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

2019-01-02 375 views

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.*

2018-12-18 557 views

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 […]

A type III radio burst automatic analysis system and statistic results for a half solar cycle with Nançay Decameter Array data
by Zhang et al.*

2018-12-11 370 views

Type III radio bursts are the most frequent radio bursts observed from the solar corona, which are generated by weakly relativistic electron beams moving outward along open magnetic field lines from solar active regions. According to the classic plasma emission mechanism (Melrose, 1985), the frequency drift rate of type III bursts depends both on the radial velocity of the exciter electrons and on the gradient of the background electron density […]

First high-resolution look at the quiet Sun with ALMA at 3 mm
by A. Nindos et al.*

2018-11-27 484 views

Observations of the radio continuum at millimeter (mm) wavelengths provide a unique chromospheric diagnostic. The quiet Sun mm-wavelength emission mechanism is free-free and electrons are almost always in local thermodynamic equilibrium (e.g. Shibasaki et al. 2011 and Wedemeyer et al. 2016). The availability of mm-wavelength solar observations with ALMA can advance our knowledge on the chromosphere because of the instrument’s unique spatial resolution and sensitivity. In a previous study (Alissandrakis […]

Coronal Densities Probed by Type III Radio Burst Imaging
by P. McCauley et al.*

2018-11-13 326 views

Type III solar radio bursts are caused by electron beams accelerated to modest fractions of light speed by magnetic reconnection, the process that drives solar flares. The beams stimulate oscillations in the ambient plasma, which in turn produce short periods of intense radio emission. The standard theory predicts emission at either the fundamental electron plasma frequency (fp) or its harmonic (2fp). These values are proportional to the square root of […]

Shock location and CME 3-D reconstruction of a solar type II radio burst with LOFAR
by P. Zucca et al.*

2018-10-30 337 views

Type II radio bursts are the result of shocks in the solar atmosphere and they can be observed ranging from sub-metric to kilometric wavelengths (~400 MHz to ~0.4 MHz). Coronal mass ejections initiate most of the metric type II (m-type II) bursts. The region of a CME responsible for driving the shock might be different for each event and has not yet been comprehensively identified. Multiple scenarios have been suggested, […]

Non-radial propagation of energetic electrons in solar corona by A. Klassen et al.

2018-10-16 385 views

STEREO and near-Earth multi-spacecraft observations of solar energetic particle (SEP) events have revealed that some events show quite unexpected intensity distributions at 1 AU (Dresing et al. 2012, Lario et al. 2013). They can be much broader (circumsolar) (Gómez-Herrero et al. 2015), non-symmetric, and sometimes irregular showing so-called finger distribution (Klassen et al. 2016). It had been suggested that these non-symmetric and irregular distributions, among others, may result from non-radial […]

Alternative zebra-structure models in solar radio emission
by Chernov G.P.

2018-10-02 238 views

There is ongoing discussion in the literature about the nature of zebra-structure (ZS) in type IV radio bursts (Chernov, 2011).  We showed the possibility of a model with whistler waves to explain many thin components of ZS stripes, taking into account the effects of scattering of the whistlers on fast particles. Here, we show some complex examples of observations of ZS bursts in different wave ranges, which are difficult to […]

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