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1.
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
2.
We analyze multiwavelength observations of an M2.9/1N flare that occurred in AR NOAA 11112 on 16 October 2010. AIA 211 Å EUV images reveal the presence of a faster coronal wave (decelerating from ≈?1390 to ≈?830 km?s?1) propagating ahead of a slower wave (decelerating from ≈?416 to ≈?166 km?s?1) towards the western limb. The dynamic radio spectrum from Sagamore Hill radio telescope shows the presence of a metric type II radio burst, which reveals the presence of a coronal shock wave (speed ≈?800 km?s?1). The speed of the faster coronal wave, derived from AIA 211 Å images, is found to be comparable to the coronal shock speed. AIA 171 Å high-cadence observations showed that a coronal loop, which was located at a distance of ≈?0.32R ⊙ to the west of the flaring region, started to oscillate by the end of the impulsive phase of the flare. The results indicate that the faster coronal wave may be the first driver of the transversal oscillations of coronal loop. As the slower wave passed through the coronal loop, the oscillations became even stronger. There was a plasmoid eruption observed in EUV and a white-light CME was recorded, having velocity of ≈?340?–?350 km?s?1. STEREO 195 Å images show an EIT wave, propagating in the same direction as the lower-speed coronal wave observed in AIA, but decelerating from ≈?320 to ≈?254 km?s?1. These observations reveal the co-existence of both waves (i.e. coronal Moreton and EIT waves), and the type II radio burst seems to be associated with the coronal Moreton wave. 相似文献
3.
We report on the analysis of a fast (>2,000 km/s) CME-driven shock event observed with the UVCS telescope operating aboard SoHO on 23 July 2002. The same shock was also detected in the metric band by several ground-based radiospectrographs. The peculiarity of this event is the presence in the radio spectra of two intense metric type II bursts features drifting at different rates, together with clear shock/related broadenings of the O VI doublet lines observed by UVCS that were found to be temporally associated with the above radio features. The nature of these multiple radio lanes in the metric band is still under debate. One possible explanation is that they are produced by multiple shock waves generated by different ejections or, alternatively, by the flare and the associated CME. Also, emission from the upstream and downstream shock regions can produce split bands. By adopting a plausible CME model, together with a detailed analysis of the white-light, UV, and radio data associated with this event, we are able to conclude that both the radio and the UV shock signatures were produced by a single shock wave surface generated by the expanding CME. 相似文献
4.
The SOL2001-12-26 moderate solar eruptive event (GOES importance M7.1, microwaves up to 4000 sfu at 9.4 GHz, coronal mass ejection (CME) speed 1446 km?s?1) produced strong fluxes of solar energetic particles and ground-level enhancement (GLE) of cosmic-ray intensity (GLE63). To find a possible reason for the atypically high proton outcome of this event, we study multi-wavelength images and dynamic radio spectra and quantitatively reconcile the findings with each other. An additional eruption probably occurred in the same active region about half an hour before the main eruption. The latter produced two blast-wave-like shocks during the impulsive phase. The two shock waves eventually merged around the radial direction into a single shock traced up to \(25~\mathrm{R}_{\odot}\) as a halo ahead of the expanding CME body, in agreement with an interplanetary Type II event recorded by the Radio and Plasma Wave Investigation (WAVES) experiment on the Wind spacecraft. The shape and kinematics of the halo indicate an intermediate regime of the shock between the blast wave and bow shock at these distances. The results show that i) the shock wave appeared during the flare rise and could accelerate particles earlier than usually assumed; ii) the particle event could be amplified by the preceding eruption, which stretched closed structures above the developing CME, facilitated its lift-off and escape of flare-accelerated particles, enabled a higher CME speed and stronger shock ahead; iii) escape of flare-accelerated particles could be additionally facilitated by reconnection of the flux rope, where they were trapped, with a large coronal hole; and iv) the first eruption supplied a rich seed population accelerated by a trailing shock wave. 相似文献
5.
We investigate coronal transients associated with a GOES M6.7 class flare and a coronal mass ejection (CME) on 13 July 2004. During the rising phase of the flare, a filament eruption, loop expansion, a Moreton wave, and an ejecta were observed. An EIT wave was detected later on. The main features in the radio dynamic spectrum were a frequency-drifting continuum and two type II bursts. Our analysis shows that if the first type II burst was formed in the low corona, the burst heights and speed are close to the projected distances and speed of the Moreton wave (a chromospheric shock wave signature). The frequency-drifting radio continuum, starting above 1 GHz, was formed almost two minutes prior to any shock features becoming visible, and a fast-expanding piston (visible as the continuum) could have launched another shock wave. A possible scenario is that a flare blast overtook the earlier transient and ignited the first type II burst. The second type II burst may have been formed by the same shock, but only if the shock was propagating at a constant speed. This interpretation also requires that the shock-producing regions were located at different parts of the propagating structure or that the shock was passing through regions with highly different atmospheric densities. This complex event, with a multitude of radio features and transients at other wavelengths, presents evidence for both blast-wave-related and CME-related radio emissions. 相似文献
6.
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
7.
We study the 17 January 2010 flare–CME–wave event by using STEREO/SECCHI-EUVI and -COR1 data. The observational study is combined with an analytic model that simulates the evolution of the coronal wave phenomenon associated with the event. From EUV observations, the wave signature appears to be dome shaped having a component propagating on the solar surface ( $\overline{v}\approx280~\mathrm{km}\,\mathrm{s}^{-1}$ ) as well as one off-disk ( $\overline{v}\approx 600~\mathrm{km}\,\mathrm{s}^{-1}$ ) away from the Sun. The off-disk dome of the wave consists of two enhancements in intensity, which conjointly develop and can be followed up to white-light coronagraph images. Applying an analytic model, we derive that these intensity variations belong to a wave–driver system with a weakly shocked wave, initially driven by expanding loops, which are indicative of the early evolution phase of the accompanying CME. We obtain the shock standoff distance between wave and driver from observations as well as from model results. The shock standoff distance close to the Sun (<?0.3 R ⊙ above the solar surface) is found to rapidly increase with values of ≈?0.03?–?0.09 R ⊙, which gives evidence of an initial lateral (over)expansion of the CME. The kinematical evolution of the on-disk wave could be modeled using input parameters that require a more impulsive driver (duration t=90 s, acceleration a=1.7 km?s?2) compared to the off-disk component (duration t=340 s, acceleration a=1.5 km?s?2). 相似文献
8.
We present a multi-wavelength study of a solar eruption event on 20 July 2004, comprising observations in H??, EUV, soft X-rays, and in radio waves with a wide frequency range. The analyzed data show both oscillatory patterns and shock wave signatures during the impulsive phase of the flare. At the same time, large-scale EUV loops located above the active region were observed to contract. Quasi-periodic pulsations with ???10 and ???15 s oscillation periods were detected both in microwave??C?millimeter waves and in decimeter??C?meter waves. Our calculations show that MHD oscillations in the large EUV loops ?C but not likely in the largest contracting loops ?C could have produced the observed periodicity in radio emission, by triggering periodic magnetic reconnection and accelerating particles. As the plasma emission in decimeter??C?meter waves traces the accelerated particle beams and the microwave emission shows a typical gyrosynchrotron flux spectrum (emission created by trapped electrons within the flare loop), we find that the particles responsible for the two different types of emission could have been accelerated in the same process. Radio imaging of the pulsed decimetric??C?metric emission and the shock-generated radio type II burst in the same wavelength range suggest a rather complex scenario for the emission processes and locations. The observed locations cannot be explained by the standard model of flare loops with an erupting plasmoid located above them, driving a shock wave at the CME front. 相似文献
9.
It is well known that there is a temporal relationship between coronal mass ejections (CMEs) and associated flares. The duration of the acceleration phase is related to the duration of the rise phase of a flare. We investigate CMEs associated with slow long duration events (LDEs), i.e. flares with the long rising phase. We determined the relationships between flares and CMEs and analyzed the CME kinematics in detail. The parameters of the flares (GOES flux, duration of the rising phase) show strong correlations with the CME parameters (velocity, acceleration during main acceleration phase, and duration of the CME acceleration phase). These correlations confirm the strong relation between slow LDEs and CMEs. We also analyzed the relation between the parameters of the CMEs, i.e. a velocity, an acceleration during the main acceleration phase, a duration of the acceleration phase, and a height of a CME at the end of the acceleration phase. The CMEs associated with the slow LDEs are characterized by high velocity during the propagation phase, with the median equal to 1423 km?s?1. In half of the analyzed cases, the main acceleration was low (a<300 m?s?2), which suggests that the high velocity is caused by the prolonged acceleration phase (the median for the duration of the acceleration phase is equal 90 minutes). The CMEs were accelerated up to several solar radii (with the median ≈?7 R ⊙), which is much higher than in typical impulsive CMEs. Therefore, slow LDEs may potentially precede extremely strong geomagnetic storms. The analysis of slow LDEs and associated CMEs may give important information for developing more accurate space-weather forecasts, especially for extreme events. 相似文献
10.
Particle Acceleration and Propagation in Strong Flares without Major Solar Energetic Particle Events
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
11.
A. Kouloumvakos S. Patsourakos A. Hillaris A. Vourlidas P. Preka-Papadema X. Moussas C. Caroubalos P. Tsitsipis A. Kontogeorgos 《Solar physics》2014,289(6):2123-2139
On 13 June 2010, an eruptive event occurred near the solar limb. It included a small filament eruption and the onset of a relatively narrow coronal mass ejection (CME) surrounded by an extreme ultraviolet (EUV) wave front recorded by the Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was accompanied by a GOES M1.0 soft X-ray flare and a Type-II radio burst; high-resolution dynamic spectra of the latter were obtained by the Appareil de Routine pour le Traitement et l’Enregistrement Magnetique de l’Information Spectral (ARTEMIS IV) radio spectrograph. The combined observations enabled a study of the evolution of the ejecta and the EUV wave front and its relationship with the coronal shock manifesting itself as metric Type-II burst. By introducing a novel technique, which deduces a proxy of the EUV compression ratio from AIA imaging data and compares it with the compression ratio deduced from the band-split of the Type-II metric radio burst, we are able to infer the potential source locations of the radio emission of the shock on that AIA images. Our results indicate that the expansion of the CME ejecta is the source for both EUV and radio shock emissions. Early in the CME expansion phase, the Type-II burst seems to originate in the sheath region between the EUV bubble and the EUV shock front in both radial and lateral directions. This suggests that both the nose and the flanks of the expanding bubble could have driven the shock. 相似文献
12.
Wahab Uddin Ramesh Chandra Syed Salman Ali 《Journal of Astrophysics and Astronomy》2006,27(2-3):267-276
We observed 4B/X17.2 flare in Hα from super-active region NOAA 10486 at ARIES, Nainital. This is one of the largest flares
of current solar cycle 23, which occurred near the Sun’s center and produced extremely energetic emission almost at all wavelengths
from γ-ray to radio-waves. The flare is associated with a bright/fast full-halo earth directed CME, strong type II, type III
and type IV radio bursts, an intense proton event and GLE. This flare is well observed by SOHO, RHESSI and TRACE. Our Hα observations
show the stretching/de-twisting and eruption of helically twisted S shaped (sigmoid) filament in the south-west direction
of the active region with bright shock front followed by rapid increase in intensity and area of the gigantic flare. The flare
shows almost similar evolution in Hα, EUV and UV. We measure the speed of Hα ribbon separation and the mean value is ∼ 70
km s-1. This is used together with photospheric magnetic field to infer a magnetic reconnection rate at three HXR sources at the
flare maximum. In this paper, we also discuss the energetics of active region filament, flare and associated CME. 相似文献
13.
A solar radio type II burst (which was seen as two patches of emission, one during 07:00–07:13 UT and other one during 07:20–07:35 UT)
was observed on 22 March 1998 using the Madurai radio spectrograph. A broad range of data (from Culgoora and Hiraiso spectrographs,
white-light data from SOHO/LASCO and X-ray data from Yohkoh and GOES satellites) was also studied for this event, which was analyzed in comparison with these supplementary data. In
addition, the conditions associated with this shock were analyzed quantitatively. From the above investigations, the following
conclusions have been made. The temporal relationship between H-alpha flare and burst has shown that the active region AR 8185
is the source of this type II burst. A bright front feature observed with LASCO is also associated with this type II burst
and active region AR 8185. The time profile of the shock derived from the first patch of this type II burst coincides with
the flare starting time. Also, within error limits, the start time of the CME is same as the flare. Hence, it is not possible
to decide whether the type II originated in the flare or was driven by CME. In addition, the investigations of the second
patch alone has provided the following results. The inferred shock speed for the second patch of emission is lower than the
first and closer to the CME speed. The emission occurred below 50 MHz. These conditions imply that this patch may be a separate
burst which might have been produced by the CME alone. 相似文献
14.
I. Y. Grigoryeva V. N. Borovik M. A. Livshits V. E. Abramov-Maximov L. V. Opeikina V. M. Bogod A. N. Korzhavin 《Solar physics》2009,260(1):157-175
A CME/flare event occurred at the eastern limb on 25 January, 2007. Seven successive multi-wavelength scans in the range 1.8 cm?–?5.0 cm were obtained with the RATAN-600 radio telescope starting just at the beginning of the post-eruptive arcade formation (30 min after a C6.3 flare peak) and lasting for 3.5 hours. The conditions were favorable to study the off-limb microwave radio source associated with the post-eruptive arcade in different phases of its formation. Microwave radio emission of the arcade was rather intense initially and then considerably decreased; its maximum was co-spatial with the 195 Å Fe xii loop tops. The RATAN-600 total flux spectra of the off-limb radio source were practically flat during the first two hours indicating a predominant contribution of thermal emission. The X-ray spectrum was thermal (according to RHESSI data) at that time. Data available in the meter wavelength range during this phase were indicative of weak non-thermal processes likely due to accelerated particles. However, free?–?free emission of an isothermal source dominated in microwaves. This is indicative of the presence of a large amount of plasma in the region of arcade formation at the initial stage of the event. The weak microwave emission during the decay phase might be interpreted as the thermal cyclotron emission of the loops in the arcade. 相似文献
15.
E. W. Cliver S. W. Kahler H. V. Cane M. J. Koomen D. J. Michels R. A. Howard N. R. Sheeley Jr. 《Solar physics》1983,89(1):181-193
We use a variety of ground-based and satellite measurements to identify the source of the ground level event (GLE) beginning near 06∶30 UT on 21 August, 1979 as the 2B flare with maximum at ～06∶15 UT in McMath region 16218. This flare differed from previous GLE-associated flares in that it lacked a prominent impulsive phase, having a peak ～9 GHz burst flux density of only 27 sfu and a ?20 keV peak hard X-ray flux of ?3 × 10-6 ergs cm-2s-1. Also, McMath 16218 was magnetically less complex than the active regions in which previous cosmic-ray flares have occurred, containing essentially only a single sunspot with a rudimentary penumbra. The flare was associated with a high speed (?700 km s-1) mass ejection observed by the NRL white light coronagraph aboard P78-1 and a shock accelerated (SA) event observed by the low frequency radio astronomy experiment on ISEE-3. 相似文献
16.
Chertok I.M. Fomichev V.V. Gnezdilov A.A. Gorgutsa R.V. Grechnev V.V. Markeev A.K. Nightingale R.W. Sobolev D.E. 《Solar physics》2001,204(1-2):139-152
The 14 July 2000 (`Bastille Day') eruptive and geoeffective flare event was observed by the digital IZMIRAN radio spectrograph
in the frequency range of 25–270 MHz. This instrument allowed the analysis of various features of the dynamic radio spectrum
and their comparison with other observational data, in particular with development of a spectacular EUV post-eruption arcade
recorded aboard the Transition Region and Coronal Explorer (TRACE). (1) A compressed multi-hour radio spectrum shows that
the event caused a conspicuous weakening of the pre-existing noise storm. This phenomenon was perhaps caused by interaction
of a large halo coronal mass ejection (CME), recorded by the the Large Angle and Spectroscopic Coronagraph (LASCO) aboard
the Solar and Heliospheric Observatory (SOHO), with emitting coronal structures. (2) Several type II bands are present at
the initial and maximum phases of the flare event. The frequency drifts of the clearest bands correspond to the estimated
shock wave speed of 1100–2300 km s−1 that is comparable with the CME speed observed in the sky plane. (3) Significant broadband enhancements of the metric radio
emission took place around of 10:24–10:27 UT coinciding with sharp development of the EUV arcade in the northeast direction.
It appears to correspond to the intensification of the electron acceleration in a process of post-eruption loop formation.
(4) The high-resolution radio spectrum revealed a superposition of numerous type III-like bursts and/or pulsations with a
time scale ranging from a few seconds to several tens of seconds. These features can be attributed particularly to successive
formation of new loops of the arcade and corresponding temporal fragmentation of the electron acceleration in the course of
the post-eruption reconnection. In summary, the analysis demonstrates the correspondence between the multi-scale temporal
features of the metric radio emission and such phenomena as the CME and post-eruption EUV arcade. Some spectra, images, and
movies illustrating the event are presented also on the accompanying CD-ROM.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014224004946 相似文献
17.
We study the solar event on 27 September 2001 that consisted of three consecutive coronal mass ejections (CMEs) originating from the same active region, which were associated with several periods of radio type II burst emission at decameter–hectometer (DH) wavelengths. Our analysis shows that the first radio burst originated from a low-density environment, formed in the wake of the first, slow CME. The frequency-drift of the burst suggests a low-speed burst driver, or that the shock was not propagating along the large density gradient. There is also evidence of band-splitting within this emission lane. The origin of the first shock remains unclear, as several alternative scenarios exist. The second shock showed separate periods of enhanced radio emission. This shock could have originated from a CME bow shock, caused by the fast and accelerating second or third CME. However, a shock at CME flanks is also possible, as the density depletion caused by the three CMEs would have affected the emission frequencies and hence the radio source heights could have been lower than usual. The last type II burst period showed enhanced emission in a wider bandwidth, which was most probably due to the CME–CME interaction. Only one shock that could reliably be associated with the investigated CMEs was observed to arrive near Earth. 相似文献
18.
N. J. Lehtinen S. Pohjolainen K. Huttunen-Heikinmaa R. Vainio E. Valtonen A. E. Hillaris 《Solar physics》2008,247(1):151-169
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
19.
We report on the thermal and nonthermal radio emissions from a coronal mass ejection (CME) observed at meter-decameter wavelengths using the Clark Lake multifrequency radioheliograph. From white-light observations of the Solar Maximum Mission Coronagraph/Polarimeter instrument the CME was found to have a speed of 450 km s–1. Since there was no nonthermal radio emission in the beginning of the event and the one which occurred later was quite weak, we were able to observe the thermal structure of the CME in radio. Type III bursts and a nonthermal continuum started several minutes after the CME onset. We use the radio and optical observations to show that the CME was not driven by the flare. We investigate the thermal structure and geometry of the mass ejection in radio and compare it with the optical evidence. Finally we develop a schematic model of the event and point out that particle acceleration high in the corona is possible. 相似文献
20.
We present a multiwavelength analysis of a long-duration, white-light solar flare (M8.9/3B) event that occurred on 04 June 2007 from AR NOAA 10960. The flare was observed by several spaceborne instruments, namely SOHO/MDI, Hinode/SOT, TRACE, and STEREO/SECCHI. The flare was initiated near a small, positive-polarity, satellite sunspot at the center of the active region, surrounded by opposite-polarity field regions. MDI images of the active region show a considerable amount of changes in the small positive-polarity sunspot of δ configuration during the flare event. SOT/G-band (4305 Å) images of the sunspot also suggest the rapid evolution of this positive-polarity sunspot with highly twisted penumbral filaments before the flare event, which were oriented in a counterclockwise direction. It shows the change in orientation, and also the remarkable disappearance of twisted penumbral filaments (≈35?–?40%) and enhancement in umbral area (≈45?–?50%) during the decay phase of the flare. TRACE and SECCHI observations reveal the successive activation of two helically-twisted structures associated with this sunspot, and the corresponding brightening in the chromosphere as observed by the time-sequence of SOT/Ca?ii H line (3968 Å) images. The secondary, helically-twisted structure is found to be associated with the M8.9 flare event. The brightening starts six?–?seven minutes prior to the flare maximum with the appearance of a secondary, helically-twisted structure. The flare intensity maximizes as the secondary, helically-twisted structure moves away from the active region. This twisted flux tube, associated with the flare triggering, did not launch a CME. The location of the flare activity is found to coincide with the activation site of the helically-twisted structures. We conclude that the activation of successive helical twists (especially the second one) in the magnetic-flux tubes/ropes plays a crucial role in the energy build-up process and the triggering of the M-class solar flare without a coronal mass ejection (CME). 相似文献