Sizes of solar radio sources observed by LOFAR

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

<p>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.</p><p>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  developed by Kontar et al. 2019 (Astrophys.J., 884, 122).</p>

scholarly journals Low Frequency Radio Astronomy from Above the Ionosphere

2002 ◽  
Vol 199 ◽  
pp. 488-489
Author(s):  
D. L. Jones
Keyword(s):  
High Resolution ◽  
Radio Astronomy ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
Low Frequency ◽  
Dramatic Improvement ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Low Frequencies ◽  
High Resolution Images

The GMRT represents a dramatic improvement in ground-based observing capabilities for low frequency radio astronomy. At sufficiently low frequencies, however, no ground-based facility will be able to produce high resolution images while looking through the ionosphere. A space-based array will be needed to explore the objects and processes which dominate the sky at the lowest radio frequencies. An imaging radio interferometer based on a large number of small, inexpensive satellites would be able to track solar radio bursts associated with coronal mass ejections out to the distance of Earth, determine the frequency and duration of early epochs of nonthermal activity in galaxies, and provide unique information about the interstellar medium.

scholarly journals Characterization of Selected Solar Radio Bursts Based on Solar Activity Detected by e-CALLISTO (Malaysia)

2014 ◽  
Vol 32 ◽  
pp. 144-154
Author(s):  
Zety Sharizat Hamidi ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Solar Flare ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
Low Frequency ◽  
Weather Condition ◽  
Impulsive Phase ◽  
Primary Energy ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Solar Burst

One of the main reasons to study more about the dynamics of solar radio bursts is because solar these bursts can interfere with the Global Positioning System (GPS) and communications systems. More importantly, these bursts are a key to understand the space weather condition. Recent work on the interpretation of the low frequency region of a main solar burst is discussed. Continuum radio bursts are often related to the solar activities such as an indication of the formation of sunspot, impulsive phase of solar flares and Coronal Mass Ejections (CMEs) and their frequencies correspond to the densities supposed to exist in the primary energy release volume. Specifically, solar burst in low frequency play an important role in interpretation of Sun activities. In this work, we have selected few solar bursts that successfully detected by our station at the National Space Centre, Banting Selangor. Our objective is to correlate the solar burst with Sun activities by looking at the main sources that responsibility with the trigger of solar burst. It is found that type II burst is dominant with Coronal Mass Ejections (CMEs), type III burst associated with solar flare, IV burst with the formation of active region and type U burst high solar flare. We believed that this work is a good start to monitor Sun’s activities in Malaysia as equatorial country.

Nonrelativistic electron beam expansion in the solar corona/wind  and their type III radio bursts observed with LOFAR

2021 ◽  
Author(s):  
Hamish Reid ◽  
Eduard Kontar
Keyword(s):  
Electron Beam ◽  
Energy Density ◽  
Solar Corona ◽  
Electron Beams ◽  
Low Frequency ◽  
High Energy ◽  
High Energy Density ◽  
Moderate Intensity ◽  
Radio Bursts ◽  
Type Iii

<div> <div><span>Solar type III radio bursts contain a wealth of information about the dynamics of near-relativistic electron beams in the solar corona and the inner heliosphere; this information is currently unobtainable through other means.  Whilst electron beams expand along their trajectory, the motion of different regions of an electron beam (front, middle, and back) had never been systematically analysed before.  Using LOw Frequency ARray (LOFAR) observations between 30-70 MHz of type III radio bursts, and kinetic simulations of electron beams producing derived type III radio brightness temperatures, we explored the expansion as electrons propagate away from the Sun.  From relatively moderate intensity type III bursts, we found mean electron beam speeds for the front, middle and back of 0.2, 0.17 and 0.15 c, respectively.  Simulations demonstrated that the electron beam energy density, controlled by the initial beam density and energy distribution have a significant effect on the beam speeds, with high energy density beams reaching front and back velocities of 0.7 and 0.35 c, respectively.  Both observations and simulations found that higher inferred velocities correlated with shorter FWHM durations of radio emission at individual frequencies.  Our radial predictions of electron beam speed and expansion can be tested by the upcoming in situ electron beam measurements made by Solar Orbiter and Parker Solar Probe.</span></div> </div>

On Low‐Frequency Type III Solar Radio Bursts Observed in Interplanetary Space

2004 ◽  
Vol 605 (1) ◽  
pp. 503-510 ◽  
Author(s):  
C. S. Wu ◽  
M. J. Reiner ◽  
P. H. Yoon ◽  
H. N. Zheng ◽  
S. Wang
Keyword(s):  
Solar Radio ◽  
Interplanetary Space ◽  
Low Frequency ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Type Iii

scholarly journals Radio Data and Computer Simulations for Shock Waves Generated by Solar Flares

1980 ◽  
Vol 91 ◽  
pp. 251-255
Author(s):  
Alan Maxwell ◽  
Murray Dryer
Keyword(s):  
Shock Waves ◽  
Solar Corona ◽  
Computer Simulations ◽  
Solar Flares ◽  
Solar Radio ◽  
Radio Bursts ◽  
Type Ii ◽  
Fast Mode ◽  
Solar Radio Bursts ◽  
Radio Data

Solar radio bursts of spectral type II provide a prime diagnostic for the passage of shock waves, generated by solar flares, through the solar corona. In this investigation we have compared radio data on the shocks with computer simulations for the propagation of fast-mode MHD shocks through the solar corona. The radio data were recorded at the Harvard Radio Astronomy Station, Fort Davis, Texas. The computer simulations were carried out at NOAA, Boulder, Colorado.

scholarly journals First Type III Solar Radio Bursts of Solar Cycle 25

Solar Physics ◽  
2021 ◽  
Vol 296 (4) ◽  
Author(s):  
Juha Kallunki ◽  
Derek McKay ◽  
Merja Tornikoski
Keyword(s):  
Solar Cycle ◽  
Solar Radio ◽  
Low Frequency ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Type Iii ◽  
Receiver Array ◽  
Imaging Receiver ◽  
Solar Bursts ◽  
Cycle 24

AbstractThe minimum of the previous solar cycle, Solar Cycle 24, occurred in December 2019, which also marked the start of the new Solar Cycle 25. The first radio bursts of the new solar cycle were observed in the spring season 2020. In this work we will present three type III solar bursts which were observed in May and June 2020 at radio frequencies between 18 – 90 MHz. There are two radio observatories in Finland that are capable of doing low-frequency solar radio observations: Aalto University Metsähovi Radio Observatory (MRO) and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) of the Sodankylä Geophysical Observatory, University of Oulu. The instruments of the two institutes have different design and characteristics, and they operate in rather different radio interference environments. We will compare simultaneous observations from these two instruments and we will also discuss the properties of these type III solar bursts.

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