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1.
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
2.
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
3.
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
4.
We analyze the relationship between the dynamics of the coronal mass ejection (CME) of 15 May 2001 and the energy release in the associated flare. The flare took place behind the east limb and was disclosed by a growing system of hot soft X-ray (SXR) loops that appeared from behind the limb around the onset of the rapid acceleration of the CME. The highly correlated behavior of the SXR light-curve derivative and the time profile of the CME acceleration reveals an intrinsic relationship between the CME dynamics and the flare energy release. Furthermore, we found that the CME acceleration peak occurs simultaneously with the fastest growth (100 km s-1) of X-ray loops, indicating that the reconnection plays an essential role in the eruption. Inspecting the CME/flare morphology we recognized in the Yohkoh-SXT images an oval feature that formed within the rising structure at the onset of the rapid acceleration phase, simultaneously with the appearance of the X-ray loops. The eruptive prominence was imbedded within the lower half of the oval, suggestive of a flux-rope/prominence magnetic configuration. We interpret the observed morphological evolution in terms of a reconnection process in the current sheet that presumably formed below the erupting flux-rope at the onset of the CME acceleration. Measurements of the tip-height of the cusped X-ray loop system and the height of the lower edge of the oval, enable us to trace the stretching of the current sheet. The initial distance between the oval and the loops amounted to 35 – 40 Mm. In about 1 h the inferred length of the current sheet increased to 150 – 200 Mm, which corresponds to a mean elongation speed of 35 – 45 km s-1. The results are discussed in the framework of CME models that include the magnetic reconnection below the erupting flux-rope. 相似文献
5.
A giant post-flare arch observed on 2-3 November 1991 was analyzed using the soft X-ray telescope (SXT) on board Yohkoh and the Mark III (MK3) K-coronameter at the High Altitude Observatory/Mauna Loa Solar Observatory. The rising arch was observed in both soft X-ray and K-corona observations. The estimated rising speed from the MK3 observation was approximately 4 km s-1. A V-shaped depression area was observed on the south side of the giant arch. Change in the K-corona observations was faint while the arch was rising. According to the solar wind observations by the Pioneer Venus Orbiter and the Interplanetary Cometary Explorer, this giant arch event may have been associated with an interplanetary shock. 相似文献
6.
The evolution of the soft X-ray and EUV coronal loops related to the April 15, 1998 solar flare–CME event is studied with multiwavelength observations including hard X-rays (BATSE), microwaves (NoRP, CNAO) and magnetograms (SOHO/MDI), as well as images from Yohkoh/SXT and SOHO/EIT at 195 Å. It is shown that: (1) two soft X-ray and EUV loops rose, crossed and turned bright, (2) near one footpoint of these loops, the background magnetic field decreased, (3) there were similar quasi periodic oscillations in the time profiles of hard X-ray and microwave emissions, which characterized the loop–loop coalescence instability, (4) after the loop–loop reconnection, two new loops formed, the small one stayed at the original place, and the large one ejected out as part of the constructed prominence cloud. Based upon these observations, we argue that the decrease of the background magnetic field near these loops caused them to rise and approach each other, and in turn, the fast loop–loop coalescence instability took place and triggered the flare and the CME. 相似文献
7.
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
8.
We study active region NOAA 9684 (N06L285) which produced an X1.0/3B flare on November 4, 2001 associated with a fast CME
(1810 km s−1) and the largest proton event (31 700 pfu) in cycle 23. SOHO/MDI continuum image data show that a large leading sunspot rotated
counter-clockwise around its umbral center for at least 4 days prior to the flare. Moreover, it is found from SOHO/MDI 96
m line-of-sight magnetograms that the systematic tilt angle of the bipolar active region, a proxy for writhe of magnetic fluxtubes,
changed from a positive value to a negative one. This signifies a counter-clockwise rotation of the spot-group as a whole.
Using vector magnetograms from Huairou Solar Observing Station (HSOS), we find that the twist of the active region magnetic
fields is dominantly left handed (αbest = −0.03), and that the vertical current and current helicity are predominantly negative, and mostly distributed within the
positive rotating sunspot. The active region exhibits a narrow inverse S-shaped Hα filament and soft X-ray sigmoid distributed along the magnetic neutral line. The portion of the filament which is most closely
associated with the rotating sunspot disappeared on November 4, and the corresponding portion of the sigmoid was observed
to erupt, producing the flare and initiating the fast CME and proton event. These results imply that the sunspot rotation
is a primary driver of helicity production and injection into the corona. We suggest that the observed active region dynamics
and subsequent filament and sigmoid eruption are driven by a kink instability which occurred due to a large amount of the
helicity injection. 相似文献
9.
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
10.
Hei 10830 Å spectroheliograms of a major 3N two-ribbon flare occurring in Boulder Region 3885/3886 early on 4 September, 1982 are discussed and compared with H and soft X-ray observations of the event. This flare, observed for more than 60 hr in Hei 10830, was associated with the eruption of a large filament in the active region complex, the formation of coronal holes, a long-duration soft X-ray event, and was the probable source of a earthward coronal mass ejection and the largest geomagnetic storm of this solar cycle. The results of this study suggest the Hei flare is a chromospheric manifestation of the X-ray coronal loop structures associated with flares.Visitor, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
11.
J. A. Vorpahl E. G. Gibson P. B. Landecker D. L. McKenzie J. H. Underwood 《Solar physics》1975,45(1):199-216
132 soft X-ray flare events have been observed with The Aerospace Corporation/Marshall Space Flight Center S-056 X-ray telescope that was part of the ATM complement of instruments aboard Skylab. Analyses of these data are reported in this paper. The observations are summarized and a detailed discussion of the X-ray flare structures is presented. The data indicated that soft X-rays emitted by a flare come primarily from an intense well-defined core surrounded by a region of fainter, more diffuse emission. Loop structures are found to constitute a fundamental characteristic of flare cores and arcades of loops are found to play a more important role in the flare phenomena than previously thought. Size distributions of these core features are presented and a classification scheme describing the brightest flare X-ray features is proposed. The data show no correlations between the size of core features and: (1) the peak X-ray intensity, as indicated by detectors on the SOLRAD satellite; (2) the rise time of the X-ray flare event, or (3) the presence of a nonthermal X-ray component. An analysis of flare evolution indicates evidence for preliminary heating and energy release prior to the main phase of the flare. Core features are found to be remarkably stable and retain their shape throughout a flare. Most changes in the overall configuration seem to be the result of the appearance, disappearance or change in brightness of individual features, rather than the restructuring or re-orientation of these features. Brief comparisons with several theories are presented. 相似文献
12.
Innes D.E. Inhester B. Srivastava N. Brekke P. Harrison R.A. Matthews S.A. Noëns J.C. Schmieder B. Thompson B.J. 《Solar physics》1999,186(1-2):337-361
The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the emergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the time of the flare. Yohkoh images, taken about 15 min later, show that this cavity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an H surge or small filament eruption occurs about 50 arc sec northwards along the limb from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected by hot loops near their bases. Both jets disappear within a few minutes of one another.Clear evidence of the CME first appeared in the Large Angle Spectrometric Coronagraph (LASCO) and EIT images 40 min after the flare and onset of the filament ejection. It seems to come from a region between the two X-ray jets. This leads to the speculation that magnetic field reconnection near one footpoint of a loop system triggers reconnection near its other footpoint. The loop system is destabilized and ultimately gives rise to the CME. This possibility is supported by magnetic field and H images taken when the active region was at disk center which show that the active region had a double bipole structure with dark H filaments between the bipoles. 相似文献
13.
It is well known that the oscillating MHD waves drive periodic variations in the magnetic field. But how the MHD waves can be triggered in the flaring loops is not yet well known. It seems to us that this problem should be connected with the physical processes occurring in the flare loop during a solar flare. A peculiar solar flare event at 04:00–04:51 UT on May 23, 1990 was observed simultaneously with time resolutions 1 s and 10 ms by Nanjing University Observatory and Beijing Normal University Observatory, which are about 1000 km apart, at 3.2 cm and 2 cm wavelengths, respectively. Two kinds of pulsations with quasi-periods 1.5 s and 40 s were found in radio bursts at the two short centimeter waves; however, the shorter quasi-periodic pulsations were superimposed upon the longer ones. From the data analysis of the above-mentioned quasi-periodic pulsations and associated phenomena in radio and soft X-ray emissions during this flare event published in Solar Geophysical Data (SGD), the authors suggest that the sudden increase in plasma pressure inside (or underlying) the flare kernel due to the upward moving chromospheric evaporated gas, which is caused by the explosive collision heating of strong non-thermal electrons injected downwards from the microwave burst source, plays the important role of triggering agents for MHD oscillations (fast magneto-acoustic mode and Alfvén mode) of the flare loop. These physical processes occurring in the flare loop during the impulsive phase of the solar flare may be used to account for the origin and observational characteristics of quasi-periodic pulsations in solar radio bursts at the two short centimeter wavelengths during the flare event of 1990 May 23. In addition, the average physical parameters N, T, B inside or underlying the flare kernel can be also evaluated. 相似文献
14.
We analyze hard and soft X-ray, microwave and meter wave radio, interplanetary particle, and optical data for the complex energetic solar event of 22 July 1972. The flare responsible for the observed phenomena most likely occurred 20° beyond the NW limb of the Sun, corresponding to an occultation height of 45 000 km. A group of type III radio bursts at meter wavelengths appeared to mark the impulsive phase of the flare, but no impulsive hard X-ray or microwave burst was observed. These impulsive-phase phenomena were apparently occulted by the solar disk as was the soft X-ray source that invariably accompanies an H flare. Nevertheless essentially all of the characteristic phenomena associated with second-stage acceleration in flares - type II radio burst, gradual second stage hard X-ray burst, meter wave flare continuum (FC II), extended microwave continuum, energetic electrons and ions in the interplanetary medium - were observed. The spectrum of the escaping electrons observed near Earth was approximately the same as that of the solar population and extended to well above 1 MeV.Our analysis of the data leads to the following results: (1) All characteristics are consistent with a hard X-ray source density n
i
108 cm–3 and magnetic field strength 10 G. (2) The second-stage acceleration was a physically distinct phenomenon which occurred for tens of minutes following the impulsive phase. (3) The acceleration occurred continuously throughout the event and was spatially widespread. (4) The accelerating agent was very likely the shock wave associated with the type II burst. (5) The emission mechanism for the meter-wave flare continuum source may have been plasma-wave conversion, rather than gyrosynchrotron emission. 相似文献
15.
M. J. Reiner K.-L. Klein M. Karlický K. Jiřička A. Klassen M. L. Kaiser J.-L. Bougeret 《Solar physics》2008,249(2):337-354
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
16.
An X17 class (GOES soft X-ray) two-ribbon solar flare on October 28, 2003 is analyzed in order to determine the relationship
between the timing of the impulsive phase of the flare and the magnetic shear change in the flaring region. EUV observations
made by the Transition Region and Coronal Explorer (TRACE) show a clear decrease in the shear of the flare footpoints during the flare. The shear change stopped in the middle
of the impulsive phase. The observations are interpreted in terms of the splitting of the sheared envelope field of the greatly
sheared core rope during the early phase of the flare. We have also investigated the temporal correlation between the EUV
emission from the brightenings observed by TRACE and the hard X-ray (HXR) emission (E > 150 keV) observed by the anticoincidence system (ACS) of the spectrometer SPI on board the ESA INTEGRAL satellite. The
correlation between these two emissions is very good, and the HXR sources (RHESSI) late in the flare are located within the
two EUV ribbons. These observations are favorable to the explanation that the EUV brightenings mainly result from direct bombardment
of the atmosphere by the energetic particles accelerated at the reconnection site, as does the HXR emission. However, if there
is a high temperature (T > 20 MK) HXR source close to the loop top, a contribution of thermal conduction to the EUV brightenings cannot be ruled out. 相似文献
17.
V. V. Grechnev A. M. Uralov V. A. Slemzin I. M. Chertok B. P. Filippov G. V. Rudenko M. Temmer 《Solar physics》2014,289(1):289-318
This is the first of four companion papers, which comprehensively analyze a complex eruptive event of 18 November 2003 in active region (AR) 10501 and the causes of the largest Solar Cycle 23 geomagnetic storm on 20 November 2003. Analysis of a complete data set, not considered before, reveals a chain of eruptions to which hard X-ray and microwave bursts responded. A filament in AR 10501 was not a passive part of a larger flux rope, as usually considered. The filament erupted and gave origin to a coronal mass ejection (CME). The chain of events was as follows: i) a presumable eruption at 07:29 UT accompanied by a not reported M1.2 class flare probably associated with the onset of a first southeastern CME (CME1), which most likely is not responsible for the superstorm; ii) a confined eruption (without a CME) at 07:41 UT (M3.2 flare) that destabilized the large filament; iii) the filament acceleration around 07:56 UT; iv) the bifurcation of the eruptive filament that transformed into a large “cloud”; v) an M3.9 flare in AR 10501 associated to this transformation. The transformation of the filament could be due to the interaction of the eruptive filament with the magnetic field in the neighborhood of a null point, located at a height of about 100 Mm above the complex formed by ARs 10501, 10503, and their environment. The CORONAS-F/SPIRIT telescope observed the cloud in 304 Å as a large Y-shaped darkening, which moved from the bifurcation region across the solar disk to the limb. The masses and kinematics of the cloud and the filament were similar. Remnants of the filament were not clearly observed in the second southwestern CME (CME2), previously regarded as a source of the 20 November geomagnetic storm. These facts do not support a simple scenario, in which the interplanetary magnetic cloud is considered as a flux rope formed from a structure initially associated with the pre-eruption filament in AR 10501. Observations suggest a possible additional eruption above the bifurcation region close to solar disk center between 08:07 and 08:17 UT, which could be the source of the 20 November superstorm. 相似文献
18.
We studied the M7.9 flare on April 9, 2001 that occurred within a δ-sunspot of active region NOAA 9415. We used a multi-wavelength
data set, which includes Yohkoh, TRACE, SOHO, and ACE spacecraft observations, Potsdam and Ondřejov radio data and Big Bear Solar Observatory (BBSO) images
in order to study the large-scale structure of this two-ribbon flare that was accompanied by a very fast coronal mass ejection
(CME). We analyzed light curves of the flare emission as well as the structure of the radio emission and report the following:
the timing of the event, i.e., the fact that the initial brightenings, associated with the core magnetic field, occurred earlier than the remote brightening
(RB), argue against the break-out model in the early phase of this event. We thus conclude that the M7.9 flare and the CME
were triggered by a tether-cutting reconnection deep in the core field connecting the δ-spot and this reconnection formed
an unstable flux rope. Further evolution of the erupted flux rope could be described either by the “standard“ flare model
or a break-out type of the reconnection. The complex structure of flare emission in visible, X-ray, and radio spectral ranges
point toward a scenario which involves multiple reconnection processes between extended closed magnetic structures. 相似文献
19.
Hudson Hugh S. Khan Josef I. Lemen James R. Nitta Nariaki V. Uchida Yutaka 《Solar physics》2003,212(1):121-149
Recent extreme ultraviolet (EUV) observations from SOHO have shown the common occurrence of flare-associated global coronal
waves strongly correlated with metric type II bursts, and in some cases with chromospheric Moreton waves. Until now, however,
few direct soft X-ray detections of related global coronal waves have been reported. We have studied Yohkoh Soft X-ray Telescope (SXT) imaging observations to understand this apparent discrepancy, and describe the problems in this
paper. We have found good X-ray evidence for a large-scale coronal wave associated with a major flare on 6 May 1998. The earliest
direct trace of the wave motion on 6 May consisted of an expanding volume within 20 Mm (projected) of the flare-core loops,
as established by loop motions and a dimming signature. Wavefront analyses of the soft X-ray observations point to this region
as the source of the wave, which began at the time of an early hard X-ray spike in the impulsive phase of the flare. The emission
can be seen out to a large radial distance (some 220 Mm from the flare core) by SXT, and a similar structure at a still greater
distance by EIT (the Extreme Ultraviolet Imaging Telescope) on SOHO. The radio dynamic spectra confirm that an associated
disturbance started at a relatively high density, consistent with the X-ray observations, prior to the metric type II burst
emission onset. The wavefront tilted away from the vertical as expected from refraction if the Alfvén speed increases with
height in the corona. From the X-ray observations we estimate that the electron temperature in the wave, at a distance of
120 Mm from the flare core, was on the order of 2–4 MK, consistent with a Mach number in the range 1.1–1.3.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022904125479
deceased 相似文献
20.
Pierre Kaufmann Gordon D. Holman Yang Su C. Guillermo Gimenez de?Castro Emilia Correia Luis O. T. Fernandes Rodney V. de Souza Adolfo Marun Pablo Pereyra 《Solar physics》2012,279(2):465-475
The GOES X28 flare of 4 November 2003 was the largest ever recorded in its class. It produced the first evidence for two spectrally separated emission components, one at microwaves and the other in the THz range of frequencies. We analyzed the pre-flare phase of this large flare, twenty?minutes before the onset of the major impulsive burst. This period is characterized by unusual activity in X-rays, sub-THz frequencies, H??, and microwaves. The CME onset occurred before the onset of the large burst by about 6?min. It was preceded by pulsations of 3??C?5?s periods at sub-THz frequencies together with X-ray and microwave enhancements. The sub-THz pulsations faded out as impulsive bursts were detected at 100??C?300?keV and 7?GHz, close to the time of the first H?? brightening and the CME onset. The activities detected prior to and at the CME onset were located nearly 2?arcmin south of the following large flare, suggesting they were separate events. This unusual activity brings new clues to understanding the complex energy buildup mechanisms prior to the CME onset, occurring at a distinct location and well before the major flare that exploded afterwards. 相似文献