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1.
We present a statistical study of decimetric type Ⅲ radio bursts,coronal mass ejections(CMEs),and Hα flares observed in the period from July 2000 to March2005.In total,we investigated 395 decimetric type Ⅲ radio burst events,21% of which showed apparent correlation to CMEs that were associated with Hα flares.We noticed that the Hα flares which were strongly associated with CMEs were gradual events,and82% of them took place before CMEs appeared in the field of view of LASCO C2;that most of the CME-associated radio bursts started in the frequency range around750 MHz with a frequency drifting rate of several hundred MHz s-1,of which both positive and negative ones were recognized; and that the correlation of type Ⅲ radio bursts to CMEs without associated flares is fairly vague,less than 9%.  相似文献   

2.
Seventy-one occurrences of coronal mass ejections(CMEs) associated with radio bursts,seemingly associated with type Ⅲ bursts/fine structures(FSs),in the centimeter-metric frequency range during 2003-2005,were obtained with the spectrometers at the National Astronomical Observatories,Chinese Academy of Sciences(NAOC) and the Culgoora radio spectrometer and are presented.The statistical results of 68 out of 71 events associated with the radio type III bursts or FSs during the initiation or early stages of the...  相似文献   

3.
We present a, large complex radio burst and its associated fast tune structures observed on 2001 April 10 in the frequency range of 0.65-7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a bipolar, a tripolar (a 'bipolar + remote unipolar'), and a quadrupolar structure. This suggests that the radio burst is generated from a very complicated loop structure. According to the spectral and image observations, we assume that the beginning of this flare was caused by a single bipolar loop configuration with a 'Y-type' re-connection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type III bursts, and slowly drifting and no-drift structures. The tripolar configurations may form a double-loop with a 'three-legged' structure, which is an important source of the various types of fast time structures. The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively. Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the 'inverted Y-type' (bipolar) and the 'three-legged' structures (tripolar or quadrupolar).  相似文献   

4.
Three particularly complex radio bursts (2001 October 19, 2001 April 10 and 2003 October 26) obtained with the spectrometers (0.65-7.6GHz) at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC, Beijing and Yunnan) and other in- struments (NoRH, TRACE and SXT) are presented. They each have two groups of peaks occurring in different frequency ranges (broad-band microwave and narrow-band decimeter wavelengths). We stress that the second group of burst peaks that occurred in the late phase of the flares and associated with post-flare loops may be homologous radio bursts. We think that they are driven by the post-flare loops. In contrast to the time profiles of the radio bursts and the images of coronal magnetic polarities, we are able to find that the three events are caused by the active regions including main single-bipole magnetic structures, which are associated with multipole magnetic structures during the flare evolutions. In particular, we point out that the later decimetric radio bursts are possibly the radio counterparts of the homologous flares (called "homologous radio bursts" by us), which are also driven by the single-bipole mag- netic structures. By examining the evolutions of the magnetic polarities of sources (17GHz), we could presume that the drivers of the homologous radio bursts are new and/or recurring appearances/disappearances of the magnetic polarities of radio sources, and that the triggers are the magnetic reconnections of single-bipole configurations.  相似文献   

5.
To investigate the dependence of large gradual solar energetic particle(SEP) events on the associated flares and coronal mass ejections(CMEs), the correlation coefficients(CCs) between peak intensities of E 10 MeV(I_(10)), E 30 MeV(I_(30)) and E 50 MeV(I_(50)) protons and soft X-ray(SXR) emission of associated flares and the speeds of associated CMEs in the three longitudinal areas W0–W39, W40–W70(hereafter the well connected region) and W71–W90 have been calculated.Classical correlation analysis shows that CCs between SXR emission and peak intensities of SEP events always reach their largest value in the well connected region and then decline dramatically in the longitudinal area outside the well connected region, suggesting that they may contribute to the production of SEPs in large SEP events. Both classical and partial correlation analyses show that SXR fluence is a better parameter describing the relationship between flares and SEP events. For large SEP events with source location in the well connected region, the CCs between SXR fluence and I_(10), I_(30) and I_(50) are0.58±0.12, 0.80±0.06 and 0.83±0.06 respectively, while the CCs between CME speed and I_(10), I_(30) and I_(50) are 0.56±0.12, 0.52±0.13 and 0.48±0.13 respectively. The partial correlation analyses show that in the well connected region, both CME shock and SXR fluence can significantly affect I_(10), but SXR peak flux makes no additional contribution. For E 30 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I_(30), and the CME shock makes a small contribution to I_(30), but SXR peak flux makes no additional contribution. For E 50 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I_(50), but both CME shock and SXR peak flux make no additional contribution. We conclude that these findings provide statistical evidence that for SEP events with source locations in the well connected region, a CME shock is only an effective accelerator for E 30 MeV protons. However, flares are not only effective accelerators for E 30 MeV protons, but also for E 30 MeV protons, and E 30 MeV protons may be mainly accelerated by concurrent flares.  相似文献   

6.
The remnants of two gamma-ray bursts, GRB 030329 and GRB 041227, have been resolved by Very Long Baseline Interferometry observations. The radio counterparts were observed to expand with time. These observations provide an important way to test the dynamics of the standard fireball model. We show that the observed size evolution of these two events cannot be explained by a simple jet model, rather, it can be satisfactorily explained by the two-component jet model. It strongly hints that gamma-ray burst ejecta may have complicated structures.  相似文献   

7.
Inspired by the finding that the large waiting time of solar flares presents a power-law distribution, we investigate the waiting time distribution (WTD) of coronal mass ejections (CMEs). SOHO/LASCO CME observations from 1996 to 2003 are used in this study. It is shown that the observed CMEs have a similar power-law behavior to the flares, with an almost identical power-law index. This strongly supports the viewpoint that solar flares and CMEs are different manifestations of the same physical process. We have also investigated separately the WTDs of fast-type and slow-type CMEs and found that their indices are identical, which imply that both types of CME may originate from the same physical mechanism.  相似文献   

8.
Fast radio bursts show large dispersion measures,much larger than the Galactic dispersion measure foreground.Therefore,they evidently have an extragalactic origin.We investigate possible contributions to the dispersion measure from host galaxies.We simulate the spatial distribution of fast radio bursts and calculate the dispersion measures along the sightlines from fast radio bursts to the edge of host galaxies by using the scaled NE2001 model for thermal electron density distributions.We find that contributions to the dispersion measure of fast radio bursts from the host galaxy follow a skew Gaussian distribution.The peak and the width at half maximum of the dispersion measure distribution increase with the inclination angle of a spiral galaxy,to large values when the inclination angle is over 70°.The largest dispersion measure produced by an edge-on spiral galaxy can reach a few thousand pc cm~(-3),while the dispersion measures from dwarf galaxies and elliptical galaxies have a maximum of only a few tens of pc cm~(-3).Notice,however,that additional dispersion measures of tens to hundreds of pc cm~(-3) can be produced by high density clumps in host galaxies.Simulations that include dispersion measure contributions from the Large Magellanic Cloud and the Andromeda Galaxy are shown as examples to demonstrate how to extract the dispersion measure from the intergalactic medium.  相似文献   

9.
This paper deals with the detailed analysis of frequency drift rates of solar"drift pair"(DP)bursts observed from 2015 July 10 to 12 during a type Ⅲ burst storm.The observations were conducted by the UTR-2 radio telescope at 9–33 MHz with high frequency and time resolution.DPs were recorded drifting from higher to lower frequencies(forward DPs)as well as from lower to higher ones(reverse DPs).Patterns on their dynamic spectrum had various inclines and occupied different bandwidths.The frequency drift rate versus frequency dependence of these bursts has been studied.The fitting model to describe the peak evolution of these bursts in the frequency-time plane is presented.The relationship between DPs and type Ⅲ solar bursts is discussed.  相似文献   

10.
On 2017 September 10, a fast coronal mass ejection(CME) erupted from the active region(AR)12673, leading to a ground level enhancement(GLE) event at Earth. Using the 2D improved Particle Acceleration and Transport in the Heliosphere(iPATH) model, we model the large solar energetic particle(SEP) event of 2017 September 10 observed at Earth, Mars and STEREO-A. Based on observational evidence, we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption, which is modeled by a double Gaussian velocity profile in this simulation. We apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model parameters. The modeled time intensity profiles and fluence for energetic protons are then compared with observations. Reasonable agreements with observations at Mars and STEREO-A are found. The simulated results at Earth differ from observations of GOES-15. However, the simulated results at a heliocentric longitude 20° west to Earth fit reasonably well with the GOES observation. This can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker field.Our results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.  相似文献   

11.
We compare two contrasting X-class flares in terms of magnetic free energy, relative magnetic helicity and decay index of the active regions(ARs) in which they occurred. The events in question are the eruptive X2.2 flare from AR 11158 accompanied by a halo coronal mass ejection(CME) and the confined X3.1 flare from AR 12192 with no associated CME. These two flares exhibit similar behavior of free magnetic energy and helicity buildup for a few days preceding them. A major difference between the two flares is found to lie in the time-dependent change of magnetic helicity of the ARs that hosted them. AR 11158 shows a significant decrease in magnetic helicity starting ～4 hours prior to the flare, but no apparent decrease in helicity is observed in AR 12192. By examining the magnetic helicity injection rates in terms of sign, we confirmed that the drastic decrease in magnetic helicity before the eruptive X2.2 flare was not caused by the injection of reversed helicity through the photosphere but rather the CME-related change in the coronal magnetic field. Another major difference we find is that AR 11158 had a significantly larger decay index and therefore weaker overlying field than AR 12192. These results suggest that the coronal magnetic helicity and the decay index of the overlying field can provide a clue about the occurrence of CMEs.  相似文献   

12.
A rare Type I-like noise storm was observed with the solar radio spectrometers (1.0-2.0 GHz and 2.60-3.8 GHz) at National Astronomical Observatories of China (NAOC) on September 23, 1998. We concentrate on checking the Type I-like noise storm occurred in the decay phase of a Type IV radio burst. This noise storm consists of many Type I bursts and isolated Type Ⅲ or Type Ⅲ pair bursts. It has a bandwidth of ≤ 0.5 GHz. The duration of each Type Ⅰ burst is of the order of 100-300ms. The total duration is greater than 11 minutes. The circular polarization degree of the components of Type Ⅰ and associated Type Ⅲ bursts are about 40%-100% and almost 100%, respectively, which is greater than that of the background continuum (nearly the precision of our instrument). This short decimetric Type I-like storm may be another kind or the extension of the kind of metric Type Ⅰ storm, and may possess the duality of metric and decimetric radio emission. It may be in favor of an earlier emission mechanism of the fundamental plasma radiation due to the coalescence of Langmuir waves with low-frequency waves.  相似文献   

13.
In this paper we investigate three novel rising submillimeter(THz) bursts that occurred sequentially in Super Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu GHz-1(corresponding to spectral index α of 1.6) for the THz spectral components of the2003 October 28 and November 4 bursts, but it attained values of 235 sfu GHz-1(α = 4.8) in the 2003 November 2 burst. The steeply rising THz spectrum can be produced by a population of highly relativistic electrons with a low-energy cutoff of 1 Me V, but it only requires a low-energy cutoff of 30 ke V for the two slowly rising THz bursts, via gyrosynchrotron(GS) radiation based on our numerical simulations of burst spectra in the magnetic dipole field case. The electron density variation is much larger in the THz source than in the microwave(MW) source. It is interesting that the THz source radius decreased by 20%–50%during the decay phase for the three events, but the MW source increased by 28% for the 2003 November2 event. In the paper we will present a formula that can be used to calculate the energy released by ultrarelativistic electrons, taking the relativistic correction into account for the first time. We find that the energy released by energetic electrons in the THz source exceeds that in the MW source due to the strong GS radiation loss in the THz range, although the modeled THz source area is 3–4 orders smaller than the modeled MW source one. The total energies released by energetic electrons via the GS radiation in radio sources are estimated, respectively, to be 5.2 × 1033, 3.9 × 1033 and 3.7 × 1032 erg for the October 28, November 2and 4 bursts, which are 131, 76 and 4 times as large as the thermal energies of 2.9 × 1031, 2.1 × 1031and5.2 × 1031 erg estimated from soft X-ray GOES observations.  相似文献   

14.
The Astrophysics Directorate of CONIDA has installed two radio spectrometer stations belonging to the e-CALLISTO network in Lima, Peru. Given their strategic location near the Equator, it is possible to observe the Sun evenly throughout the whole year. The receiver located at Pucusana, nearby the capital city of Lima, took data from October 2014 until August 2016 in the metric and decimetric bands looking for radio bursts. During this period, this e-CALLISTO detector was unique in its time-zone coverage. To asses the suitability of the sites and the performance of the antennas, we analyzed the radio ambient background and measured their radiation pattern and beamwidth. To demonstrate the capabilities of the facilities for studying solar dynamics in these radio frequencies, we have selected and analyzed type Ⅲ Solar Radio Bursts. The study of this kind of burst helps to understand the electron beams traversing the solar corona and the solar atmospheric density. We have characterized the most common radio bursts with the following mean values: a negative drift rate of –25.8 ± 3.7 MHz s~(-1), a duration of 2.6 ± 0.3 s and 35 MHz bandwidth in the frequency range of 114 to 174 MHz. In addition, for some events, it was possible to calculate a global frequency drift which on average was 0.4 ± 0.1 MHz s~(-1).  相似文献   

15.
Observations indicate that solar coronal mass ejections (CMEs) are closely associated with reconnection-favored flux emergence, which was explained in the emerging flux trigger mechanism for CMEs by Chen & Shibata based on numerical simulations. We present a parametric survey of the triggering agent: its polarity orientation, position, and the amount of the unsigned flux. The results suggest that whether a CME can be triggered depends on both the amount and location of the emerging flux, in addition to its polarity orientation. A diagram is presented to show the eruption and non-eruption regimes in the parameter space. The work is aimed at providing useful information for the space weather forecast.  相似文献   

16.
In this paper, the new models of the generation mechanism of the observed solar corona type II radio burst and the interplanetary type III radio emission are presented. The synchrotron-maser theory of type II solar is proposed. The electrostatic waves with frequencies close to twice the plasma frequency can be excited,and can naturclly change into electromagnetic waves when they propagate in a plasma in which the plasma density decreases spatially.Emission of electromagnetic waves with frequencies close to the plasma frequency and/or its second harmonic have been frequently observed in solar corona and interplanetary space. In the pass a number of theories have been suggested to explain the generation mechanism of the observed radiation.  相似文献   

17.
The measurement of positions and sizes of radio sources in observations is important for understanding of the flare evolution. For the first time, solar radio spectral fine structures in an M6.5 flare that occurred on 2013 April 11 were observed simultaneously by several radio instruments at four different observatories: Chinese Solar Broadband Radio Spectrometer at Huairou(SBRS/Huairou), Ondˇrejov Radio Spectrograph in the Czech Republic(ORSC/Ondˇrejov), Badary Broadband Microwave Spectropolarimeter(BMS/Irkutsk), and spectrograph/IZMIRAN(Moscow, Troitsk). The fine structures included microwave zebra patterns(ZPs), fast pulsations and fiber bursts. They were observed during the flare brightening located at the tops of a loop arcade as shown in images taken by the extreme ultraviolet(EUV) telescope onboard NASA's satellite Solar Dynamics Observatory(SDO). The flare occurred at 06:58–07:26 UT in solar active region NOAA 11719 located close to the solar disk center. ZPs appeared near high frequency boundaries of the pulsations, and their spectra observed in Huairou and Ondˇrejov agreed with each other in terms of details. At the beginning of the flare's impulsive phase, a strong narrowband ZP burst occurred with a moderate left-handed circular polarization. Then a series of pulsations and ZPs were observed in almost unpolarized emission. After 07:00 UT a ZP appeared with a moderate right-handed polarization.In the flare decay phase(at about 07:25 UT), ZPs and fiber bursts become strongly right-hand polarized.BMS/Irkutsk spectral observations indicated that the background emission showed a left-handed circular polarization(similar to SBRS/Huairou spectra around 3 GHz). However, the fine structure appeared in the right-handed polarization. The dynamics of the polarization was associated with the motion of the flare exciter, which was observed in EUV images at 171 ?A and 131 ?A by the SDO Atmospheric Imaging Assembly(AIA). Combining magnetograms observed by the SDO Helioseismic and Magnetic Imager(HMI) with the homologous assumption of EUV flare brightenings and ZP bursts, we deduced that the observed ZPs correspond to the ordinary radio emission mode. However, future analysis needs to verify the assumption that zebra radio sources are really related to a closed magnetic loop, and are located at lower heights in the solar atmosphere than the source of pulsations.  相似文献   

18.
A statistical analysis is made on the correlation between solar proton events with energies >10Mev and solar radio bursts during the four-year period from 1997 November to 2000 November. We examine 28 solar proton events and their corresponding solar radio bursts at 15400, 8800, 4995, 2695, 1415, 606, 410 and 245 MHz. The statistical result shows that there is a close association between solar proton events and ≥3 solar radio bursts occurring at several frequencies, one or two days before. In particular, it is noteworthy that proton events occurring  相似文献   

19.
Active galactic nuclei(AGNs) can be divided into two major classes,namely radio-loud and radio-quiet AGNs.A small subset of the radio-loud AGNs is called blazars,which are believed to be unified with Fanaroff-Riley type Ⅰ and type Ⅱ(FRIⅡ) radio galaxies.Following our previous work,we present a latest sample of 966 sources with measured radio flux densities of the core and extended components.The sample includes 83 BL Lacs,473 flat spectrum radio quasars,101 Seyferts,245 galaxies,52 FRIsⅡs and12 unidentified sources.We then calculate the radio core-dominance parameters and spectral indices and study their relationship.Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources.We also confirm that the correlation between core-dominance parameter and radio spectral index extends over all the sources in a large sample presented.  相似文献   

20.
Active galactic nuclei(AGNs) can be divided into two major classes, namely radio-loud and radio-quiet AGNs. A small subset of the radio-loud AGNs is called blazars, which are believed to be unified with Fanaroff-Riley type Ⅰ/Ⅱ(FRI/Ⅱ) radio galaxies. Following our previous work(Fan et al.), we present a sample of 2400 sources with measured radio flux densities of the core and extended components. The sample contains 250 BL Lacs, 520 quasars, 175 Seyferts, 1178 galaxies, 153 FRI or FRⅡ galaxies and 104 unidentified sources. We then calculate the radio core-dominance parameters and spectral indices, and study their relationship. Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources. We also confirm that the correlation between core-dominance parameter and spectral index exists for a large sample presented in this work.  相似文献   

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