By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ej...By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ejections associated with X-class flares appear to be among the most energetic events in solar activity given the size of the flares, the speed of the CMEs and the intense geomagnetic storms they produce. Out of eighty-six (86) X-class halo CMEs, thirty-seven (37) or 43% are highly geoeffective;twenty-four (24) or approximately 28% are moderately geoeffective and twenty-five (25) or 29% are not geoeffective. Over the two solar cycles (1996 to 2019), 71% of storms were geoeffective and 29% were not. For solar cycle 23, about 78% of storms were geoeffective, while for solar cycle 24, about 56% were geoeffective. For the statistical study based on speed, 85 halo CMEs associated with X-class flares were selected because the CME of 6 December 2006 has no recorded speed value. For both solar cycles, 75.29% of the halo CMEs associated with X-class flares have a speed greater than 1000 km/s. The study showed that 42.18% of halo (X) CMEs with speeds above 1000 km/s could cause intense geomagnetic disturbances. These results show the contribution (in terms of speed) of each class of halo (X) CMEs to the perturbation of the Earth’s magnetic field. Coronal mass ejections then become one of the key indicators of solar activity, especially as they affect the Earth.展开更多
A catalogue of type II bursts and the associated coronal mass ejections （CMEs） observed by the solar and heliospheric observatory （SOHO） mission is used to select the twenty three CMEs events with CME speed equal ...A catalogue of type II bursts and the associated coronal mass ejections （CMEs） observed by the solar and heliospheric observatory （SOHO） mission is used to select the twenty three CMEs events with CME speed equal to and less than 450 km/sec （i.e., less than and equal to the average solar wind speed） during 1997-2008. Our observational results clearly indicate that even slow speed CMEs are capable to produce the cosmic ray and geomagnetic disturbances on day to day basis. The depression in cosmic ray intensity is larger three days after the arrival of the CMEs along with the maximum disturbance in geomagnetic activity on the same day （i.e., after three days from the arrival of CMEs）. Fluctuations in cosmic ray intensity and the geomagnetic activity are also observed before the arrival of the CMEs.展开更多
In heart failure with preserved ejection fraction,significant left ventricular diastolic abnormalities are present,despite a normal systolic ejection fraction.This article will consider whether this is consistent with...In heart failure with preserved ejection fraction,significant left ventricular diastolic abnormalities are present,despite a normal systolic ejection fraction.This article will consider whether this is consistent with the law of conservation of energy,also know as the first law of thermodynamics.展开更多
BACKGROUND Obesity has become a serious public health issue,significantly elevating the risk of various complications.It is a well-established contributor to Heart failure with preserved ejection fraction(HFpEF).Evalu...BACKGROUND Obesity has become a serious public health issue,significantly elevating the risk of various complications.It is a well-established contributor to Heart failure with preserved ejection fraction(HFpEF).Evaluating HFpEF in obesity is crucial.Epicardial adipose tissue(EAT)has emerged as a valuable tool for validating prognostic biomarkers and guiding treatment targets.Hence,assessing EAT is of paramount importance.Cardiovascular magnetic resonance(CMR)imaging is acknowledged as the gold standard for analyzing cardiac function and mor-phology.We hope to use CMR to assess EAT as a bioimaging marker to evaluate HFpEF in obese patients.AIM To assess the diagnostic utility of CMR for evaluating heart failure with preserved ejection fraction[HFpEF;left ventricular(LV)ejection fraction≥50%]by measuring the epicardial adipose tissue(EAT)volumes and EAT mass in obese patients.METHODS Sixty-two obese patients were divided into two groups for a case-control study based on whether or not they had heart failure with HFpEF.The two groups were defined as HFpEF+and HFpEF-.LV geometry,global systolic function,EAT volumes and EAT mass of all subjects were obtained using cine magnetic resonance sequences.RESULTS Forty-five patients of HFpEF-group and seventeen patients of HFpEF+group were included.LV mass index(g/m2)of HFpEF+group was higher than HFpEF-group(P<0.05).In HFpEF+group,EAT volumes,EAT volume index,EAT mass,EAT mass index and the ratio of EAT/[left atrial(LA)left-right(LR)diameter]were higher compared to HFpEF-group(P<0.05).In multivariate analysis,Higher EAT/LA LR diameter ratio was associated with higher odds ratio of HFpEF.CONCLUSION EAT/LA LR diameter ratio is highly associated with HFpEF in obese patients.It is plausible that there may be utility in CMR for assessing obese patients for HFpEF using EAT/LA LR diameter ratio as a diagnostic biomarker.Further prospective studies,are needed to validate these proof-of-concept findings.展开更多
Objective:To determine factors that affect the health-related quality of life(HRQOL)of congestive heart failure(CHF)patients with preserved and reduced ejection fraction.Methods:A cross-sectional study design was used...Objective:To determine factors that affect the health-related quality of life(HRQOL)of congestive heart failure(CHF)patients with preserved and reduced ejection fraction.Methods:A cross-sectional study design was used for this study.The stratified random sampling was applied for each subgroup.HRQOL was measured with the Minnesota Living with Hear t Failure Questionnaire.The data were analyzed using chi-square,Spearman's correlation analysis,and independent t-test.Results:A number of 67 respondents participated in the recent study.The total mean scores of HRQOL were significantly different(P=0.001)between heart failure(HF)patients with reduced and preserved ejection fractions,41.07±7.54 and 54.97±4.36,respectively.It related with the physical(mean±standard deviation[SD]=10.4±2.14;t=-10.08,95%CI=-12.46 to-8.34;P-value=0.001)and psychological(mean±SD=3.5±0.5;t=-6.68,95%CI=-4.55 to-2.45;P-value=0.001)domain.Strong correlation was found between age(r=-0.898,P<0.05),NYHA functional classes(r=-0.858,P<0.01),duration of HF(r=-0.807,P<0.01),family support(r=0.927,P<0.01),and quality of life(Qo L).Conclusions:HRQOL in HF patients with reduced ejection fraction was higher than in those with preserved ejection fraction.Family suppor t is a fur ther determinant factor that has a positive correlation to the Qo L.展开更多
To investigate the dependence of large gradual solar energetic particle（SEP） events on the associated flares and coronal mass ejections（CMEs）, the correlation coefficients（CCs） between peak intensities of E 〉 1...To investigate the dependence of large gradual solar energetic particle（SEP） events on the associated flares and coronal mass ejections（CMEs）, the correlation coefficients（CCs） between peak intensities of E 〉 10 MeV（I10）, E 〉 30 MeV（I30） and E 〉 50 MeV（I50） protons and soft X-ray（SXR） emission of associated flares and the speeds of associated CMEs in the three longitudinal areas W0–W39, W40–W70（hereafter the well connected region） and W71–W90 have been calculated.Classical correlation analysis shows that CCs between SXR emission and peak intensities of SEP events always reach their largest value in the well connected region and then decline dramatically in the longitudinal area outside the well connected region, suggesting that they may contribute to the production of SEPs in large SEP events. Both classical and partial correlation analyses show that SXR fluence is a better parameter describing the relationship between flares and SEP events. For large SEP events with source location in the well connected region, the CCs between SXR fluence and I10, I30 and I50 are0.58±0.12, 0.80±0.06 and 0.83±0.06 respectively, while the CCs between CME speed and I10, I30 and I50 are 0.56±0.12, 0.52±0.13 and 0.48±0.13 respectively. The partial correlation analyses show that in the well connected region, both CME shock and SXR fluence can significantly affect I10, but SXR peak flux makes no additional contribution. For E 〉 30 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I30, and the CME shock makes a small contribution to I30, but SXR peak flux makes no additional contribution. For E 〉 50 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I50, but both CME shock and SXR peak flux make no additional contribution. We conclude that these findings provide statistical evidence that for SEP events with source locations in the well connected region, a CME shock is only an effective accelerator for E 〈 30 MeV protons. However, flares are not only effective accelerators for E 〈 30 MeV protons, but also for E 〉 30 MeV protons, and E 〉 30 MeV protons may be mainly accelerated by concurrent flares.展开更多
The objective of this article was to carry out a statistical study of the occurrences of CMEs from solar cycles 23 and 24 and to deduce interpretations as a contribution to a greater understanding of heliosphere dynam...The objective of this article was to carry out a statistical study of the occurrences of CMEs from solar cycles 23 and 24 and to deduce interpretations as a contribution to a greater understanding of heliosphere dynamics. Thus, from the statistical examination of the occurrences according to the phases it appeared that solar cycle 23 (SC23) counted 13207 occurrences of CMEs while 16510 were counted for solar cycle 24 (SC24). These occurrences of CMEs are correlated to the sunspot cycle because in each of these cycles we would note the predominance of the phase maximum (1478 for SC23 and 2338 for SC24) over the ascending phases (550 for SC23 and 1559 for the SC24) and descending (1197 for the SC23 and 1178 for the SC24) and these predominate on the minimum phase (206 for the SC23 and 834 for the SC24). However, the percentages per phase in each cycle show that SC23 was only predominant over SC24 at the maximum phase (43.08% for SC23 and 39.57% for SC24). From this correlation, some authors therefore suggest that the toroidal magnetic field would be the cause of the ejections of these CMEs. The annual statistical examination confirms the correlation with the sunspot cycle but nevertheless reveals in the descending phase of SC23 two unusual peaks in 2005 and 2007 and a drop-in sunspot activity of 42% from SC23 to SC24 while that we would note an increase in the activity of CME occurrences of 36% at SC24, thus suggesting that CMEs can occur without the toroidal magnetic field being the cause, particularly from the coronal holes. The seasonal statistical examination shows for its part that out of the total of 29717 occurrences of CMEs of the two cycles that spring (28%) was the most active than summer (25%) and summer over autumn (24%) and finally autumn over winter (23%) thus revealing that: The ascending phase of the cycle was only the most active during the winter seasons in spring and the descending phase only during the rest of the seasons. Finally, the monthly statistical examination of the occurrences of CMEs corroborates the seasonal statistical examination by the presence of two maximum peaks (May and October) and two minimum peaks (February and August).展开更多
To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray（SXR） emission, ...To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray（SXR） emission, and coronal mass ejection（CME） linear speed in the three longitudinal areas W0-W39, W40-W70 and W71-W90 have been calculated respectively. Classical correlation analysis shows that the correlation coefficients between CME speeds and I100 in the three longitudinal areas are0.28±0.21, 0.35±0.21 and 0.04±0.30 respectively. The classical correlation coefficients between I100 and SXR peak flux in the three longitudinal areas are 0.48±0.17, 0.72±0.13 and 0.02±0.30 respectively, while the correlation coefficients between I100 and SXR fluence in the three longitudinal areas are 0.25±0.21, 0.84±0.07 and 0.10±0.30 respectively. Partial correlation analysis shows that for solar proton events with source location in the well connected region（W40-W70）, only SXR fluence can significantly affect the peak intensity of E ≥ 100 MeV protons, but SXR peak flux has little influence on the peak intensities of E ≥ 100 MeV protons; moreover, CME speed has no influence on the peak intensities of E ≥ 100 MeV protons. We conclude that these findings provide statistical evidence that E ≥ 100 MeV protons may be mainly accelerated by concurrent flares.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
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
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 metri...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 arc 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 associated 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.展开更多
Recently, S. W. Kahler studied the timescales of solar energetic particle （SEP） events asso- ciated with coronal mass ejections （CMEs） from analysis of spacecraft data. They obtained different timescales for SEP e...Recently, S. W. Kahler studied the timescales of solar energetic particle （SEP） events asso- ciated with coronal mass ejections （CMEs） from analysis of spacecraft data. They obtained different timescales for SEP events, such as TO, the onset time from CME launch to SEP onset, TR, the rise time from onset to half the peak intensity （0.5/p）, and TD, the duration of the SEP intensity above 0.5Ip. In this work, we solve the transport equation for SEPs considering interplanetary coronal mass ejection （ICME） shocks as energetic particle sources. With our modeling assumptions, our simulations show similar results to Kahler＇s analysis of spacecraft data, that the weighted average of TD increases with both CME speed and width. Moreover, from our simulation results, we suggest TD is directly dependent on CME speed, but not dependent on CME width, which were not found in the analysis of observational data.展开更多
The issue of the influence of coronal holes （CHs） on coronal mass ejections （CMEs） in causing solar energetic particle （SEP） events is revisited. It is a continuation and extension of our previous work, in which...The issue of the influence of coronal holes （CHs） on coronal mass ejections （CMEs） in causing solar energetic particle （SEP） events is revisited. It is a continuation and extension of our previous work, in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events. This result is consistent with the conclusion obtained by Kahler in 2004. We extrapolate the coronal magnetic field, define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008. Three key parameters, CH proximity, CH area and CH relative position, are involved in the analysis. The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events.展开更多
Sympathetic coronal mass ejections (CMEs) usually occur in different active regions connected by interconnecting magnetic loops, while homologous CMEs occur within the same active region with an almost the same backgr...Sympathetic coronal mass ejections (CMEs) usually occur in different active regions connected by interconnecting magnetic loops, while homologous CMEs occur within the same active region with an almost the same background magnetic field, and so are similar in shapes. Two sympathetic CMEs erupted within 3 hours on 2002 May 22, originating from the same active region, AR 9948. Their multi-wavelength data were collected and analyzed. It is suggested that emerging flux triggered the occurrence of the first CME and the corresponding flare, the reconnection inflow of which in turn triggered the eruption of the second CME. Based on the fact that the two sympathetic CMEs have many similarities, in their shapes, their low-lying dimming areas, etc., we tentatively propose, for the first time, the phenomenon of sympathetic homologous CMEs.展开更多
文摘By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ejections associated with X-class flares appear to be among the most energetic events in solar activity given the size of the flares, the speed of the CMEs and the intense geomagnetic storms they produce. Out of eighty-six (86) X-class halo CMEs, thirty-seven (37) or 43% are highly geoeffective;twenty-four (24) or approximately 28% are moderately geoeffective and twenty-five (25) or 29% are not geoeffective. Over the two solar cycles (1996 to 2019), 71% of storms were geoeffective and 29% were not. For solar cycle 23, about 78% of storms were geoeffective, while for solar cycle 24, about 56% were geoeffective. For the statistical study based on speed, 85 halo CMEs associated with X-class flares were selected because the CME of 6 December 2006 has no recorded speed value. For both solar cycles, 75.29% of the halo CMEs associated with X-class flares have a speed greater than 1000 km/s. The study showed that 42.18% of halo (X) CMEs with speeds above 1000 km/s could cause intense geomagnetic disturbances. These results show the contribution (in terms of speed) of each class of halo (X) CMEs to the perturbation of the Earth’s magnetic field. Coronal mass ejections then become one of the key indicators of solar activity, especially as they affect the Earth.
文摘A catalogue of type II bursts and the associated coronal mass ejections （CMEs） observed by the solar and heliospheric observatory （SOHO） mission is used to select the twenty three CMEs events with CME speed equal to and less than 450 km/sec （i.e., less than and equal to the average solar wind speed） during 1997-2008. Our observational results clearly indicate that even slow speed CMEs are capable to produce the cosmic ray and geomagnetic disturbances on day to day basis. The depression in cosmic ray intensity is larger three days after the arrival of the CMEs along with the maximum disturbance in geomagnetic activity on the same day （i.e., after three days from the arrival of CMEs）. Fluctuations in cosmic ray intensity and the geomagnetic activity are also observed before the arrival of the CMEs.
文摘In heart failure with preserved ejection fraction,significant left ventricular diastolic abnormalities are present,despite a normal systolic ejection fraction.This article will consider whether this is consistent with the law of conservation of energy,also know as the first law of thermodynamics.
基金National Natural Science Foundation of China,No.81873887National Natural Science Foundation of China Youth Project,No.82101981Shanghai Jiao Tong University School of Medicine Double Hundred Outstanding Person Project,No.20191904。
文摘BACKGROUND Obesity has become a serious public health issue,significantly elevating the risk of various complications.It is a well-established contributor to Heart failure with preserved ejection fraction(HFpEF).Evaluating HFpEF in obesity is crucial.Epicardial adipose tissue(EAT)has emerged as a valuable tool for validating prognostic biomarkers and guiding treatment targets.Hence,assessing EAT is of paramount importance.Cardiovascular magnetic resonance(CMR)imaging is acknowledged as the gold standard for analyzing cardiac function and mor-phology.We hope to use CMR to assess EAT as a bioimaging marker to evaluate HFpEF in obese patients.AIM To assess the diagnostic utility of CMR for evaluating heart failure with preserved ejection fraction[HFpEF;left ventricular(LV)ejection fraction≥50%]by measuring the epicardial adipose tissue(EAT)volumes and EAT mass in obese patients.METHODS Sixty-two obese patients were divided into two groups for a case-control study based on whether or not they had heart failure with HFpEF.The two groups were defined as HFpEF+and HFpEF-.LV geometry,global systolic function,EAT volumes and EAT mass of all subjects were obtained using cine magnetic resonance sequences.RESULTS Forty-five patients of HFpEF-group and seventeen patients of HFpEF+group were included.LV mass index(g/m2)of HFpEF+group was higher than HFpEF-group(P<0.05).In HFpEF+group,EAT volumes,EAT volume index,EAT mass,EAT mass index and the ratio of EAT/[left atrial(LA)left-right(LR)diameter]were higher compared to HFpEF-group(P<0.05).In multivariate analysis,Higher EAT/LA LR diameter ratio was associated with higher odds ratio of HFpEF.CONCLUSION EAT/LA LR diameter ratio is highly associated with HFpEF in obese patients.It is plausible that there may be utility in CMR for assessing obese patients for HFpEF using EAT/LA LR diameter ratio as a diagnostic biomarker.Further prospective studies,are needed to validate these proof-of-concept findings.
文摘Objective:To determine factors that affect the health-related quality of life(HRQOL)of congestive heart failure(CHF)patients with preserved and reduced ejection fraction.Methods:A cross-sectional study design was used for this study.The stratified random sampling was applied for each subgroup.HRQOL was measured with the Minnesota Living with Hear t Failure Questionnaire.The data were analyzed using chi-square,Spearman's correlation analysis,and independent t-test.Results:A number of 67 respondents participated in the recent study.The total mean scores of HRQOL were significantly different(P=0.001)between heart failure(HF)patients with reduced and preserved ejection fractions,41.07±7.54 and 54.97±4.36,respectively.It related with the physical(mean±standard deviation[SD]=10.4±2.14;t=-10.08,95%CI=-12.46 to-8.34;P-value=0.001)and psychological(mean±SD=3.5±0.5;t=-6.68,95%CI=-4.55 to-2.45;P-value=0.001)domain.Strong correlation was found between age(r=-0.898,P<0.05),NYHA functional classes(r=-0.858,P<0.01),duration of HF(r=-0.807,P<0.01),family support(r=0.927,P<0.01),and quality of life(Qo L).Conclusions:HRQOL in HF patients with reduced ejection fraction was higher than in those with preserved ejection fraction.Family suppor t is a fur ther determinant factor that has a positive correlation to the Qo L.
基金funded by the National Basic Research Program of China (973 Program,Grants 2012CB957801 and 2014CB744203)the National Natural Science Foundation of China (Grant Nos.41074132,41274193,41474166,41304144,11303017 and 11533005)the National Standard Research Program (Grant 200710123)
文摘To investigate the dependence of large gradual solar energetic particle（SEP） events on the associated flares and coronal mass ejections（CMEs）, the correlation coefficients（CCs） between peak intensities of E 〉 10 MeV（I10）, E 〉 30 MeV（I30） and E 〉 50 MeV（I50） protons and soft X-ray（SXR） emission of associated flares and the speeds of associated CMEs in the three longitudinal areas W0–W39, W40–W70（hereafter the well connected region） and W71–W90 have been calculated.Classical correlation analysis shows that CCs between SXR emission and peak intensities of SEP events always reach their largest value in the well connected region and then decline dramatically in the longitudinal area outside the well connected region, suggesting that they may contribute to the production of SEPs in large SEP events. Both classical and partial correlation analyses show that SXR fluence is a better parameter describing the relationship between flares and SEP events. For large SEP events with source location in the well connected region, the CCs between SXR fluence and I10, I30 and I50 are0.58±0.12, 0.80±0.06 and 0.83±0.06 respectively, while the CCs between CME speed and I10, I30 and I50 are 0.56±0.12, 0.52±0.13 and 0.48±0.13 respectively. The partial correlation analyses show that in the well connected region, both CME shock and SXR fluence can significantly affect I10, but SXR peak flux makes no additional contribution. For E 〉 30 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I30, and the CME shock makes a small contribution to I30, but SXR peak flux makes no additional contribution. For E 〉 50 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I50, but both CME shock and SXR peak flux make no additional contribution. We conclude that these findings provide statistical evidence that for SEP events with source locations in the well connected region, a CME shock is only an effective accelerator for E 〈 30 MeV protons. However, flares are not only effective accelerators for E 〈 30 MeV protons, but also for E 〉 30 MeV protons, and E 〉 30 MeV protons may be mainly accelerated by concurrent flares.
文摘The objective of this article was to carry out a statistical study of the occurrences of CMEs from solar cycles 23 and 24 and to deduce interpretations as a contribution to a greater understanding of heliosphere dynamics. Thus, from the statistical examination of the occurrences according to the phases it appeared that solar cycle 23 (SC23) counted 13207 occurrences of CMEs while 16510 were counted for solar cycle 24 (SC24). These occurrences of CMEs are correlated to the sunspot cycle because in each of these cycles we would note the predominance of the phase maximum (1478 for SC23 and 2338 for SC24) over the ascending phases (550 for SC23 and 1559 for the SC24) and descending (1197 for the SC23 and 1178 for the SC24) and these predominate on the minimum phase (206 for the SC23 and 834 for the SC24). However, the percentages per phase in each cycle show that SC23 was only predominant over SC24 at the maximum phase (43.08% for SC23 and 39.57% for SC24). From this correlation, some authors therefore suggest that the toroidal magnetic field would be the cause of the ejections of these CMEs. The annual statistical examination confirms the correlation with the sunspot cycle but nevertheless reveals in the descending phase of SC23 two unusual peaks in 2005 and 2007 and a drop-in sunspot activity of 42% from SC23 to SC24 while that we would note an increase in the activity of CME occurrences of 36% at SC24, thus suggesting that CMEs can occur without the toroidal magnetic field being the cause, particularly from the coronal holes. The seasonal statistical examination shows for its part that out of the total of 29717 occurrences of CMEs of the two cycles that spring (28%) was the most active than summer (25%) and summer over autumn (24%) and finally autumn over winter (23%) thus revealing that: The ascending phase of the cycle was only the most active during the winter seasons in spring and the descending phase only during the rest of the seasons. Finally, the monthly statistical examination of the occurrences of CMEs corroborates the seasonal statistical examination by the presence of two maximum peaks (May and October) and two minimum peaks (February and August).
基金jointly funded by the National Basic Research Program of China (973 Program, Grants 2012CB957801 and 2014CB744203)the National Natural Science Foundation of China (Grants 41074132, 41274193, 41474166, 41304144, 11303017 and 11533005)the National Standard Research Program (Grant 200710123)
文摘To investigate the possible solar source of high-energy protons, correlation coefficients between the peak intensities of E ≥ 100 MeV protons, I100, and the peak flux and fluence of solar soft X-ray（SXR） emission, and coronal mass ejection（CME） linear speed in the three longitudinal areas W0-W39, W40-W70 and W71-W90 have been calculated respectively. Classical correlation analysis shows that the correlation coefficients between CME speeds and I100 in the three longitudinal areas are0.28±0.21, 0.35±0.21 and 0.04±0.30 respectively. The classical correlation coefficients between I100 and SXR peak flux in the three longitudinal areas are 0.48±0.17, 0.72±0.13 and 0.02±0.30 respectively, while the correlation coefficients between I100 and SXR fluence in the three longitudinal areas are 0.25±0.21, 0.84±0.07 and 0.10±0.30 respectively. Partial correlation analysis shows that for solar proton events with source location in the well connected region（W40-W70）, only SXR fluence can significantly affect the peak intensity of E ≥ 100 MeV protons, but SXR peak flux has little influence on the peak intensities of E ≥ 100 MeV protons; moreover, CME speed has no influence on the peak intensities of E ≥ 100 MeV protons. We conclude that these findings provide statistical evidence that E ≥ 100 MeV protons may be mainly accelerated by concurrent flares.
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 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 China.
文摘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 arc 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 associated 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.
基金partly supported by the National Natural Science Foundation of China(Grant Nos.41304135,41574172,41374177 and 41125016)the CMA(Grant GYHY201106011)the Specialized Research Fund for State Key Laboratories of China
文摘Recently, S. W. Kahler studied the timescales of solar energetic particle （SEP） events asso- ciated with coronal mass ejections （CMEs） from analysis of spacecraft data. They obtained different timescales for SEP events, such as TO, the onset time from CME launch to SEP onset, TR, the rise time from onset to half the peak intensity （0.5/p）, and TD, the duration of the SEP intensity above 0.5Ip. In this work, we solve the transport equation for SEPs considering interplanetary coronal mass ejection （ICME） shocks as energetic particle sources. With our modeling assumptions, our simulations show similar results to Kahler＇s analysis of spacecraft data, that the weighted average of TD increases with both CME speed and width. Moreover, from our simulation results, we suggest TD is directly dependent on CME speed, but not dependent on CME width, which were not found in the analysis of observational data.
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.40904046,40874075 and 40525014)the 973 National Basic Research Program(2006CB806304)+2 种基金the Ministry of Education of China(200530)the Program for New Century Excellent Talents in University(NCET-08-0524)the Chinese Academy of Sciences(KZCX2-YW-QN511, KJCX2-YW-N28 and the startup fund)
文摘The issue of the influence of coronal holes （CHs） on coronal mass ejections （CMEs） in causing solar energetic particle （SEP） events is revisited. It is a continuation and extension of our previous work, in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events. This result is consistent with the conclusion obtained by Kahler in 2004. We extrapolate the coronal magnetic field, define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008. Three key parameters, CH proximity, CH area and CH relative position, are involved in the analysis. The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events.
基金Supported by the National Natural Science Foundation of China.
文摘Sympathetic coronal mass ejections (CMEs) usually occur in different active regions connected by interconnecting magnetic loops, while homologous CMEs occur within the same active region with an almost the same background magnetic field, and so are similar in shapes. Two sympathetic CMEs erupted within 3 hours on 2002 May 22, originating from the same active region, AR 9948. Their multi-wavelength data were collected and analyzed. It is suggested that emerging flux triggered the occurrence of the first CME and the corresponding flare, the reconnection inflow of which in turn triggered the eruption of the second CME. Based on the fact that the two sympathetic CMEs have many similarities, in their shapes, their low-lying dimming areas, etc., we tentatively propose, for the first time, the phenomenon of sympathetic homologous CMEs.
