Community of European Solar Radio Astronomers – Page 7

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

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 […]

The active region source of a type III radio storm observed by Parker Solar Probe during encounter 2
by L. Harra et al*

2021-09-16

During encounter 2 of NASA’s PSP mission there was a large amount of radio activity and, in particular, a noise storm of frequent, small type III bursts from 31 March to 6 April 2019. Our aim is to investigate the source of these small and frequent bursts. We studied the behaviour of active region 12737, whose emergence and evolution coincides with the timing of the radio noise storm and determined the […]

Langmuir wave motion observed in the most intense radio sources in the sky
by H. Reid and E. Kontar

2021-08-31

The Sun routinely produces energetic electrons in its outer atmosphere that subsequently travel through interplanetary space. These electron beams generate Langmuir waves in the background plasma, producing type III radio bursts that are the brightest radio sources in the sky (Suzuki & Dulk, 1985). These solar radio bursts also provide a unique opportunity to understand particle acceleration and transport which is important for our prediction of extreme space weather events […]

Quasi-Periodic Particle Acceleration in a Solar Flare
by B. Clarke et al.*

2021-08-17

Quasi-periodic pulsations (QPPs) are defined as intensity modulations in the flare electromagnetic radiation as a function of time. These modulations have been found to have characteristic periodicities that range from < 1 s up to several minutes. QPPs were first associated with the impulsive phase of flares and observed in the hard X-ray (HXR) and radio wavebands (Parks & Winkler 1969). They have more recently been observed within the thermal […]

New results on the direct observations of thermal radio emission from a solar coronal mass ejection
by R. Ramesh et al.*

2021-08-03

Coronal mass ejections (CMEs) are large scale and energetic eruptions in the solar atmosphere during which $\approx$10$^{12}$-10$^{16}$g of magnetized coronal plasma are ejected into the heliosphere at speeds ranging from $\approx$100-3000km/s. They are mostly observed in whitelight using coronagraphs which use an occulter to block the bright light from the solar photosphere so that structures like CMEs can be observed with better contrast. But the size of the coronagraph occulters […]

New treatment of gyroresonance and free-free radio emissions from multi-thermal multi-component plasma
by A. Kuznetsov et al.*

2021-07-20

Thermal plasma in the solar corona is often characterized by a range of temperatures. This plasma can be described by the differential emission measure (DEM), which is a distribution of the thermal electron density square over temperature. The DEM-based treatment is widely used in application to the optically thin EUV and X-ray emissions. However, there has been no corresponding treatment in the radio domain, where optical depth of emission can […]

Energy budget of plasma motions, heating, and electron acceleration in a three-loop solar flare
by G. Motorina et al.*

2021-07-06

The solar flare phenomenon is a complex process in the solar atmosphere where non-potential magnetic energy is released and converted into other forms of energy, such as nonthermal energy of accelerated particles, thermal energy of heated flaring plasma, kinetic energy of eruptions, jets, up/down flows, and stochastic (turbulent) plasma motions. The processes lying behind initial division between energy components, distribution of these components among flaring loops and their evolution are […]

Narrowband Spikes Observed during the 2013 November 7 Flare
by M. Karlicky et al.

2021-06-22

Narrowband dm-spikes belong to the most interesting fine structures of solar radio bursts that are closely connected to primary flare energy-release processes (Krueger 1979) and observed in some cases near the Type III burst starting frequency. They occur in clouds of narrowband bursts with a typical duration less than 100 ms, frequency relative bandwidth 1-3 %, and brightness temperature up to $10^{15}$ K. For them several radio emission models were suggested. Earlier models suggested […]

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