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1.
We report on the detailed analysis of i) differences between the properties of type IIs with various starting frequencies (high: ≥100 MHz; low: ≤50 MHz; mid: 50 MHz ≤f≤ 100 MHz) and ii) the properties of CMEs and flares associated with them. For this study, we considered a sample of type II radio bursts observed by Culgoora radio spectrograph from January 1998 to December 2000. The X-ray flares and CMEs associated with these events are identified using GOES and SOHO/LASCO data. The secondary aim is to study the frequency dependence on other properties of type IIs, flares, and CMEs. We found that the type IIs with high starting frequencies have larger drift rate, relative drift rate, and shock speed than the type IIs with low starting frequencies. The flares associated with high frequency type IIs are of impulsive in nature with shorter rise time, duration and delay between the flare start and type II start times than the low frequency type IIs. There is a distinct power – law relationship between the flare parameters and the starting frequencies of type II bursts, whereas the trend in the CME parameters shows low correlation. While the mean speed of CMEs is larger for the mid-frequency group, it is nearly the same for the high and low frequency groups. On the other hand, the percentage of CME association (90%) is larger for low frequency type IIs than for the high frequency type IIs (75%).  相似文献   

2.
CMEs and flares are the two energetic phenomena on the Sun responsible for generating shocks. Our main aim is to study the relation between the physical properties of CMEs and flares associated with and without type II radio bursts. We considered a set of 290 SOHO/LASCO CMEs associated with GOES X-ray flares observed during the period from January 1997 to December 2000. The relationship between the flares and CMEs is examined for the two sets i) with metric-type IIs and ii) without metric-type IIs. Physical properties such as rise time, duration, and strength of the flares and width, speed, and acceleration of CMEs are considered. We examined the energy relationship and temporal relationship between the CMEs and flares. First, all the events in each group were considered, and then the limb events in each group were considered separately. While there is a relationship between the temporal characteristics of flares and CME properties in the case of with-type IIs, it is absent in the case of all without-type IIs. Among all the relations studied, the correlation between flare duration and CME properties is found to be highly significant compared to the other relations. Also, the relationship between flare strength and CME speed found in the with-type II events is absent in the case of all without-type II events. However, when the limb without-type II events (with reduced time window between flare and CME) are studied separately, we found the energy relationship and the temporal relationship.  相似文献   

3.
We have analyzed a set of 147 metric Type II radio bursts observed by Culgoora radio spectrograph from November 1997 to December 2006. These events were divided into two sets: The first subset contains Type II events that started during the impulsive phase of the associated solar flares and the second subset contains those starting during the decaying phase of flares. Our main aim is to differentiate the metric Type IIs, flares and coronal mass ejections (CMEs) of these two subsets. It is found that while Type II burst characteristics of both subsets are very similar, there are significant differences between flare and CME properties for these two subsets. Considering all analyzed relationships between the characteristics of Type IIs, flares and CMEs in these two Type II subsets, we conclude that most of the coronal shocks causing metric Type II bursts are driven by CMEs, but that a fraction of events are probably ignited by solar flares.  相似文献   

4.
We have re-evaluated the association of type II solar radio bursts with flares and/or coronal mass ejections (CMEs) using the year 2000 solar maximum data. For this, we consider 52 type II events whose associations with flares or CMEs were absent or not clearly identified and reported. These events are classified as follows; group I: 11 type IIs for which there are no reports of GOES X-ray flares and CMEs; group II: 12 type IIs for which there are no reports of GOES X-ray flares; and group III: 29 type IIs for which the flare locations are not reported. By carefully re-examining their association from GOES X-ray and H, Yohkoh SXT and EIT-EUV data, we attempt to answer the following questions: (i) if there really were no X-ray flares associated with the above 23 type IIs of groups I and II; (ii) whether they can be regarded as backside events whose X-ray emission might have been occulted. From this analysis, we have found that two factors, flare background intensity and flare location, play important roles in the complete reports about flare–type II–CME associations. In the above 23 cases, for more than 50% of the cases in total, the X-ray flares were not noticed and reported, because the background intensity of X-ray flux was high. In the remaining cases, the X-ray intensity might be greatly reduced due to occultation. From the H flare data, Yohkoh SXT data and EIT-EUV data, we found that ten cases out of 23 might be frontside events, and the remaining are backside events. While the flare–type II association is found to be nearly 90%, the type II–CME association is roughly around 75%. This analysis might be useful to reduce some ambiguities regarding the association among type IIs, flares and CMEs.  相似文献   

5.
We attempt to study the origin of coronal shocks by comparing several flare characteristics for two groups of flares: those with associated metric type II bursts and coronal mass ejections (CMEs) and those with associated metric type II bursts but no CMEs. CMEs accompany about 60% of all flares with type II bursts for solar longitudes greater than 30°, where CMEs are well observed with the NRL Solwind coronagraph. H flare areas, 1–8 Å X-ray fluxes, and impulsive 3 cm fluxes are all statistically smaller for events with no CMEs than for events with CMEs. It appears that both compact and large mass ejection flares are associated with type II bursts. The events with no CMEs imply that at least many type II shocks are not piston-driven, but the large number of events of both groups with small 3 cm bursts does not support the usual assumption that type II shocks are produced by large energy releases in flare impulsive phases. The poor correlation between 3 cm burst fluxes and the occurrence of type II bursts may be due to large variations in the coronal Alfvén velocity.Sachs/Freeman Associates, Inc., Bowie, MD 20715, U.S.A.  相似文献   

6.
We have analyzed a set of 25 interacting events which are associated with the DH type II bursts. These events are selected from the Coronal Mass Ejections (CMEs) observed during the period 1997–2010 in SOHO/LASCO and DH type IIs observed in Wind/WAVES. Their pre and primary CMEs from nearby active regions are identified using SOHO/LASCO and EIT images and their height–time diagrams. Their interacting time and height are obtained, and their associated activities, such as, flares and Solar Energetic Particles (>10 pfu) are also investigated. Results from the analysis are: primary CMEs are much faster than the pre-CMEs, their X-ray flares are also stronger (X- and M-class) compared to the flares (C- and M-class) of pre-CMEs. Most of the events (22/25) occurred during the period 2000–2006. From the observed width and speed of pre and primary CMEs, it is found that the pre-CMEs are found to be less energetic than the primary CMEs. While the primary CMEs are tracked up to the end of LASCO field of view (30 Rs), most of the pre-CMEs can be tracked up to <26 Rs. The SEP intensity is found to be related with the integrated flux of X-ray flares associated with the primary CMEs for nine events originating from the western region.  相似文献   

7.
Kocharov  Leon  Torsti  Jarmo  Laitinen  Timo  Teittinen  Matti 《Solar physics》1999,190(1-2):295-307
We have analyzed five solar energetic particle (SEP) events observed aboard the SOHO spacecraft during 1996–1997. All events were associated with impulsive soft X-ray flares, Type II radio bursts and coronal mass ejections (CMEs). Most attention is concentrated on the SEP acceleration during the first 100 minutes after the flare impulsive phase, post-impulsive-phase acceleration, being observed in eruptions centered at different solar longitudes. As a representative pattern of a (nearly) well-connected event, we consider the west flare and CME of 9 July 1996 (S10 W30). Similarities and dissimilarities of the post-impulsive-phase acceleration at large heliocentric-angle distance from the eruption center are illustrated with the 24 September 1997 event (S31 E19). We conclude that the proton acceleration at intermediate scales, between flare acceleration and interplanetary CME-driven shock acceleration, significantly contributes to the production of ≳10 MeV protons. This post-impulsive-phase acceleration seems to be caused by the CME lift-off.  相似文献   

8.
We present an analysis of all the events (around 400) of coronal shocks for which the shock-associated metric type IIs were observed by many spectrographs during the period April 1997– December 2000. The main objective of this analysis is to give evidence for the type IIs related to only flare-blast waves, and thus to find out whether there are any type II-associated coronal shocks without mass ejections. By carefully analyzing the data from multi-wavelength observations (Radio, GOES X-ray, Hα, SOHO/LASCO and SOHO/EIT-EUV data), we have identified only 30 events for which there were actually no reports of CMEs. Then from the analysis of the LASCO and EIT running difference images, we found that there are some shocks (nearly 40%, 12/30) which might be associated with weak and narrow mass ejections. These weak and narrow ejections were not reported earlier. For the remaining 60% events (18/30), there are no mass ejections seen in SOHO/LASCO. But all of them are associated with flares and EIT brightenings. Pre-assuming that these type IIs are related to the flares, and from those flare locations of these 18 cases, 16 events are found to occur within the central region of the solar disk (longitude ≤45^∘). In this case, the weak CMEs originating from this region are unlikely to be detected by SOHO/LASCO due to low scattering. The remaining two events occurred beyond this longitudinal limit for which any mass ejections would have been detected if they were present. For both these events, though there are weak eruption features (EIT dimming and loop displacement) in the EIT images, no mass ejection was seen in LASCO for one event, and a CME appeared very late for the other event. While these two cases may imply that the coronal shocks can be produced without any mass ejections, we cannot deny the strong relationship between type IIs and CMEs.  相似文献   

9.
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   

10.
We present the study of 20 solar flares observed by “Solar X-ray Spectrometer (SOXS)” mission during November 2003 to December 2006 and found associated with coronal mass ejections (CMEs) seen by LASCO/SOHO mission. In this investigation, X-ray emission characteristics of solar flares and their relationship with the dynamics of CMEs have been presented. We found that the fast moving CMEs, i.e., positive acceleration are better associated with short rise time (< 150 s) flares. However, the velocity of CMEs increases as a function of duration of the flares in both 4.1–10 and 10–20 keV bands. This indicates that the possibility of association of CMEs with larger speeds exists with long duration flare events. We observed that CMEs decelerate with increasing rise time, decay time and duration of the associated X-ray flares. A total 10 out of 20 CMEs under current investigation showed positive acceleration, and 5 of them whose speed did not exceed 589 km/s were associated with short rise time (< 150 s) and short duration (< 1300 s) flares. The other 5 CMEs were associated with long duration or large rise time flare events. The unusual feature of all these positive accelerating CMEs was their low linear speed ranging between 176 and 775 km/s. We do not find any significant correlation between X-ray peak intensity of the flares with linear speed as well as acceleration of the associated CMEs. Based on the onset time of flares and associated CMEs within the observing cadence of CMEs by LASCO, we found that in 16 cases CME preceded the flare by 23 to 1786 s, while in 4 cases flare occurred before the CME by 47 to 685 s. We argue that both events are closely associated with each other and are integral parts of one energy release system.  相似文献   

11.
D–H type II radio bursts are widely thought to be caused by coronal mass ejections (CMEs). However, it is still unclear where the exact source of the type IIs on the shock surface is. We identify the source regions of the decameter–hectometric (D–H) type IIs based on imaging observations from SOHO/LASCO and the radio dynamic spectrum from Wind/Waves. The analysis of two well-observed events suggests that the sources of these two events are located in the interaction regions between shocks and streamers, and that the shocks are enhanced significantly in these regions.  相似文献   

12.
We re-examine observations bearing on the origin of metric type II bursts for six impulsive solar events in November 1997. Previous analyses of these events indicated that the metric type IIs were due to flares (either blast waves or ejecta). Our point of departure was the study of Zhang et al. (2001) based on the Large Angle and Spectrometric Coronagraphs C1 instrument (occulting disk at 1.1 R0) that identified the rapid acceleration phase of coronal mass ejections (CMEs) with the rise phase of soft X-ray light curves of associated flares. We find that the inferred onset of rapid CME acceleration in each of the six cases occurred 1–3 min before the onset of metric type II emission, in contrast to the results of previous studies for certain of these events that obtained CME launch times 25–45 min earlier than type II onset. The removal of the CME-metric type II timing discrepancy in these events and, more generally, the identification of the onset of the rapid acceleration phase of CMEs with the flare impulsive phase undercuts a significant argument against CMEs as metric type II shock drivers. In general, the six events exhibited: (1) ample evidence of dynamic behavior [soft X-ray ejecta, extreme ultra-violet imaging telescope (EIT) dimming onsets, and wave initiation (observed variously in H, EUV, and soft X-rays)] during the inferred fast acceleration phases of the CMEs, consistent with the cataclysmic disruption of the low solar atmosphere one would expect to be associated with a CME; and (2) an organic relationship between EIT dimmings (generally taken to be source regions of CMEs) and EIT waves (which are highly associated with metric type II bursts) indicative of a CME-driver scenario. Our analysis indicates that the broad (90 to halo) CMEs observed in the outer LASCO coronagraphs for these impulsive events began life as relatively small-scale structures, with angular spans of 15 in the low corona. A review of on-going work bearing on other aspects (than timing) of the question of the origin of metric type II bursts (CME association; connectivity of metric and decametric-hectometric type II shocks; spatial relationship between CMEs and metric shocks) leads to the conclusion that CMEs remain a strong candidate to be the principal/sole driver of metric type II shocks vis-à-vis flare blast waves/ejecta.  相似文献   

13.
We present a statistical study of the characteristics of type-II radio bursts observed in the metric (m) and deca-hectometer (DH) wavelength range during 1997–2008. The collected events are divided into two groups: Group I contains the events of m-type-II bursts with starting frequency ≥ 100 MHz, and group II contains the events with starting frequency of m-type-II radio bursts < 100 MHz. We have analyzed both samples considering three different aspects: i) statistical properties of type-II bursts, ii) statistical properties of flares and CMEs associated with type-II bursts, and iii) time delays between type-II bursts, flares, and CMEs. We find significant differences in the properties of m-type-II bursts in duration, bandwidth, drift rate, shock speed and delay between m- and DH-type-II bursts. From the timing analysis we found that the majority of m-type-II bursts in both groups occur during the flare impulsive phase. On the other hand, the DH-type-II bursts in both groups occur during the decaying phase of the associated flares. Almost all m-DH-type-II bursts are found to be associated with CMEs. Our results indicate that there are two kinds of shock in which group I (high frequency) m-type-II bursts seem to be ignited by flares whereas group II (low frequency) m-type-II bursts are CME-driven.  相似文献   

14.
A detailed statistical investigation of solar Type II radio bursts during the last solar maximum period 1999–2001 has been made to address the question if there exist two kinds of coronal shock sources. For this, the Type II bursts were classified into two classes: (i) those associated with flares only (Class I); and (ii) those associated with flares and CMEs (Class II) according to their temporal association. While the properties of all the type IIs agree in general with the common range of values, the properties of the shocks of the two classes differ slightly. For example, while the duration and shock speed for Class II are higher than those of Class I, the ending frequency for Class II is significantly lower. We have also examined in detail the physical association with other solar and interplanetary activities (Type IV bursts, Long Duration Events, Wind/WAVES deca-hectometric Type IIs, and interplanetary shocks) using the data in 2000. As a result, we have found noticeable differences between these two classes in terms of the following physical characteristics: First, the associations of these activities for Class II are much higher than those of Class I. Second, the correlation values between the flare parameters and the Type II properties for Class II are significantly smaller. Third, observed double Type IIs exist in only Class II events. The above results suggest that there are two kinds of coronal shocks or, rather, two general classes of coronal shock sources.  相似文献   

15.
By performing certain spatial and temporal criteria, we obtained 492 CME events simultaneously associated with GBM solar flare events (hereafter, GBM-flare–CME) from the total number 5123 Gamma-ray Burst Monitor (GBM) solar flares and 15228 Coronal Mass Ejections (CMEs) detected during the solar cycle 24 (2008–2019). Among these 492 events, which represent about 9.6% of the total number of the detected GBM flares, there are just 381 events (77.4%) representing the CMEs associated with the flares that are detected instantly by both GBM and RHESSI detectors. We found no significant distinction in the results after applying the spatial criteria compared with those arising from applying the temporal criteria only.Actually, all CMEs are ejected within the flare's preflare and the impulsive phases only. From our results, we conclude that the GBM flares whose long duration are most frequently associated with faster and wider CMEs and vice versa. In addition, the longer the flare's duration, the more interval time between the start time of GBM solar flare and CME's ejection time through a linear correlation [Mean Interval = 0.464 × Duration (min)] with a correlation coefficient equals 0.93. We conclude also that, the highly probable, γ-ray emitting flares (detected by GBM only) have a shorter duration and time interval than X-ray flares (detected also by RHESSI). As well as the GBM - CMEs events, without RHESSI associated CMEs are faster and wider than those associated with RHESSI events.  相似文献   

16.
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   

17.

We have statistically analyzed a set of 115 low frequency (Deca-Hectometer wavelengths range) type II and type III bursts associated with major Solar Energetic Particle (SEP: Ep?>?10 MeV) events and their solar causes such as solar flares and coronal mass ejections (CMEs) observed from 1997 to 2014. We classified them into two sets of events based on the duration of the associated solar flares:75 impulsive flares (duration <?60 min) and 40 gradual flares (duration >?60 min).On an average, the peak flux (integrated flux) of impulsive flares?×?2.9 (0.32 J m?2) is stronger than that of gradual flares M6.8 (0.24 J m?2). We found that impulsive flare-associated CMEs are highly decelerated with larger initial acceleration and they achieved their peak speed at lower heights (??27.66 m s?2 and 14.23 Ro) than the gradual flare-associated CMEs (6.26 m s?2 and 15.30 Ro), even though both sets of events have similar sky-plane speed (space speed) within LASCO field of view. The impulsive flare-associated SEP events (Rt?=?989.23 min: 2.86 days) are short lived and they quickly reach their peak intensity (shorter rise time) when compared with gradual flares associated events (Rt?=?1275.45 min: 3.34 days). We found a good correlation between the logarithmic peak intensity of all SEPs and properties of CMEs (space speed: cc?=?0.52, SEcc?=?0.083), and solar flares (log integrated flux: cc?=?0.44, SEcc?=?0.083). This particular result gives no clear cut distinction between flare-related and CME-related SEP events for this set of major SEP events. We derived the peak intensity, integrated intensity, duration and slope of these bursts from the radio dynamic spectra observed by Wind/WAVES. Most of the properties (peak intensity, integrated intensity and starting frequency) of DH type II bursts associated with impulsive and gradual flare events are found to be similar in magnitudes. Interestingly, we found that impulsive flare-associated DH type III bursts are longer, stronger and faster (31.30 min, 6.43 sfu and 22.49 MHz h?1) than the gradual flare- associated DH type III bursts (25.08 min, 5.85 sfu and 17.84 MHz h?1). In addition, we also found a significant correlation between the properties of SEPs and key parameters of DH type III bursts. This result shows a closer association of peak intensity of the SEPs with the properties of DH type III radio bursts than with the properties DH type II radio bursts, atleast for this set of 115 major SEP events.

  相似文献   

18.
We present study of relationship of GSXR flares with Hα flares, hard X-ray (HXR) bursts, microwave (MW) bursts at 15.4 GHz, type II/IV radio bursts, coronal mass ejections (CMEs), protons flares (>10 MeV) and ground level enhancement (GLE) events we find that about 85.7%, 93%, 97%, 69%, 60%, 11.1%, 79%, 46%, and 23%% GSXR flares are related/associated with observed Hα flares, HXR bursts, MW bursts at 15.4 GHz, type II radio bursts, type IV radio bursts, GLE events, CMEs, halo CMEs, and proton flares (>10 MeV), respectively. In the paper we have studied the onset time delay of GSXR flares with Hα flares, HXR, and MW bursts which shows the during majority GSXR flares SXR emissions start before the Hα, HXR and MW emissions, respectively while during 15–20% of GSXR flares the SXR emissions start after the onset of Hα, HXT and MW emissions, respectively indicating two types of solar flares. The, onset time interval between SXR emissions and type II radio bursts, type IV radio bursts, GLE events CMEs, halo CMEs, and protons flares are 1–15 min, 1–20 min, 21–30 min, 21–40 min, 21–40 min, and 1–4 hrs, respectively. Following the majority results we are of the view that the present investigations support solar flares models which suggest flare triggering first in the corona and then move to chromospheres/ photosphere to starts emissions in other wavelengths. The result of the present work is largely consistent with “big flare syndrome” proposed by Kahler (1982).  相似文献   

19.
Statistical analysis of the relationship between type II radio bursts appearing in the metric (m) and decameter-to-hectometer (DH) wavelength ranges is presented. The associated X-ray flares and coronal mass ejections (CMEs) are also reported. The sample is divided into two classes using the frequency-drift plots: Class I, representing those events where DH-type-II bursts are not continuation of m-type-II bursts and Class II, where the DH-type-II bursts are extensions of m-type-II bursts. Our study consists of three steps: i) comparison of characteristics of the Class I and II events; ii) correlation of m-type-II and DH-type-II burst characteristics with X-ray flare properties and iii) correlation of m-type-II and DH-type-II burst characteristics with CME properties. We have found no clear correlation between properties of m-type-II bursts and DH-type-II bursts. For example, there is no correlation between drift rates of m-type-II bursts and DH-type-II bursts. Similarly there is no correlation between their starting frequencies. In Class I events we found correlations between X-ray flare characteristics and properties of m-type-II bursts and there is no correlation between flare parameters and DH-type-II bursts. On the other hand, the correlation between CME parameters and m-type-II bursts is very weak, but it is good for CME parameters and DH-type-II bursts. These results indicate that Class I m-type-II bursts are related to the energy releases in flares, whereas DH-type-II bursts tend to be related to CMEs. On the contrary, for Class II events in the case of m-type-II and DH-type-II bursts we have found no clear correlation between both flare and CMEs.  相似文献   

20.
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   

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