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1.
The famous extreme solar and particle event of 20 January 2005 is analyzed from two perspectives. Firstly, using multi-spectral data, we study temporal, spectral, and spatial features of the main phase of the flare, when the strongest emissions from microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin of solar energetic particles (SEP) arriving at Earth, i.e., acceleration in flares, or shocks ahead of coronal mass ejections (CMEs). Our analysis shows that all electromagnetic emissions from microwaves up to 2.22 MeV line gamma-rays during the main flare phase originated within a compact structure located just above sunspot umbrae. In particular, a huge (≈ 105 sfu) radio burst with a high frequency maximum at 30 GHz was observed, indicating the presence of a large number of energetic electrons in very strong magnetic fields. Thus, protons and electrons responsible for various flare emissions during its main phase were accelerated within the magnetic field of the active region. The leading, impulsive parts of the ground-level enhancement (GLE), and highest-energy gamma-rays identified with π 0-decay emission, are similar and closely correspond in time. The origin of the π 0-decay gamma-rays is argued to be the same as that of lower-energy emissions, although this is not proven. On the other hand, we estimate the sky-plane speed of the CME to be 2 000 – 2 600 km s−1, i.e., high, but of the same order as preceding non-GLE-related CMEs from the same active region. Hence, the flare itself rather than the CME appears to determine the extreme nature of this event. We therefore conclude that the acceleration, at least, to sub-relativistic energies, of electrons and protons, responsible for both the major flare emissions and the leading spike of SEP/GLE by 07 UT, are likely to have occurred nearly simultaneously within the flare region. However, our analysis does not rule out a probable contribution from particles accelerated in the CME-driven shock for the leading GLE spike, which seemed to dominate at later stages of the SEP event. S.N. Kuznetsov deceased 17 May 2007.  相似文献   

2.
Solar energetic particles (SEPs) detected in space are statistically associated with flares and coronal mass ejections (CMEs). But it is not clear how these processes actually contribute to the acceleration and transport of the particles. The present work addresses the question why flares accompanied by intense soft X-ray bursts may not produce SEPs detected by observations with the GOES spacecraft. We consider all X-class X-ray bursts between 1996 and 2006 from the western solar hemisphere. 21 out of 69 have no signature in GOES proton intensities above 10 MeV, despite being significant accelerators of electrons, as shown by their radio emission at cm wavelengths. The majority (11/20) has no type III radio bursts from electron beams escaping towards interplanetary space during the impulsive flare phase. Together with other radio properties, this indicates that the electrons accelerated during the impulsive flare phase remain confined in the low corona. This occurs in flares with and without a CME. Although GOES saw no protons above 10 MeV at geosynchronous orbit, energetic particles were detected in some (4/11) confined events at Lagrangian point L1 aboard ACE or SoHO. These events have, besides the confined microwave emission, dm-m wave type II and type IV bursts indicating an independent accelerator in the corona. Three of them are accompanied by CMEs. We conclude that the principal reason why major solar flares in the western hemisphere are not associated with SEPs is the confinement of particles accelerated in the impulsive phase. A coronal shock wave or the restructuring of the magnetically stressed corona, indicated by the type II and IV bursts, can explain the detection of SEPs when flare-accelerated particles do not reach open magnetic field lines. But the mere presence of these radio signatures, especially of a metric type II burst, is not a sufficient condition for a major SEP event.  相似文献   

3.
Kocharov  L.  Torsti  J. 《Solar physics》2002,207(1):149-157
We summarize ERNE/SOHO observations of solar energetic particle events associated with impulsive soft X-ray flares and LASCO coronal mass ejections (CMEs). The new observational data support an idea that the >10 MeV proton acceleration may be initiated at different coronal sources, operating in the flaring active region and on the global coronal scale, in concert with CME development. However, the particle acceleration continues beyond the coronal scales and may culminate at the interplanetary CME well after the flare. We emphasize the importance of CME liftoff/aftermath processes in the solar corona and the possible role of seed particle re-acceleration, which may explain the existence of hybrid solar energetic particle events.  相似文献   

4.
The origin of relativistic solar protons during large flare/CME events has not been uniquely identified so far. We perform a detailed comparative analysis of the time profiles of relativistic protons detected by the worldwide network of neutron monitors at Earth with electromagnetic signatures of particle acceleration in the solar corona during the large particle event of 20 January 2005. The intensity – time profile of the relativistic protons derived from the neutron monitor data indicates two successive peaks. We show that microwave, hard X-ray, and γ-ray emissions display several episodes of particle acceleration within the impulsive flare phase. The first relativistic protons detected at Earth are accelerated together with relativistic electrons and with protons that produce pion-decay γ rays during the second episode. The second peak in the relativistic proton profile at Earth is accompanied by new signatures of particle acceleration in the corona within ≈1R ⊙ above the photosphere, revealed by hard X-ray and microwave emissions of low intensity and by the renewed radio emission of electron beams and of a coronal shock wave. We discuss the observations in terms of different scenarios of particle acceleration in the corona.  相似文献   

5.
In December 2006, a single active region produced a series of proton solar flares, with X-ray class up to the X9.0 level, starting on 5 December 2006 at 10:35 UT. A feature of this X9.0 flare is that associated MeV particles were observed at Venus and Mars by Venus Express (VEX) and Mars Express (MEX), which were ∼80° and ∼125° east of the flare site, respectively, in addition to the Earth, which was ∼79° west of the flare site. On December 5, 2006, the plasma instruments ASPERA-3 and ASPERA-4 on board MEX and VEX detected a large enhancement in their respective background count levels. This is a typical signature of solar energetic particle (SEP) events, i.e., intensive MeV particle fluxes. The timings of these enhancements were consistent with the estimated field-aligned travel time of particles associated with the X9.0 flare that followed the Parker spiral to reach Venus and Mars. Coronal mass ejection (CME) signatures that might be related to the proton flare were twice identified at Venus within <43 and <67 h after the flare. Although these CMEs did not necessarily originate from the X9.0 flare on December 5, 2006, they most likely originated from the same active region because these characteristics are very similar to flare-associated CMEs observed on the Earth. These observations indicate that CME and flare activities on the invisible side of the Sun may affect terrestrial space weather as a result of traveling more than 90° in both azimuthal directions in the heliosphere. We would also like to emphasize that during the SEP activity, MEX data indicate an approximately one-order of magnitude enhancement in the heavy ion outflow flux from the Martian atmosphere. This is the first observation of the increase of escaping ion flux from Martian atmosphere during an intensive SEP event. This suggests that the solar EUV flux levels significantly affect the atmospheric loss from unmagnetized planets.  相似文献   

6.
The series of nine impulsive, highly collimated beams of near-relativistic electrons seen by ACE/EPAM on 26 and 27 June 2004 occurred at a quiet time with respect to solar flare and CME production. However, they were accompanied by decametric type III radio bursts observed by WIND/WAVES, which had progressively higher starting frequencies, suggestive of coronal acceleration. There were no CMEs seen by SOHO/LASCO in association with any of the type III bursts except possibly the first. The energy spectrum of the electrons was soft, typically E−4.5 but extended up to at least ∼200 keV. We suggest that the source region for these events is in the high corona. We discuss this result in the context of solar electron acceleration at other times.  相似文献   

7.
We present a multiwavelength study of the large-scale coronal disturbances associated with the CME?–?flare event recorded on 24 December 1996. The kinematics of the shock wave signature, the type II radio burst, is analyzed and compared with the flare evolution and the CME kinematics. We employ radio dynamic spectra, position of the Nançay Radioheliograph sources, and LASCO-C1 observations, providing detailed study of this limb event. The obtained velocity of the shock wave is significantly higher than the contemporaneous CME velocity (1000 and 235 km?s?1, respectively). Moreover, since the main acceleration phase of the CME took place 10?–?20 min after the shock wave was launched, we conclude that the shock wave on 24 December 1996 was probably not driven by the CME. However, the shock wave was closely associated with the flare impulsive phase, indicating that it was ignited by the energy release in the flare.  相似文献   

8.
Dryer  M.  Andrews  M. D.  Aurass  H.  DeForest  C.  Galvin  A. B.  Garcia  H.  Ipavich  F. M.  Karlický  M.  Kiplinger  A.  Klassen  A.  Meisner  R.  Paswaters  S. E.  Smith  Z.  Tappin  S. J.  Thompson  B. J.  Watari  S. I.  Michels  D. J.  Brueckner  G. E.  Howard  R. A.  Koomen  M. J.  Lamy  P.  Mann  G.  Arzner  K.  Schwenn  R. 《Solar physics》1998,181(1):159-183
The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio observations of the type II shock, and GOES disk-integrated soft X-ray flux during an extended period that included energy build-up in this active region.The LASCO coronagraphs measured a significant coronal mass ejection (CME) on the solar west limb beginning on 8 July at about 09:53 UT. The GOES 8 soft X-ray flux (0.1–0.8 nm) had started to increase on the previous day from below the A-level background (10-8 W m-2). At the start time of the CME, it was at the mid-B level and continued to climb. This CME is similar to many events which have been seen by LASCO and which are being interpreted as disruption of existing streamers by emerging flux ropes.LASCO and EIT were not collecting data at the time of the X-flare due to a temporary software outage. A larger CME was in progress when the first LASCO images were taken after the flare. Since the first image of the 'big' CME was obtained after the flare's start time, we cannot clearly demonstrate the physical connection of the CME to the flare. However, the LASCO CME data are consistent with an association of the flare and the CME. No eruptive filaments were observed during this event.We used the flare evidence noted above to employ in real time a simplified Shock-Time-of-Arrival (STOA) algorithm to estimate the arrival of a weak shock at the WIND spacecraft. We compare this prediction with the plasma and IMF data from WIND and plasma data from the SOHO/CELIAS instrument and suggest that the flare - and possibly the interplanetary consequences of the 'big' CME - was the progenitor of the mild, high-latitude, geomagnetic storm (daily sum of Kp=16+, Ap=8) on 12 July 1996. We speculate that the shock was attenuated enroute to Earth as a result of interaction with the heliospheric current/plasma sheet.presently at High Altitude Observatory, Boulder, CO80309, U.S.A.presently at Naval Research Laboratory, Washington DC, 20375, U.S.A.  相似文献   

9.
We report here on the solar origin of distinctive radiation characteristics observed for a decametric type III solar radio burst that was associated with a major solar flare and CME on 11 April 2001. The associated decimeter (Ond?ejov) and meter (Potsdam) wavelength emissions, as well as the GOES soft X-ray lightcurve, suggest that there were two successive events of energy release and electron acceleration associated with this solar eruption. The Nançay radioheliograph images and additional evidence of plasmoid propagation suggest that the second event of electron acceleration resulted from coronal reconfigurations, likely caused by the erupting CME. These observational analyses provide new insights into the physical origin of the distinguishing characteristics of complex type III-like radio emissions that are typically observed at decameter wavelengths during major solar eruptive events.  相似文献   

10.
It is generally believed that gradual solar energetic particles (SEPs) are accelerated by shocks associated with coronal mass ejections (CMEs). Using an ice-cream cone model, the radial speed and angular width of 95 CMEs associated with SEP events during 1998 – 2002 are calculated from SOHO/LASCO observations. Then, we investigate the relationships between the kinematic properties of these CMEs and the characteristic times of the intensity-time profile of their accompanied SEP events observed at 1 AU. These characteristic times of SEP are i) the onset time from the accompanying CME eruption at the Sun to the SEP arrival at 1 AU, ii) the rise time from the SEP onset to the time when the SEP intensity is one-half of peak intensity, and iii) the duration over which the SEP intensity is within a factor of two of the peak intensity. It is found that the onset time has neither significant correlation with the radial speed nor with the angular width of the accompanying CME. For events that are poorly connected to the Earth, the SEP rise time and duration have no significant correlation with the radial speed and angular width of the associated CMEs. However, for events that are magnetically well connected to the Earth, the SEP rise time and duration have significantly positive correlations with the radial speed and angular width of the associated CMEs. This indicates that a CME event with wider angular width and higher speed may more easily drive a strong and wide shock near to the Earth-connected interplanetary magnetic field lines, may trap and accelerate particles for a longer time, and may lead to longer rise time and duration of the ensuing SEP event.  相似文献   

11.
In an effort to examine the relationship between flare flux and corresponding CME mass, we temporally and spatially correlate all X-ray flares and CMEs in the LASCO and GOES archives from 1996 to 2006. We cross-reference 6733 CMEs having well-measured masses against 12 050 X-ray flares having position information as determined from their optical counterparts. For a given flare, we search in time for CMEs which occur 10 – 80 minutes afterward, and we further require the flare and CME to occur within ± 45° in position angle on the solar disk. There are 826 CME/flare pairs which fit these criteria. Comparing the flare fluxes with CME masses of these paired events, we find CME mass increases with flare flux, following an approximately log-linear, broken relationship: in the limit of lower flare fluxes, log (CME mass)∝0.68×log (flare flux), and in the limit of higher flare fluxes, log (CME mass)∝0.33×log (flare flux). We show that this broken power-law, and in particular the flatter slope at higher flare fluxes, may be due to an observational bias against CMEs associated with the most energetic flares: halo CMEs. Correcting for this bias yields a single power-law relationship of the form log (CME mass)∝0.70×log (flare flux). This function describes the relationship between CME mass and flare flux over at least 3 dex in flare flux, from ≈ 10−7 – 10−4 W m−2.  相似文献   

12.
Shocks driven by fast coronal mass ejections (CMEs) are the dominant particle accelerators in large, “gradual” solar energetic particle (SEP) events. In these events, the event-integrated value of the iron-to-oxygen ratio (Fe/O) is typically ～?0.1, at least at energies of a few MeV/nucleon. However, at the start of some gradual events, when intensities are low and growing, initially Fe/O is ～?1. This value is also characteristic of small, “impulsive” SEP events, in which particle acceleration is due to magnetic reconnection. These observations suggested that SEPs in gradual events also include a direct contribution from the flare that accompanied the CME launch. If correct, this interpretation is of critical importance: it indicates a clear path to interplanetary space for particles from the reconnection region beneath the CME. A key issue for the flare origin is “magnetic connectedness”, i.e., proximity of the flare site to the solar footpoint of the observer’s magnetic field line. We present two large gradual events observed in 2001 by Wind at L1 and by Ulysses, when it was located at >?60° heliolatitude and beyond 1.6 AU. In these events, transient Fe/O enhancements at 5?–?10 MeV/nucleon were seen at both spacecraft, even though one or both is not “well-connected” to the flare. These observations demonstrate that an initial Fe/O enhancement cannot be cited as evidence for a direct flare component. Instead, initial Fe/O enhancements are better understood as a transport effect, driven by the different mass-to-charge ratios of Fe and O. We further demonstrate that the time-constant of the roughly exponential decay of the Fe/O ratio scales as R 2, where R is the observer’s radial distance from the Sun. This behavior is consistent with radial diffusion. These observations thus also provide a potential constraint on models in which SEPs reach high heliolatitudes by cross-field diffusion.  相似文献   

13.
We investigate the early phase of the 13 February 2009 coronal mass ejection (CME). Observations with the twin STEREO spacecraft in quadrature allow us to compare for the first time in one and the same event the temporal evolution of coronal EUV dimmings, observed simultaneously on-disk and above-the-limb. We find that these dimmings are synchronized and appear during the impulsive acceleration phase of the CME, with the highest EUV intensity drop occurring a few minutes after the maximum CME acceleration. During the propagation phase two confined, bipolar dimming regions, appearing near the footpoints of a pre-flare sigmoid structure, show an apparent migration away from the site of the CME-associated flare. Additionally, they rotate around the ‘center’ of the flare site, i.e., the configuration of the dimmings exhibits the same ‘sheared-to-potential’ evolution as the postflare loops. We conclude that the motion pattern of the twin dimmings reflects not only the eruption of the flux rope, but also the ensuing stretching of the overlying arcade. Finally, we find that: i) the global-scale dimmings, expanding from the source region of the eruption, propagate with a speed similar to that of the leaving CME front; ii) the mass loss occurs mainly during the period of strongest CME acceleration. Two hours after the eruption Hinode/EIS observations show no substantial plasma outflow, originating from the ‘open’ field twin dimming regions.  相似文献   

14.
R. P. Kane 《Solar physics》2008,248(1):177-190
From the LASCO CME (Coronal Mass Ejection) catalog, the occurrence frequencies of all CMEs (all strong and weak CMEs, irrespective of their widths) were calculated for 3-month intervals and their 12-month running means determined for cycle 23 (1996 – 2007) and were compared with those of other solar parameters. The annual values of all-CME frequency were very well correlated (+ 0.97) with sunspot numbers, but several other parameters also had similarly high correlations. Comparisons of 12-month running means indicated that the sunspot numbers were very well correlated with solar electromagnetic radiations (Lyman-α, 2800-MHz flux, coronal green line index, solar flare indices, and X-ray background); but for corpuscular radiations [proton fluxes, solar energetic particles (SEP), CMEs, interplanetary CMEs (ICMEs), and stream interaction regions (SIR)] and solar open magnetic fields, the correlations were lower. A notable feature was the appearance of two peaks during 2000 – 2002, and those double peaks in different parameters matched approximately except for proton fluxes and SEP and SIR frequencies. When hemispheric intensities were considered, north – south asymmetries appeared, more in some parameters than in others. When intensities in smaller latitude belts (10°) were compared, sunspot group numbers (SGN) were found to be confined mostly to latitudes within ± 30° of the solar equator, showing two peaks in all latitude belts, and during the course of the 11-year cycle, the double peaks shifted from middle to equatorial solar latitudes, just as seen in the Maunder butterfly diagrams. In contrast, CME frequency was comparable at all latitude belts (including high, near-polar latitudes), having more than two peaks in almost all latitude belts, and the peaks were almost simultaneous in all latitude belts. Thus, the matching of SGN peaks with those of CME peaks was poor. Incidentally, the CME frequency data for all events (all widths) after 2003 are not comparable to earlier data, owing to inclusion of very weak (narrow) CMEs in later years. The frequencies are comparable with earlier data only for widths exceeding about 70°.  相似文献   

15.
The aim of this paper is studying the relation between the coronal mass ejections (CMEs), and their associated solar flares. I used the CMEs data (obtained from CME catalogue) which observed by SOHO/LASCO, during the Solar Cycle 23rd (1996–2006), during this period I selected 12,433 CME records. Also I used the X-ray flares data which provided geostationary operational environmental satellite (GOES), during the same interval in the 1–8 Å GOES channel, the recorded flare events are 22,688. I filtered these CMEs and solar flare events to select 529 CME-Flare events. I found that there is a moderate relation between the solar flare fluxes and their associated CME energies, where R = 58 %. In addition I found that 61 % of the CME-Flare associated events ejected from the solar surface after the occurrence of the associated flare. Furthermore I found that the CME-Flare relation improved during the period of high solar activity. Finally, I examined the CME association rate as a function of flare longitude and I found that the CME association rate of the total 529 selected CME-Flare events are mostly disk-Flare events.  相似文献   

16.
A high-speed, halo-type coronal mass ejection (CME), associated with a GOES M4.6 soft X-ray flare in NOAA AR 0180 at S12W29 and an EIT wave and dimming, occurred on 9 November 2002. A complex radio event was observed during the same period. It included narrow-band fluctuations and frequency-drifting features in the metric wavelength range, type III burst groups at metric – hectometric wavelengths, and an interplanetary type II radio burst, which was visible in the dynamic radio spectrum below 14 MHz. To study the association of the recorded solar energetic particle (SEP) populations with the propagating CME and flaring, we perform a multi-wavelength analysis using radio spectral and imaging observations combined with white-light, EUV, hard X-ray, and magnetogram data. Velocity dispersion analysis of the particle distributions (SOHO and Wind in situ observations) provides estimates for the release times of electrons and protons. Our analysis indicates that proton acceleration was delayed compared to the electrons. The dynamics of the interplanetary type II burst identify the burst source as a bow shock created by the fast CME. The type III burst groups, with start times close to the estimated electron-release times, trace electron beams travelling along open field lines into the interplanetary space. The type III bursts seem to encounter a steep density gradient as they overtake the type II shock front, resulting in an abrupt change in the frequency drift rate of the type III burst emission. Our study presents evidence in support of a scenario in which electrons are accelerated low in the corona behind the CME shock front, while protons are accelerated later, possibly at the CME bow shock high in the corona.  相似文献   

17.
A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring flux tubes. We conclude that “tether cutting” reconnection in the sheared arcade progressively transforms it to a twisted flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure and neighboring magnetic fields. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   

18.
The flare plasma temperature calculated from GOES-11 (1.5–12.4 and 3.1–24.8 keV) data is compared with the solar nonthermal fluxes in various energy ranges in the December 6, 2006 event. Particle acceleration and plasma heating episodes took place in the pre-flare and impulsive phases; a hard (ACS SPI > 150 keV) X-ray emission was observed 5 min before the onset of the GOES X-ray flare and was not accompanied by a temperature rise. A close correlation has been found between the flare plasma temperature and the hard X-ray intensity. The temperature delayed by 0.4 min turned out to be directly proportional to the logarithm of the ACS SPI count rate within the first 3 min of the impulsive phase. This shows that the accelerated electrons responsible for the X-ray emission were the main plasma heating source in the pre-flare and impulsive phases. The correlation between the temperature and the hard X-ray intensity disappears after the observation of a resonance peak at a frequency of 245 MHz. Significant electron fluxes may no longer be able to effectively heat the expanding plasma when its density in the interaction region reaches ∼109 cm−3. The observations of the July 23, 2002 and December 5, 2006 events confirm the trends found.  相似文献   

19.
Jordan  Stuart  Garcia  Adriana  Bumba  Vaclav 《Solar physics》1997,173(2):359-376
A time series of K3 spectroheliograms taken at the Coimbra Observatory exhibits an erupting loop on the east limb on July 9, 1982 in active region NOAA 3804. The Goddard SMM Hard X-Ray Burst Spectrometer (HXRBS) observations taken during this period reveal a hard X-ray flare occurring just before the loop eruption is observed, and SMS-GOES soft X-ray observations reveal a strong long-duration event (LDE) following the impulsive phase of the flare. A Solwind coronagram exhibits a powerful coronal mass ejection (CME) associated with the erupting loop. H flare and prominence observations as well as centimeter and decimeter radio observations of the event are also reviewed. A large, north–south-oriented quiescent prominence reported within the upper part of the CME expansion region may play a role in the eruption as well. The spatial and temporal correlations among these observations are examined in the light of two different current models for prominence eruption and CME activation: (1) The CME is triggered by the observed hard X-ray impulsive flare. (2) The CME is not triggered by a flare, and the observed soft X-ray flare is an LDE due to reconnection within the CME bubble. It is concluded that this event is probably of a mixed type that combines characteristics of models (1) and (2). The July 9 event is then compared to three other energetic CME and flare eruptions associated with the same active-region complex, all occurring in the period July 9 through September 4, 1982. It is noted that these four energetic events coincide with the final evolutionary phase of a long-lasting active-region complex, which is discussed in a companion paper (Bumba, Garcia, and Jordan, 1997). The paper concludes by addressing the solar flare myth controversy in the light of this work.  相似文献   

20.
The purpose of the present study is to investigate the association of solar energetic particle (SEP) events with halo coronal mass ejections (CME) and with their associated solar flares during the period 1997–2014 (solar cycle 23 and 24). We have found that halo CMEs are more effective in producing SEP events. The occurrence probability and peak fluxes of SEPs strongly depend on the halo CMEs speed (V) as follows. The highest associations, 56% for occurrence probability and 90% for average peak fluxes, are found for the halo CMEs with V> 1400 km s−1 but the lowest associations, 20% for occurrence probability and 5% for average peak fluxes, are found for halo CMEs with speed range 600 ≤ V ≤ 1000 km s−1. We have also examined the relationship between SEP events and halo CME associated solar flares and found that 73% of events are associated with western solar flares while only 27% are with eastern solar flares. For longitudinal study, 0–20° belt is found to be more dominant for the SEP events. The association of SEP events with latitudinal solar flares is also examined in the study. 51% of events are associated with those halo CMEs associated solar flares which occur in the southern hemisphere of the Sun while 49% are with those solar flares that occur in the northern hemisphere of the Sun. Also, 10–20° latitudinal belt is found to be likely associated with the SEP events. Further, 45% of SEP events are associated with M-class solar flares while 44% and 11% are with X and C-class respectively. Maximum number of SEP events are found for the fast halo CME associated X- class solar flares (68%) than M and C- class solar flares.  相似文献   

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