scholarly journals Interferometric imaging with LOFAR remote baselines of the fine structures of a solar type-IIIb radio burst

2020 ◽  
Vol 639 ◽  
pp. A115
Author(s):  
PeiJin Zhang ◽  
Pietro Zucca ◽  
Sarrvesh Seethapuram Sridhar ◽  
ChuanBing Wang ◽  
Mario M. Bisi ◽  
...  
Keyword(s):  
Radio Burst ◽  
Solar Radio ◽  
Source Size ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Harmonic Emission ◽  
Apparent Source ◽  
Solar Type ◽  
Fine Structures ◽  
Source Motion

Context. Solar radio bursts originate mainly from high energy electrons accelerated in solar eruptions like solar flares, jets, and coronal mass ejections. A sub-category of solar radio bursts with short time duration may be used as a proxy to understand wave generation and propagation within the corona. Aims. Complete case studies of the source size, position, and kinematics of short term bursts are very rare due to instrumental limitations. A comprehensive multi-frequency spectroscopic and imaging study was carried out of a clear example of a solar type IIIb-III pair. Methods. In this work, the source of the radio burst was imaged with the interferometric mode, using the remote baselines of the LOw Frequency ARray (LOFAR). A detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging was conducted. Results. The study shows how the fundamental and harmonic components have a significantly different source motion. The apparent source of the fundamental emission at 26.56 MHz displaces away from the solar disk center at about four times the speed of light, while the apparent source of the harmonic emission at the same frequency shows a speed of < 0.02 c. The source size of the harmonic emission observed in this case is smaller than that in previous studies, indicating the importance of the use of remote baselines.

Source size and Position of a Type IIIb-III Pair with LOFAR

2020 ◽  
Author(s):  
Peijin Zhang ◽  
Pietro Zucca ◽  
Sarrvesh Sridhar ◽  
Chuanbing Wang
Keyword(s):  
Radio Source ◽  
Solar Radio ◽  
High Energy ◽  
Source Size ◽  
Radio Bursts ◽  
Time Duration ◽  
Solar Radio Bursts ◽  
Type Iiib ◽  
Apparent Source ◽  
Source Motion

&lt;p&gt;Solar radio bursts originate mainly from high energy electrons accelerated by solar eruptions like solar flares, jets, and coronal mass ejections (CMEs). &amp;#160;A sub-category of solar radio bursts with a short time duration may be used as a proxy to understand the wave generation and propagation within the corona. &amp;#160;Complete case studies of the source size, position, and kinematics of short-term bursts are very limited due to instrumental limitations.&lt;br&gt;LOw-Frequency-ARray (LOFAR) is an advanced radio antenna array. It is capable of a variety of processing operations including correlation for standard interferometric imaging, the tied-array beam-forming, and the real-time triggering on incoming station data-streams. With recently upgraded LOFAR, we can achieve high spatial and temporal imaging for solar radio bursts.&lt;br&gt;Here we present a detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging, the radio source of a type IIIb-III pair was imaged with the interferometric mode using the remote baselines of the (LOFAR). This study shows how the fundamental and harmonic components have a significant different source motion. &amp;#160;The apparent source of the fundamental emission at 26 MHz is about 4 times the speed of light, while the apparent source of the harmonic emission shows a speed of &lt; 0.02 c. &amp;#160;We show that the apparent speed of the fundamental source is more affected by the scattering and refraction of the coronal medium.&lt;/p&gt;

scholarly journals Satellite Observations of Solar Radio Bursts

1980 ◽  
Vol 86 ◽  
pp. 387-400
Author(s):  
J.L. Steinberg
Keyword(s):  
Solar Radio ◽  
Source Size ◽  
Type I ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Burst Source ◽  
Radiation Mechanism ◽  
3 Dimensional ◽  
Type Iii ◽  
Group Delays

Space observations of solar radio bursts have provided the following information:– From a single spacecraft:Measurements within the burst source or close to it: fundamental and harmonic type III radio emission, the corresponding plasma waves and spectra of the exciting electrons.– From a spacecraft and the earth or from two spacecrafts:A better evaluation of the influence of the ionosphere on some ground-based observations.Measurements of the beaming of the emission which yield constraints on the radiation mechanism and/or the role of coronal propagation in determining the source size and directivity (type I and III's).Measurements of the differential time delay which yield for type III:At short (m- and dam-) wavelengths, some evidence of group delays,At long (hm- and km-) wavelengths one coordinate of the source.Complete (3-dimensional) localization of the source at long wavelengths and therefore maps of the heliosphere magnetic field and electron density as well as the source size and, in the future, its polarization.The results of these observations and their interpretation are reviewed and discussed.

scholarly journals Separation of solar radio bursts in a complex spectrum

2010 ◽  
Vol 6 (S274) ◽  
pp. 150-152
Author(s):  
Hana Mészárosová ◽  
Ján Rybák ◽  
Marian Karlický ◽  
Karel Jiřička
Keyword(s):  
Radio Emission ◽  
Current Sheet ◽  
Solar Flares ◽  
Solar Radio ◽  
Radio Spectrum ◽  
New Method ◽  
Complex Spectrum ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Fine Structures

AbstractRadio spectra, observed during solar flares, are usually very complex (many bursts and fine structures). We have developed a new method to separate them into individual bursts and analyze them separately. The method is used in the analysis of the 0.8–2.0 GHz radio spectrum of the April 11, 2001 event, which was rich in drifting pulsating structures (DPSs). Using this method we showed that the complex radio spectrum consists of at least four DPSs separated with respect to their different frequency drifts (−115, −36, −23, and −11 MHz s−1). These DPSs indicate a presence of at least four plasmoids expected to be formed in a flaring current sheet. These plasmoids produce the radio emission on close frequencies giving thus a mixture of superimposed DPSs observed in the radio spectrum.

A Study of Solar Radio Bursts with Fine Structures during Flare/CME Events

Solar Physics ◽  
2008 ◽  
Vol 253 (1-2) ◽  
pp. 143-160 ◽  
Author(s):  
J. Huang ◽  
Y. H. Yan ◽  
Y. Y. Liu
Keyword(s):  
Solar Radio ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Fine Structures

Characteristics of the fine structures in solar radio bursts at 3.2 cm

1997 ◽  
Vol 21 (3) ◽  
pp. 339-346
Author(s):  
Zhi-hai Qin ◽  
Guang-li Huang ◽  
Qi-jun Yao
Keyword(s):  
Solar Radio ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Fine Structures

scholarly journals SOLAR RADIO BURSTS WITH SPECTRAL FINE STRUCTURES IN PREFLARES

2015 ◽  
Vol 799 (1) ◽  
pp. 30 ◽  
Author(s):  
Yin Zhang ◽  
Baolin Tan ◽  
Marian Karlický ◽  
Hana Mészárosová ◽  
Jing Huang ◽  
...  
Keyword(s):  
Solar Radio ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Fine Structures

scholarly journals On the Relative Position and Origin of Harmonics in the Spectra of Solar Radio Bursts of Spectral Types II And III

1962 ◽  
Vol 15 (2) ◽  
pp. 180 ◽  
Author(s):  
SF Smerd ◽  
JP Wild ◽  
KV Sheridan
Keyword(s):  
Solar Atmosphere ◽  
Relative Position ◽  
Solar Radio ◽  
Second Harmonic ◽  
Simple Theory ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Harmonic Emission ◽  
Type Iii

Observational results are given concerning the relative positions on the Sun's disk of the fundamental and second-harmonic emissions of solar radio bursts of spectral types II and III. Contrary to simple theory, the results indicate that it is common for the harmonic emission in type II bursts to arrive from directions corresponding to much lower heights in the solar atmosphere than the fundamental. The results for type III bursts are inconclusive but suggest the same trend.

Using supervised machine learning to automatically detect type II and III solar radio bursts

2020 ◽  
Author(s):  
Eoin Carley
Keyword(s):  
Machine Learning ◽  
Radio Burst ◽  
Solar Radio ◽  
Machine Learning Algorithms ◽  
Supervised Machine Learning ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Dynamic Spectra

&lt;p&gt;Solar flares are often associated with high-intensity radio emission known as `solar radio bursts' (SRBs). SRBs are generally observed in dynamic spectra and have five major spectral classes, labelled type I to type V depending on their shape and extent in frequency and time. Due to their morphological complexity, a challenge in solar radio physics is the automatic detection and classification of such radio bursts. Classification of SRBs has become necessary in recent years due to large data rates (3 Gb/s) generated by advanced radio telescopes such as the Low Frequency Array (LOFAR). Here we test the ability of several supervised machine learning algorithms to automatically classify type II and type III solar radio bursts. We test the detection accuracy of support vector machines (SVM), random forest (RF), as well as an implementation of transfer learning of the Inception and YOLO convolutional neural networks (CNNs). The training data was assembled from type II and III bursts observed by the Radio Solar Telescope Network (RSTN) from 1996 to 2018, supplemented by type II and III radio burst simulations. The CNNs were the best performers, often exceeding &gt;90% accuracy on the validation set, with YOLO having the ability to perform radio burst burst localisation in dynamic spectra. This shows that machine learning algorithms (in particular CNNs) are capable of SRB classification, and we conclude by discussing future plans for the implementation of a CNN in the LOFAR for Space Weather (LOFAR4SW) data-stream pipelines.&lt;/p&gt;

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