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1.
We present observations of the solar flare on 1980 June 27, 16:14–16:33 UT, which was observed by a balloon-borne 300 cm2 phoswich hard X-ray detector and by the IKARUS radio spectrometer. This flare shows intense hard X-ray (HXR) emission and an extreme productivity of (at least 754) type III bursts at 200–400 MHz. A linear correlation was found between the type III burst rate and the HXR fluence, with a coefficient of 7.6 × 1027 photons keV–1 per type III burst at 20 keV. The occurrence of 10 type III bursts per second, and also the even higher rate of millisecond spikes, suggests a high degree of fragmentation in the acceleration region. This high quantization of injected beams, assuming the thick-target model, shows up in a linear relationship between hard X-ray fluence and the type III rate, but not as fine structures in the HXR time profile.The generation of a superhot isothermal HXR component in the decay phase of the flare coincides with the fade-out of type III production.Universities Space Research Associates.ST Systems Corporation.  相似文献   

2.
On 23 May 1967 energetic (10–50 keV) solar flare X-rays were observed by the OGO-III ion chamber during the period 1808–2100 UT. The time-intensity profile for the X-ray event showed three distinct peaks at 1810, 1841 and 1942 UT. The second peak, which is equivalent to 2.9 × 10–3 ergs cm–2sec–1 above 20 keV, is the largest X-ray burst observed so far by the OGO-I and OGO-III ion chambers. The soft (2–12 Å) X-ray observations reported by Van Allen (1968) also show similar peaks, roughly proportional in magnitude to the energetic X-ray peaks. However, the intensity of energetic X-rays peaked in each case 5–10 min earlier than the soft X-ray intensity indicating a relatively hard photon energy spectrum near the peak of the energetic X-ray emission. The corresponding time-intensity profile for the solar radio emission also showed three peaks in the microwave region nearly coincident with the energetic X-ray peaks. The third radio peak was relatively rich in the metric emission. Beyond this peak both the energetic X-rays and the microwave emission decayed with a time constant of 8 min while the corresponding time constant for the soft X-rays was 43 min. In view of the earlier findings about the energetic X-rays it is indicated that the 23 May solar X-ray event was similar to those observed earlier. During the 23 May event the integral energy flux spectrum at the time of peak intensity is found to be consistent with the form e –E/E 0, E 0 being about 3.4 and 3.7 keV for the peaks at 1841 and 1942 UT, respectively. Assumption of a similar spectrum during the decay phase indicates that the spectral index E 0 decreased nearly exponentially with time.The OGO-III ion chamber, which is also sensitive to protons 12 MeV, observed a solar particle event starting at 2100 UT on 23 May. It could not be determined uniquely which of the two principal X-ray peaks was associated with the particle event, and in fact both may have contributed. The particle intensity reached its maximum value at 1003 UT on 25 May 1967. The equivalent peak radiation dosage was 24 R/hour behind the 0.22 g cm–2 thick aluminum wall of the chamber. This peak radiation dosage was considerably smaller than the maximum dosage (60 R/hour) during the 2 September 1966 solar particle event, the largest event observed so far by the OGO-I and OGO-III satellites. The temporal relationship between the solar X-ray and particle events on 23 May 1967 was similar to that observed in the solar flare events on 7 July 1966, 28 August 1966 and 27 February 1967.  相似文献   

3.
We have developed expressions which give the effective color temperatures and corresponding emission measures for solar X-ray events observed with instruments onboard any of the GOES satellites. Since 1976, these satellites have been used to monitor continuously the full-Sun X-ray emission in two broadband wavelength intervals (approximately 0.5–4 Å and 1–8 Å) with a time resolution of 3 s. To simulate the solar X-ray input at a variety of plasma temperatures, we used theoretical spectra provided by D. L. McKenzie. These spectra were folded through the wavelength dependent transfer functions for the two GOES detectors as given by Donnelly et al. (1977). The resulting detector responses and their ratio as a function of plasma temperature were then fit with simple analytic curves. Over the entire range between 5 and 30 million degrees, these fits reproduce the calculated color temperatures within 2% and the calculated emission measures within 5%. With the theoretical spectra provided by McKenzie, we can determine similar expressions for any pair of broadband X-ray detectors whose sensitivities are limited to wavelengths between 0.2 and 100 Å.  相似文献   

4.
Spectroheliograms of resolution about 2 arc sec obtained simultaneously in He 10830 Å and H show in the network a very close agreement in position of dark H mottles and of bright H plage remnants with 10830 Å absorption, though there is not a one-to-one relation between the intensities; the typical intensity in 10830 Å, corrected for overlapping lines, is I 0.91 of the continuum. Some parts of the network do not appear in 10830 Å. This line is much weaker over supergranule centres (I 0.98), though near active regions dark H fibrils coincide with faint 10830 Å fibrils (I0.93–0.98).Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

5.
An experiment has been performed to search for the existence of a flux of solar neutrons at the earth using a detector sensitive to neutrons in the energy region 20–120 MeV. The instrument was carried by balloon to an atmospheric depth of 4 g/cm2, from Palestine, Texas on the morning of November 2, 1967 and flown through sunrise and for about 7 hours into the day. Numerous flares of importance 1B or less occurred during the float period. By comparison of night and day counting rates we have deduced that the upper limit to the continuous emission of solar neutrons at the earth is 2 × 10–2 neutrons/cm2 sec in the above energy region. Using a theoretical form for the neutron differential energy spectrum we have expressed this result as an upper limit differential solar neutron flux. If neutrons were emitted in association with any of the small flares then the maximum flux at the earth was less than 4 × 10–2 neutron/cm2 sec in the same energy region. The minimum detectable flux with the present instrument is therefore well below the predicted flux from a 3B flare (e.g., Nov. 12, 1960) of 550 neutrons/cm2 sec.  相似文献   

6.
The profiles of six photospheric absorption spectral lines (Fei 5250 Å, Fei 5324 Å, Fei 5576 Å, Cai 5590 Å, Cai 6103 Å and Fei 6165 Å), measured in the kernel of a 2N solar flare and in a quiet-Sun area, were compared. The observations were carried out with an echelle spectrograph of the Crimean Astrophysical Observatory. It was shown that, compared to the quiet-Sun profiles, the flare profiles are shallower in the line core and are less steep in the wings. Therefore, measurements of the longitudinal magnetic field made with a magnetograph system which uses the Cai 6103 Å  spectral line, can be underestimated by 18–25% in areas of bright H ribbons of a moderate solar flare. Modeling of the solar photosphere performed by using a synthesis method showed that, in a solar flare, the enhanced core emission seems to be related to heating of the photosphere by the flare, whereas the decrease of the slope of the wings was presumably caused by the inhomogeneity of the photospheric magnetic field.  相似文献   

7.
We report on observations of a large eruptive event associated with a flare that occurred on 27 September 1998 made with the Richard B. Dunn Solar Telescope at Sacramento Peak Observatory (several wave bands including off-line-center H), in soft and hard X-rays (GOES and BATSE), and in several TRACE wave bands (including Feix/x 171 Å, Fexii 195 Å, and Civ 1550 Å). The flare initiation is signaled by two H foot-point brightenings which are closely followed by a hard X-ray burst and a subsequent gradual increase in other wavelengths. The flare light curves show a complicated, three-component structure which includes two minor maxima before the main GOES class C5.2 peak after which there is a characteristic exponential decline. During the initial stages, a large spray event is observed within seconds of the hard X-ray burst which can be directly associated with a two-ribbon flare in H. The emission returns to pre-flare levels after about 35 min, by which time a set of bright post-flare loops have begun to form at temperatures of about 1.0–1.5 MK. Part of the flare plasma also intrudes into the penumbra of a large sunspot, generally a characteristic of very powerful flares, but the flare importance in GOES soft X-rays is in fact relatively modest. Much of the energy appears to be in the form of a second ejection which is observed in optical and ultraviolet bands, traveling out via several magnetic flux tubes from the main flare site (about 60° from Sun center) to beyond the limb.  相似文献   

8.
The H observations of a limb flare, which were associated with exceptional gamma-ray and hard X-ray emission, are presented and discussed. The good spatial and temporal resolution of the H data allow us to investigate the detailed structure of the elevated flare loops and the intensity variations of the loops, footpoints and surrounding chromosphere during each phase of the flare event. A delay time of 12 s was found between at least one of the hard X-ray (28–485 keV) peaks and corresponding H intensity maximum at a loop footpoint. A comparison is made between this event and another well-observed limb flare with many similar characteristics to seek evidence for the large difference in their levels of energy release.  相似文献   

9.
Broadband sensors aboard the Naval Research Laboratory's SOLRAD 11 satellites measured solar emission in the 0.5 to 3 Å, 1 to 8 Å, 8 to 20 Å, 100 to 500 Å, 500 to 800 Å, and 700 to 1030 Å bands between March 1976 and October 1979. Measurements of EUV and soft X-ray emission from a large number of solar flares were obtained. Although solar flare measurements in the soft X-ray bands are continuously made and used as a standard of a flare's geophysical significance, direct measurements of flare EUV emission are quite rare. We present measurements of the X-ray and EUV emission from several flares with special emphasis on the relative EUV response associated with flares in different categories determined by 1 to 8 Å soft X-ray flux. An example of a flare exhibiting an impulsive (nonthermal) phase is included.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 Semptember 1980, Scheveningen, The Netherlands.  相似文献   

10.
This paper presents an integrated analysis of GOES 6, 7 and neutron monitor observations of solar cosmic-ray event following the 1990 May 24 solar flare. We have used a model which includes particle injection at the Sun and at the interplanetary shock front and particle propagation through the interplanetary medium. The model does not attempt to simulate the physical processes of coronal transport and shock acceleration, therefore the injections at the Sun and at the shock are represented by source functions in the particle transport equation. By fitting anisotropy and angle-average intensity profiles of high-energy (>30 MeV) protons as derived from the model to the ones observed by neutron monitors and at GOES 6 and 7, we have determined the parameters of particle transport, the injection rate and spectrum at the source. We have made a direct fit of uncorrected GOES data with both primary and secondary proton channels taken into account.The 1990 May 24–26 energetic proton event had a double-peaked temporal structure at energies 100 MeV. The Moreton (shock) wave nearby the flare core was seen clearly before the first injection of accelerated particles into the interplanetary medium. Some (correlated with this shock) acceleration mechanism which operates in the solar corona at a height up to one solar radius is regarded as a source of the first (prompt) increase in GOES and neutron monitor counting rates. The proton injection spectrum during this increase is found to be hard (spectral index 1.6) at lower energies ( 30 MeV) with a rapid steepening above 300 MeV. Large values of the mean free path ( 1.8 AU for 1 GV protons in the vicinity of the Earth) led to a high anisotropy of arriving protons. The second (delayed) proton increase was presumably produced by acceleration/injection of particles by an interplanetary shock wave at height of 10 solar radii. Our analysis of the 1990 May 24–26 event is in favour of the general idea that a number of components of energetic particles may be produced while the flare process develops towards larger spatial/temporal scales.Visiting Associate from St. Petersburg State Technical University, St. Petersburg 195251, Russia.  相似文献   

11.
We have observed 10 solar bursts during the thermal phase using the Haystack radio telescope at 22 GHz. We show that these high frequency flux observations, when compared with soft X-ray band fluxes, give useful information about the temperature profile in the flare loops. The microwave and X-ray band fluxes provide determinations of the maximum loop temperature, the total emission measure, and the index of the differential emission measure (q(T)/T = cT–1). The special case of an isothermal loop ( = ) has been considered previously by Thomas et al. (1985), and we confirm their diagnostic calculations for the GOES X-ray bands, but find that the flare loops we observed departed significantly from the isothermal regime. Our results ( = 1–3.5) imply that, during the late phases of flares, condensation cooling ( 3.5) competes with radiative cooling ( 1.5). Further, our results appear to be in good agreement with previous deductions from XUV rocket spectra ( 2–3).  相似文献   

12.
Results are given of the detailed analysis of fourteen Fe xxv-xxiii lines ( = 1.850–1.870 Å) in the spectra of a solar flare on 16 Nov. 1970. The spectra were obtained with a resolution of about 4 × 10–4 Å, which revealed lines not previously observed and allowed the measurement of line profiles. The measured values of the wavelengths and emission fluxes are presented and compared with theoretical calculations. The analysis of the contour of the Fe xxv line ( = 1.850 Å) leads to the conclusion that there is unidirectional macroscopic gas motion in the flare region with the velocity (projection on the line of sight) ± 90 km s–1.Measurements of the 8.42 Å Mg xii and 9.16 Å Mg xi lines in the absence of solar flares indicate prolonged existence of active regions on the solar disk with T e = 4–6 × 106K and emission measure ME 1048 cm–3. The profile of the Mg xii line indicates a macroscopic ion motion with a velocity up to 100 km s–1.  相似文献   

13.
T. Landscheidt 《Solar physics》1986,107(1):195-199
The Blackman-Tukey power spectrum of flare generated X-ray bursts X1 observed from 1970 to 1982 by satellite instrumentation (SOLRAD/SMS/GOES) shows prominent peaks at 156, 4.8, 2.8, and 1.1 months. According to a statistical test of the significance of the deviation of these peaks from Markov red noise, the peaks at 2.8 and 1.1 months are significant at the 99% confidence level while the peak at 4.8 months reaches the 95% level. A replication by means of the maximum entropy spectral analysis (MEM) yields the same prominent peaks at the same frequencies.  相似文献   

14.
The diffuse far UV radiation ( 1350–1480 Å) observed in the sky region ofl II180°, 0°b II40° is analyzed in connection with the distributions of stars and dust grains as well as with optical properties of grains. Its intensity (starlight+scattered light) is about 6×10–7 erg cm–2 sec–1 sr–1 Å–1 in the direction ofb II0° andl II180°. The latitude dependence of the intensity is in approximate agreement with the plane parallel slab model of the galaxy with a reasonable set of parameters. The interstellar scattering gives an albedo close to unity and forward phase function of about 0.6, which are not inconsistent with the model of interstellar grains of Wickramasinghe. The upper limit of the extragalactic UV is 2×10–8 erg cm–2 sec–1 sr–1 Å–1 in the same region of wave-length.  相似文献   

15.
Simultaneous observations of hard X-ray and optical emission from Sco X-1 were carried out at Hyderabad, India, on April 16 and 19, 1972. During the first and the second observations Sco X-1 was on the average in a bright phase ofB=12.5 mag. and a slightly darker phase ofB=12.7 mag. respectively. During the first observation the X-ray intensity in the energy range 20–40 keV measured with balloon borne scintillation counters showed an enhancement of a factor of about two in coincidence with an optical flare ofB0.2 mag., whereas the apparent temperature derived from the X-ray spectrum observed in the energy range 20–35 keV showed no appreciable change. Both the X-ray intensity and the apparent temperature observed on April 19 are considerably lower than those observed on April 16. Taking into account the effect of radiative transfer in a hot plasma, the electron density and the optical depth for electron scattering of the plasma cloud are derived asn e 3×1016 cm–3 and es 10 for the quiescent bright phase. The flare is explained by an increase of the plasma mass by about 30% and an increase of es by es 1 without appreciable change of the plasma temperature. The results on April 19 is interpreted as indicating that the quiescent dark phase may be characterized by a decrease of the plasma mass, its contraction and lower temperature.  相似文献   

16.
The Very Large Array (VLA) has been used at 20 cm wavelength to study the evolution of a burst loop with 4 resolution on timescales as short as 10 s. The VLA observations show that the coronal loop began to heat up and change its structure about 15 min before the eruption of two impulsive bursts. The first of these bursts occurred near the top of the loop that underwent preburst heating, while the second burst probably occurred along the legs of an adjacent loop. These observations evoke flare models in which coronal loops twist, develop magnetic instabilities and then erupt. We also combine the VLA observations with GOES X-ray data to derive a peak electron temperature of T e = 2.5 × 107 K and an average electron density of N e 1 × 1010 cm–3 in the coronal loop during the preburst heating phase.  相似文献   

17.
Innes  D.E.  McKenzie  D.E.  Wang  Tongjiang 《Solar physics》2003,217(2):267-279
An X1.5 flare on the west limb of the Sun on 21 April 2002 developed a large supra-arcade about 30 min after flare onset. The growth of the supra-arcade can be followed in both TRACE 195 Å images and SUMER spectra. Its growth seems to be associated with dark (in TRACE images), sunward moving channels that descend onto the arcade from above. SUMER recorded Doppler shifts of 800–1000 km s–1 in Fexxi 1354 Å from positions where this sunward flow interacts with the arcade tops. We describe the observations, focusing on the relationship of the high Fexxi line shifts to the sunward moving dark flows.  相似文献   

18.
Recently, Wheatland and Litvinenko (2001) have suggested that over the solar cycle both the flaring rate and the magnetic free energy in the corona lag behind the energy supply to the system. To test this model result, we analyzed the evolution of solar flare occurrence with regard to sunspot numbers (as well as sunspot areas), using H flare data available for the period 1955–2002, and soft X-ray flare data (GOES 1–8 Å) for the period 1976–2002. For solar cycles 19, 21, and 23, we find a characteristic time lag between flare activity and sunspot activity in the range 1015 months, consistent with the model predictions by Wheatland and Litvinenko (2001). The phenomenon turns out to be more prominent for highly energetic flares. The investigation of solar activity separately for the northern and southern hemisphere allows us to exclude any bias due to overlapping effects from the activity of both hemispheres and confirms the dynamic relevance of the delay phenomenon. Yet, no characteristic time lag >0 is found for solar cycles 20 and 22. The finding that in odd-numbered cycles flare activity is statistically delayed with respect to sunspot activity, while in even-numbered cycles it is not, suggests a connection to the 22-year magnetic cycle of the Sun. Further insight into the connection to the 22-year magnetic cycle could possibly be gained when a 22-year variation in the energy supply rate is taken into account in the Wheatland and Litvinenko (2001) model. The existence of a 22-year modulation in the energy supply rate is suggested by the empirical Gnevyshev – Ohl rule, and might be caused by a relic solar field.  相似文献   

19.
We present the analysis of spectrograms obtained during quiescence and during an ordinary outburst of the SU UMa type dwarf nova WX Hyi (ESO 3.6m telescope, B&C spectrograph with Image Disector Scanner, 171 Åmm–1, range 4000–7000 Å, time resolution 6min.). The radial velocities of these spectra have been discussed by Schoembs and Vogt (1981) who also derived the orbital elements of WX Hyi. The phasesmax refer to these elements. All velocities discussed here are with respect to the white dwarf, not to the center of mass of the binary system.Inquiescent state we did not find significant radial velocity variations. The equivalent widths W of the He I emission lines revealed periodic variations with an amplitude of 30%, maximal values of W were observed atmax=0.0...0.2. In contrast, the equivalent widths of the Balmer lines were not variable.Duringoutburst we found periodic radial velocity variations of the emission peak of H, H and He I 5875 with an amplitude of100 km s–1,max0.5. Also the broad Balmer absorption lines revealed periodic radial velocity variations, with a similar amplitude (max=0.3...0.5). The equivalent width of the H central emission peak varies with an amplitude of30%,max0.85. No variations of the equivalent width of the Balmer absorption lines were found.The outburst observations suggest that the preceeding part of the disc is brighter than the following one (in orbital motion). This is probably due to heating of the preceeding part by collisions with circumbinary matter, which seems to have an enhanced density in outburst as compared to the quiescent state. The emission lines are formed in outer layers or in a halo around the disc. The equivalent width variations can be interpreted in terms of interactions between this halo and the optically thick part of the disc.A more detailed discussion of the data is being published elsewhere.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986  相似文献   

20.
We describe a balloon payload designed to study the processes of energy release, particle acceleration, and heating of the active corona, in hard X-ray microflares and normal flares. An array of liquid nitrogen-cooled germanium detectors together with large area phoswich scintillation detectors provide the highest sensitivity (500 cm2) and energy resolution (0.7 keV) ever achieved for solar hard X-ray (15–600 keV) measurements. These detectors were flown in February 1987 from Australia on a long duration RAdiation COntrolled balloON (RACOON) flight (LDBF) which provided 12 days of observations before cutdown in Brazil. The payload includes solar cells for power, pointing and navigation sensors, a microprocessor controlled data system with VCR tape storage, and transmitters for GOES and ARGOS spacecraft. This successful flight illustrates the potential of LDBF's for solar flare studies.Also Physics Department.Presently at Space Sciences Laboratory, University of California, Berkeley CA 94720.  相似文献   

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