Community of European Solar Radio Astronomers – Page 19

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

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

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

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

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

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

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 […]

Size distributions of solar proton events and their asso-ciated soft X-ray flares based on the maximum likelihood estimator
by E.W. Cliver and E. D’Huys

2018-09-18

It has been known for some time that the size distributions of solar radio bursts and soft X-ray (SXR) flares have steeper power-law slopes (~1.8) than those (~1.2) of solar energetic proton (SEP) events. Hudson (1978) suggested three possibilities for this difference: (1) proton flares are fundamentally different from ordinary flares; (2) proton flares represent the large end of the total energy distribution of ordinary flares; and (3) proton flare […]

Decimetric emission 500 arcseconds away from a flaring site: Possible scenarios from GMRT solar radio observations
by Bisoi et al.*

2018-09-04

The displaced positions of radio sources away from the true source locations are usually observed in radio images at metric and decimetric wavelengths (Duncan 1979, Benz et al. 2002, Kundu et al., 2006, Kontar et al., 2017, Mann et al., 2018). The displaced radio source location is the apparent source position, that result from the scattering of radio waves (Kontar et al. 2017) or by coronal propagation effects (Mann et […]

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