On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with near-Earth spacecraft （e.g. SOHO, Wind） situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle （...On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with near-Earth spacecraft （e.g. SOHO, Wind） situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle （SEP） event in Solar Cycle 24. Two successive coronal mass ejections （CMEs） have been detected close in time. From the multi-point in-situ observations, it can be found that this SEP event was caused by the first CME, but the second one was not involved. Using velocity dispersion analysis （VDA）, we find that for a well magnetically connected point, the energetic protons and electrons are released nearly at the same time. The path lengths to STEREO-B （STB） for protons and electrons have a distinct difference and deviate remarkably from the nominal Parker spiral path length, which is likely due to the presence of interplanetary magnetic structures situated between the source and STB. Also, the VDA method seems to only obtain reasonable results at well-connected locations and the inferred release times of energetic particles in different energy channels are similar. We suggest that good-connection is crucial for obtaining both an accurate release time and path length simultaneously, agreeing with the modeling result of Wang ＆ Qin （2015）.展开更多
Kinematic properties of coronal mass ejections （CMEs） suffer from projection effects,and it is expected that the real velocity should be larger and the real angular width should be smaller than the apparent values.S...Kinematic properties of coronal mass ejections （CMEs） suffer from projection effects,and it is expected that the real velocity should be larger and the real angular width should be smaller than the apparent values.Several attempts have been taken to correct the projection effects,which however led to an inflated average velocity probably due to the biased choice of CME events.In order to estimate the overall influence of the projection effects on the kinematic properties of the CMEs,we perform a forward modeling of real distributions of CME properties,such as the velocity,the angular width,and the latitude,by requiring their projected distributions to best match observations.Such a matching is conducted by Monte Carlo simulations.According to the derived real distributions,we found that （1） the average real velocity of all non-full-halo CMEs is about 514 km s-1,and the average real angular width is about 33°,in contrast to the corresponding apparent values of 418 km s-1 and 42.7° in observations;（2） For the CMEs with the angular width in the range of 20°-120°,the average real velocity is 510 km s-1 and the average real angular width is 43.4°,in contrast to the corresponding apparent values of 392 km s-1 and 52° in observations.展开更多
Halo coronal mass ejections （CMEs） have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs t...Halo coronal mass ejections （CMEs） have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs that clearly display loopshaped frontal loops. The observational results show a strong tendency that slower CMEs are weaker in white-light intensity. Then, we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of ～523km s -1. The Thomson scattering of these events is calculated when they are assumed to be observed as limb and halo events, respectively. It is found that the white-light inten-sity of many slow CMEs becomes remarkably reduced when they turn from being viewed as a limb event to being viewed as a halo event. When the intensity is below the background solar wind fluctuation, it is assumed that they would be missed by coronagraphs. The average velocity of ＂detectable＂ halo CMEs is ～922km s -1, very close to the observed value. This also indicates that wider events are more likely to be recorded. The results soundly suggest that the higher average velocity of halo CMEs is due to that a majority of slow events and some of narrow fast events carrying less material are so faint that they are blended with the solar wind fluctuations, and therefore are not observed.展开更多
Observations from multiple spacecraft show that there are energy spectral ＂breaks＂ at 1-10 MeV in some large CME-driven shocks. However, numerical models can hardly simulate this property due to high computational e...Observations from multiple spacecraft show that there are energy spectral ＂breaks＂ at 1-10 MeV in some large CME-driven shocks. However, numerical models can hardly simulate this property due to high computational expense. The present paper focuses on analyzing these energy spectral ＂breaks＂ by Monte Carlo particle simulations of an isolated CME-driven shock. Taking the 2006 Dec 14 CME-driven shock as an example, we investigate the formation of this energy spectral property. For this purpose, we apply different values for the scattering time in our isolated shock model to obtain the highest energy ＂tails,＂ which can potentially exceed the ＂break＂ energy range. However, we have not found the highest energy ＂tails＂ beyond the ＂break＂ energy range, but instead find that the highest energy ＂tails＂ reach saturation near the range of energy at 5 MeV. So, we believe that there exists an energy spectral ＂cut off＂ in an isolated shock. If there is no interaction with another shock, there would not be formation of the energy spectral ＂break＂ property.展开更多
In a solar flare or coronal mass ejection （CME）, observations of the subse- quent interplanetary shock provide us with strong evidence of particle acceleration to energies of multiple MeV, even up to GeV. Diffusive ...In a solar flare or coronal mass ejection （CME）, observations of the subse- quent 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 ofa 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, par- ticle injection, and energy spectrum are presented. We find that our simulation results give a good fit to the observations from multiple spacecraft.展开更多
基金supported at NUIST by the National Natural Science Foundation of China(NSFC)-41304150 for Ding L.G.at CMA by NSFC-41274193 and 41474166 for Le G.M
文摘On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with near-Earth spacecraft （e.g. SOHO, Wind） situated between the two STEREO spacecraft, observed an extremely large global solar energetic particle （SEP） event in Solar Cycle 24. Two successive coronal mass ejections （CMEs） have been detected close in time. From the multi-point in-situ observations, it can be found that this SEP event was caused by the first CME, but the second one was not involved. Using velocity dispersion analysis （VDA）, we find that for a well magnetically connected point, the energetic protons and electrons are released nearly at the same time. The path lengths to STEREO-B （STB） for protons and electrons have a distinct difference and deviate remarkably from the nominal Parker spiral path length, which is likely due to the presence of interplanetary magnetic structures situated between the source and STB. Also, the VDA method seems to only obtain reasonable results at well-connected locations and the inferred release times of energetic particles in different energy channels are similar. We suggest that good-connection is crucial for obtaining both an accurate release time and path length simultaneously, agreeing with the modeling result of Wang ＆ Qin （2015）.
基金supported by the National Basic Research Program of China(No.2011CB811402)the National Natural Science Foundation of China (Grant Nos.11025314,10403003,10933003 and 10673004)
文摘Kinematic properties of coronal mass ejections （CMEs） suffer from projection effects,and it is expected that the real velocity should be larger and the real angular width should be smaller than the apparent values.Several attempts have been taken to correct the projection effects,which however led to an inflated average velocity probably due to the biased choice of CME events.In order to estimate the overall influence of the projection effects on the kinematic properties of the CMEs,we perform a forward modeling of real distributions of CME properties,such as the velocity,the angular width,and the latitude,by requiring their projected distributions to best match observations.Such a matching is conducted by Monte Carlo simulations.According to the derived real distributions,we found that （1） the average real velocity of all non-full-halo CMEs is about 514 km s-1,and the average real angular width is about 33°,in contrast to the corresponding apparent values of 418 km s-1 and 42.7° in observations;（2） For the CMEs with the angular width in the range of 20°-120°,the average real velocity is 510 km s-1 and the average real angular width is 43.4°,in contrast to the corresponding apparent values of 392 km s-1 and 52° in observations.
基金Supported by the National Natural Science Foundation of Chinasupported by the Chinese foundations (GYHY200706013, 2006CB806302)+1 种基金the National Natural Science Foundation of China (Grant Nos. 10403003, 10933003 and 10673004)SOHO is a project of international cooperation between ESA and NASA
文摘Halo coronal mass ejections （CMEs） have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs that clearly display loopshaped frontal loops. The observational results show a strong tendency that slower CMEs are weaker in white-light intensity. Then, we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of ～523km s -1. The Thomson scattering of these events is calculated when they are assumed to be observed as limb and halo events, respectively. It is found that the white-light inten-sity of many slow CMEs becomes remarkably reduced when they turn from being viewed as a limb event to being viewed as a halo event. When the intensity is below the background solar wind fluctuation, it is assumed that they would be missed by coronagraphs. The average velocity of ＂detectable＂ halo CMEs is ～922km s -1, very close to the observed value. This also indicates that wider events are more likely to be recorded. The results soundly suggest that the higher average velocity of halo CMEs is due to that a majority of slow events and some of narrow fast events carrying less material are so faint that they are blended with the solar wind fluctuations, and therefore are not observed.
基金supported by the Xinjiang Natural Science Foundation(No.2014211A069)funded by the Key Laboratory of Solar Activity of NAOC,the Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University)Ministry of Education,and the China Scholarship Council(CSC)
文摘Observations from multiple spacecraft show that there are energy spectral ＂breaks＂ at 1-10 MeV in some large CME-driven shocks. However, numerical models can hardly simulate this property due to high computational expense. The present paper focuses on analyzing these energy spectral ＂breaks＂ by Monte Carlo particle simulations of an isolated CME-driven shock. Taking the 2006 Dec 14 CME-driven shock as an example, we investigate the formation of this energy spectral property. For this purpose, we apply different values for the scattering time in our isolated shock model to obtain the highest energy ＂tails,＂ which can potentially exceed the ＂break＂ energy range. However, we have not found the highest energy ＂tails＂ beyond the ＂break＂ energy range, but instead find that the highest energy ＂tails＂ reach saturation near the range of energy at 5 MeV. So, we believe that there exists an energy spectral ＂cut off＂ in an isolated shock. If there is no interaction with another shock, there would not be formation of the energy spectral ＂break＂ property.
基金supported by the National Natural Science Foundation of China (Grant No. 10921303)the National Basic Research Program of the Ministry of Science and Technology (MOST Grant No. 2011CB 811401)
文摘In a solar flare or coronal mass ejection （CME）, observations of the subse- quent 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 ofa 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, par- ticle injection, and energy spectrum are presented. We find that our simulation results give a good fit to the observations from multiple spacecraft.
