Radio Probing of Solar Wind Sources in Coronal Magnetic Fields
 by A. Koval et al.*

2022-01-18 147 views

The magnetic fields of the Sun govern the solar corona structure where the solar wind emanates and further accelerates supersonically. Therefore, the accurate observational data about the topology, and more significantly, quantities of the coronal magnetic field are pivotal for identifying the solar wind sources as well as for the Space Weather modeling where these data specify initial conditions. Magnetic-field strength values in the solar wind sources are derived from […]

Searching for optical/EUV counterparts of type IIs in a complex metric burst

by Costas Alissandrakis et al.*

2021-12-07 182 views

Solar type II bursts are sporadic emissions characterized by their narrow bandwidth and slow frequency drift in dynamic spectra (Nelson & Melrose, 1985; Vršnak & Cliver 2008; Nindos et al. 2008; Pick & Vilmer 2008). They are attributed to shock waves produced by flare/CME eruptions. However, the association of type IIs with optical or EUV features is not clear; the leading edge or flanks of CMEs, the front of an […]

Properties of High-Frequency Type II Radio Bursts and Their Relation to the Associated Coronal Mass Ejections
by A.C. Umuhire et al.*

2021-09-28 204 views

Type II radio bursts are slow-drifting and long-lasting radio emission produced by nonthermal electrons accelerated at shocks propagating through the solar corona and interplanetary medium (Nelson & Melrose, 1985). The accelerated electrons generate Langmuir waves, which get converted into electromagnetic radiation by the plasma emission mechanism first identified by Ginzburg & Zhelezniakov (1958). Currently, there is a common understanding that type II radio bursts are produced by shocks formed ahead […]

Analyzing the propagation of EUV waves and their connection with type II radio bursts by combining numerical simulations and multi-instrument observations
by A. Koukras et al.*

2021-03-16 134 views

EUV (EIT) waves are wavelike disturbances of enhanced extreme ultraviolet (EUV) emission that propagate away from an eruptive region. Recent years have seen much debate over their nature, with three main interpretations: the fast-mode MHD wave, the apparent wave (reconfiguration of the magnetic field), and the hybrid wave (combination of the previous two). Observations of such waves are often accompanied by type II radio bursts, which are widely considered as signature […]

Electromagnetic Emission Produced by Three-wave Interactions in a Plasma with Continuously Injected Counterstreaming Electron Beams
by Vladimir Annenkov and Igor Timofeev

2021-01-19 211 views

Weakly turbulent processes of three-wave interactions between Langmuir and electromagnetic waves in plasma with unstable electron flows are believed to be the main cause of type II and III solar radio emissions. The narrow band of type II bursts requires assuming that this radiation is generated in some local regions of shock fronts traveling in the solar corona, where the specific conditions for the enhancement of electromagnetic emissions near the […]

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

2020-12-01 172 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 […]

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

2020-06-09 175 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

2020-05-26 382 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 […]

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