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

Solar radio bursts originate mainly from high energy electrons accelerated by solar eruptions like solar flares, jets, and coronal mass ejections (CMEs). &#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. &#160;Complete case studies of the source size, position, and kinematics of short-term bursts are very limited due to instrumental limitations. 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. 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. &#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 < 0.02 c. &#160;We show that the apparent speed of the fundamental source is more affected by the scattering and refraction of the coronal medium.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037733 ◽

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.

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Satellite Observations of Solar Radio Bursts

Symposium - International Astronomical Union ◽

10.1017/s007418090003713x ◽

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.

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Harmonic relation of type IIIb-III solar radio bursts in 6.25, 12.5, and 25.0 MHz octaves

Solar Physics ◽

10.1007/bf00146306 ◽

1984 ◽

Vol 91 (2) ◽

pp. 377-381 ◽

Cited By ~ 6

Author(s):

E. P. Abranin ◽

L. L. Bazelyan ◽

Ya. G. Tsybko

Keyword(s):

Solar Radio ◽

Radio Bursts ◽

Solar Radio Bursts ◽

Type Iiib

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Sizes of solar radio sources observed by LOFAR

10.5194/egusphere-egu21-15852 ◽

2021 ◽

Author(s):

Mykola Gordovskyy ◽

Eduard Kontar ◽

Daniel Clarkson ◽

Philippa Browning

Keyword(s):

Solar Corona ◽

Radio Wave ◽

Solar Radio ◽

Low Frequency ◽

Theoretical Models ◽

High Energy ◽

Emission Sources ◽

Radio Sources ◽

Radio Bursts ◽

Solar Radio Bursts

Decametric radio emission provides a unique insight into the physics of solar and heliospheric plasmas. Along with dynamic spectra, the spatial characteristics of the emission sources observed in solar radio bursts yield important information about the behaviour of high-energy non-thermal electrons, and the state of thermal plasma in the upper solar corona. Recently, it has been shown that sizes and locations of radio sources in the 10-100 MHz range can be used as a diagnostic tool for plasma turbulence in the upper corona and inner heliosphere. However, observations in this spectral range can be strongly affected by limited spatial resolution of the instrument, as well as by the effect of the Earth's ionosphere on radio wave propagation.We describe a new method for correcting radio intensity maps for instrumental and ionospheric effects using observations of a known radio source at an arbitrary location in the sky. Based on this method, we derive sizes and areas of the emission sources in the solar radio bursts observed by the Low-Frequency Array (LOFAR) in 30-45 MHz range. It is shown that the sizes of sources are of the order of ten arcminutes and decrease with increasing frequency. Overall, we find that the sizes and their variation, as well as the shapes of the sources in the considered events are consistent with the theoretical models of turbulent radio-wave scattering in the solar corona &#160;developed by Kontar et al. 2019 (Astrophys.J., 884, 122).

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Theory of type IIIb solar radio bursts

The Astrophysical Journal ◽

10.1086/154528 ◽

1976 ◽

Vol 207 ◽

pp. 605 ◽

Cited By ~ 20

Author(s):

R. A. Smith ◽

J. de La Noe

Keyword(s):

Solar Radio ◽

Radio Bursts ◽

Solar Radio Bursts ◽

Type Iiib

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Type II Solar Radio Bursts over Solar Cycle 21

International Astronomical Union Colloquium ◽

10.1017/s025292110002546x ◽

1994 ◽

Vol 144 ◽

pp. 283-284

Author(s):

G. Maris ◽

E. Tifrea

Keyword(s):

Solar Radio ◽

Interplanetary Space ◽

Impulsive Phase ◽

Radio Bursts ◽

Type Ii ◽

Solar Radio Bursts ◽

Strong Energy ◽

Mass Ejection ◽

Geophysical Effect ◽

Radio Event

The type II solar radio bursts produced by a shock wave passing through the solar corona are one of the most frequently studied solar activity phenomena. The scientific interest in this type of phenomenon is due to the fact that the presence of this radio event in a solar flare is an almost certain indicator of a future geophysical effect. The origin of the shock waves which produce these bursts is not at all simple; besides the shocks which are generated as a result of a strong energy release during the impulsive phase of a flare, there are also the shocks generated by a coronal mass ejection or the shocks which appear in the interplanetary space due to the supplementary acceleration of the solar particles.

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