Community of European Solar Radio Astronomers – Page 5

Imaging preflare broadband pulsations in the decimetric-metric wavelengths by Lv et al

2023-07-04

Solar radio pulsations represent (quasi-)periodic or irregular short fluctuations observed from the radio flux curves or the dynamic spectra, in almost all wavelength ranges from metric to microwave (See the review by Nindos & Aurass 2007). They can be classified as broadband pulsations (BBPs) and narrowband pulsations (NBPs). Most earlier studies have focused on pulsations taking place during the impulsive or decay phases of solar flares. During the preflare stage, […]

Electron acceleration efficiency during the impulsive phase of a solar flare: X-ray and microwave observations by Kontar et al

2023-06-20

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in magnetic reconnection events at the Sun (and similar astrophysical settings) presents a major challenge in Astrophysics (e.g. Holman et al 2011). Accelerated electrons with energies above $\sim 20$ keV are revealed by hard X-ray (HXR) bremsstrahlung emission, while accelerated electrons with even higher energies usually manifest themselves through radio gyrosynchrotron emission. […]

Radio measurements of coronal magnetic fields in fan-spine configurations on the Sun by B. Ryabov and A. Vrublevskis

2023-06-06

We are striving for more accurate coronal magnetography based on changes in radio polarization as microwaves cross magnetic field lines at nearly right angles. The theory of using quasi-transverse propagation for coronal field measurements includes weak dependence on two parameters: plasma density $N_e$ and the magnetic field divergence $L_d$ (see Alissandrakis and Gary, 2021 for a review). We evaluate coronal plasma density from local differential emission measure computed from the […]

Automated Detection and Statistical Study of Solar Radio Spikes by P.R. Lv et al

2023-04-26

Solar radio spikes’ most typical observational features are their short duration and narrow bandwidth. They appear on the solar radio dynamic spectrogram as a large number of narrow-band type-III bursts, spikes, dots, sub-second clumps, groups, chains, and other narrow-band structures from decimeter to decameter wavelengths (Feng et al.(2018), Tan et al.(2019)). We have improved the YOLOv5s network model for these characteristics by adding inclined bounding frames and attention and feature […]

Solar Radio Spikes and Type IIIb Striae Manifestations Triggered by a Coronal Mass Ejection by Clarkson et al

2023-04-11

Radio bursts are frequently emitted in the outer solar corona due to the acceleration of energetic electrons in solar flares and coronal mass ejections (CME). The shortest observed bursts are radio spikes, which have narrow spectral widths and are emitted over decades in frequency. Despite being studied for many years, imaging observations are sparse and restricted to localisation of the emission at decimetre frequencies (e.g. Benz, 2002). Recently, LOw Frequency […]

Temporal and Spatial Association Between Microwaves and Type III Bursts in the Upper Corona by Altyntsev et al.

2023-03-28

One important task connected with the corona heating problem is exploring the physical mechanisms that produce, accelerate, and transport energetic particles in the upper corona. The magnetic connectivity between the sources of meter emission in the upper corona and electron acceleration sites in low corona are studied using the temporal correlation between hard X-ray (HXR) bursts and type III emission (Kane 1972; Aschwanden et al. 1995; Reid & Vilmer 2017). […]

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 […]

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