Community of European Solar Radio Astronomers – Page 17

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 […]

Are Solar Energetic Particle Events and Type II Bursts Associated with Fast and Narrow Coronal Mass Ejections?
by S. W. Kahler et al.*

2019-12-10

Gradual solar energetic (E > 10 MeV) particle (SEP) events, lasting several days, are produced in coronal/interplanetary shocks driven by fast (VCME ≥ 900 kms−1) coronal mass ejections (CMEs) associated with type II radio bursts. The basic paradigm is that CMEs with VCME > Vf, the plasma fast-mode speed, drive shocks that can accelerate seed particles to the high energies observed as SEP events in space as well as electrons […]

Anisotropic radio-wave scattering in the solar corona
Nicolina Chrysaphi et al.*

2019-11-26

Solar radio emission is produced in the turbulent medium of the solar atmosphere, and its observed properties (source position, size, time profile, polarization, etc.) are significantly affected by the propagation of the radio waves from the emitter to the observer. Scattering of radio waves on random density irregularities has long been recognized as an important process for the interpretation of radio source sizes (e.g., Steinberg et al. 1971), positions (e.g., […]

Split-Band Feature of a Solar Flare Termination Shock
by Chen et al

2019-11-12

In many space and astrophysical plasma contexts, shocks are considered as one of the most important mechanisms for accelerating charged particles up to relativistic speeds. Different types of shocks are present on the Sun. One of the most well-known types is shocks driven by coronal mass ejections (see, e.g., Morosan et al. 2019, and recent CESRA Nuggets by Mancuso et al., Chrysaphi et al., Zucca et al.). There is another […]

A microflare associated with periodic particle acceleration
by A. Mohan et al.*

2019-10-29

Microflares are weaker cousins of large flares with 103 to 106 times less energies. They are also much more ubiquitous and frequent than larger flares. A very common phenomena of the Extreme Ultra-Violet (EUV) corona, namely the Active Region Transient Brightening (ARTB; Shimizu, 1996) event is known to be associated with microflares. The ARTBs are associated with active coronal loops of length ranging from 5 – 40 Mm and often […]

Imaging spectroscopy of fiber bursts
by C. Alissandrakis*

2019-10-15

Fibers are short metric/decimetric bursts with a drift rate between type II and type III bursts, usually appearing in groups embedded in type IV continua. In most cases they show both absorption and emission ridges, the absorption having a slightly lower frequency than the emission. They are, most probably, manifestations of whistler-Langmuir wave interaction and they travel upwards along post flare loops (Kuijpers 1975). In a recent work (Bouratzis et […]