Standing shocks are believed to be responsible for stationary Type II solar radio bursts, whereas drifting Type II bursts are excited by moving shocks often related to coronal mass ejections (CMEs). Observations of either stationary or drifting Type II bursts are common, but a transition between the two states has not yet been reported. Here, we present a Type II burst which shows a clear, continuous transition from a stationary to a drifting state, the first observation of its kind. Moreover, band splitting is observed in the stationary parts of the burst, as well as intriguing negative and positive frequency-drift fine structures within the stationary emissions. The relation of the radio emissions to an observed jet and a narrow CME was investigated across multiple wavelengths, and the mechanisms leading to the transitioning Type II burst were determined. We find that a jet eruption generates a streamer-puff CME and that the interplay between the CME-driven shock and the streamer is likely to be responsible for the observed radio emissions.
One of the most important products of solar flares are nonthermal energetic particles which may carry up to 50\% energy releasing in the flaring processes. In radio observations, nonthermal particles generally manifest as spectral fine structures with fast frequency drifting rates, named as solar fast drifting radio bursts (FDRBs). This work demonstrated three types of FDRBs, including type III pair bursts, narrow band stochastic spike bursts following the type III bursts and spike-like bursts superimposed on type II burst in an X1.3 flare on 2014 April 25. We find that although all of them ha…
For the 2017 September 6 flare (SOL2017-Sep-06T11:53) we present not only unusual radio bursts, but also their interesting time association with the other flare phenomena observed in EUV, white-light, X-ray, and $γ$-ray emissions. Using our new method based on wavelets we found quasi-periodic pulsations (QPPs) in several locations of the whole time-frequency domain of the analyzed radio spectrum (11:55-12:07 UT and 22-5000 MHz). Among them the drifting QPPs are new and the most interesting, especially a bi-directional QPP at the time of the hard X-ray and $γ$-ray peaks, and a sunquake start. I…
Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pair parameters are qualitatively analyzed and compared with the newly-developed Monte Carlo ray-tracing technique simulating radio-wave propagation in the inhomogeneous anisotropic turbulent solar corona. The results suggest that the drift-pair bursts …
At the beginning of the 4 November 2015 flare, in the 1300 -- 2000 MHz frequency range, we observed a very rare slowly positively drifting burst. We searched for associated phenomena in simultaneous EUV observations made by IRIS, SDO/AIA, Hinode/XRT and in H alpha observations. We found that this radio burst was accompanied with the bright blob, visible at transition region, coronal, and flare temperatures, falling down to the chromosphere along the dark loop with the velocity of about 280 km/s. The dark loop was visible in H alpha but disappeared afterwards. Furthermore, we found that the fal…
A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. II. CMEs, Shock Waves, and Drifting Radio Bursts
我们继续我们对2003年11月18日地球效应事件的研究（Grechnev et al.（2013），doi：10.1007/s11207-013-0316-6; Paper I）。为了了解那天观测到的日冕瞬变对地球空间的可能影响，我们研究了它们在极紫外线、LASCO白光图像和动态射电光谱中的太阳近地表表现。我们调和近地表活动与日冕物质抛射（CME）的扩张，并确定其相对于地球方向的方向。运动学测量、动力学射电光谱、微波和X射线光变曲线都有助于综合事件的整体图像，并证实了在08：07 - 08：20 UT靠近论文I中假定的太阳盘中心的额外爆发。喷射的不寻常特征似乎与11月20日超级风暴的来源相匹配，但使LASCO图像中的检测变得无望。另一方面，LASCO观测到的CME似乎都不是超级风暴源的有希望的候选者，最多只能对地球的磁层产生一次轻微的打击。我们的分析证实了在事件中揭示的冲击波的自由传播，并将其运动学与“EUV波”和动态无线电频谱协调起来，最高可达十米。
We present multispectral analysis (radio, H$α$, UV/EUV, and hard X-ray) of a confined flare from 2015 March 12. This flare started within the active region NOAA 12 297 and then it expanded into a large preexisting magnetic rope embedded with a cold filament. The expansion started with several brightenings located along the rope. This process was accompanied by a group of slowly positively drifting bursts in the 0.8--2 GHz range. The frequency drift of these bursts was 45 -- 100 MHz s$^{-1}$. One of the bursts had an S-like form. During the brightening of the rope we observed an unique bright E…
A GOES M1.9 flare took place in active region AR 11153 on February 9,2011. With the resolution of 200 kHz and a time cadence of 80 ms, the reverse-drifting (RS) type III bursts, intermittent sequence of type U bursts, drifting pulsation structure (DPS), and fine structures were observed by the Yunnan Observatories Solar Radio Spectrometer(YNSRS). Combined information revealed by the multi-wavelength data indicated that after the DPS which observed by YNSRS, the generation rate of type U bursts suddenly increased 5 times than before. In this event, the generation rate of type U bursts may depen…
Drift pairs are an unusual type of fine structure sometimes observed in dynamic spectra of solar radio emission. They appear as two identical short narrowband drifting stripes separated in time; both positive and negative frequency drifts are observed. Using the Low Frequency Array (LOFAR), we report unique observations of a cluster of drift pair bursts in the frequency range of 30-70 MHz made on 12 July 2017. Spectral imaging capabilities of the instrument have allowed us for the first time to resolve the temporal and frequency evolution of the source locations and sizes at a fixed frequency …
Drifting pulsation structures (DPSs) are important radio fine structures usually observed at the beginning of eruptive solar flares. It has been suggested that DPSs carry important information on the energy release processes in solar flares. We study DPS observed in an X8.2-class flare on 2017 September 10 in the context of spatial and spectral diagnostics provided by microwave, EUV, and X-ray observations. We describe DPS and its sub-structures that were observed for the first time. We use a new wavelet technique to reveal characteristic periods in DPS and their frequency bands. Comparing the…
Aims. We examine high time resolution dynamic spectra for fine structures in type II solar radio bursts Methods. We used data obtained with the (SAO) receiver of the Artemis-JLS (ARTEMIS-IV) solar radio spectrograph in the 450-270 MHz range at 10 ms cadence and identified more than 600 short, narrowband features. Their characteristics, such as instantaneous relative bandwidth and total duration were measured and compared with those of spikes embedded in type IV emissions. Results. Type II associated spikes occur mostly in chains inside or close to the slowly drifting type II emission. These sp…
We analyze the short cosmic ray intensity increase ("cosmic ray burst": CRB) on June 22, 2015 utilizing a global network of muon detectors and derive the global anisotropy of cosmic ray intensity and the density (i.e. the omnidirectional intensity) with 10-minute time resolution. We find that the CRB was caused by a local density maximum and an enhanced anisotropy of cosmic rays both of which appeared in association with Earth's crossing of the heliospheric current sheet (HCS). This enhanced anisotropy was normal to the HCS and consistent with a diamagnetic drift arising from the spatial gradi…
Stellar coronal mass ejections remain experimentally unconstrained, unlike their stellar flare counterparts which are observed ubiquitously across the electromagnetic spectrum. Low frequency radio bursts in the form of a type II burst offer the best means of identifying and constraining the rate and properties of stellar CMEs. CME properties can be further improved through the use of proposed solar-stellar scaling relations and multi-wavelength observations of CMEs through the use of type II bursts and the associated flare expected to occur occur alongside. We report on 20 hours of observation…
Context. Some of of the most prominent sources for energetic particles in our Solar System are huge eruptions of magnetised plasma from the Sun called coronal mass ejections (CMEs), which usually drive shocks that accelerate charged particles up to relativistic energies. In particular, energetic electron beams can generate radio bursts through the plasma emission mechanism. The main types of bursts associated with CME shocks are type II and herringbone bursts. However, it is currently unknown where early accelerated electrons that produce metric type II bursts and herringbones propagate and wh…
Aims. Coronal Mass Ejections (CMEs) are the most fascinating explosion in the solar system; however, their formation is still not fully understood. Methods. Here, we investigate a well-observed CME on 2021 May 07 that showed a typical three-component structure and was continuously observed from 0 to 3 Rsun by a combination of SDO/AIA (0--1.3 Rsun), PROBA2/SWAP (0--1.7 Rsun) and MLSO/K-Cor (1.05--3 Rsun). Furthermore, we compare the morphological discrepancy between the CME white-light bright core and EUV blob. In the end, we explore the origin of various radio bursts closely related to the int…
Observation of fast radio bursts (FRBs) are rising very quickly with the advent of specialised instruments and surveys, and it has recently been shown that some of them repeat quasi-periodically. In particular, evidence of a $P=16.35$ day period has been reported for FRB 180916.J0158+65. We seek an explanation within the frame of our orbiting asteroid model, whereby FRBs are produced in the plasma wake of asteroids immersed in the wind of a pulsar or a magnetar. We used the data reported by the CHIME/FRB collaboration in order to infer the orbital characteristics of asteroid swarms, and perfor…
Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves
从里尔蒙斯和布鲁尼岛无线电频谱仪的无线电发射观测进行分析，以确定一个离散的，周期性的无线电\lq火花\rq（有限带宽，短持续时间的孤立的无线电功能）的训练的性质之前的II型突发。我们分析了SDO/AIA在多个波长的极紫外（EUV）成像，并确定了一系列准周期性的快速传播增强，我们解释为一个快速的波列，并将这些检测到的无线电功能。利用运行差分图像和时距分析记录了周期性快速传播快波和日冕物质抛射（CME）的速度和位置。从频率的无线电火花的发射位置的局部电子密度估计为每个。使用经验模型的密度在电晕的缩放，计算的电子密度被用来获得的高度以上的表面上发生的发射，和发射位置的传播速度。射电火花的周期$δt_\mathrm{r}$ = 1.78 $\pm$ 0.04 min，与在171 $Å$观测到的快波列周期$δt_\mathrm{EUV}$ = 1.7 $\pm$ 0.2 min相匹配。射电火花发射位置的推断速度为630 km s $^{-1}$，与CME前缘的测量速度500 km s $^{-1}$相当，以及由II类车道的漂移得出的速度。计算出的射电辐射高度（从密度中获得）与观测到的日冕物质抛射前缘位置相匹配。根据上述证据，我们认为射电火花是由准周期快波引起的，并且是在它们追赶CME的前缘并与之相互作用时产生的。
Kinetic Processes to Radio Burst: First Observational-driven Study in Coronal Loops
Yunnan Observatories, Chinese Academy of Science（中国科学院云南天文台）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Institute of Frontier and Interdisciplinary Science, Shandong University（山东大学前沿交叉科学研究中心）；School of Space Science and Physics, Shandong University（山东大学空间科学与物理学院）；University of Chinese Academy of Sciences（中国科学院大学）；Yunnan Key Laboratory of Solar Physics and Space Science（云南省太阳物理与空间科学重点实验室）
Eruptive activity in the solar corona can often lead to the propagation of shock waves. In the radio domain the primary signature of such shocks are type II radio bursts, observed in dynamic spectra as bands of emission slowly drifting towards lower frequencies over time. These radio bursts can sometimes have inhomogeneous and fragmented fine structure, but the cause of this fine structure is currently unclear. Here we observe a type II radio burst on 2019-March-20th using the New Extension in Nançay Upgrading LOFAR (NenuFAR), a radio interferometer observing between 10-85 MHz. We show that th…
Herringbone structures during an X-class eruptive flare
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences（中国科学院国家空间科学中心太阳活动与空间天气国家重点实验室）；Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Yunnan Key Laboratory of Solar Physics and Space Science（云南省太阳物理与空间科学重点实验室）；School of Science, Nanjing University of Posts and Telecommunications（南京邮电大学理学院）
Radio, X-ray, and EUV signatures of internal and external reconnection of an erupting flux rope
Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；University of Applied Sciences and Arts Northwestern Switzerland（瑞士西北应用科学与艺术大学）；Space Sciences Laboratory, University of California Berkeley（加州大学伯克利分校空间科学实验室）；Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Astronomical Institute, Slovak Academy of Sciences（斯洛伐克科学院天文研究所）
Observational detection of quasi-periodic drifting fine structures in a type III radio burst associated with a solar flare SOL2015-04-16T11:22, with Low Frequency Array, is presented. Although similar modulations of the type III emission have been observed before and were associated with the plasma density fluctuations, the origin of those fluctuations was unknown. Analysis of the striae of the intensity variation in the dynamic spectrum allowed us to reveal two quasi-oscillatory components. The shorter component has the apparent wavelength of $\sim2$ Mm, phase speed of $\sim657$ km s$^{-1}$, …
