Characterising coronal turbulence using snapshot imaging of radio bursts in 80 – 200 MHz
by Atul Mohan

2022-01-04 161 views

Metrewave solar type-III radio bursts offer a unique means to study the properties of turbulence across coronal heights. Theoretical models have shown that the apparent intensity and size of the burst sources evolve at sub-second scales due to turbulent scattering of radio waves close to their generation sites (Arzner & Magun, 1999; Kontar et al., 2019). The advent of high cadence snapshot spectroscopic imaging capabilities in meter wavebands have made […]

Particle-in-cell simulation of plasma emission in solar radio bursts
by T. M. Li et al.

2021-12-21 143 views

Solar radio radiation is one of the most sensitive emissions during solar eruptions, where type III radio bursts can provide clues for electron acceleration and propagation. Type III radio bursts are widely accepted to result from the plasma emission, which is observationally supported by the presence of Langmuir waves, and excited electromagnetic waves at fundamental and harmonic frequencies from the nonlinear wave coupling (Ginzburg & Zhelezniakov 1958). Such a mechanism […]

Searching for optical/EUV counterparts of type IIs in a complex metric burst

by Costas Alissandrakis et al.*

2021-12-07 201 views

Solar type II bursts are sporadic emissions characterized by their narrow bandwidth and slow frequency drift in dynamic spectra (Nelson & Melrose, 1985; Vršnak & Cliver 2008; Nindos et al. 2008; Pick & Vilmer 2008). They are attributed to shock waves produced by flare/CME eruptions. However, the association of type IIs with optical or EUV features is not clear; the leading edge or flanks of CMEs, the front of an […]

PIC simulations of harmonic maser emissions
by Ning et al.*

2021-11-23 346 views

Electron cyclotron maser emission (ECME) represents a major class of coherent emission mechanism of solar radio bursts. ECME usually occurs in strongly magnetized plasmas with the frequency ratio $\omega_{pe} / \Omega_{ce} < 1$, induced by energetic electrons with $\partial f /\partial v >0$, where $f$ represents the velocity distribution function. In solar active regions, this mechanism has been applied to millisecond spikes which are characterized by high brightness temperatures, short […]

Radio Interferometric Observations of the Sun Using Commercial Dish TV Antennas
by G. V. S. Gireesh et al.*

2021-11-09 247 views

Commercial dish TV antennas are parabolic structures designed to receive radio waves from a communication satellite. The antennas and the associated front end receiver systems have improved with advances in the TV systems. They operate typically over the frequency range 10.7 – 11.7 GHz (Ku-band) and provide very good signal-to-noise ratio (SNR). It is well known that the Sun emits intense radio emission in the above frequency range with brightness […]

Radio, X-ray and extreme-ultraviolet observations of weak energy releases in the ‘quiet’ Sun
by Ramesh et. al.

2021-10-26 127 views

Small scale energy releases on the Sun e.g., flaring bright points, active region transient brightenings, etc. have been studied using X-ray and radio observations. The observations of low frequency radio type III bursts in associated with X-ray bright point flares (Kundu et. al. 1980) and coronal X-ray jets (Aurass et. al. 1994) indicated that the latter are capable of accelerating particles to non-thermal energies, as well as producing the heated […]

First Frequency-time-resolved Imaging Spectroscopy Observations of Solar Radio Spikes
by D. L. Clarkson et al.*

2021-10-12 287 views

Solar radio spikes are short duration, narrowband radio bursts that are signature of the acceleration of non-thermal electrons in solar flares. They are observed over a wide range of frequencies from the tens of MHz (Melnik et al. 2014) to the GHz range (Benz et al. 1992), and have some of the shortest durations and narrow bandwidths of any solar radio bursts. The origin of spikes is not fully understood. […]

Properties of High-Frequency Type II Radio Bursts and Their Relation to the Associated Coronal Mass Ejections
by A.C. Umuhire et al.*

2021-09-28 226 views

Type II radio bursts are slow-drifting and long-lasting radio emission produced by nonthermal electrons accelerated at shocks propagating through the solar corona and interplanetary medium (Nelson & Melrose, 1985). The accelerated electrons generate Langmuir waves, which get converted into electromagnetic radiation by the plasma emission mechanism first identified by Ginzburg & Zhelezniakov (1958). Currently, there is a common understanding that type II radio bursts are produced by shocks formed ahead […]

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