共查询到20条相似文献，搜索用时 15 毫秒
1.
V. N. Melnik A. I. Brazhenko A. A. Konovalenko H. O. Rucker A. V. Frantsuzenko V. V. Dorovskyy M. Panchenko A. A. Stanislavskyy 《Solar physics》2014,289(1):263-278
An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s?1) at frequencies higher than 22 MHz and negative (100 kHz?s?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈103 s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed. 相似文献
2.
M. L. Kaiser 《Solar physics》1975,45(1):181-187
Over 500 days of low-frequency (<1 MHz) radio observations from the IMP-6 spacecraft have been accumulated to produce a two-dimensional map (frequency vs elongation) of solar type III burst occurrences. This map indicates that most solar bursts in this frequency range are observed at the second harmonic of the plasma frequency rather than the fundamental. The map also shows that the solar wind electron density varies as R ?γ , where γ can be somewhat less than 2 to perhaps 3 or higher. 相似文献
3.
High-time resolution spectral measurements of solar radio emission close to 264 MHz are reported. Instrumental resolutions of the order of a few kHz in frequency and tenths of milliseconds in time were used to resolve the burst fine structure in the time-frequency plane. Fine structures, having narrow bandwidths and durations of some 5 to 30 ms, have been observed mostly in association with type I and type III bursts. These very short duration bursts have negative frequency drifts of about - 50 to- 60 MHz s-1. They can occur individually or in small groups where they sometimes display a quasi-periodicity of a few milliseconds. 相似文献
4.
James W. Warwick 《Solar physics》1968,5(1):111-117
A major radio burst at decametric frequencies at 1638 UT on June 9, 1959 is apparently a Type-IV continuum burst of the kind that drifts from high to low frequencies. We present observations of flux variations and East-West positions of the emission at both 18 and 38 MHz. The burst moves outward at a speed of about 4700 km·sec?1 at each frequency to a height of about 3 R ⊙ from the sun's center and then returns to the sun. This behavior is not simultaneous at 18 MHz and 38 MHz; the outward moving phase of 18 MHz emission occurs during the return phase of 38 MHz. We suspect that a solitary Alfvén wave or shock traverses the outer corona at the time of this burst. Relativistic electrons created low in the solar atmosphere travel freely along radial lines of force up to the coronal-streamer heights of the Type-IV burst. Upon encountering the shock, the electrons emit locally intense synchrotron emission, and pass through the shock on out into interplanetary space. This model appears to be consistent with other shock front phenomena in interplanetary space and the corona. Finally, the Razin effect (Boischot and Clavelier, 1967) suggests that low-frequency cut-offs in Type-IV bursts ought to be quite constant in frequency, and not higher than between 0.4 to 4 MHz. 相似文献
5.
The dynamic radio spectrum of the class 3B solar flare of 1972, August 7, 15: 00 UT, over the band 10 to 2000 MHz is examined. Type II and type IV bursts in the spectrum are interpreted in terms of a piston-driven shock, which appeared to be travelling at a velocity of about 1500 km s?1 and which generated pulsations in the band 100 to 200 MHz as it passed through the corona. The progress of the shock through the interplanetary plasma was subsequently monitored by Malitson et al. with radio equipment covering the band 0.03 to 2.6 MHz on the IMP-6 satellite.
相似文献6.
E. P. Abranin L. L. Bazelyan V. V. Zaitsev V. O. Rapoport Ya. G. Tsybko 《Solar physics》1982,78(1):179-186
Some properties of solar radio bursts observed at the Earth are mainly due to propagation effects in the corona. A radio echo of short-time narrow-band bursts is observed by a decameter radioheliograph on the basis of UTR-2 antenna. Propagation effects are manifested in the marked regular change of the burst intensity-time profile at 25 MHz during a half-rotation of the Sun. A displacement of limb diffuse bursts deep into the solar atmosphere of 1.5 - 2R
has been also found during the burst lifetime. 相似文献
7.
D. McConnell 《Solar physics》1982,78(2):253-269
Observations of the solar radio spectrum have been made with high time and frequency resolution. Spectra were recorded over six 3-MHz bands between 30 and 82 MHz. The receivers used were capable of time and frequency resolutions of 1 ms and 2 kHz, respectively. A large number of radio bursts exhibiting a variety of find spectral structure were recorded.The bursts, referred to here as S bursts, were observed throughout the 30–82 MHz frequency range but were most numerous in the 33–44 MHz band and were very rare at 80 MHz. On a dynamic spectrum the bursts appeared as narrow sloping lines with the centre frequency of each burst decreasing with time. The rate of frequency drift was about 1/3 that of type III bursts. Most bursts were observed over only a limited frequency range (< 5 MHz) but some drifted for more than 10 MHz. The durations measured at a single frequency and the instantaneous bandwidths of S bursts were small; t = 49 ± 34 ms and f = 123 ± 56 kHz for bursts observed near 40 MHz. A significant number had t 20 ms. Flux densities of S burst sources were estimated to fall in the range 1023-5 × 1021 Wm–1 Hz–1.A small proportion (1–2%) of bursts showed a fine structure in which the burst source apparently only emitted at discrete, regularly spaced frequencies causing the spectrogram to exhibit a series of bands or fringes. The fringe spacing increased with wave frequency and was f - 90 kHz for fringes near 40 MHz. The bandwidths of fringes was narrow, often less than 30 kHz and in some cases down to 10–15 kHz.New address: Astronomy Program, University of Maryland, College Park, MD, U.S.A. 相似文献
8.
太阳米波和分米波的射电观测是对太阳爆发过程中耀斑和日冕物质抛射现象研究的重要观测手段。米波和分米波的太阳射电暴以相干等离子体辐射为主导,表现出在时域和频域的多样性和复杂性。其中Ⅱ型射电暴是激波在日冕中运动引起电磁波辐射的结果。在Ⅱ型射电暴方面,首先对米波Ⅱ型射电暴的激波起源问题和米波Ⅱ型射电暴与行星际Ⅱ型射电暴的关系问题进行了讨论;其次,结合Lin-Forbes太阳爆发理论模型对Ⅱ型射电暴的开始时间和起始频率进行讨论:最后,对Ⅱ型射电暴信号中包含的两种射电精细结构,Herringbone结构(即鱼骨结构)和与激波相关的Ⅲ型射电暴也分别进行了讨论。Ⅲ型射电暴是高能电子束在日冕中运动产生电磁波辐射的结果。在Ⅲ型射电暴方面,首先介绍了利用Ⅲ型射电暴对日冕磁场位形和等离子体密度进行研究的具体方法;其次,对利用Ⅲ型射电暴测量日冕温度的最新理论进行介绍;最后,对Ⅲ型射电暴和Ⅱ型射电暴的时间关系、Ⅲ型射电暴和粒子加速以及Ⅲ型射电暴信号中包含的射电精细结构(例如斑马纹、纤维爆发及尖峰辐射)等问题进行讨论并介绍有关的最新研究进展。 相似文献
9.
C. De Jager 《Solar physics》1967,2(3):327-346
A hard solar X-ray burst was observed by J-P. Legrand on 18 September 1963, 13:56 UT, at balloon altitude. It lasted a few minutes; a steep increase was followed by an exponential decay. During its declining phase a weak radio burst was observed on 3 and 10 cm, not on longer wavelengths.Maximum radio intensity occurred two minutes after that of the X-ray burst. The X-ray and radio bursts ended almost simultaneously. Optically a small shortlived (some minutes) flare point occurred simultaneously with the X-ray burst in a magnetically interesting part of the active region of September 1963. The X-burst photons seem to have had an energy of about 0.5 MeV. The burst was therefore of a fairly rare type, since very few other bursts with similar photon energies have been detected up to now.It is suggested that a mass of gas, magnetically confined to a volume of about 5·1025 cm3 in the low corona, containing about 3·1035 electrons was accelerated to energies of about 0.5 MeV. The gas gradually expanded, partly also to higher levels. The gyro-synchrotron radiation, emitted by the plasma became observable after about two minutes. At the lower radio frequencies the radiation was absorbed by overlying undisturbed coronal matter. Quantitative computations justify this model. A detailed summary of the events, and some numerical data are given in the concluding Section 8 and in Table V. 相似文献
10.
Richard R. Weber 《Solar physics》1978,59(2):377-385
Flux density spectra have been determined for ninety-one simple type III solar bursts observed by the Goddard Space Flight Center radio astronomy experiment on the IMP-6 spacecraft during 1971 and 1972. Spectral peaks were found to occur at frequencies ranging from 44 kHz up to 2500 kHz. Half of the bursts peaked between 250 kHz and 900 kHz, corresponding to emission at solar distances of about 0.3 to 0.1 AU. Maximum burst flux density sometimes exceeds 10–14 W m–2 Hz–1. The primary factor controlling the spectral peak frequency of these bursts appears to be variation in intrinsic power radiated by the source as the exciter moves outward from the Sun, rather than radio propagation effects between the source and IMP-6. Thus, a burst spectrum strongly reflects the evolution of the properties of the exciting electron beam, and according to current theory, beam deceleration could help account for the observations. 相似文献
11.
An analysis has been made of type III bursts recorded during a decametric solar storm observed from July 29 to August 16, 1975 with the UTR-2 antenna (Kharkov, IRE Acad. Sci. Ukr. SSR). The bursts were recorded with a dynamic spectrograph and radiometers at 25.0, 20.0, 16.7, and 12.5 MHz. Daily observations have yielded histograms of the type III burst distribution with respect to the frequency drift rate in three subbands between 25.0 and 12.5 MHz. During the middle stage of the storm the drift rate was about twice as high as at the onset and the final stage of the storm. Abrupt changes in the mean frequency drift rate were registered some two to three days after the active region McMath 13790 had come onto the limb and also before it disappeared behind the solar disk. Sudden changes in the drift rates of the type III bursts were accompanied by sudden changes of their mean duration. The rather long burst durations observed at 25.0 MHz at the beginning and the end of the radio storm coincided with such at the twice lower frequency, i.e. 12.5 MHz, during the period when an increased drift rate was observed.Similar variations of type III burst parameters can be interpreted in the framework of the plasma mechanism of burst generation in the corona, assuming that at the middle stage of the storm the bursts observed in the 25.0–12.5 MHz range were emitted at the fundamental whereas when the emitting region was near the limb the bursts received corresponded to the second harmonic of the Langmuir oscillations in the range of 12.5 to 6.25 MHz excited at greater heights. 相似文献
12.
与太阳射电爆发相比,通常认为频率较低的行星际射电爆发产生于远离低日冕的行星际空间.地球电离层的截止导致地基设备无法对其进行观测.美国国家航空航天局(National Aeronautics and Space Administration, NASA)发射的帕克太阳探测器(Parker Solar Probe, PSP)是迄今为止距离太阳最近的空间探测器.其搭载的射电频谱仪能够对10 k Hz–19.17 MHz频段范围内的射电辐射进行观测. PSP能够靠近甚至可能穿越行星际III型射电爆发的辐射源区,因此使用PSP对行星际射电爆发进行观测具有前所未有的优势.简要介绍了目前为止使用PSP的射电观测数据对行星际III型射电爆发的多方面研究,包括爆发的发生率、偏振、散射、截止频率、可能的辐射机制和相关的辐射源区等方面的研究进展,并讨论了其未来的研究前景. 相似文献
13.
A detailed comparison is made between hard X-ray spikes and decimetric type III radio bursts for a relatively weak solar flare on 1981 August 6 at 10: 32 UT. The hard X-ray observations were made at energies above 30 keV with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and with a balloon-born coarse-imaging spectrometer from Frascati, Italy. The radio data were obtained in the frequency range from 100 to 1000 MHz with the analog and digital instruments from Zürich, Switzerland. All the data sets have a time resolution of 0.1 s or better. The dynamic radio spectrum shows many fast drift type III radio bursts with both normal and reverse slope, while the X-ray time profile contains many well resolved short spikes with durations of 1 s. Some of the X-ray spikes appear to be associated in time with reverse-slop bursts suggesting either that the electron beams producing the radio bursts contain two or three orders of magnitude more fast electrons than has previously been assumed or that the electron beams can trigger or occur in coincidence with the acceleration of additional electrons. One case is presented in which a normal slope radio burst at 600 MHz occurs in coincidence with the peak of an X-ray spike to within 0.1 s. If the coincidence is not merely accidental and if it is meaningful to compare peak times, then the short delay would indicate that the radio signal was at the harmonic and that the electrons producing the radio burst were accelerated at an altitude of 4 × 109 cm. Such a short delay is inconsistent with models invoking cross-field drifts to produce the electron beams that generate type III bursts but it supports the model incorporating a MASER proposed by Sprangle and Vlahos (1983). 相似文献
14.
The Source Regions of Impulsive Solar Electron Events 总被引：1，自引：0，他引：1
Benz Arnold O. Lin Robert P. Sheiner Olga A. Krucker Säm Fainberg Joe 《Solar physics》2001,203(1):131-144
Low-energy (2–19 keV) impulsive electron events observed in interplanetary space have been traced back to the Sun, using their interplanetary type III radiation and metric/decimetric radio-spectrograms. For the first time we are able to study the highest frequencies and thus the radio signatures closest to the source region. All the selected impulsive solar electron events have been found to be associated with an interplanetary type III burst. This allows to time the particle events at the 2 MHz plasma level and identify the associated coronal radio emissions. Except for 5 out of 27 cases, the electron events were found to be associated with a coronal type III burst in the metric wavelength range. The start frequency yields a lower limit to the density in the acceleration region. We also search for narrow-band spikes at the start of the type III bursts. In about half of the observed cases we find metric spikes or enhancements of type I bursts associated with the start of the electron event. If interpreted as the plasma emission of the acceleration process, the observed average frequency of spikes suggests a source density of the order of 3×108 cm–3 consistent with the energy cut-off observed. 相似文献
15.
The UCSD X-ray telescope on OSO-3 scanned Jupiter for 33 days during February and March 1968. We have searched the data for a steady Jovian flux, and for a burst component at times of decametric radio bursts. Neither component was detected at a sensitivity of ～0.1 photon (cm2sec)?1 for hv > 7.7 keV. At 4.4AU, the 3σ upper limits correspond to X-ray luminosities of 7.4 × 1019 ergs sec?1 for the steady component, and 2 × 1020 ergs sec?1 for the burst component. The observations occurred during a period of high solar activity, during which three sudden-commencement magnetic storms were observed at Earth. We compare the upper limits with several different calculations of the expected flux levels, and conclude that major improvements in X-ray detection techniques will be required before Jovian X rays can be detected with near-Earth observations. 相似文献
16.
J. Van Nieuwkoop 《Solar physics》1986,103(1):129-140
In the dynamic spectrograms of the 60-channel solar radiospectrograph at Dwingeloo coherent groups of Type I bursts have been selected. At 243 MHz the positions of the bursts were measured. Within many groups the bursts showed a systematic angular displacement with time. Movements with apparent velocities up to 15000 km s–1 have been observed. The burst positions have been obtained with a two-element interferometer. A special data reduction method used the amplitude variation of the Type I bursts as a parameter for selection against the background radiation. 相似文献
17.
To locate two-dimensional positions of the solar decametric radio bursts a heliograph was developed on the basis of the UTR-2 radiotelescope (Khar'kov) operated in the range 10–26 MHz. The beamwidth of the heliograph rapid-scanning pencil-beam is 25 arc min at 25 MHz, and its field of view is about 3.5° (E-W) × 2.0° (N-S). The instrument yields rapidly forty records of the radio brightness of all (8 × 5) elementary parts (each 25 arc min in diameter) of the investigated sky area during every period of 1/4 s. Both coordinates of a burst center are measured with an accuracy 5 arc min. The bandwidth of the receiving system is 10 kHz. The heliograph operates in conjunction with a radiospectrograph connected to the output of a N-S arm of the UTR-2 array. The data observations with the UTR-2 correspond only to one linear polarized component.The ionospheric distortion of the test records of the radio source Cassiopeia-A that occurred sometimes is illustrated.First results of 25 MHz observations of the solar radio storm in August, 1976 with the heliograph are presented here. This storm is accompanied by the compact sunspot group travelling all over the optical disk. The type III and stria bursts were predominant during the storm. On the given day the scattering regions of their apparent centers were overlapped and the sizes of these regions were usually not more than 5 arc min. On some days there occurred additional burst sources displaced in position from the persistent storm region. It was found out that, as a rule, 25 MHz stria-bursts from the type IIIb chain coincided in position with the following type III burst at the same frequency. The difference of the daily averaged coordinates of both stria and type III bursts was considerably smaller than the mean diameter of their sources.The radial distance of the 25 MHz storm region from the solar center was calculated by using the three methods. The storm height was estimated as 1.8R
from the rotation rate close to the central meridian of the storm center. Definite association of the spots with the storm near the limb allowed to determine the average value 2.1R
for the height. The limb measurements give the mean height of 2.3R
.The center-to-limb variation of the storm source height is a known fact in the meter-wavelength range. This is the evidence of the propagation effects in the solar corona being essential to interpret the results of the radio source location. 相似文献
18.
On April 21, 2002, a broadband solar radio burst was observed at about 01:00 – 03:00 UT with the digital spectrometers of
National Astronomical Observatories of China (NAOC). Also many fiber bursts superposed on the continuum bursts were detected
in the frequency range of 2.6 – 3.8 GHz during the time interval. After data processing, some parameters of the fibers such
as frequency drift rate, duration, bandwidth, and relative bandwidth were determined. The mean value of the frequency drift
was in the range of 42.3 – 87.4 MHz s−1 (negative). A theoretical interpretation for the fibers was presented based upon a model of the velocity of Alfvén solitons.
In this model, the source of the fiber emission was considered as the ducting of the solitons within the magnetic-mirror loop.
Then the magnetic field strength of the fiber source was estimated to be about 130 ≤ B0 ≤ 270 G. Also a comparison of the magnetic field estimation was made with another model of whistler group velocity. 相似文献
19.
G. P. Chernov A. A. Stanislavsky A. A. Konovalenko E. P. Abranin V. V. Dorovsky G. O. Rucker 《Astronomy Letters》2007,33(3):192-202
We have performed a comparative analysis of the fine structure of two decametric type II bursts observed on July 17 and August 16, 2002, with the 1024-channel spectrograph of the UTR-2 radio telescope in the frequency range 18.5–29.5 MHz and with the IZMIRAN spectrograph in the frequency range 25–270 MHz. The August 16 burst was weak, ～2–5 s.f.u., but exhibited an unusual fine structure in the form of broadband fibers (Δf e > 250–500 kHz) that drifted at a rate characteristic of type II bursts and consisted of regular narrow-band fibers (Δf e > 50–90 kHz at 24 MHz) resembling a rope of fibers. The July 17 burst was three orders of magnitude more intense (up to 4500 s.f.u. at 20 MHz) and included a similar fiber structure. The narrow fibers were irregular and shorter in duration. They differed from an ordinary rope of fibers by the absence of absorption from the low-frequency edge and by slow frequency drift (slower than that of a type II burst). Both type II bursts were also observed in interplanetary space in the WIND/WAVES RAD2 spectra, but without any direct continuation. Analysis of the corresponding coronal mass ejections (CMEs) based on SOHO/LASCO C2 data has shown that the radio source of the type II burst detected on August 16 with UTR-2 was located between the narrow CME and the shock front trailing behind that was catching up with the CME. The July 17 type II fiber burst also occurred at the time when the shock front was catching up with the CME. Under such conditions, it would be natural to assume that the emission from large fibers is related to the passage of the shock front through narrow inhomogeneities in the CME tail. Resonant transition radiation may be the main radio emission mechanism. Both events are characterized by the possible generation of whistlers between the leading CME edge and the shock front. The whistlers excited at shock fronts manifest themselves only against the background of enhanced emission from large fibers (similar to the continuum modulation in type IV bursts). The reduction in whistler group velocity inside inhomogeneities to 760 km s?1 may be responsible for the unusually low drift rate of the narrow fibers. The magnetic field inside inhomogeneities determined from fiber parameters at 24 MHz is ～0.9 G, while the density should be increased by at least a factor of 2. 相似文献
20.
V. N. Melnik A. A. Konovalenko V. V. Dorovskyy H. O. Rucker E. P. Abranin V. N. Lisachenko A. Lecacheux 《Solar physics》2005,231(1-2):143-155
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