Estimate of Plasma Temperatures across a CME-driven Shock from a Comparison between EUV and Radio Data
by F. Frassati et al.*

2020-12-01 141 views

Type II radio bursts, produced near the local plasma frequency and/or its harmonic by energetic electrons accelerated by shock waves moving outward through the inner heliosphere, have long been recognized as evidence of shock waves origin and propagation in the solar corona. In this work, we analyze the early evolution of a coronal shock wave, associated with a prominence eruption, with the aim of investigating the properties of the compressed […]

Polarisation and source structure of solar stationary type IV radio bursts
by C. Salas-Matamoros and L. Klein

2020-09-08 188 views

A coronal mass ejection (CME) is a phenomenon which produces large-scale ejections of mass and magnetic field from the lower corona into the interplanetary space (e.g. Forbes, 2000). The ejection of CMEs is often accompanied by the radio emission from non-thermal electrons. Particularly, stationary type IV continua are thought to be emitted by electrons in closed magnetic structures in the wake of the rising CME. Although basic properties, such as […]

Fast CME caused by the eruption of a quiescent prominence
by V. Grechnev and I. Kuzmenko

2020-06-09 168 views

CMEs can be the sources of space-weather disturbances. Shock waves expanding ahead of fast CMEs and associated flares are the probable sources of energetic protons. Two categories of CMEs have traditionally been identified depending on the presence of conspicuous chromospheric emissions during their development. Flare-associated CMEs erupt from active regions, carry stronger magnetic fields, can reach higher speeds and cause stronger space-weather disturbances. Non-flare-associated CMEs develop in eruptions of large […]

First observation of a transitioning Type II solar radio burst using the Low-Frequency Array (LOFAR)
by Nicolina Chrysaphi et al

2020-05-26 359 views

Type II solar radio bursts are believed to be excited by shock waves. They are often linked to shocks driven by solar eruptive events like Coronal Mass Ejections (CMEs) and solar flares, and are characterised by a slow drift from high to low frequencies thought to reflect the speed with which the shock propagates away from the Sun.  Shock-excited emissions that show very little or no frequency drift are known […]

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

2020-03-03 306 views

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 […]

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

2020-02-04 193 views

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 […]

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

2019-12-10 197 views

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 […]

Imaging spectroscopy of fiber bursts
by C. Alissandrakis*

2019-10-15 342 views

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 […]

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