We have studied the dynamic proton spectra for the two solar energetic particle(SEP)events on2000 July 14(hereafter GLE59)and 2005 January 20(hereafter GLE69).The source locations of GLE59 and GLE69 are N22 W07 and N1...We have studied the dynamic proton spectra for the two solar energetic particle(SEP)events on2000 July 14(hereafter GLE59)and 2005 January 20(hereafter GLE69).The source locations of GLE59 and GLE69 are N22 W07 and N12 W58 respectively.Proton fluxes>30 Me V have been used to compute the dynamic spectral indices of the two SEP events.Our results show that spectral indices of the two SEP events increased more swiftly at early times,suggesting that the proton fluxes>30 Me V might be accelerated particularly by the concurrent flares at early times for the two SEP events.For the GLE69 with source location at N12 W58,both flare site and shock nose are well connected with the Earth at the earliest time.However,only the particles accelerated by the shock driven by eastern flank of the CME can propagate along the interplanetary magnetic field line to the Earth after the flare.For the GLE59 with source location at N22 W07,only the particles accelerated by the shock driven by western flank of the associated CME can reach the Earth after the flare.Our results also show that there was slightly more than one hour during which the proton spectra for GLE69 are softer than that for GLE59 after the flares,suggesting that the shock driven by eastern flank of the CME associated with GLE69 is weaker than the shock driven by the western flank of the CME associated with GLE59.The results support that quasi-perpendicular shock has stronger potential in accelerating particles than the quasi-parallel shock.These results also suggest that only a small part of the shock driven by western flank of the CME associated with the GLE59 is quasi-perpendicular.展开更多
The maximum flux density of a gyrosynchrotron radiation spectrum in a magnetic diploe model with self absorption and gyroresonance is calculated. Our calculations show that the maximum flux density of the gyrosynchrot...The maximum flux density of a gyrosynchrotron radiation spectrum in a magnetic diploe model with self absorption and gyroresonance is calculated. Our calculations show that the maximum flux density of the gyrosynchrotron spectrum increases with increasing low-energy cutoff, number density, input depth of energetic electrons, magnetic field strength and viewing angle, and with decreasing energy spectral index of energetic electrons, number density and temperature of thermal electrons. It is found that there are linear correlations between the logarithms of the maximum flux density and the above eight parameters with correlation coefficients higher than 0.91 and fit accuracies better than 10%. The maximum flux density could be a good indicator of the changes of these source parameters. In addition, we find that there are very good positive linear correlations between the logarithms of the maximum flux density and peak frequency when the above former five parameters vary respectively. Their linear correlation coefficients are higher than 0.90 and the fit accuracies are better than 0.5%.展开更多
Major solar eruptions （flares, coronal mass ejections （CMEs） and solar energetic particles （SEPs）） strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is n...Major solar eruptions （flares, coronal mass ejections （CMEs） and solar energetic particles （SEPs）） strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood and requires a detailed study of the energetic relationship among these eruptive phenomena. From this perspective, we investigate 30 flares （observed by RHESSI）, followed by weak to strong geomagnetic storms. Spectral analysis of these flares suggests a new power-law relationship （r - 0.79） between the hard X-ray （HXR） spectral index （before flarepeak） and linear speed of the associated CME observed by LASCO/SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law （r - 0.9） between the hardest X-ray flare spectrum and the hardest SEP spectrum. Furthermore, a strong correlation is obtained between the linear speed of the CME and the hardest spectrum of the corresponding SEP event （r - 0.96）. We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help improve our current understanding of the Sun-Earth relationship, which is a major goal of research programs in heliophysics.展开更多
Data from the Solar Wind Ion Composition Spectrometer （SWICS） on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 （from 1990 to end of 2003）. ...Data from the Solar Wind Ion Composition Spectrometer （SWICS） on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 （from 1990 to end of 2003）. In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes （PCHs） appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH.展开更多
Heating and acceleration of electrons in solar impulsive hard X-ray （HXR） flares are studied according to the two-stage acceleration model developed by Zhang for solar ^3Herich events. It is shown that electrostatic...Heating and acceleration of electrons in solar impulsive hard X-ray （HXR） flares are studied according to the two-stage acceleration model developed by Zhang for solar ^3Herich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons （up to 40 MK） through landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flareproduced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager （RHESSI） HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements.展开更多
The gyrosynchrotron spectra are computed in a nonuniform magnetic field case, taking into account the self- and gyroresonance absorption. It is found that the peak frequency νp of the gyrosynchrotron spectrum systema...The gyrosynchrotron spectra are computed in a nonuniform magnetic field case, taking into account the self- and gyroresonance absorption. It is found that the peak frequency νp of the gyrosynchrotron spectrum systematically increases with the increasing photosphere magnetic field strength B0 and increasing viewing angle θ. It is also found for the first time that there are good positive linear correlations between νp and B0, and between log νp and log θ, with linear correlation coefficient 0.99 between νp and B0 and 0.95 between log νp and log θ. We apply the correlations to analyze two burst events observed with OVSA and find that the evolution tendencies of the photosphere magnetic field strength B0 estimated from the above expression are comparable with the observational results of SOHO/MDI. We also give a comparison of the diagnostic results of coronal magnetic field strength in both uniform and nonuniform source models.展开更多
Superhalo electrons appear to be continuously present in the interplane- tary medium, even during very quiet times, with a power-law spectrum at energies above ～2 keV. Here we numerically investigate the generation o...Superhalo electrons appear to be continuously present in the interplane- tary medium, even during very quiet times, with a power-law spectrum at energies above ～2 keV. Here we numerically investigate the generation of superhalo electrons by magnetic reconnection in the solar wind source region, using magnetohydrody- namics and test particle simulations for both single X-line reconnection and multiple X-line reconnection. We find that the direct current electric field, produced in the mag- netic reconnection region, can accelerate electrons from an initial thermal energy of T ～105 K up to hundreds of keV. After acceleration, some of the accelerated elec- trons, together with the nascent solar wind flow driven by the reconnection, propagate upwards along the newly-opened magnetic field lines into interplanetary space, while the rest move downwards into the lower atmosphere. Similar to the observed superhalo electrons at 1 AU, the flux of upward-traveling accelerated electrons versus energy dis- plays a power-law distribution at ～ 2-100 keV, f（E）～ E^-δ, with a 6 of ～1.5 - 2.4. For single （multiple） X-line reconnection, the spectrum becomes harder （softer） as the anomalous resistivity parameter a （uniform resistivity η） increases. These modeling results suggest that the acceleration in the solar wind source region may contribute to superhalo electrons.展开更多
The measurement of positions and sizes of radio sources in observations is important for un- derstanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred ...The measurement of positions and sizes of radio sources in observations is important for un- derstanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred on 2013 April 11 were observed simultaneously by several radio instruments at four different observatories： Chinese Solar Broadband Radio Spectrometer at Huairou （SBRS/Huairou）, Ondrejov Radio Spectrograph in the Czech Republic （ORSC/Ondrejov）, Badary Broadband Microwave Spectropolarimeter （BMS/Irkutsk）, and spectrograph/IZMIRAN （Moscow, Troitsk）. The fine structures included microwave zebra patterns （ZPs）, fast pulsations and fiber bursts. They were observed during the flare brightening lo- cated at the tops of a loop arcade as shown in images taken by the extreme ultraviolet （EUV） telescope onboard NASA＇s satellite Solar Dynamics Observatory （SDO）. The flare occurred at 06：58-07：26 UT in solar active region NOAA 11719 located close to the solar disk center. ZPs appeared near high frequency boundaries of the pulsations, and their spectra observed in Huairou and Ondrejov agreed with each other in terms of details. At the beginning of the flare＇s impulsive phase, a strong narrowband ZP burst occurred with a moderate left-handed circular polarization. Then a series of pulsations and ZPs were observed in almost unpolarized emission. After 07：00 UT a ZP appeared with a moderate right-handed polarization. In the flare decay phase （at about 07：25 UT）, ZPs and fiber bursts become strongly right-hand polarized. BMS/Irkutsk spectral observations indicated that the background emission showed a left-handed circular polarization （similar to SBRS/Huairou spectra around 3 GHz）. However, the fine structure appeared in the right-handed polarization. The dynamics of the polarization was associated with the motion of the flare ex- citer, which was observed in EUV images at 171 A and 131 A by the SDO Atmospheric Imaging Assembly （AIA）. Combining magnetograms observe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
In this paper we investigate three novel rising submillimeter （THz） bursts that occurred sequen- tially in Super Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu GHz...In this paper we investigate three novel rising submillimeter （THz） bursts that occurred sequen- tially in Super Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu GHz-1 （corresponding to spectral index α of 1.6） for the THz spectral components of the 2003 October 28 and November 4 bursts, but it attained values of 235 sfu GHz-1 （α = 4.8） in the 2003 November 2 burst. The steeply rising THz spectrum can be produced by a population of highly relativistic electrons with a low-energy cutoff of 1 MeV, but it only requires a low-energy cutoff of 30 keV for the two slowly rising THz bursts, via gyrosynchrotron （GS） radiation based on our numerical simulations of burst spectra in the magnetic dipole field case. The electron density variation is much larger in the THz source than in the microwave （MW） source. It is interesting that the THz source radius decreased by 20%-50% during the decay phase for the three events, but the MW source increased by 28% for the 2003 November 2 event. In the paper we will present a formula that can be used to calculate the energy released by ultrarel- ativistic electrons, taking the relativistic correction into account for the first time. We find that the energy released by energetic electrons in the THz source exceeds that in the MW source due to the strong GS radi- ation loss in the THz range, although the modeled THz source area is 3-4 orders smaller than the modeled MW source one. The total energies released by energetic electrons via the GS radiation in radio sources are estimated, respectively, to be 5.2 × 10^33, 3.9 × 10^33 and 3.7 × 10^32 erg for the October 28, November 2 and 4 bursts, which are 131, 76 and 4 times as large as the thermal energies of 2.9 × 10^31, 2.1 × 10^31 and 5.2 × 10^31 erg estimated from soft X-ray GOES observations.展开更多
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
This is a study designed to analyze the relationship between ground level enhancements（GLEs）and their associated solar active regions during solar cycles 22and 23.Results show that 90.3%of the GLE events that are in...This is a study designed to analyze the relationship between ground level enhancements（GLEs）and their associated solar active regions during solar cycles 22and 23.Results show that 90.3%of the GLE events that are investigated are accompanied by X-class flares,and that 77.4%of the GLE events originate from super active regions.It is found that the intensity of a GLE event is strongly associated with the specific position of an active region where the GLE event occurs.As a consequence,the GLE events having a peak increase rate exceeding 50%occur in a longitudinal range from W20 to W100.Moreover,the largest GLE events occur in a heliographic longitude at roughly W60.Additionally,an analysis is made to understand the distributional pattern of the Carrington longitude of the active regions that have generated the GLE events.展开更多
The intensity-time profiles of solar proton events（SPEs） are grouped into three types in the present study. The Type-I means that the intensity-time profile of an SPE has one peak, which occurs shortly after the ass...The intensity-time profiles of solar proton events（SPEs） are grouped into three types in the present study. The Type-I means that the intensity-time profile of an SPE has one peak, which occurs shortly after the associated solar flare and coronal mass ejection（CME）. The Type-II means that the SPE profile has two peaks： the first peak occurs shortly after the solar eruption, the second peak occurs at the time when the CME-driven shock reaches the Earth, and the intensity of the second peak is lower than the first one.If the intensity of the second peak is higher than the first one, or the SPE intensity increases continuously until the CME-driven shock reaches the Earth, this kind of intensity-time profile is defined as Type-III. It is found that most CMEs associated with Type-I SPEs have no geoeffectiveness and only a small part of CMEs associated with Type-I SPEs can produce minor（–50 n T ≤ Dst ≤–30 n T） or moderate geomagnetic storms（–100 n T≤ Dst ≤–50 n T）, but never an intense geomagnetic storm（–200 n T ≤ Dst 〈-100 n T）. However,most of the CMEs associated with Type-II and Type-III SPEs can produce intense or great geomagnetic storms（Dst ≤-200 n T）. The solar wind structures responsible for the geomagnetic storms associated with SPEs with different intensity-time profiles have also been investigated and discussed.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.41674166).
文摘We have studied the dynamic proton spectra for the two solar energetic particle(SEP)events on2000 July 14(hereafter GLE59)and 2005 January 20(hereafter GLE69).The source locations of GLE59 and GLE69 are N22 W07 and N12 W58 respectively.Proton fluxes>30 Me V have been used to compute the dynamic spectral indices of the two SEP events.Our results show that spectral indices of the two SEP events increased more swiftly at early times,suggesting that the proton fluxes>30 Me V might be accelerated particularly by the concurrent flares at early times for the two SEP events.For the GLE69 with source location at N12 W58,both flare site and shock nose are well connected with the Earth at the earliest time.However,only the particles accelerated by the shock driven by eastern flank of the CME can propagate along the interplanetary magnetic field line to the Earth after the flare.For the GLE59 with source location at N22 W07,only the particles accelerated by the shock driven by western flank of the associated CME can reach the Earth after the flare.Our results also show that there was slightly more than one hour during which the proton spectra for GLE69 are softer than that for GLE59 after the flares,suggesting that the shock driven by eastern flank of the CME associated with GLE69 is weaker than the shock driven by the western flank of the CME associated with GLE59.The results support that quasi-perpendicular shock has stronger potential in accelerating particles than the quasi-parallel shock.These results also suggest that only a small part of the shock driven by western flank of the CME associated with the GLE59 is quasi-perpendicular.
基金Supported by the National Natural Science Foundation of China
文摘The maximum flux density of a gyrosynchrotron radiation spectrum in a magnetic diploe model with self absorption and gyroresonance is calculated. Our calculations show that the maximum flux density of the gyrosynchrotron spectrum increases with increasing low-energy cutoff, number density, input depth of energetic electrons, magnetic field strength and viewing angle, and with decreasing energy spectral index of energetic electrons, number density and temperature of thermal electrons. It is found that there are linear correlations between the logarithms of the maximum flux density and the above eight parameters with correlation coefficients higher than 0.91 and fit accuracies better than 10%. The maximum flux density could be a good indicator of the changes of these source parameters. In addition, we find that there are very good positive linear correlations between the logarithms of the maximum flux density and peak frequency when the above former five parameters vary respectively. Their linear correlation coefficients are higher than 0.90 and the fit accuracies are better than 0.5%.
基金the CAWSES-India Program, supported by the Indian Space Research Organization (ISRO), Dept. of Space, Govt. of India
文摘Major solar eruptions （flares, coronal mass ejections （CMEs） and solar energetic particles （SEPs）） strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood and requires a detailed study of the energetic relationship among these eruptive phenomena. From this perspective, we investigate 30 flares （observed by RHESSI）, followed by weak to strong geomagnetic storms. Spectral analysis of these flares suggests a new power-law relationship （r - 0.79） between the hard X-ray （HXR） spectral index （before flarepeak） and linear speed of the associated CME observed by LASCO/SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law （r - 0.9） between the hardest X-ray flare spectrum and the hardest SEP spectrum. Furthermore, a strong correlation is obtained between the linear speed of the CME and the hardest spectrum of the corresponding SEP event （r - 0.96）. We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help improve our current understanding of the Sun-Earth relationship, which is a major goal of research programs in heliophysics.
文摘Data from the Solar Wind Ion Composition Spectrometer （SWICS） on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 （from 1990 to end of 2003）. In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes （PCHs） appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH.
基金NASA Grant （NNG04GD59G A/C 2-302-14-3380-119） National Science Foundation （ATM 00-70385）.
文摘Heating and acceleration of electrons in solar impulsive hard X-ray （HXR） flares are studied according to the two-stage acceleration model developed by Zhang for solar ^3Herich events. It is shown that electrostatic H-cyclotron waves can be excited at a parallel phase velocity less than about the electron thermal velocity and thus can significantly heat the electrons （up to 40 MK） through landau resonance. The preheated electrons with velocities above a threshold are further accelerated to high energies in the flare-acceleration process. The flareproduced electron spectrum is obtained and shown to be thermal at low energies and power law at high energies. In the non-thermal energy range, the spectrum can be double power law if the spectral power index is energy dependent or related. The electron energy spectrum obtained by this study agrees quantitatively with the result derived from the Reuven Ramaty High Energy Solar Spectroscopic Imager （RHESSI） HXR observations in the flare of 2002 July 23. The total flux and energy flux of electrons accelerated in the solar flare also agree with the measurements.
基金the National Natural Science Foundation of China.
文摘The gyrosynchrotron spectra are computed in a nonuniform magnetic field case, taking into account the self- and gyroresonance absorption. It is found that the peak frequency νp of the gyrosynchrotron spectrum systematically increases with the increasing photosphere magnetic field strength B0 and increasing viewing angle θ. It is also found for the first time that there are good positive linear correlations between νp and B0, and between log νp and log θ, with linear correlation coefficient 0.99 between νp and B0 and 0.95 between log νp and log θ. We apply the correlations to analyze two burst events observed with OVSA and find that the evolution tendencies of the photosphere magnetic field strength B0 estimated from the above expression are comparable with the observational results of SOHO/MDI. We also give a comparison of the diagnostic results of coronal magnetic field strength in both uniform and nonuniform source models.
基金Supported by the National Natural Science Foundation of China
文摘Superhalo electrons appear to be continuously present in the interplane- tary medium, even during very quiet times, with a power-law spectrum at energies above ～2 keV. Here we numerically investigate the generation of superhalo electrons by magnetic reconnection in the solar wind source region, using magnetohydrody- namics and test particle simulations for both single X-line reconnection and multiple X-line reconnection. We find that the direct current electric field, produced in the mag- netic reconnection region, can accelerate electrons from an initial thermal energy of T ～105 K up to hundreds of keV. After acceleration, some of the accelerated elec- trons, together with the nascent solar wind flow driven by the reconnection, propagate upwards along the newly-opened magnetic field lines into interplanetary space, while the rest move downwards into the lower atmosphere. Similar to the observed superhalo electrons at 1 AU, the flux of upward-traveling accelerated electrons versus energy dis- plays a power-law distribution at ～ 2-100 keV, f（E）～ E^-δ, with a 6 of ～1.5 - 2.4. For single （multiple） X-line reconnection, the spectrum becomes harder （softer） as the anomalous resistivity parameter a （uniform resistivity η） increases. These modeling results suggest that the acceleration in the solar wind source region may contribute to superhalo electrons.
基金supported by the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(Grant No.2011T1J20)funded by Chinese Academy of Sciences President’s International Fellowship Initiative(Grant No.2015VMA014)+3 种基金supported by the Russian Foundation for Basic Research(Grants:13-02-00044,13-02-90472,14-02-91157 and 14-02-00367)the National Natural Science Foundation of China(Grant Nos.11273030,11103044,11103039,11221063,11373039 and 113111042)MOST(Grant2011CB811401)the National Major Scientific Equipment R&D Project(ZDYZ 2009-3 and P209/12/00103 GA CR)
文摘The measurement of positions and sizes of radio sources in observations is important for un- derstanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred on 2013 April 11 were observed simultaneously by several radio instruments at four different observatories： Chinese Solar Broadband Radio Spectrometer at Huairou （SBRS/Huairou）, Ondrejov Radio Spectrograph in the Czech Republic （ORSC/Ondrejov）, Badary Broadband Microwave Spectropolarimeter （BMS/Irkutsk）, and spectrograph/IZMIRAN （Moscow, Troitsk）. The fine structures included microwave zebra patterns （ZPs）, fast pulsations and fiber bursts. They were observed during the flare brightening lo- cated at the tops of a loop arcade as shown in images taken by the extreme ultraviolet （EUV） telescope onboard NASA＇s satellite Solar Dynamics Observatory （SDO）. The flare occurred at 06：58-07：26 UT in solar active region NOAA 11719 located close to the solar disk center. ZPs appeared near high frequency boundaries of the pulsations, and their spectra observed in Huairou and Ondrejov agreed with each other in terms of details. At the beginning of the flare＇s impulsive phase, a strong narrowband ZP burst occurred with a moderate left-handed circular polarization. Then a series of pulsations and ZPs were observed in almost unpolarized emission. After 07：00 UT a ZP appeared with a moderate right-handed polarization. In the flare decay phase （at about 07：25 UT）, ZPs and fiber bursts become strongly right-hand polarized. BMS/Irkutsk spectral observations indicated that the background emission showed a left-handed circular polarization （similar to SBRS/Huairou spectra around 3 GHz）. However, the fine structure appeared in the right-handed polarization. The dynamics of the polarization was associated with the motion of the flare ex- citer, which was observed in EUV images at 171 A and 131 A by the SDO Atmospheric Imaging Assembly （AIA）. Combining magnetograms observe
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 the National Natural Science Foundation of China(Grant Nos.11333009 and 11573072)the"973"program(No.2014CB744200)
文摘In this paper we investigate three novel rising submillimeter （THz） bursts that occurred sequen- tially in Super Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu GHz-1 （corresponding to spectral index α of 1.6） for the THz spectral components of the 2003 October 28 and November 4 bursts, but it attained values of 235 sfu GHz-1 （α = 4.8） in the 2003 November 2 burst. The steeply rising THz spectrum can be produced by a population of highly relativistic electrons with a low-energy cutoff of 1 MeV, but it only requires a low-energy cutoff of 30 keV for the two slowly rising THz bursts, via gyrosynchrotron （GS） radiation based on our numerical simulations of burst spectra in the magnetic dipole field case. The electron density variation is much larger in the THz source than in the microwave （MW） source. It is interesting that the THz source radius decreased by 20%-50% during the decay phase for the three events, but the MW source increased by 28% for the 2003 November 2 event. In the paper we will present a formula that can be used to calculate the energy released by ultrarel- ativistic electrons, taking the relativistic correction into account for the first time. We find that the energy released by energetic electrons in the THz source exceeds that in the MW source due to the strong GS radi- ation loss in the THz range, although the modeled THz source area is 3-4 orders smaller than the modeled MW source one. The total energies released by energetic electrons via the GS radiation in radio sources are estimated, respectively, to be 5.2 × 10^33, 3.9 × 10^33 and 3.7 × 10^32 erg for the October 28, November 2 and 4 bursts, which are 131, 76 and 4 times as large as the thermal energies of 2.9 × 10^31, 2.1 × 10^31 and 5.2 × 10^31 erg estimated from soft X-ray GOES observations.
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 Natural Science Foundation of China (Grant Nos. 41074132, 41274193, 40931056 and 41031064)the National Basic Research Program of China (973 Program, Grant Nos. 2012CB957801 and 2011CB811406)+1 种基金the National Standard Research Program (Grant No. 10-123)the program SOA Key Laboratory for Polar Science, Polar Research Institute of China (Grant No. KP201206)
文摘This is a study designed to analyze the relationship between ground level enhancements（GLEs）and their associated solar active regions during solar cycles 22and 23.Results show that 90.3%of the GLE events that are investigated are accompanied by X-class flares,and that 77.4%of the GLE events originate from super active regions.It is found that the intensity of a GLE event is strongly associated with the specific position of an active region where the GLE event occurs.As a consequence,the GLE events having a peak increase rate exceeding 50%occur in a longitudinal range from W20 to W100.Moreover,the largest GLE events occur in a heliographic longitude at roughly W60.Additionally,an analysis is made to understand the distributional pattern of the Carrington longitude of the active regions that have generated the GLE events.
基金supported by the National Basic Research Program of China (973 Program,Grant No.2012CB957801)the National Natural Science Foundation of China (Grant Nos.41074132,41274193,41674166,41031064 and 11303017)+1 种基金the National Standard Research Program (Grant No.200710123)the project 985 of Nanjing University,the Advanced Discipline Construction Project of Jiangsu Province and the NKBRSF (Grant No.2014CB744203)
文摘The intensity-time profiles of solar proton events（SPEs） are grouped into three types in the present study. The Type-I means that the intensity-time profile of an SPE has one peak, which occurs shortly after the associated solar flare and coronal mass ejection（CME）. The Type-II means that the SPE profile has two peaks： the first peak occurs shortly after the solar eruption, the second peak occurs at the time when the CME-driven shock reaches the Earth, and the intensity of the second peak is lower than the first one.If the intensity of the second peak is higher than the first one, or the SPE intensity increases continuously until the CME-driven shock reaches the Earth, this kind of intensity-time profile is defined as Type-III. It is found that most CMEs associated with Type-I SPEs have no geoeffectiveness and only a small part of CMEs associated with Type-I SPEs can produce minor（–50 n T ≤ Dst ≤–30 n T） or moderate geomagnetic storms（–100 n T≤ Dst ≤–50 n T）, but never an intense geomagnetic storm（–200 n T ≤ Dst 〈-100 n T）. However,most of the CMEs associated with Type-II and Type-III SPEs can produce intense or great geomagnetic storms（Dst ≤-200 n T）. The solar wind structures responsible for the geomagnetic storms associated with SPEs with different intensity-time profiles have also been investigated and discussed.
