Community of European Solar Radio Astronomers – Page 3

Microwave imaging of quasi-periodic pulsations at flare current sheet by Yuankun Kou et al.

2023-01-03 282 views

Quasi-periodic pulsations (QPPs; also known as quasi-periodic oscillations, i.e., QPOs) are phenomena that electromagnetic emissions vary quasi-periodically with time. They appear in celestial transient events with different temporal/spatial scales, such as stellar flares, gamma ray bursts and fast radio bursts, and etc. The Sun is a normal but the closest star from us, where flares with QPPs appear frequently (e.g. Zimovets et al. 2021 as a review). In the standard […]

Zebra Stripes with High Gyro-Harmonic Numbers by Jan Benacek and Marian Karlicky

2022-12-20 148 views

The solar radio zebra patterns, or zebras, provide detailed diagnostics of plasma density and magnetic field in the corona. The zebras appear in radiograms during Type IV solar radio bursts as a series of parallel stripes that are narrow in frequency. The main emission model of radio zebras relies on a double plasma resonance, a resonance between the plasma frequency, gyro-harmonic of the cyclotron frequency, and the frequency of unstable upper-hybrid (UH) […]

Flares detected in ALMA single-dish images
by I. Skokic et al

2022-12-06 292 views

The (sub)millimeter radiation of solar flares, explosive events detected as brightenings across the electromagnetic spectrum, is poorly understood (Krucker et al. 2013). The major limit of the previous >100 GHz observations was spatial resolution, impeding the combination with observations at other wavelengths. The Atacama Large Millimeter-submillimeter Array (ALMA) offers sufficient resolution for the first time. Shimizu et al. (2021) reported a microflare observed in interferometric mode. However, used as an […]

Third and fourth harmonics of electromagnetic emissions by a weak beam in a solar wind plasma with random density fluctuations by C. Krafft

2022-11-22 145 views

Electromagnetic emissions at the third harmonic of the plasma frequency $\omega _{p}$ have been reported during the occurrence of type II and type III solar radio bursts (e.g. Zlotnik 1978, Zlotnik et al. 1998, Cairns; 1986), even if rarely and sometimes controversially. Recently the Wind spacecraft detected several events exhibiting third harmonic emissions in interplanetary type III bursts observed locally near 1 AU (Reiner and MacDowald; 2019). For the first […]

Characteristics of stripes-pattern radio-emission sources by Khaled Alielden

2022-10-18 119 views

Investigating the generation mechanism for the stripes-pattern radio spectra is important to understand the dynamics of non-thermal electrons in several astronomical objects, including the Sun, Jupiter, and the Crab Pulsar. A new analytical study is carried out to identify the plasma characteristics of fiber- and zebra-pattern emission sources without an underlying density or magnetic model. The study suggests that the plasma condition of the source region for zebra pattern emission […]

Narrowband Spikes Observed During the 13 June 2012 Flare in the 800 – 2000 MHz Range by Marian Karlicky et al

2022-09-06 127 views

The solar radio spikes can provide detailed information about plasma processes in solar flares on kinetic scales. Among them, the decimetric spikes belong to the most interesting ones because they are recorded in some cases close to the starting frequency of Type-III bursts and in relation to hard X-ray emissions. Stepanov et al. (1999) and Bárta and Karlický (2001) presented models where spike frequencies correspond to those of the upper-hybrid […]

Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm by Devojyoti Kansabanik et al

2022-08-23 91 views

The solar corona comprises hot magnetized plasma. Coronal magnetic fields are well known to be one of the crucial parameters determining the physics of the solar corona and are vital drivers of Space Weather. Despite the fact that the importance of coronal magnetic fields has been recognised for a long, in practice, they remain rather hard to measure. The polarization properties of coronal emission at low radio frequencies can, in […]

First detection of metric emission from a solar surge by Costas Alissandrakis et al.*

2022-07-19 339 views

Practically all solar phenomena observed in radio wavelengths have their counterpart in other regions of the electromagnetic spectrum. Metric solar bursts are an exception to the above statement. Although we have a basic understanding of their origin, some of their counterparts in other spectral ranges have not been identified, with the exception of the so called “radio CMEs”. This is apparently because metric bursts result from coherent plasma emission, which […]

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