severe geomagnetic effects of solar storms or coronal mass ejections (CMEs) are to a large degree determined by their propagation direction with respect to Earth. There is a lack of understanding of the processes that determine their non-radial propagation. Here we present a synthesis of data from seven different space missions of a fast CME, which originated in an active region near the disk centre and, hence, a significant geomagnetic impact was forecasted. However, the CME is demonstrated to be channelled during eruption into a direction +37±10° (longitude) away from its source region, leading only to minimal geomagnetic effects. In situ observations near Earth and Mars confirm the channelled CME motion, and are consistent with an ellipse shape of the CME-driven shock provided by the new Ellipse Evolution model, presented here. The results enhance our understanding of CME propagation and shape, which can help to improve space weather forecasts.

Modelling large solar proton events with the shock-and-particle model

We have developed a new version of a model that combines a two-dimensional Sun-to-Earth magnetohydrodynamic (MHD) simulation of the propagation of a CME-driven shock and a simulation of the transport of particles along the interplanetary magnetic field (IMF) line connecting the shock front and the observer. We assume that the shock-accelerated particles are injected at the point along the shock front that intersects this IMF line, i.e. at the cobpoint. Novel features of the model are an improved solar wind model and an enhanced fully automated algorithm to extract the necessary plasma characteristics from the shock simulation. In this work, the new algorithms have been employed to simulate the 2000 April 4 and the 2006 December 13 SEP events. In addition to quantifying the performance of the new model with respect to results obtained using previous versions of the shock-and-particle model, we investigate the semi-empirical relation between the injection rate of shock-accelerated particles, Q , and the jump in speed across the shock, VR, known as the Q (VR) relation. Our results show that while the magnetic field and density compression at the shock front is markedly different than in our previous modeling, the evolution of VR remains largely similar. As a result, we confirm that a simple relation can still be established between Q and VR, which enables the computation of synthetic intensity-time profiles at any location in interplanetary space. Furthermore, the new shock extraction tool is found to yield improved results being in general more robust. These results are important not only with regard to efforts to develop coupled magnetohydrodynamic and particle simulation models, but also to improve space weather related software tools that aim to predict the peak intensities, fluences and proton intensity-time profiles of SEP events (such as the SOLPENCO tool).

An Interpretation of a Possible Mechanism for the First Ground-Level Enhancement of Solar Cycle 24

It is well known that solar flares and shocks driven by coronal mass ejections (CMEs) are high-energy particle acceleration processes that might cause a high-energy particle event known as a ground-level enhancement (GLE). In this context, we have attempted to understand the processes responsible for the first GLE event (GLE71 17 May 2012 01:50 UT) of Solar Cycle 24. We studied the spatial and spectral data from the Solar Dynamics Observatory (SDO) the Culgoora radio-heliograph, and Wind/WAVES instrument, and analyzed the temporal data of the solar-flare components, the solar radio-flux density, and the electron fluxes from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the Geostationary Operational Environmental Satellite (GOES), the Radio Solar Telescope Network (RSTN), and Wind spacecraft. The flare had two ribbons separated by the neutral line between negative and positive magnetic polarity. Their structure was also almost consistent with the contours of some flare components, which were almost saturated during the flare-peak time. As indicated by the metric–kilometric Type-II burst, and because it extended over a wide heliolongitude (> ≈ 41∘) range, the CME-driven shock was fast enough to cause high-energy particle acceleration at a high altitude in the solar corona. Moreover, the CME and flare-flash phases were aligned along the same direction, which implies that if the CME-driven shock played the leading role in causing the GLE, preceding flare components may have contributed to the shock.

THE SOLAR ENERGETIC PARTICLE EVENT ON 2013 APRIL 11: AN INVESTIGATION OF ITS SOLAR ORIGIN AND LONGITUDINAL SPREAD

We investigate the solar phenomena associated with the origin of the solar energetic particle (SEP) event observed on 2013 April 11 by a number of spacecraft distributed in the inner heliosphere over a broad range of heliolongitudes. We use Extreme UltraViolet (EUV) and white-light coronagraph observations from the Solar Dynamics Observatory (SDO), the SOlar and Heliospheric Observatory (SOHO) and the twin Solar TErrestrial RElations Observatory spacecraft (STEREO-A and STEREO-B) to determine the angular extent of the EUV wave and coronal mass ejection (CME) associated with the origin of the SEP event. We compare the estimated release time of SEPs observed at each spacecraft with the arrival time of the structures associated with the CME at the footpoints of the field lines connecting each spacecraft with the Sun. Whereas the arrival of the EUV wave and CME-driven shock at the footpoint of STEREO-B is consistent, within uncertainties, with the release time of the particles observed by this spacecraft, the EUV wave never reached the footpoint of the field lines connecting near-Earth observers with the Sun, even though an intense SEP event was observed there. We show that the west flank of the CME-driven shock propagating at high altitudes above the solar surface was most likely the source of the particles observed near Earth, but it did not leave any EUV trace on the solar disk. We conclude that the angular extent of the EUV wave on the solar surface did not agree with the longitudinal extent of the SEP event in the heliosphere. Hence EUV waves cannot be used reliably as a proxy for the solar phenomena that accelerates and injects energetic particles over broad ranges of longitudes.

ARE THE FAINT STRUCTURES AHEAD OF SOLAR CORONAL MASS EJECTIONS REAL SIGNATURES OF DRIVEN SHOCKS?

Recently, several studies have assumed that the faint structures ahead of coronal mass ejections (CMEs) are caused by CME-driven shocks. In this study, we have conducted a statistical investigation to determine whether or not the appearance of such faint structures depends on CME speeds. For this purpose, we use 127 Solar and Heliospheric Observatory/Large Angle Spectroscopic COronagraph (LASCO) front-side halo (partial and full) CMEs near the limb from 1997 to 2011. We classify these CMEs into two groups by visual inspection of CMEs in the LASCO-C2 field of view: Group 1 has the faint structure ahead of a CME and Group 2 does not have such a structure. We find the following results. (1) Eighty-seven CMEs belong to Group 1 and 40 CMEs belong to Group 2. (2) Group 1 events have much higher speeds (average = 1230 km s–1 and median = 1199 km s–1) than Group 2 events (average = 598 km s–1 and median = 518 km s–1). (3) The fraction of CMEs with faint structures strongly depends on CME speeds (V): 0.93 (50/54) for fast CMEs with V ≥ 1000 km s–1, 0.65 (34/52) for intermediate CMEs with 500 km s–1 ≤ V < 1000 km s–1, and 0.14 (3/21) for slow CMEs with V < 500 km s–1. We also find that the fraction of CMEs with deca-hecto metric type II radio bursts is consistent with the above tendency. Our results indicate that the observed faint structures ahead of fast CMEs are most likely an enhanced density manifestation of CME-driven shocks.

Global simulation of extremely fast coronal mass ejection on 23 July 2012

The July 23, 2012 CME was an extremely fast backside event, reaching ∼1AU (STEREO-A) within 20h as compared to ∼3–6 days for typical CME events. Here, we present results from a simulation study of the CME and its driven shock using a combined kinematic and magnetohydrodynamic (MHD) simulation model, H3DMHD. In general, the model results match well with in situ measurements in the arrival time of the CME-driven shock and the total magnetic field strength, assuming an initial CME speed of 3100km/s. Based on extrapolation of an empirical model, the fast CME and its large magnetic field (|B|∼120nT) are capable of producing an extremely large geomagnetic storm (Dst∼−545nT), comparable to the well-known Halloween storm in 2003, if the CME had made a direct impact to the Earth. We investigated the effect of the adiabatic index (γ). It is found that the shock tends to arrive slightly later for a smaller γ value, and γ=5/3 provides the best agreement for the shock arrival time. We also demonstrate that the strength (the Mach number) of the CME-driven fast-mode shock is not the largest at the “nose” of the CME. This is mainly due to the manifestation of fast-mode wave speed upstream of the shock.

SIMULATION OF ENERGETIC NEUTRAL ATOMS FROM SOLAR ENERGETIC PARTICLES

Energetic neutral atoms (ENAs) provide the only way to observe the acceleration site of coronal-mass-ejection-driven (CME-driven) shock-accelerated solar energetic particles (SEPs). In gradual SEP events, energetic protons can charge exchange with the ambient solar wind or interstellar neutrals to become ENAs. Assuming a CME-driven shock with a constant speed of 1800 km s{sup –1} and compression ratio of 3.5, propagating from 1.5 to 40 R{sub S} , we calculate the accelerated SEPs at 5-5000 keV and the resulting ENAs via various charge-exchange interactions. Taking into account the ENA losses in the interplanetary medium, we obtain the flux-time profiles of these solar ENAs reaching 1 AU. We find that the arriving ENAs at energies above ∼100 keV show a sharply peaked flux-time profile, mainly originating from the shock source below 5 R{sub S} , whereas the ENAs below ∼20 keV have a flat-top time profile, mostly originating from the source beyond 10 R{sub S} . Assuming the accelerated protons are effectively trapped downstream of the shock, we can reproduce the STEREO ENA fluence observations at ∼2-5 MeV/nucleon. We also estimate the flux of ENAs coming from the charge exchange of energetic storm protons, accelerated by the fast CME-driven shock near 1 AU, with interstellarmore » hydrogen and helium. Our results suggest that appropriate instrumentation would be able to detect ENAs from SEPs and to even make ENA images of SEPs at energies above ∼10-20 keV.« less

TRACKING THE CME-DRIVEN SHOCK WAVE ON 2012 MARCH 5 AND RADIO TRIANGULATION OF ASSOCIATED RADIO EMISSION

We present a multiwavelength study of the 2012 March 5 solar eruptive event, with an emphasis on the radio triangulation of the associated radio bursts. The main points of the study are reconstruction of the propagation of shock waves driven by coronal mass ejections (CMEs) using radio observations and finding the relative positions of the CME, the CME-driven shock wave, and its radio signatures. For the first time, radio triangulation is applied to different types of radio bursts in the same event and performed in a detailed way using goniopolarimetric observations from STEREO/Waves and WIND/Waves spacecraft. The event on 2012 March 5 was associated with a X1.1 flare from the NOAA AR 1429 situated near the northeast limb, accompanied by a full halo CME and a radio event comprising long-lasting interplanetary type II radio bursts. The results of the three-dimensional reconstruction of the CME (using SOHO/LASCO, STEREO COR, and HI observations), and modeling with the ENLIL cone model suggest that the CME-driven shock wave arrived at 1 AU at about 12:00 UT on March 7 (as observed by SOHO/CELIAS). The results of radio triangulation show that the source of the type II radio burst was situated on the southern flankmore » of the CME. We suggest that the interaction of the shock wave and a nearby coronal streamer resulted in the interplanetary type II radio emission.« less

AN INTERPRETATION OF GLE71 CONCURRENT CME-DRIVEN SHOCK WAVE

Particle accelerations in solar flares and CME-driven shocks can sometimes result in very high-energy particle events (>= 1 GeV) that are known as ground level enhancements (GLEs). Recent studies on the first GLE event (GLE71 2012 May 17 01:50 UT) of solar cycle 24 suggested that CME-driven shock played a leading role in causing the event. To verify this claim, we have made an effort to interpret the GLE71 concurrent shock wave. For this, we have deduced the possible speed and height of the shock wave in terms of the frequency (MHz) of the solar radio type II burst and its drift rate (MHz min(-1)), and studied the temporal evolution of the particle intensity profiles at different heights of the solar corona. For a better perception of the particle acceleration in the shock, we have studied the solar radio type II burst with concurrent solar radio and electron fluxes. When the particle intensity profiles are necessarily shifted in time at similar to 1 AU, it is found that the growth phases of the electron and cosmic ray intensity fluxes are strongly correlated (>0.91; >= 0.87) with the frequency drift rate of the type II burst, which is also consistent with the intensive particle accelerations at upper coronal heights (similar to >= 0.80 R-S < 1.10 R-S). Thus, we conclude that the CME-driven shock was possibly capable of producing the high-energy particle event. However, since the peaks of some flare components are found to be strongly associated with the fundamental phase of the type II burst, the preceding flare is supposed to contribute to the shock acceleration process.

TRANSMISSION AND EMISSION OF SOLAR ENERGETIC PARTICLES IN SEMI-TRANSPARENT SHOCKS

While major solar energetic particle (SEP) events are associated with coronal mass ejection (CME)-driven shocks in solar wind, accurate SEP measurements reveal that more than one component of energetic ions exist in the beginning of the events. Solar electromagnetic emissions, including nuclear gamma-rays, suggest that high-energy ions could also be accelerated by coronal shocks, and some of those particles could contribute to SEPs in interplanetary space. However, the CME-driven shock in solar wind is thought to shield any particle source beneath the shock because of the strong scattering required for the diffusive shock acceleration. In this Letter, we consider a shock model that allows energetic particles from the possible behind-shock source to appear in front of the shock simultaneously with SEPs accelerated by the shock itself. We model the energetic particle transport in directions parallel and perpendicular to the magnetic field in a spherical shock expanding through the highly turbulent magnetic sector with an embedded quiet magnetic tube, which makes the shock semi-transparent for energetic particles. The model energy spectra and time profiles of energetic ions escaping far upstream of the shock are similar to the profiles observed during the first hour of some gradual SEP events.

Determination of coronal magnetic fields from 10 to 26R ⊙ using the density compression ratios of CME-driven shocks

Recently, the estimation of coronal magnetic field using new methods, such as standoff distance method or density compression ratio method has been reported. In the present work, we utilized the density compression ratio of CME-driven shocks for 10 events at 29 different locations in the upper solar corona (10–26R ⊙) and determined the coronal magnetic field for two different adiabatic indices (γ=4/3 and 5/3). In addition, radial dependence of shock parameters in the corona is studied. It is found that the magnetic field estimated in the above range agree with the general trend. In addition, we obtained a radial profile of magnetic field [B(R)=623R −1.4] in the entire upper corona (3–30R ⊙) by combining the magnetic field estimated by Kim et al. (Astrophys. J. 746:118, 2012) in the range 3–15R ⊙ and that estimated in the present study in the range (10–26R ⊙). The power-law indices are nearly in agreement with recent results of CME-driven shocks reported in the literature. The results are discussed with the comparison of newly reported coronal magnetic field values obtained by different techniques and found that the power-law relation closely follow the literature values.

On the possible mechanism of the first ground level enhancement in cosmic ray intensity of solar cycle 24

We have carried out this work to comprehend the possible mechanisms of the first ground level enhancement (GLE71 17 May 2012 01:50 UT) in cosmic ray intensity of the solar cycle 24. For this, the cosmic ray intensities registered by neutron monitors at several sites have been analyzed and studied with concurrent solar flares of different energy channels. To assess empirically whether the GLE might have been caused by the energy released from solar flare or CME-driven shock, we identify the possible time line in terms of the lowest spectral index determined from proton fluxes. If the GLE is caused by the energy released from particle acceleration in solar flare, the intensive phase of the flare representing the extreme emission should exist within/around the possible time line. In this respect, it is observed that the possible time line lies within the prominent phase of CME-driven shock. For better understanding, we have checked the possible relativistic energy with respect to solar flare as well as CME-driven shock. As witnessed, if the extreme emission phase of the flare is considered as the reason for the causation of GLE peak, the flare components procured insufficient amount of energy (a parts per thousand currency signa1/40.085 GeV) to produce a GLE. If the extreme emission phase of the flare is also considered as the dominator along GLE onset, the possible energy procurement (a parts per thousand currency signa1/40.414 GeV) is still not adequate to produce a GLE. In contrast, the CME-driven shock is capable of procuring enough possible relativistic energy (a parts per thousand yena1/41.21 GeV) that is sufficient amount of the energy for a GLE production. Any amount of the energy (< 0.414 GeV) released from preceding flare components is supposed to have been contributed to the shock process. Thus, it is assumed that the GLE71 was possibly caused by the energy released from the shock acceleration, which might have been boosted by the energy emanated from preceding flare.

NUMERICAL SIMULATIONS OF CORONAL MASS EJECTION ON 2011 MARCH 7: ONE-TEMPERATURE AND TWO-TEMPERATURE MODEL COMPARISON

During Carrington rotation (CR) 2107, a fast coronal mass ejection (CME; >2000 km s −1 ) occurred in active region NOAA 11164. This event is also associated with a solar energetic particle event. In this study, we present simulations of this CME with one-temperature (1T) and two-temperature (2T: coupled thermodynamics of the electron and proton populations) models. Both the 1T and 2T models start from the chromosphere with heat conduction and radiative cooling. The background solar wind is driven by Alfv´ en-wave pressure and heated by Alfv´ en-wave dissipation in which we have incorporated the balanced turbulence at the top of the closed field lines. The magnetic field of the inner boundary is set up using a synoptic map from Solar Dynamics Observatory/ Helioseismic and Magnetic Imager. The Titov–D´ emoulin flux-rope model is used to initiate the CME event. We compare the propagation of fast CMEs and the thermodynamics of CME-driven shocks in both the 1T and 2T CME simulations. Also, the synthesized white light images are compared with the Solar and Heliospheric Observatory/ Large Angle and Spectrometric Coronagraph observations. Because there is no distinction between electron and proton temperatures, heat conduction in the 1T model creates an unphysical temperature precursor in front of the CME-driven shock and makes the shock parameters (e.g., shock Mach number, compression ratio) incorrect. Our results demonstrate the importance of the electron heat conduction in conjunction with proton shock heating in order to produce the physically correct CME structures and CME-driven shocks.

ELECTRON AND PROTON ACCELERATION DURING THE FIRST GROUND LEVEL ENHANCEMENT EVENT OF SOLAR CYCLE 24

High-energy particles were recorded by near-Earth spacecraft and ground-based neutron monitors (NMs) on 2012 May 17. This event was the first ground level enhancement (GLE) of solar cycle 24. In this study, we try to identify the acceleration source(s) of solar energetic particles by combining in situ particle measurements from the WIND/3DP, GOES 13, and solar cosmic rays registered by several NMs, as well as remote-sensing solar observations from SDO/AIA, SOHO/LASCO, and RHESSI. We derive the interplanetary magnetic field (IMF) path length (1.25 +/- 0.05 AU) and solar particle release time (01:29 +/- 00:01 UT) of the first arriving electrons by using their velocity dispersion and taking into account contamination effects. We found that the electron impulsive injection phase, indicated by the dramatic change in the spectral index, is consistent with flare non-thermal emission and type III radio bursts. Based on the potential field source surface concept, modeling of the open-field lines rooted in the active region has been performed to provide escape channels for flare-accelerated electrons.Meanwhile, relativistic protons are found to be released 10 minutes later than the electrons, assuming their scatter-free travel along the same IMF path length. Combining multi-wavelength imaging data of the prominence eruption and coronal mass ejection (CME), we obtain evidence that GLE protons, with an estimated kinetic energy of 1.12 GeV, are probably accelerated by the CME-driven shock when it travels to 3.07 solar radii. The time-of-maximum spectrum of protons is typical for shock wave acceleration.

Super- and sub-critical regions in shocks driven by radio-loud and radio-quiet CMEs

White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a “radio-loud” fast CME, while the second one was a “radio quiet” slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfvén Mach numbers for the general case of an oblique shock. It turns out that the “radio-loud” CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the “radio-quiet” CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles.

Analysis of the CME-driven shock from the SEP event that occurred on 2006 December 14

In a solar flare or coronal mass ejection (CME), observations of the subsequent interplanetary shock provide us with strong evidence of particle acceleration to energies of multiple MeV, even up to GeV. Diffusive shock acceleration is an efficient mechanism for particle acceleration. For investigating the shock structure, the energy injection and energy spectrum of a CME-driven shock, we perform a dynamical Monte Carlo simulation of the CME-driven shock that occurred on 2006 December 14 using an anisotropic scattering law. The simulated results of the shock's fine structure, particle injection, and energy spectrum are presented. We find that our simulation results give a good fit to the observations from multiple spacecraft.

AN INTERPRETATION OF THE POSSIBLE MECHANISMS OF TWO GROUND-LEVEL ENHANCEMENT EVENTS

We have carried out this work to clarify the possible mechanisms of two important high-energy particle events (GLE69 2005 January 20, 06: 46 UT and GLE70 2006 December 13, 02: 45 UT). For this purpose, the cosmic-ray intensities registered by neutron monitors at several sites have been analyzed and studied with concurrent solar flares of different energy bands. To determine whether the ground-level enhancement (GLE) might be caused by the energy released from a solar flare or a CME-driven shock, we identify the particle injection time in terms of the lowest value of the spectral indices deduced from proton fluxes. If the GLE is caused by the energy released from particle acceleration in a solar flare, the intensive phase of the flare representing extreme emission should lie within the injection time. While fulfilling this criterion, it is further necessary to understand the possible relativistic energy computed in terms of the possible travel time deduced by employing the observational time lag between the GLE and the concurrent solar flare. Accordingly, we have found that GLE69 is procured with sufficient possible relativistic energy (similar to 1.619 GeV) by the energy released from particle accelerations in the intensive phases of a solar flare components that have been corroborated by the injection time. The intensive phases of the flare components have also been justified with the prominent phases of a solar radio type III burst. For event GLE70, the particle injection time lies within the CME-driven shock justified by a solar radio type II burst which seems to be capable of procuring sufficient possible relativistic energies (similar to 1.231 to similar to 2.017 GeV). It is also noted that any fractional amount of energy (similar to 0.226 to similar to 0.694 GeV) from preceding flare components might be considered as a contribution to the shock acceleration process. Thus, GLE70 is presumably caused by the sum of the energy released mostly from a CME-driven shock and partially from preceding flare components.

THE COUPLED EVOLUTION OF ELECTRONS AND IONS IN CORONAL MASS EJECTION-DRIVEN SHOCKS

We present simulations of coronal mass ejections (CMEs) performed with a new two-temperature coronal model developed at the University of Michigan, which is able to address the coupled thermodynamics of the electron and proton populations in the context of a single fluid. This model employs heat conduction for electrons, constant adiabatic index (γ = 5/3), and includes Alfven wave pressure to accelerate the solar wind. The Wang-Sheeley-Arge empirical model is used to determine the Alfven wave pressure necessary to produce the observed bimodal solar wind speed. The Alfven waves are dissipated as they propagate from the Sun and heat protons on open magnetic field lines to temperatures above 2 MK. The model is driven by empirical boundary conditions that includes GONG magnetogram data to calculate the coronal field, and STEREO/EUVI observations to specify the density and temperature at the coronal boundary by the Differential Emission Measure Tomography method. With this model, we simulate the propagation of fast CMEs and study the thermodynamics of CME-driven shocks. Since the thermal speed of the electrons greatly exceeds the speed of the CME, only protons are directly heated by the shock. Coulomb collisions low in the corona couple the protons and electrons allowing heat exchange between the two species. However, the coupling is so brief that the electrons never achieve more than 10% of the maximum temperature of the protons. We find that heat is able to conduct on open magnetic field lines and rapidly propagates ahead of the CME to form a shock precursor of hot electrons.

Simulation of a CME-driven shock by anisotropic scattering angular distributions

AbstractObservations of the interplanetary shock provide us with strong evidences of particle acceleration to multi-MeV protons in a coronal mass ejection (CME). Diffusive shock acceleration (DSA) is an efficient mechanism for cosmic ray (CR). This work presents a dynamical Monte Carlo simulation of a CME-driven shock on 14-Dec-2006 by using a series of Gaussian scattering angular distributions. With the simulated results, we find that particle energy spectrum is affected by energy injection processes under the anisotropic scattering law.