Community of European Solar Radio Astronomers – Page 12

Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe
by V. Krupar et al.*

2020-03-31

Type III bursts belong among the strongest radio signals routinely observed by both space-borne and ground-based instrumentations. They are generated via the plasma emission mechanism, when beams of suprathermal electrons interact with the ambient plasma triggering radio emissions at the plasma frequency (the fundamental emission) or at its second harmonic (the harmonic emission). As the electron beams propagate outward from the Sun, radio emissions are generated at progressively lower frequencies […]

Fast reconnection in turbulent media
by A. Lazarian

2020-03-17

Solar flares, similar to many other astrophysical energetic processes, are related to magnetic reconnection. During these events magnetic energy is transferred from other forms of energy, mostly heat and energetic particles. Traditionally, the goal of various models of magnetic reconnection was to explain the rate of this energy transfer. However, the flares are just one of the processes that involves magnetic reconnection. If one imagines any complex motion in a […]

Spectral Structures of Type II Solar Radio Bursts and Solar Energetic Particles
by K. Iwai

2020-03-03

Solar eruptive phenomena, such as flares and coronal mass ejections (CMEs), generate high-energy particles called solar energetic particles (SEPs). Severe SEP events sometimes cause satellite anomalies and radiation exposure to humans in space. Hence, understanding and forecasting SEPs is an important issue in space weather. Type II solar radio bursts are nonthermal radio emissions with negative frequency drift observed between the metric and kilometric frequency range. They are thought to […]

The multi-thermal chromosphere: inversions of ALMA and IRIS data
by J. M. da Silva Santos et al.

2020-02-18

Observations in the ultraviolet (UV) taken with the Interface Region Imaging Spectrograph (IRIS) have shown that the bright magnetic patches, known as plage, typically feature broader and brighter MgII h and k lines, which suggests that the chromosphere above plage is hotter and denser than in the quiet-Sun (e.g., Carlsson et al. 2015). However, not all line broadening is thermal; a nonthermal broadening component of up to 10 km s$^{-1}$ […]

Evolution of Coronal and Interplanetary Shock Waves Inferred from a Radio Burst
by Khaled Alielden

2020-02-04

Estimating the kinematics of Type II radio-burst sources, which are recognized as a shock waves, using electron-density models is inaccurate and restricted. In this article, a blast-expansion technique is used for the first time for estimating the kinematics of a Type II radio-burst source without using electron-density models by studying the density variation along the leading surface of the coronal mass ejections (CMEs) (herein: ejecta) during Type-II radio-burst emission. This […]

On the Source Position and Duration of a Solar Type III Radio Burst Observed by LOFAR
by P. Zhang et al.*

2020-01-21

Type III radio bursts are generated by non-thermal electron beams propagating through the solar corona and interplanetary space. In dynamic spectra, the flux of solar type III radio bursts have a time profile of rising and decay phases at a given frequency, which has been actively studied since the 1970s. There are several factors that may contribute to the observed duration of a type III radio burst: 1) The velocity […]

First observation of the solar Type III burst decay and its interpretation
by V. Melnik et al*

2020-01-07

Wild (1950) was the first to register and describe Type III bursts properties. These bursts are tracks of radio emission, which drift from high frequencies to low frequencies. Profiles of Type III bursts have a quick rise and slower fall. Wild supposed that electrons with high velocities, up to 0.3c (c is the speed of light), were responsible for Type III bursts based on their high frequency drift rates. Ginzburg […]

First imaging spectroscopy observations of puzzling solar drift pair bursts
by A. Kuznetsov and E. Kontar

2019-12-17

Drift pairs are a rare and puzzling type of solar radio emission, firstly identified by Roberts (1958). They occur at low frequencies (~10-100 MHz) and look like two parallel frequency-drifting narrow-band stripes separated in time. The drift rates (typically ~2-8 MHz/s) are intermediate between those of type II and type III bursts; both positive and negative frequency drifts are observed. The most enigmatic characteristic of drift pair bursts is that […]

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