Community of European Solar Radio Astronomers – Page 18

Short-period Waves in Flare Loops: Possible Vehicle for Flare Energy Transport
by Sijie Yu et al

2019-03-26

Solar flares involve the sudden release of magnetic energy in the solar corona. Accelerated nonthermal electrons have been often invoked as the primary means for transporting the bulk of the released energy to the lower solar atmosphere. However, significant challenges remain for this scenario, especially in accounting for the large number of accelerated electrons inferred from observations. Propagating magnetohydrodynamics (MHD) waves, particularly those with subsecond/second-scale periods, have been proposed as […]

Large area solar flare ribbons as the model to explain puzzling millimeter emission
by G.G. Motorina et al.*

2019-03-12

Solar flares are sudden explosive processes, that convert the energy of the magnetic field into the kinetic energy of electrons and ions. Since the beginning of the century, millimeter observations of solar flares became routinely possible at a few frequencies with limited spatial resolution (see Kaufmann 2012, as a review). One of the most puzzling aspects of the observations at millimeter wavelengths (200-400 GHz) is the presence, in some flares, […]

Source Imaging of a Moving Type-IV Solar Radio Burst and its Role in Tracking Coronal Mass Ejection From the Inner to the Outer Corona
by Y. Chen et al.

2019-02-26

T-IV solar radio bursts are wideband continuum observed with dynamic spectrographs at metric to decametric wavelengths. They can be classified into static and moving ones, according to whether the sources remain basically static or move outward. The static ones are related to solar flares with frequencies extending up to GHz, while the moving ones (T-IVms) are related to coronal mass ejections (CMEs) with frequencies sometimes shifting to tens of MHz. […]

Temperature constraints from inversions of synthetic solar optical, UV and radio spectra
by J. M. da Silva Santos et al*

2019-02-12

While the solar chromosphere has been routinely observed in high-resolution from ground-based optical telescopes such as the Swedish Solar Telescope (SST), and more recently in the UV from space-borne telescopes such as the Interface Region Imaging Spectrograph (IRIS), radio observations lag behind despite their great potential. Distinctly from photospheric lines, most chromospheric diagnostics such as Ca II 854.2 nm and Mg II h and k form under non-LTE conditions, therefore […]

Coronal Mass Ejection-driven Type II solar radio burst structure with LOFAR and radio-wave scattering
by Nicolina Chrysaphi et al.*

2019-01-29

Coronal Mass Ejections (CMEs) are often viewed as the major drivers of space weather disturbances in the Sun-Earth system. Shocks driven by CMEs can excite radio emissions characterised by a slow frequency drift across dynamic spectra. These radio emissions are known as Type II solar radio bursts and can consist of two bands with a frequency ratio of 1:2. Each of these bands can split into two thinner sub-bands, a […]

Synthetic Radio Imaging in Quiet and Eruptive Solar Cases
by S. P. Moschou et. al.*

2019-01-15

A diverse set of radio production mechanisms makes the radio wavelengths a unique observational window into the universe. Radio emission can be produced by both quiescent and eruptive phenomena, e.g. flares and coronal mass ejections (CMEs). The morphology of the quiet Sun in radio depends on macroscopic MHD quantities, such as the density, the temperature and the magnetic field, and the type of the emission. Lee at al. (2009) showed […]

Simulation of Focusing Effect of Traveling Ionospheric Disturbances on Meter-Decameter Solar Dynamic Spectra
by A. Koval et al*

2019-01-02

Traveling ionospheric disturbances (TIDs) are one particular type of the Earth’s ionosphere irregularities (Hunsucker, 1982). They represent wave-like electron density structures propagating in the ionosphere. The motion of TIDs modulates the electron density distribution in space. It leads to a modification of plasma parameters, namely the refractive index, and affects the propagation of radio waves. In particular cases, the variations of plasma parameters strongly affect the lower-frequency electromagnetic waves that […]

Coronal mass ejections associated to a super-active region
by H. Cremades et al.*

2018-12-18

During its transit through central meridian, and along four consecutive days, from 13 to 16 February 2011, NOAA active region (AR) 11158 generated coronal mass ejections (CMEs) in association with waves observed in the extreme ultraviolet (EUV) low corona, and even with a Moreton wave. On those dates, the spacecraft of the STEREO mission were located in quadrature with SOHO and SDO, enabling the exceptional observation of this series of […]

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