Community of European Solar Radio Astronomers – Page 4

Solar coronal density turbulence and magnetic field strength at the source regions of two successive metric type II radio bursts by Ramesh et. al.

2023-03-14

Solar type II radio bursts appear in the spectrograph records as slowly drifting emission lanes from high to low frequencies. They are due to plasma oscillations caused by the electrons accelerated at the MHD shocks propagating outward in the solar atmosphere (Nelson et al. 1985, Mann et al. 1995). The plasma emission in a magnetic field gets split as ordinary ($O$) and extraordinary ($X$) modes. Since the propagation characteristics of […]

The frequency ratio and time delay of fundamental and harmonic components in solar radio bursts by X. Chen et al

2023-02-28

Solar radio bursts generated through the plasma emission mechanism produce radiation near the local plasma frequency (fundamental emission, hereafter, F) and double the plasma frequency (harmonic, hereafter, H). While the theoretical ratio of these two frequencies is close to 2, simultaneous observations give ratios ranging from 1.6 to 2, suggesting either a ratio different from 2, a delay of the F emission, or both. Observations suggest that a delayed F […]

The Radial Variation of the Solar Wind Turbulence Spectra near the Kinetic Break Scale from Parker Solar Probe Measurements, by Lotz et al

2023-02-14

The Parker Solar Probe (PSP) has enabled unprecedented opportunity to study the plasma and magnetic field properties of the solar wind from near the Earth (~1 au radial distance r) to very close to the sun (r < 0.1 au). We are interested in the turbulence characteristics of the solar wind and how it evolves from close to the sun to far away. This information is crucial to the understanding […]

Special issue “Recent progress in the physics of the Sun and heliosphere”, by E. Kontar and I. Ballai

2023-02-10

The present Special Issue published in Advances of Space Research contains a collection of peer-reviewed contributions that builds on the recent observational and theoretical advances, surveying the existing knowledge in reconnecting magnetic fields, flares and plasma heating, the generation, evolutions and dynamics of small-scale solar jets, dynamics in various layers of the solar atmosphere, recent advances in coronal spectroscopy and the evolution of the solar wind inspired by European Solar […]

The First Flare Observation with a New Solar Microwave Spectrometer Working in 35–40 GHz, By Yan et al.

2023-01-31

Microwave emission of solar flares can be excited by energetic electrons through the gyrosynchrotron (GS) radiation. Thus, the microwave spectra contain valuable/unique information not only about energetic electrons accelerated during solar flares, but also about the underlying magnetic field and energy release process. The typical microwave spectra peak below or around, say, ~10 GHz, at which the spectral slope turns over from positive — the optically thick regime — to […]

Radio Scintillation Observations of the Plasma Tail of Interstellar Comet 2I/Borisov, by P K Manoharan et al.*

2023-01-17

Comet 2I/Borisov was only the second interstellar object known to have entered the solar system. The highly eccentric, hyperbolic orbit of 2I/Borisov and its high inclination to the ecliptic plane demonstrated that the comet had an extrasolar system origin (e.g., Manzini et al. 2020). Polarimetric observations of this comet suggested a remarkably smooth, pristine coma with a high concentration of carbon monoxide, that had likely never interacted with the solar […]

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

2023-01-03

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

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) […]

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