We investigated 64 pairs of interacting-CME events identified from simultaneous observations by the SOHO and STEREO spacecraft from January 2010 to August 2014, to examine the relationship between large SEP events in ...We investigated 64 pairs of interacting-CME events identified from simultaneous observations by the SOHO and STEREO spacecraft from January 2010 to August 2014, to examine the relationship between large SEP events in the energy range of ~25 to~60 MeV and properties of the interacting CMEs.We found that during CME interactions, the large SEP events in this study were all generated by CMEs with the presence of enhanced type Ⅱ radio bursts, which also have wider longitudinal distributions compared to events without a type Ⅱ radio burst or its enhancement(almost always associated with small SEP events).It seems that the signature of type Ⅱ radio burst enhancement is a good discriminator between large SEP and small or no SEP event producers during CME interactions. The type Ⅱ radio burst enhancement is more likely to be generated by CME interactions, with the main CME having a larger speed(v), angular width(WD), mass(m) and kinetic energy(Ek), and taking over the preceding CMEs. The preceding CMEs in these instances have higher v, WD, m and Ekthan those in CME pairs missing type Ⅱ radio bursts or enhancements. Generally, the values of these properties in the type-Ⅱ-enhanced events are typically higher than the corresponding non-type-Ⅱ or non-type-Ⅱ-enhanced cases for both the main and preceding CMEs. Our analysis also revealed that the intensities of associated SEP events correlate negatively with the intersection height of the two CMEs. Moreover, the overlap width of two CMEs is typically larger in type-Ⅱ-enhanced events than in non-type-Ⅱ or non-type-Ⅱ-enhanced events. Most type-Ⅱ-enhanced events and SEP events are coincident and are almost always made by the fast and wide main CMEs that sweep fully over relatively slower and narrower preceding CMEs. We suggest that a fast CME with enough energy completely overtaking a relatively narrower preceding CME, especially at low height, can drive a more energetic shock signified by the enhanced type Ⅱ radio bursts. The shock may accelerate ambient particles(likely provided by the preceding CME) and lead to large SEP events more easily.展开更多
On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at Earth.Using the 2D improved Particle Acceleration and Transport in the H...On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at Earth.Using the 2D improved Particle Acceleration and Transport in the Heliosphere(iPATH)model,we model the large solar energetic particle(SEP)event of 2017 September 10 observed at Earth,Mars and STEREO-A.Based on observational evidence,we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption,which is modeled by a double Gaussian velocity profile in this simulation.We apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model parameters.The modeled time intensity profiles and fluence for energetic protons are then compared with observations.Reasonable agreements with observations at Mars and STEREO-A are found.The simulated results at Earth differ from observations of GOES-15.However,the simulated results at a heliocentric longitude 20°west to Earth fit reasonably well with the GOES observation.This can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker field.Our results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.展开更多
In large Solar Energetic Particle (SEP) events, ions can be accelerated at coronal mass ejection (CME)-driven shocks to very high energies. The spectra of heavy ions in many large SEP events show features such as ...In large Solar Energetic Particle (SEP) events, ions can be accelerated at coronal mass ejection (CME)-driven shocks to very high energies. The spectra of heavy ions in many large SEP events show features such as roll-overs or spectral breaks. In some events when the spectra are plotted in terms of energy/nucleon, they can be shifted relative to each other to make the spectral breaks align. The amount of shift is charge to mass ratio (Q/A) dependent and varies from event to event. This can be understood if the spectra of heavy ions are organized by the diffusion coefficients (Cohen et al. 2005). In the work of Li et al. (2009), the Q/A dependence of the scaling is related to shock geometry when the CME-driven shock is close to the Sun. For events where multiple in-situ spacecraft observations exist, one may expect that different spacecraft are connected to different portions of the CME-driven shock that have different shock geometries, therefore yielding different Q/A dependence. In this work, we examine one SEP event which occurred on 2013 November 4. We study the Q/A dependence of the energy scaling for heavy ion spectra using helium, oxygen and iron ions. Observations from STEREO-A, STEREO-B and ACE are examined. We find that the scalings are different for different spacecraft. We suggest that this is because ACE, STEREO- A and STEREO-B are connected to different parts of the shock that have different shock geometries. Our analysis indicates that studying the Q/A scaling of in-situ particle spectra can serve as a powerful tool to remotely examine the shock geometry for large SEP events.展开更多
We review and summarize the applications of the Grad-Shafranov(GS) reconstruction technique to space plasma structures in the Earth's magnetosphere and in the interplanetary space. We organize our presentations fo...We review and summarize the applications of the Grad-Shafranov(GS) reconstruction technique to space plasma structures in the Earth's magnetosphere and in the interplanetary space. We organize our presentations following the branches of the "academic family tree" rooted on Prof. Bengt U. ? Sonnerup, the inventor of the GS method. Special attentions are paid to validations of the GS reconstruction results via(1) the direct validation by co-spatial in-situ measurements among multiple spacecraft, and(2) indirect validation by implications and interpretations of the physical connection between the structures reconstructed and other related processes. For the latter, the inter-comparison and interconnection between the large-scale magnetic flux ropes(i.e., Magnetic Clouds) in the solar wind and their solar source properties are presented. In addition, we also summarize various GS-type(or-like) reconstruction and an extension of the GS technique to toroidal geometry. In particular,we point to a possible advancement with added complexity of "helical symmetry" and mixed helicity, in the hope of stimulating interest in future development. We close by offering some thoughts on appreciating the scientific merit of GS reconstruction in general.展开更多
An observation-based Galactic Cosmic Ray(GCR)spectral model for heavy nuclei is developed.Zhao and Qin[J.Geophys.Res.Space Phys.118,1837(2013)]proposed an empirical elemental GCR spectra model for nuclear charge 5≤z...An observation-based Galactic Cosmic Ray(GCR)spectral model for heavy nuclei is developed.Zhao and Qin[J.Geophys.Res.Space Phys.118,1837(2013)]proposed an empirical elemental GCR spectra model for nuclear charge 5≤z≤28 over the energy range^30 to 500 Me V/nuc,which is proved to be successful in predicting yearly averaged GCR heavy nuclei spectra.Based on the latest highly statistically precise measurements from ACE/CRIS,a further elemental GCR model with monthly averaged spectra is presented.The model can reproduce the past and predict the future GCR intensity monthly by correlating model parameters with the continuous sunspot number(SSN)record.The effects of solar activity on GCR modulation are considered separately for odd and even solar cycles.Compared with other comprehensive GCR models,our modeling results are satisfyingly consistent with the GCR spectral measurements from ACE/SIS and IMP-8,and have comparable prediction accuracy as the Badhwar&O’Neill 2014 model.A detailed error analysis is also provided.Finally,the GCR carbon and iron nuclei fluxes for the subsequent two solar cycles(SC 25 and 26)are predicted and they show a potential trend in reduced flux amplitude,which is suspected to be relevant to possible weak solar cycles.展开更多
In the solar system, our Sun is Nature's most efficient particle accelerator. In large solar flares and fast coronal mass ejections(CMEs), protons and heavy ions can be accelerated to over ~GeV/nucleon. Large flar...In the solar system, our Sun is Nature's most efficient particle accelerator. In large solar flares and fast coronal mass ejections(CMEs), protons and heavy ions can be accelerated to over ~GeV/nucleon. Large flares and fast CMEs often occur together. However there are clues that different acceleration mechanisms exist in these two processes. In solar flares, particles are accelerated at magnetic reconnection sites and stochastic acceleration likely dominates. In comparison, at CME-driven shocks,diffusive shock acceleration dominates. Besides solar flares and CMEs, which are transient events, acceleration of particles has also been observed in other places in the solar system, including the solar wind termination shock, planetary bow shocks, and shocks bounding the Corotation Interaction Regions(CIRs). Understanding how particles are accelerated in these places has been a central topic of space physics. However, because observations of energetic particles are often made at spacecraft near the Earth,propagation of energetic particles in the solar wind smears out many distinct features of the acceleration process. The propagation of a charged particle in the solar wind closely relates to the turbulent electric field and magnetic field of the solar wind through particle-wave interaction. A correct interpretation of the observations therefore requires a thorough understanding of the solar wind turbulence. Conversely, one can deduce properties of the solar wind turbulence from energetic particle observations. In this article I briefly review some of the current state of knowledge of particle acceleration and transport in the inner heliosphere and discuss a few topics which may bear the key features to further understand the problem of particle acceleration and transport.展开更多
In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting wh...In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.展开更多
基金supported at NUIST by the National Natural Science Foundation of China (NSFC) (Grant Nos. U1731105 and 41304150)the Natural Science Foundation of Jiangsu Province of China (No. BK20171456)+3 种基金sponsored also by the Qing Lan Project of Jiangsu Province for L.G. Ding (2016)supported by NSFC (Grant Nos.11522328, 11473070 and 11427803)the Youth Innovation Promotion Associationthe specialized research fund from the State Key Laboratory of Space Weather for financial support
文摘We investigated 64 pairs of interacting-CME events identified from simultaneous observations by the SOHO and STEREO spacecraft from January 2010 to August 2014, to examine the relationship between large SEP events in the energy range of ~25 to~60 MeV and properties of the interacting CMEs.We found that during CME interactions, the large SEP events in this study were all generated by CMEs with the presence of enhanced type Ⅱ radio bursts, which also have wider longitudinal distributions compared to events without a type Ⅱ radio burst or its enhancement(almost always associated with small SEP events).It seems that the signature of type Ⅱ radio burst enhancement is a good discriminator between large SEP and small or no SEP event producers during CME interactions. The type Ⅱ radio burst enhancement is more likely to be generated by CME interactions, with the main CME having a larger speed(v), angular width(WD), mass(m) and kinetic energy(Ek), and taking over the preceding CMEs. The preceding CMEs in these instances have higher v, WD, m and Ekthan those in CME pairs missing type Ⅱ radio bursts or enhancements. Generally, the values of these properties in the type-Ⅱ-enhanced events are typically higher than the corresponding non-type-Ⅱ or non-type-Ⅱ-enhanced cases for both the main and preceding CMEs. Our analysis also revealed that the intensities of associated SEP events correlate negatively with the intersection height of the two CMEs. Moreover, the overlap width of two CMEs is typically larger in type-Ⅱ-enhanced events than in non-type-Ⅱ or non-type-Ⅱ-enhanced events. Most type-Ⅱ-enhanced events and SEP events are coincident and are almost always made by the fast and wide main CMEs that sweep fully over relatively slower and narrower preceding CMEs. We suggest that a fast CME with enough energy completely overtaking a relatively narrower preceding CME, especially at low height, can drive a more energetic shock signified by the enhanced type Ⅱ radio bursts. The shock may accelerate ambient particles(likely provided by the preceding CME) and lead to large SEP events more easily.
基金NASA grants NNX17AI17G,80NSSC19K0075 and 80NSSC19K0629。
文摘On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at Earth.Using the 2D improved Particle Acceleration and Transport in the Heliosphere(iPATH)model,we model the large solar energetic particle(SEP)event of 2017 September 10 observed at Earth,Mars and STEREO-A.Based on observational evidence,we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption,which is modeled by a double Gaussian velocity profile in this simulation.We apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model parameters.The modeled time intensity profiles and fluence for energetic protons are then compared with observations.Reasonable agreements with observations at Mars and STEREO-A are found.The simulated results at Earth differ from observations of GOES-15.However,the simulated results at a heliocentric longitude 20°west to Earth fit reasonably well with the GOES observation.This can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker field.Our results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.
基金supported at UAH by NSF grants AGS-1135432 and AGS-1622391NASA grant NNX15AJ93G+5 种基金at APL by NASA grant NNX13AR20G/115828 (ACE/ULEIS and STEREO/SIT)NASA subcontract SA4889-26309 from the University of California Berkeleyat Caltech by NNX13A66G, NNX11A075Gsubcontract 00008864 of NNX15AG09Gby NSF grant AGS-1156004at SwRI partially by NSF grant AGS-1460118
文摘In large Solar Energetic Particle (SEP) events, ions can be accelerated at coronal mass ejection (CME)-driven shocks to very high energies. The spectra of heavy ions in many large SEP events show features such as roll-overs or spectral breaks. In some events when the spectra are plotted in terms of energy/nucleon, they can be shifted relative to each other to make the spectral breaks align. The amount of shift is charge to mass ratio (Q/A) dependent and varies from event to event. This can be understood if the spectra of heavy ions are organized by the diffusion coefficients (Cohen et al. 2005). In the work of Li et al. (2009), the Q/A dependence of the scaling is related to shock geometry when the CME-driven shock is close to the Sun. For events where multiple in-situ spacecraft observations exist, one may expect that different spacecraft are connected to different portions of the CME-driven shock that have different shock geometries, therefore yielding different Q/A dependence. In this work, we examine one SEP event which occurred on 2013 November 4. We study the Q/A dependence of the energy scaling for heavy ion spectra using helium, oxygen and iron ions. Observations from STEREO-A, STEREO-B and ACE are examined. We find that the scalings are different for different spacecraft. We suggest that this is because ACE, STEREO- A and STEREO-B are connected to different parts of the shock that have different shock geometries. Our analysis indicates that studying the Q/A scaling of in-situ particle spectra can serve as a powerful tool to remotely examine the shock geometry for large SEP events.
基金supported by National Aeronautics and Space Administration (NASA) and National Science Foundation (NSF) (Grants Nos. AGS-1062050, NNG04GF47G, NNG06GD41G, NNX12AF97G, NNX12AH50G, NNH13ZDA001N, and NNX14AF41G)
文摘We review and summarize the applications of the Grad-Shafranov(GS) reconstruction technique to space plasma structures in the Earth's magnetosphere and in the interplanetary space. We organize our presentations following the branches of the "academic family tree" rooted on Prof. Bengt U. ? Sonnerup, the inventor of the GS method. Special attentions are paid to validations of the GS reconstruction results via(1) the direct validation by co-spatial in-situ measurements among multiple spacecraft, and(2) indirect validation by implications and interpretations of the physical connection between the structures reconstructed and other related processes. For the latter, the inter-comparison and interconnection between the large-scale magnetic flux ropes(i.e., Magnetic Clouds) in the solar wind and their solar source properties are presented. In addition, we also summarize various GS-type(or-like) reconstruction and an extension of the GS technique to toroidal geometry. In particular,we point to a possible advancement with added complexity of "helical symmetry" and mixed helicity, in the hope of stimulating interest in future development. We close by offering some thoughts on appreciating the scientific merit of GS reconstruction in general.
基金supported by the National Natural Science Foundation of China(Grant Nos.41174165,and 41504133)the partial support of the National Science Foundation of USA(Grant Nos.EPSCo R RII-Track-1 Cooperative Agreement OIA-1655280,NASA grants NNX08AJ33G,Subaward 37gvfv102-2,NNX14AC08G,NNX14AJ53G,A99132BT,RR185-447/4944336 and NNX12AB30G)+1 种基金partial support of National Key R&D Program of China(Grant Nos.2018YFC1407304,and 2018YFF01013706)the Open Fund of Key Laboratory(Grant Nos.201801003,and 315030409)
文摘An observation-based Galactic Cosmic Ray(GCR)spectral model for heavy nuclei is developed.Zhao and Qin[J.Geophys.Res.Space Phys.118,1837(2013)]proposed an empirical elemental GCR spectra model for nuclear charge 5≤z≤28 over the energy range^30 to 500 Me V/nuc,which is proved to be successful in predicting yearly averaged GCR heavy nuclei spectra.Based on the latest highly statistically precise measurements from ACE/CRIS,a further elemental GCR model with monthly averaged spectra is presented.The model can reproduce the past and predict the future GCR intensity monthly by correlating model parameters with the continuous sunspot number(SSN)record.The effects of solar activity on GCR modulation are considered separately for odd and even solar cycles.Compared with other comprehensive GCR models,our modeling results are satisfyingly consistent with the GCR spectral measurements from ACE/SIS and IMP-8,and have comparable prediction accuracy as the Badhwar&O’Neill 2014 model.A detailed error analysis is also provided.Finally,the GCR carbon and iron nuclei fluxes for the subsequent two solar cycles(SC 25 and 26)are predicted and they show a potential trend in reduced flux amplitude,which is suspected to be relevant to possible weak solar cycles.
基金supported in part by a guest professorship grant from the School of Geophysics and Information Technology, China University of Geosciences (Beijing)
文摘In the solar system, our Sun is Nature's most efficient particle accelerator. In large solar flares and fast coronal mass ejections(CMEs), protons and heavy ions can be accelerated to over ~GeV/nucleon. Large flares and fast CMEs often occur together. However there are clues that different acceleration mechanisms exist in these two processes. In solar flares, particles are accelerated at magnetic reconnection sites and stochastic acceleration likely dominates. In comparison, at CME-driven shocks,diffusive shock acceleration dominates. Besides solar flares and CMEs, which are transient events, acceleration of particles has also been observed in other places in the solar system, including the solar wind termination shock, planetary bow shocks, and shocks bounding the Corotation Interaction Regions(CIRs). Understanding how particles are accelerated in these places has been a central topic of space physics. However, because observations of energetic particles are often made at spacecraft near the Earth,propagation of energetic particles in the solar wind smears out many distinct features of the acceleration process. The propagation of a charged particle in the solar wind closely relates to the turbulent electric field and magnetic field of the solar wind through particle-wave interaction. A correct interpretation of the observations therefore requires a thorough understanding of the solar wind turbulence. Conversely, one can deduce properties of the solar wind turbulence from energetic particle observations. In this article I briefly review some of the current state of knowledge of particle acceleration and transport in the inner heliosphere and discuss a few topics which may bear the key features to further understand the problem of particle acceleration and transport.
基金supported by the Royal Society,ERC Starting(Grant No.639217)he European Union Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Global Fellowship(Grant No.703916)+10 种基金the National Natural Science Foundation of China(Grant Nos.11233001,11773014,11633007,11403074,11333005,11503008,and 11590781)the National Basic Research Program of China(Grant No.2015CB857100)NASA(Grant No.NNX13AD28A)an ARC Future Fellowship(Grant No.FT120100363)the National Science Foundation(Grant No.PHY-1430152)the Spanish MINECO(Grant No.AYA2016-76012-C3-1-P)the ICCUB(Unidad de Excelencia’Maria de Maeztu’)(Grant No.MDM-2014-0369)EU’s Horizon Programme through a Marie Sklodowska-Curie Fellowship(Grant No.702638)the Polish National Science Center(Grant Nos.2015/17/B/ST9/03422,2015/18/M/ST9/00541,2013/10/M/ST9/00729,and 2015/18/A/ST9/00746)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA15020100)the NWO Veni Fellowship(Grant No.639.041.647)
文摘In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.