solar radio emission

Noise in Maps of the Sun at Radio Wavelengths by T. S. Bastian et al.

2025-10-28

The Sun is a powerful source of radio emissions, so much so that – unlike most celestial sources – this emission dominates the system noise of many radio telescopes. The noise resulting from such sources is referred to as “self-noise”. Two recent papers discuss self-noise in maps of the Sun at radio frequencies formed using the techniques of Fourier synthesis imaging. Examples of radio telescopes that exploit this technique include […]

Spectroscopic Imaging of the Sun with MeerKAT: Opening a New Frontier in Solar Physics by Kansabanik et al.

2024-04-10

Since the discovery of solar radio emission in the late 1940s, the Sun has been studied in great detail across a wide range of frequencies from a few tens of kHz to several hundreds of GHz. Solar radio emissions provide several unique diagnostics of the solar corona, which are otherwise simply inaccessible. Despite this long history of observations and studies, the Sun still harbors several mysteries. Improved observations from the […]

Observations of fragmented energy release during solar flare emission
by R. Ramesh et al.*

2020-07-28

Type III radio bursts from the Sun are signatures of energetic (∼1–100 keV) electrons, accelerated at the reconnection sites, propagating upward through the corona into the interplanetary medium along open magnetic field lines. The emission mechanism of the bursts is widely believed to be due to coherent plasma processes. The bursts are observed typically in the frequency range $\approx 1\,$GHz$ – 10\,$kHz, which corresponds to radial distance range between the […]

Anisotropic radio-wave scattering in the solar corona
Nicolina Chrysaphi et al.*

2019-11-26

Solar radio emission is produced in the turbulent medium of the solar atmosphere, and its observed properties (source position, size, time profile, polarization, etc.) are significantly affected by the propagation of the radio waves from the emitter to the observer. Scattering of radio waves on random density irregularities has long been recognized as an important process for the interpretation of radio source sizes (e.g., Steinberg et al. 1971), positions (e.g., […]

Solar chromospheric temperature diagnostics: A joint Hα – ALMA analysis
by K. Reardon et al

2019-10-01

There are many challenges in inferring the spatially and temporally varying temperatures of the dynamic solar chromosphere. The principal problem has been the complex formation of the spectral lines in the UV, visible, and infrared that have been the prime diagnostics to probe this region of the atmosphere. The Atacama Large Millimeter Array (ALMA), which became available for solar observations in 2016, promises to help address this issue by observing […]

Third harmonic electromagnetic radiation observed in Interplanetary Type III radio bursts by
M. Reiner et al.*

2019-09-17

Type III solar radio bursts, which appear as characteristic frequency-drifting features on radio dynamic spectra, are generated by energetic beams of electrons originating in solar active regions and propagating through the interplanetary medium. The remotely observed type III radiation consists of fundamental and harmonic components. Second harmonic electromagnetic radiation in type III solar radio bursts is well established at both high frequencies (metric and decametric wavelengths) and at low frequencies […]

Direct Observations of Traveling Ionospheric Disturbances as 
Focusers of Solar Radiation: Spectral Caustics
by A. Koval et al*

2019-08-27

The solar radiation focusing effect is related to the specific phenomenon of propagation of the Sun-emitted HF and VHF waves through the terrestrial ionosphere. This natural effect is observed with ground-based radio instruments running within the 10-200 MHz range, as distinctive patterns – the Spectral Caustics (SCs) – on the solar dynamic spectra. On the spectrograms they exhibit unusual morphology and specific time-frequency features (CESRA nugget by Koval et al., […]

Solar Physics with the Square Kilometre Array
by A. Nindos et al.*

2019-08-13

Although solar physics is one of the most mature branches of astrophysics, the Sun confronts us with a large number of outstanding problems that are fundamental in nature.  These problems include the determination of the structure and dynamics of the solar atmosphere, the magnetic field evolution in the chromosphere and corona, coronal heating, the physics of impulsive energy release, energetic particle acceleration and transport, the physics of coronal mass ejections […]

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