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

2.
A multi-wavelength spatial and temporal analysis of solar high-energy electrons is conducted using the August 20, 2002 flare of an unusually flat (γ1 = 1.8) hard X-ray spectrum. The flare is studied using RHESSI, Hα, radio, TRACE, and MDI observations with advanced methods and techniques never previously applied in the solar flare context. A new method to account for X-ray Compton backscattering in the photosphere (photospheric albedo) has been used to deduce the primary X-ray flare spectra. The mean electron flux distribution has been analysed using both forward fitting and model-independent inversion methods of spectral analysis. We show that the contribution of the photospheric albedo to the photon spectrum modifies the calculated mean electron flux distribution, mainly at energies below ∼100 keV. The positions of the Hα emission and hard X-ray sources with respect to the current-free extrapolation of the MDI photospheric magnetic field and the characteristics of the radio emission provide evidence of the closed geometry of the magnetic field structure and the flare process in low altitude magnetic loops. In agreement with the predictions of some solar flare models, the hard X-ray sources are located on the external edges of the Hα emission and show chromospheric plasma heated by the non-thermal electrons. The fast changes of Hα intensities are located not only inside the hard X-ray sources, as expected if they are the signatures of the chromospheric response to the electron bombardment, but also away from them.  相似文献   

3.
Magnetic field structures of Hα flares associated with meter-wave type III bursts during periods of low solar activity in 1975 – 1977 and 1985 – 1987 were investigated. In a statistical analysis it was confirmed that the association rate depends less on flare importance than on brightness. For subflares (95% of the sample), the location of the Hα flare in the bipolar pattern turned out to be crucial for the association rate. It is almost one order of magnitude larger for flares occurring at the border of the active regions, compared to flares located inside the general bipolar pattern. For selected typical examples of flares, extrapolations of the measured magnetic fields were performed. By matching Hα filtergrams and calculated 3-D structures it was found that the positions at the border where the flares associated with type III bursts occurred were close to open field lines extending into the corona. In most investigated cases intrusions of parasitic polarity were found in the vicinity of the flare locations. The extrapolations showed that subflares located inside the bipolar pattern but have not been associated with type III bursts were covered by dense arcades of magnetic loops.  相似文献   

4.
We suggest to identify the elementary flare bursts with the excitation of the small kernels that occur in flare loops that are observed in soft X-ray pictures of flares. We stress the need of simultaneous observations of spatial structure and time variations of hard X-ray bursts sources in various wavelength regions.  相似文献   

5.
Solar flare sympathy is the triggering of a flare in one active region by a flare in another. Statistical tests for flare sympathy have returned varying results. However, existing tests have relied on flaring rates in active regions being constant in time, or else have attempted to model the rate variation, which is a difficult task. A simple test is described which is independent of flaring rates. The test generalizes the approach of L. Fritzová-Švestkova, R.C. Chase, and Z. Švestka [Solar Phys. 48, 275, 1976], and examines the distribution of flare coincidences in pairs of active regions as a function of coincidence interval τ. The test is applied to available soft X-ray and Hα flare event listings. The soft X-ray events exhibit a deficit of flare coincidences for τ≤;20 min, which is most likely due to an event-selection effect whereby the increased soft X-ray emission due to one flare prevents a second flare being identified. The Hα events show an excess of flare coincidences for τ≤; 10 min, suggesting flare sympathy. The number of Hα event pairs occurring within 10 min of one another is higher than that expected on the basis of random coincidence by a fraction 0.12± 0.02. Nearby active regions (spatial separation <50˚) show a greater excess of coincidences for τ≤; 10 min than do active regions which are far apart (spatial separation ≥50˚). However, the active regions which are far apart still show some evidence for an excess of coincidences at very short coincidence intervals (τ≤; 2 min), which appears to exclude the possibility of a coronal disturbance propagating from one region to another.  相似文献   

6.
The “Fast X-ray Monitor” (BRM) instrument operated in the complex of the scientific instruments onboard the CORONAS-PHOTON satellite from February 19, 2009, until December 1, 2009. The instrument is intended for the registration of the hard X-ray radiation of solar flares in the 20–600 keV energy range in six differential energy channels (20–30, 30–40, 40–50, 50–70, 70–130, and 130–600 keV) with temporal resolution to 1 ms. In the instrument, a detector based on the YAP: Ce scintillator is used; this detector is 70 mm in diameter and 10 mm thick (the decay time is about 28 ns). For the decrease of the back-ground charge of the detector, the collimator limiting the angle of view of the instrument of value 12° is mounted over the scintillator. The effective area of the detector amounts to 27.7 cm2 (at the X-ray radiation energy 80 keV), and the dead time of the detector is 1 μs. Over the operation onboard the CORONAS-PHOTON satellite, the BRM instrument has registered gamma ray burst series and, perhaps, one solar flare of the class C1.3 on October 26, 2009.  相似文献   

7.
Designing a statistical solar flare forecasting technique can benefit greatly from knowledge of the flare frequency of occurrence with respect to sunspot groups. This study analyzed sunspot groups and Hα and X-ray flares reported for the period 1997 – 2007. Annual catalogs were constructed, listing the days that numbered sunspot groups were observed (designated sunspot group-days, SSG-Ds) and for each day a record for each associated Hα flare of importance category one or greater and normal or bright brightness and for each X-ray flare of intensity C 5 or higher. The catalogs were then analyzed to produce frequency distributions of SSG-Ds by year, sunspot group class, likelihood of producing at least one flare overall and by sunspot group class, and frequency of occurrence of numbers of flares per day and flare intensity category. Only 3% of SSG-Ds produced a substantial Hα flare and 7% had a significant X-ray flare. We found that mature, complex sunspot groups were more likely than simple sunspot groups to produce a flare, but the latter were more prevalent than the former. More than half of the SSG-Ds with flares had a maximum intensity flare greater than the lowest category (C-class of intensity five and higher). The fact that certain sunspot group classes had flaring probabilities significantly higher than the combined probabilities of the intensity categories when all SSG-Ds were considered suggest that it might be best to first predict the flaring probability. For sunspot groups found likely to flare, a separate diagnosis of maximum flare intensity category appears feasible.  相似文献   

8.
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   

9.
Kaufmann  P.  Trottet  G.  Giménez de Castro  C.G.  Costa  J.E.R.  Raulin  J.-P.  Schwartz  R.A.  Magun  A. 《Solar physics》2000,197(2):361-374
We present an analysis of the time profiles detected during a solar impulsive flare, observed at one-millimeter radio frequency (48 GHz) and in three hard X-ray energy bands (25–62, 62–111, and 111–325 keV) with high sensitivity and time resolution. The time profiles of all emissions exhibit fast time structures of 200–300 ms half power duration which appear in excess of a slower component varying on a typical time scale of 10 s. The amplitudes of both the slow and fast variations observed at 48 GHz are not proportional to those measured in the three hard X-ray energy bands. However, the fast time structures detected in both domains are well correlated and occur simultaneously within 64 ms, the time resolution of the hard X-ray data. In the context of a time-of-flight flare model, our results put strong constraints on the acceleration time scales of electrons to MeV energies.  相似文献   

10.
The results of observations of solar decametric drift pair bursts are presented. These observations were carried out during a Type III burst storm on July 11–21, 2002, with the decameter radio telescope UTR-2, equipped with new back-end facilities. High time and frequency resolution of the back-end allowed us to obtain new information about the structure and properties of these bursts. The statistical analysis of more than 700 bursts observed on 13–15 July was performed separately for “forward” and “reverse” drift pair bursts. Such an extensive amount of these kind of bursts has never been processed before. It should be pointed out that “forward” and “reverse” drift pair bursts have a set of similar parameters, such as time delay between the burst elements, duration of an element, and instant bandwidth of an element. Nevertheless some of their parameters are different. So, the absolute average value of frequency drift rate for “forward” bursts is 0.8 MHz s−1, while for “reverse” ones it is 2 MHz s−1. The obtained functional dependencies “drift rate vs. frequency” and “flux density vs. frequency” were found to be different from the current knowledge. We also report about the observation of unusual variants of drift pairs, in particular, of “hook” bursts and bursts with fine time and frequency structure. A possible mechanism of drift pairs generation is proposed, according to which this emission may originate from the interaction of Langmuir waves with the magnetosonic waves having equal phase and group velocities.  相似文献   

11.
Time series of daily numbers of solar Hα flares from 1955 to 1997 are studied by means of wavelet power spectra with regard to predominant periods in the range of ∼ 24 days (synodic). A 24-day period was first reported by Bai (1987) for the occurrence rate of hard X-ray flares during 1980–1985. Considering the northern and southern hemisphere separately, we find that the 24-day period is not an isolated phenomenon but occurs in each of the four solar cycles investigated (No. 19–22). The 24-day period can be established also in the occurrence rate of subflares but occurs more prominently in major flares (importance classes ≥ 1). A comparative analysis of magnetically classified active regions subdivided into magnetically complex (i.e., including a γ and/or δ configuration) and non-complex (α, β) reveals a significant relation between the appearance of the 24-day period in Hα flares and magnetically complex sunspot groups, whereas it cannot be established for non-complex groups. It is suggested that the 24-day period in solar flare occurrence is related to a periodic emergence of new magnetic flux rather than to the surface rotation of sunspots.  相似文献   

12.
Previous observations show that in many solar flares there is a causal correlation between the hard X-ray flux and the derivative of the soft X-ray flux. This so-called Neupert effect is indicative of a strong link between the primary energy release to accelerate particles and plasma heating. It suggests a flare model in which the hard X-rays are electron – ion bremsstrahlung produced by energetic electrons as they lose their energy in the lower corona and chromosphere and the soft X-rays are thermal bremsstrahlung from the “chromospheric evaporation” plasma heated by those same electrons. Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observes in a broad energy band and its high spectral resolution and coverage of the low-energy range allow us to separate the thermal continuum from the nonthermal component, which gives us an opportunity to investigate the Neupert effect. In this paper, we use the parameters derived from RHESSI observations to trace the primary energy release and the plasma response: The hard X-ray flux or spectral hardness is compared with the derivative of plasma thermal energy in three impulsive flares on 10 November 2002 and on 3 and 25 August 2005. High correlations show that the Neupert effect does hold for the two hard X-ray peaks of the 10 November 2002 flare, for the first peaks of the 3 August 2005 flare, and for the beginning period of the 25 August 2005 flare.  相似文献   

13.
The multi-wavelength analysis is performed on a flare on September 9, 2002 with data of Owens Valley Solar Arrays (OVSA), Big Bear Solar Observatory (BBSO), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and Extreme UV Imager Telescope (EIT), and The Michelson Doppler Imager (MDI) on board of the Solar and Heliospheric Observatory (SOHO). The radio sources at 4.8 and 6.2 GHz located in the intersection of two flaring loops at 195 of SOHO/EIT respectively with two dipole magnetic fields of SOHO/MDI, in which one EIT loop was coincident with an X-ray loop of RHESSI at 12–25 keV, and two Hαbright kernels a1 and a2 of BBSO, respectively at the two footpoints of this loop; the second EIT loop connected another two Hαkernels b1 and b2 and radio sources at 7.8 and 8.2 GHz of OVSA. The maximum phase of microwave bursts was evidently later than that of hard X-ray bursts and Hαkernels a1 and a2, but consistent with that of Hαkernels b1 and b2. Moreover, the flare may be triggered by the interaction of the two flaring loops, which is suggested by the cross-correlation of radio, optical, and X-ray light curves of a common quasi-periodic oscillation in the rising phase, as well as two peaks at about 7 and 9 GHz of the microwave spectra at the peak times of the oscillation, while the bi-directional time delays at two reversal frequencies respectively at 7.8 and 9.4 GHz (similar to the peak frequencies of the microwave spectra) may indicate two reconnection sites at different coronal levels. The microwave and hard X-ray footpoint sources located in different EUV and optical loops may be explained by different magnetic field strength and the pitch angle distribution of nonthermal electrons in these two loops.  相似文献   

14.
X-ray images taken by the Hard X-Ray Imaging Spectrometer (HXIS) aboard SMM during the 1980, November 18 limb flare are analysed. The temporal and spatial evolutions of the X-radiation are described. They differ significantly for hard and soft X-rays. During the elementary flare bursts energetic photons are predominantly emitted from a region close to the solar limb. In contrast, the soft X-ray sources are situated higher in the solar atmosphere. The observed X-ray spectra, in particular those emitted from small source regions at various altitudes, were fitted to power laws. Analysis of the spatial variation of the spectral index shows that there is a systematic tendency of the spectra to get harder with decreasing source altitude, especially during the elementary flare bursts. This fact is in agreement with the existence of nonthermal electron beams precipitating from the corona towards the denser layers of the solar atmosphere.  相似文献   

15.
A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring flux tubes. We conclude that “tether cutting” reconnection in the sheared arcade progressively transforms it to a twisted flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure and neighboring magnetic fields. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   

16.
H. Li  J. You  Q. Du 《Solar physics》2006,235(1-2):107-123
We present our results of high temporal resolution spectroscopic observation and study in Hα, Ca II, and He I lines for the 2B/M1.9 confined disk flare on September 9, 2001, combining with GOES soft X-ray (SXR) and Yohkoh hard X-ray (HXR) observations. Apparent redshifted and red-asymmetric profiles were observed in the initial phase. The redshift lasted until the late phase. The derived velocity depends on both the spectral line and the used method. The redshift velocities computed from the line centers of the observed emission profiles (υ0) are of the order of 10 km s−1 both inside and outside the streak area. However, the velocities determined from the excess profiles by the bisector method (υ) are larger in the streak (18–50 km s−1). Both υ and the red full widths (RFWs) derived from the excess profiles show temporal variations similar to the HXR light-curve in the streak area. Moreover, the Hα line wings of nonthermal characteristics, the redshift velocities, and the lifetime of impulsive broadening suggest that the streak is related to nonthermal electron bombardment. Spectral simulations reveal that we cannot reproduce the observed profiles in the three lines simultaneously with a set of parameters, indicating that the flare atmosphere was not homogeneous along the line-of-sight. Most of the observed Hα profiles showed a ‘flat-top’ structure, implying the flare plasma was optically thick for this line. The electron temperatures (Te) deduced from the line-center intensity of the three lines are similar and estimated to be higher than 7200 K. The obvious central reversal of the Hα profiles due to absorption of materials in the impulsive phase lasted more than 2 min. However, the far blue wings of the Ca II profiles in the impulsive phase showed low-intensity emission, which is suggestive of the existence of large turbulence or macroscopic motion (> 50 km s−1), which is inconsistent with the current flare model.  相似文献   

17.
Observations of emission in the Mgi b2 line at 5172 Å are presented for 13 flares. Also discussed are 3 flares which occurred in regions under observation but which showed no Mg emission. The Mg flare kernels resemble white-light flare kernels in their general morphology and location. Comparison of Mg filtergrams with magnetograms indicates that the Mg kernels occur at the feet of magnetic arches across neutral lines. Time-lapse Mg filtergram films indicate photospheric shearing motions near flare sites for several hours before flare onset. We have compared flare Mg emission with microwave and both hard and soft X-ray flare emissions. Examination at the time development of the 1981, July 27 flare shows that the microwave and X-ray bursts may be clearly related to the appearance of successive Mg flare kernels. We have also compared subjective, relative Mg flare importances with other flare emission measurements. For the full sample of flares, Mg importance is significantly correlated with hard and soft X-ray emission peaks, with X-ray ‘hardness’ (ratio of hard to soft peaks) and with the rise slope of soft X-ray bursts. The Mg importance does not correlate with the microwave peaks when the full sample of flares is used, but for the subset showing Mg emission there is significant correlation. No correlation with Hα importance was found. Our results suggest that Mg emission is associated with an impulsive component which may be absent from some flares. The San Fernando Observatory magnesium etalon filter system is described.  相似文献   

18.
A flare rising from behind the solar limb was recorded simultaneously by the UCSD X-ray detector on OSO-III (7.7–200 keV) and the Caltech photoheliograph on Robinson Laboratory roof (Hα). The de-occultation gives excellent spatial resolution of the X-ray source. Spectra suggest that the material was already heated to 27 000 000° and that the increase in flux was due to the de-occultation. The flux rise to maximum was proportional to the apparent area. The uniformity of this rise shows that there was no special kernel of emission. Comparison of the deduced volume with the bremsstrahlung formula gives a density of about 1010 for the 27 000 000° component of the flare; this is confirmed by consideration of the maximum possible coulomb braking. The actual decay is more likely by escape rather than coulomb braking.  相似文献   

19.
Spectral observations of the flare star EV Lac made on the 2.6-m telescope at the Byurakan Observatory in 2000–2002 are reported. A powerful flare was detected and it was possible to follow the variation in the equivalent widths of the Hα and Hβ lines, both during the flare and during the quiescent phase of the star. It is shown that the profiles and equivalent widths of the lines underwent substantial changes. The equivalent widths of these emission lines reached a maximum roughly 40 min after the flare maximum. __________ Translated from Astrofizika, Vol. 49, No. 4, pp. 573–583 (November 2006).  相似文献   

20.
A well-developed multiple impulsive microwave burst occurred on February 17, 1979 simultaneously with a hard X-ray burst and a large group of type III bursts at metric wavelengths. The whole event is composed of several subgroups of elementary spike bursts. Detailed comparisons between these three classes of emissions with high time resolution of 0.5 s reveal that individual type III bursts coincide in time with corresponding elementary X-ray and microwave spike bursts. It suggests that a non-thermal electron pulse generating a type III spike burst is produced simultaneously with those responsible for the corresponding hard X-ray and microwave spike bursts. The rise and decay characteristic time scales of the elementary spike burst are 1 s, 1 s and 3 s for type III, hard X-ray and microwave emissions respectively. Radio interferometric observations made at 17 GHz reveal that the spatial structure varies from one subgroup to others while it remains unchanged in a subgroup. Spectral evolution of the microwave burst seems to be closely related to the spatial evolution. The spatial evolution together with the spectral evolution suggests that the electron-accelerating region shifts to a different location after it stays at one location for several tens of seconds, duration of a subgroup of elementary spike bursts. We discuss several requirements for a model of the impulsive burst which come out from these observational results, and propose a migrating double-source model.  相似文献   

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