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1.
We report on a coronal shock wave inferred from the metric type II burst of 13 January 1996. To identify the shock driver, we examined mass motions in the form of X-ray ejecta and white-light coronal mass ejections (CMEs). None of the ejections could be considered fast (> 400 km s–1) events. In white light, two CMEs occurred in quick succession, with the first one associated with X-ray ejecta near the solar surface. The second CME started at an unusually large height in the corona and carried a dark void in it. The first CME decelerated and stalled while the second one accelerated, both in the coronagraph field of view. We identify the X-ray ejecta to be the driver of the coronal shock inferred from metric type II burst. The shock speed reported in the Solar Geophysical Data (1000–2000 km s–1) seems to be extremely large compared to the speeds inferred from X-ray and white-light observations. We suggest that the MHD fast-mode speed in the inner corona could be low enough that the X-ray ejecta is supermagnetosonic and hence can drive a shock to produce the type II burst. 相似文献
2.
We present a statistical analysis of the relationship between the kinematics of the leading edge and the eruptive prominence
in coronal mass ejections (CMEs). We study the acceleration phase of 18 CMEs in which kinematics was measured from the pre-eruption
stage up to the post-acceleration phase. In all CMEs, the three part structure (the leading edge, the cavity, and the prominence)
was clearly recognizable from early stages of the eruption. The data show a distinct correlation between the duration of the
leading edge (LE) acceleration and eruptive prominence (EP) acceleration. In the majority of events (78%) the acceleration
phase onset of the LE is very closely synchronized (within ± 20 min) with the acceleration of EP. However, in two events the
LE acceleration started significantly earlier than the EP acceleration (> 50 min), and in two events the EP acceleration started
earlier than the LE acceleration (> 40 min). The average peak acceleration of LEs (281 m s−2) is about two times larger than the average peak acceleration of EPs (136 m s−2). For the first time, our results quantitatively demonstrate the level of synchronization of the acceleration phase of LE
and EP in a rather large sample of events, i.e., we quantify how often the eruption develops in a “self-similar” manner. 相似文献
3.
ICME Identification from Solar Wind Ion Measurements 总被引：1，自引：0，他引：1
Interplanetary coronal mass ejections (ICMEs), the interplanetary counterpart of coronal mass ejections (CMEs), are most commonly
identified by their enhanced magnetic field strengths and rotating magnetic field orientation. However, there are other frequent
signatures in the plasma. We use a pair of these signatures, a linearly decreasing plasma bulk velocity and a cool (< 20 km s−1) ion thermal speed, to identify candidate ICMEs. Many ICMEs, identified through their magnetic signatures, are also found
by their ion signatures alone. However, many are not. These missed ICMEs appear not to be expanding, even when they are accompanied
by leading shocks. The ICMEs with both the magnetic and ion signatures appear to be expanding as judged from either set of
observations. The most clearly defined ICMEs have transit times from the Sun and growth times to the observed size that are
equal. These ropes fit the paradigm of compact magnetic structures arising low in the corona and expanding uniformly in time,
as they travel at constant center of mass speed toward 1 AU. 相似文献
4.
P. Pappa Kalaivani S. Umapathy A. Shanmugaraju O. Prakash 《Astrophysics and Space Science》2010,330(2):237-242
We have studied the characteristics of coronal mass ejections (CMEs) associated with Deca-Hectometric (DH) type II radio bursts (1–14 MHz) in the interplanetary medium during the year 1997–2005. The DH CMEs are divided into two parts: (i) DH CMEs (All) and (ii) DH CMEs (Limb). We found that 65% (177/273) of all events have the speed >900 km?s?1 and the remaining 35% (96/273) events have the speed below 900 km?s?1. The average speed of all and limb DH CMEs are 1230 and 1288 km?s?1, respectively, which is nearly three times the average speed of general population of CMEs (473 km?s?1). The average widths of all and limb DH CMEs are 105° and 106°, respectively, which is twice the average width (52°) of the general population of CMEs. We found a better correlation between the speed and width of limb DH CMEs (R=?0.61) than all DH CMEs (R=?0.53). Only 28% (177/637) of fast >900 km?s?1 general population of CMEs are reported with DH type II bursts counterpart. The above results gives that the relation between the CME properties is better for limb events. 相似文献
5.
We study the solar sources of an intense geomagnetic storm of solar cycle 23 that occurred on 20 November 2003, based on ground- and space-based multiwavelength observations. The coronal mass ejections (CMEs) responsible for the above geomagnetic storm originated from the super-active region NOAA 10501. We investigate the H?? observations of the flare events made with a 15 cm solar tower telescope at ARIES, Nainital, India. The propagation characteristics of the CMEs have been derived from the three-dimensional images of the solar wind (i.e., density and speed) obtained from the interplanetary scintillation data, supplemented with other ground- and space-based measurements. The TRACE, SXI and H?? observations revealed two successive ejections (of speeds ???350 and ???100 km?s?1), originating from the same filament channel, which were associated with two high speed CMEs (???1223 and ???1660 km?s?1, respectively). These two ejections generated propagating fast shock waves (i.e., fast-drifting type II radio bursts) in the corona. The interaction of these CMEs along the Sun?CEarth line has led to the severity of the storm. According to our investigation, the interplanetary medium consisted of two merging magnetic clouds (MCs) that preserved their identity during their propagation. These magnetic clouds made the interplanetary magnetic field (IMF) southward for a long time, which reconnected with the geomagnetic field, resulting the super-storm (Dst peak=?472 nT) on the Earth. 相似文献
6.
Thompson B.J. Reynolds B. Aurass H. Gopalswamy N. Gurman J.B. Hudson H.S. Martin S.F. St. Cyr O.C. 《Solar physics》2000,193(1-2):161-180
We report coincident observations of coronal and chromospheric flare wave transients in association with a flare, large-scale coronal dimming, metric radio activity and a coronal mass ejection. The two separate eruptions occurring on 24 September 1997 originate in the same active region and display similar morphological features. The first wave transient was observed in EUV and H data, corresponding to a wave disturbance in both the chromosphere and the solar corona, ranging from 250 to approaching 1000 km s–1 at different times and locations along the wavefront. The sharp wavefront had a similar extent and location in both the EUV and H data. The data did not show clear evidence of a driver, however. Both events display a coronal EUV dimming which is typically used as an indicator of a coronal mass ejection in the inner corona. White-light coronagraph observations indicate that the first event was accompanied by an observable coronal mass ejection while the second event did not have clear evidence of a CME. Both eruptions were accompanied by metric type II radio bursts propagating at speeds in the range of 500–750 km s–1, and neither had accompanying interplanetary type II activity. The timing and location of the flare waves appear to indicate an origin with the flaring region, but several signatures associated with coronal mass ejections indicate that the development of the CME may occur in concert with the development of the flare wave. 相似文献
7.
R. Schwenn B. Inhester S. P. Plunkett A. Epple B. Podlipnik D. K. Bedford C. J. Eyles G. M. Simnett S. J. Tappin M. V. Bout P. L. Lamy A. Llebaria G. E. Brueckner K. P. Dere R. A. Howard M. J. Koomen C. M. Korendyke D. J. Michels J. D. Moses N. E. Moulton S. E. Paswaters D. G. Socker O. C. St. Cyr D. Wang 《Solar physics》1997,175(2):667-684
The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft
has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line
emission corona can be made visible throughout the instrument's full field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured
from Sun center). Quantitative evaluations based on calibrations cannot yet be performed, but some basic signatures show up
even now: (1) There are often bright and apparently closed loop systems centered at latitudes of 30° to 45° in both hemispheres.
Their helmet-like extensions are bent towards the equatorial plane. Farther out, they merge into one large equatorial ‘streamer
sheet’ clearly discernible out to 32 R⊙. (2) At mid latitudes a more diffuse pattern is usually visible, well separated from
the high-latitude loops and with very pronounced variability. (3) All high-latitude structures remain stable on time scales
of several days, and no signature of transient disruption of high-latitude streamers was observed in these early data. (4)
Within the first 4 months of observation, only one single ‘fast’ feature was observed moving outward at a speed of 70 km s-1 close to the equator. Faster events may have escaped attention because of data gaps. (5) The centers of high-latitude loops
are usually found at the positions of magnetic neutral lines in photospheric magnetograms. The large-scale streamer structure
follows the magnetic pattern fairly precisely. Based on our observations we conclude that the shape and stability of the heliospheric
current sheet at solar activity minimum are probably due to high-latitude streamers rather than to the near-equatorial activity
belt.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004948913883 相似文献
8.
S. T. Wu W. P. Guo M. D. Andrews G. E. Brueckner R. A. Howard M. J. Koomen C. M. Korendyke D. J. Michels J. D. Moses D. G. Socker K. P. Dere P. L. Lamy A. Llebaria M. V. Bout R. Schwenn G. M. Simnett D. K. Bedford C. J. Eyles 《Solar physics》1997,175(2):719-735
We present a qualitative and quantitative comparison of a single coronal mass ejection (CME) as observed by LASCO (July 28–29,
1996) with the results of a three-dimensional axisymmetric time-dependent magnetohydrodynamic model of a flux rope interacting
with a helmet streamer. The particular CME considered was selected based on the appearance of a distinct ‘tear-drop’ shape
visible in animations generated from both the data and the model.
The CME event begins with the brightening of a pre-existing coronal streamer which evolves into a ‘tear-drop’ shaped loop
followed by a Y-shaped structure. The brightening moves slowly outward with significant acceleration reaching velocities of
∼450 km s-1 at 30 R⊙.
The observed CME characteristics are compared with the model results. On the basis of this comparison, we suggested that the
observed features were caused by the evacuation of a flux rope in the closed field region of the helmet streamer (i.e., helmet
dome). The flux rope manifests itself as the cavity of the quasi-static helmet streamer and the whole system becomes unstable
when the flux rope reaches a threshold strength. The observed ‘tear-drop’ structure is due to the deformed flux rope. The
leading edge of the flux rope interacts with the helmet dome to form the typical loop-like CME. The trailing edge of this
flux rope interacts with the local bi-polar field to form the observed Y-shaped structure. The model results for the evolution
of the magnetic-field configurations, velocity, and polarization brightness are directly compared with observations.
Animations have been generated from both the actual data and the model to illustrate the good agreement between the observation
and the model. These animations can be found on the CD-ROM which accompanies this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004923016322 相似文献
9.
K. P. Dere G. E. Brueckner R. A. Howard M. J. Koomen C. M. Korendyke R. W. Kreplin D. J. Michels J. D. Moses N. E. Moulton D. G. Socker O. C. St. Cyr J. P. Delaboudinière G. E. Artzner J. Brunaud A. H. Gabriel J. F. Hochedez F. Millier X. Y. Song J. P. Chauvineau J. P. Marioge J. M. Defise C. Jamar P. Rochus R. C. Catura J. R. Lemen J. B. Gurman W. Neupert F. Clette P. Cugnon E. L. Van Dessel P. L. Lamy A. Llebaria R. Schwenn G. M. Simnett 《Solar physics》1997,175(2):601-612
We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations
with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of
prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated
to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at
a velocity of 200–400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in
the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the
LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning
as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated
with this event as well as a considerable degree of activity near the west limb. 相似文献
10.
R. M. MacQueen 《Solar physics》1993,145(1):169-188
We have measured the brightness and latitudinal extent of the depleted (cavity) region behind the leading edge of three coronal mass ejection (CME) events from the Skylab epoch. The events chosen are among those believed to be typical of non-impulsive, loop-like CMEs (Sime, MacQueen, and Hundhausen, 1984). The pre-event coronal brightness has been matched by a model corona, assuming both a background contribution and a contribution from a range of hypothetical streamer models, distinguished by differing longitudinal extent. Then, assuming that the cavities are voided regions in which the local electron density is negligible, we estimate their minimum line-of-sight extent and find them to be comparable to, or greater than, their measured latitudinal extent. As a result, we suggest this unambiguously demonstrates the three-dimensional nature of these — and likely, this class of — events. 相似文献
11.
In late October and early November 2003, a series of space weather hazard events erupted in solar-terrestrial space. Aiming
at two intense storm (shock) events on 28 and 29 October, this paper presents a Two-Step method, which combines synoptic analysis
of space weather–`observing’ and quantitative prediction – ‘palpating’, and uses it to test predictions. In the first step,
‘observing’, on the basis of observations of the source surface magnetic field, interplanetary scintillation (IPS) and ACE
spacecraft, we find that the propagation of the shock waves is asymmetric and northward relative to the normal direction of
their solar sources due to the large-scale configuration of the coronal magnetic fields, and the Earth is located near the
direction of the fastest speed and greatest energy of the shocks. Being two fast ejection shock events, the fast explosion
of extremely high temperature and strong magnetic field, and background solar wind velocity as high as 600 and 1000 km s−1, are also helpful to their rapid propagation. According to the synoptic analysis, the shock travel times can be estimated
as 21 and 20 h, which are close to the observational results of 19.97 and 19.63 h, respectively. In the second step, ‘palpating’,
we adopt a new membership function of the fast shock events for the ISF method. The predicted results here show that for the
onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8
and 6.7%, which are consistent with the estimated results of the first step; and for the magnetic disturbance magnitude, the
relative errors between the observational and the predicted results are 4.1 and 3.1%, respectively. Furthermore, the comparison
among the predicted results of our Two-Step method with those of five other prevailing methods shows that the Two-Step method
is advantageous in predicting such strong shock event. It can predict not only shock arrival time, but also the magnitude
of magnetic disturbance. The results of the present paper tell us that understanding the physical features of shock propagation
thoroughly is of great importance in improving the prediction efficiency. 相似文献
12.
We analyze five events of the interaction of coronal mass ejections (CMEs) with the remote coronal rays located up to 90°
away from the CME as observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2 images, we estimate the kink
propagation in the coronal rays during their interaction with the corresponding CMEs ranging from 180 to 920 km s−1 within the interval of radial distances from 3 R
⊙ to 6 R
⊙. We conclude that all studied events do not correspond to the expected pattern of shock wave propagation in the corona. Coronal
ray deflection can be interpreted as the influence of the magnetic field of a moving flux rope within the CME. The motion
of a large-scale flux rope away from the Sun creates changes in the structure of surrounding field lines, which are similar
to the kink propagation along coronal rays. The retardation of the potential should be taken into account since the flux rope
moves at a high speed, comparable with the Alfvén speed. 相似文献
13.
A. I. Poland R. A. Howard M. J. Koomen D. J. Michels N. R. Sheeley Jr. 《Solar physics》1981,69(1):169-175
The Naval Research Laboratory's most recent Earth-orbiting coronagraph, called Solwind, has been observing the Sun's outer corona (2.6–10.0 R
) at 10-min intervals since March 28, 1979. These observations provide the first comprehensive view of coronal transients near the peak of a sunspot cycle. Six, well-defined transients in our quick-look data have masses ranging from 7 × 1014 g to 2 × 1016 g and outward speeds ranging from 150 km s–1 to 900 km s–1. These values are comparable to the ones that were obtained with the OSO-7 and Skylab observations during the declining phase of the last sunspot cycle. Although the amount of quick-look data is not sufficient to provide meaningful statistics, the coronal transients near sunspot maximum seem to occur with a greater frequency and a wider latitude range than the transients during the declining phase of the cycle. In both eras, there is a good, but imperfect, association between the occurrence of coronal transients and surface phenomena such as eruptive prominences and flares.On leave from the High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colo. 80307, U.S.A. Now at Goddard Space Flight Center; Greenbelt, Md. 20771, U.S.A. 相似文献
14.
H. Xie O. C. St. Cyr N. Gopalswamy S. Yashiro J. Krall M. Kramar J. Davila 《Solar physics》2009,259(1-2):143-161
We have conducted a statistical study 27 coronal mass ejections (CMEs) from January 2007 – June 2008, using the stereoscopic views of STEREO SECCHI A and B combined with SOHO LASCO observations. A flux-rope model, in conjunction with 3D triangulations, has been used to reconstruct the 3D structures and determine the actual speeds of CMEs. The origin and the dynamic evolution of the CMEs are investigated using COR1, COR2 and EUVI images. We have identified four types of solar surface activities associated with CMEs: i) total eruptive prominence (totEP), ii) partially eruptive prominence (PEP), iii) X-ray flare, and iv) X-type magnetic structure (X-line). Among the 27 CMEs, 18.5% (5 of 27) are associated with totEPs, 29.6% (8 of 27) are associated with PEPs, 26% (7 of 27) are flare related, and 26% (7 of 27) are associated with X-line structures, and 43% (3 of 7) are associated with both X-line structures and PEPs. Three (11%) could not be associated with any detectable activity. The mean actual speeds for totEP-CMEs, PEP-CMEs, flare-CMEs, and X-line-CMEs are 404 km?s?1,247 km?s?1,909 km?s?1, and 276 km?s?1, respectively; the average mean values of edge-on and broadside widths for the 27 CMEs are 52 and 85 degrees, respectively. We found that slow CMEs (V≤400 km?s?1) tend to deflect towards and propagate along the streamer belts due to the deflections by the strong polar magnetic fields of corona holes, while some faster CMEs show opposite deflections away from the streamer belts. 相似文献
15.
Kinetic Properties of CMEs Corrected for the Projection Effect 总被引：2，自引：0，他引：2
Observations of coronal mass ejections (CMEs) with coronagraphs are subject to a projection effect, which results in statistical
errors in many properties of CMEs, such as the eruption speed and the angular width. In this paper, we develop a method to
obtain the velocity and angular width distributions of CMEs corrected for the projection effect, and then re-examine the relationship
between CMEs and the associated flares. We find that (1) the mean eruption speed is 792 km s−1 and the mean angular width is 59∘, compared to the values of 549 km s−1 and 77∘, respectively before the correction; (2) after the correction, the weak correlation between CME speeds and the GOES X-ray
peak flux of the flares gets unexpectedly poorer; and (3) before correction, there is a weak correlation between the angular
width and the speed of CMEs, whereas the correlation is absent after the correction. 相似文献
16.
We study the abundances of the elements He through Pb in Fe-rich impulsive solar energetic-particle (SEP) events with measurable abundances of ions with atomic number Z>2 observed on the Wind spacecraft, and their relationship with coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). On an average the element abundances in these events are similar to coronal abundances at low Z but, for heavier elements, enhancements rise as a power law in the mass-to-charge ratio A/Q of the ions (at coronal temperatures of 2.5?–?3 MK) to a factor of 3 at Ne, 9 at Fe, and 900 for 76≤Z≤82. Energy dependences of abundances are minimal in the 2?–?15 MeV amu?1 range. The 111 of these Fe-rich impulsive SEP events we found, between November 1994 and August 2013 using the Wind spacecraft, have a 69 % association rate with CMEs. The CMEs are narrow with a median width of 75°, are characteristically from western longitudes on the Sun, and have a median speed of ≈?600 km?s?1. Nearly all SEP onsets occur within 1.5?–?5 h of the CME onset. The faster (>?700 km?s?1), wider CMEs in our sample are related to SEPs with coronal abundances indicating hot coronal plasma with fully ionized He, C, N and O and moderate enhancements of heavier elements, relative to He, but slower (<?700 km?s?1), narrower CMEs emerge from cooler plasma where higher SEP mass-to-charge ratios, A/Q, yield much greater abundance enhancements, even for C/He and O/He. Apparently, the open magnetic-reconnection region where the impulsive SEPs are accelerated also provides the energy to drive out CME plasma, accounting for a strong, probably universal, impulsive SEP-CME association. 相似文献
17.
We have investigated the characteristics of magnetic cloud (MC) and ejecta (EJ) associated coronal mass ejections (CMEs) based on the assumption that all CMEs have a flux rope structure. For this, we used 54 CMEs and their interplanetary counterparts (interplanetary CMEs: ICMEs) that constitute the list of events used by the NASA/LWS Coordinated Data Analysis Workshop (CDAW) on CME flux ropes. We considered the location, angular width, and speed as well as the direction parameter, D. The direction parameter quantifies the degree of asymmetry of the CME shape in coronagraph images, and shows how closely the CME propagation is directed to Earth. For the 54 CDAW events, we found the following properties of the CMEs: i) the average value of D for the 23 MCs (0.62) is larger than that for the 31 EJs (0.49), which indicates that the MC-associated CMEs propagate more directly toward the Earth than the EJ-associated CMEs; ii) comparison between the direction parameter and the source location shows that the majority of the MC-associated CMEs are ejected along the radial direction, while many of the EJ-associated CMEs are ejected non-radially; iii) the mean speed of MC-associated CMEs (946 km?s?1) is faster than that of EJ-associated CMEs (771 km?s?1). For seven very fast CMEs (≥?1500 km?s?1), all CMEs with large D (≥?0.4) are associated with MCs and the CMEs with small D are associated with EJs. From the statistical analysis of CME parameters, we found the superiority of the direction parameter. Based on these results, we suggest that the CME trajectory essentially determines the observed ICME structure. 相似文献
18.
Brekke P. Kjeldseth-Moe O. Brynildsen N. Maltby P. Haugan S. V. H. Harrison R. A. Thompson W. T. Pike C. D. 《Solar physics》1997,170(1):163-177
EUV spectra obtained with the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) show significant flows of plasma in active region loops, both at coronal and transition region temperatures. Wavelength shifts in the coronal lines Mgix 368 Å and Mgx 624 Å corresponding to upflows in the plasma reaching velocities of 50 km s-1 have been observed in an active region. Smaller velocities are detected in the coronal lines Fexvi 360 Å and Sixii 520 Å. Flows reaching 100 km s-1 are observed in spectral lines formed at transition region temperatures, i.e., Ov 629 Å and Oiii 599 Å, demonstrating that both the transition region and the corona are clearly dynamic in nature. Some high velocity events show even higher velocities with line profiles corresponding to a velocity dispersion of 300–400 km s-1. Even in the quiet Sun there are velocity fluctuations of 20 km s-1 in transition region lines. Velocities of the magnitude presented in this paper have never previously been observed in coronal lines except in explosive events and flares. Thus, the preliminary results from the CDS spectrometer promise to put constraints on existing models of the flows and energy balance in the solar atmosphere. The present results are compared to previous attempts to observe flows in the corona. 相似文献
19.
The solar magnetic field maps every point in the corona to a corresponding place on the solar surface. Identifying the magnetic
connection map is difficult at low latitudes near the heliospheric current sheet, but remarkably simple in coronal hole interiors.
We present a simple analytic magnetic model (‘pseudocurrent extrapolation’) that reproduces the global structure of the corona,
with significant physical advantages over other nearly analytic models such as source-surface potential field extrapolation.
We use the model to demonstrate that local horizontal structure is preserved across altitude in the central portions of solar
coronal holes, up to at least 30 Rs, in agreement with observations. We argue that the preserved horizontal structure may be used to track the magnetic footpoint
associated with the location of a hypothetical spacecraft traveling through the solar corona, to relate in situ measurements of the young solar wind at ∼10–30 Rs to particular source regions at the solar surface. Further, we discuss the relationship between readily observable geometrical
distortions and physical parameters of interest such as the field-aligned current density. 相似文献
20.
Richard A. Harrison 《Solar physics》1997,175(2):467-485
A search for microflare activity in the extreme ultraviolet (EUV) quiet Sun using the Coronal Diagnostic Spectrometer (CDS)
aboard the Solar and Heliospheric Observatory (SOHO) spacecraft has not resulted in the identification of microflare activity,
but has resulted in the identification of a hitherto unknown phenomenon: enhancements of a factor of 2–3 in the flux of transition
region lines at network junctions. A total of some 6 hours of observation of 5 different target areas showed this ‘blinker’
activity at each area, with durations ranging from 1 to 30 min and averaging 13 min, and thermal energy content of order 10-6 that of a ‘standard’ flare. Assuming that the observations are of typical quiet Sun, and projecting these data to predict
a distribution of these events over the entire Sun, the total thermal energy content of these ‘blinkers’ is insignificant
when compared to the energy required to heat the corona. The nature of these events and their significance are discussed in
this paper. 相似文献