Community of European Solar Radio Astronomers – Page 25

EUV-invisible reservoir of solar energetic particles
by G. Fleishman et al.*

2017-09-19

Large-scale magnetic structures, which likely make a “bridge” between the relatively compact particle acceleration site of a flare energy release and the interplanetary medium, are of particular importance because of their potential role as an “escape route” for solar energetic particles (SEPs). Although these escape routes can sometimes be associated with jets visible in extreme ultraviolet (EUV) and/or soft X-rays (SXRs), the jet plasma must be dense enough to be […]

Oscillations in the 45-5000 MHz Radio Spectrum of the 18 April 2014 Flare
by M. Karlicky et al.*

2017-09-05

Recently, oscillations were recognized in the global X–ray flux detected during the 18 April 2014 M7.3 flare by the Fermi/GBM instrument as well as in the spatially localized UV measurements of the IRIS satellite and the EIS/Hinode instruments (Brosius and Daw, 2015, Brosius, Dawn and Inglis, 2016, and Brannon, Longcope, and Qiu, 2015). Radio observations of this flare were also analyzed by Carley, Vilmer, and Gallagher (2016). The overall radio spectrum […]

Traveling Ionospheric Disturbances as Huge Natural Lenses: Solar Radio Emission Focusing Effect
by A. Koval et al*

2017-08-29

The solar radio emission in meter-decameter wavelengths demonstrates a plentiful variety of solar radio bursts of different types (with branching to sub-types) as well as events not belonging to any specific type (Melnik et al. 2005). The last group includes variable solar emissions that result from radiation processes affected by propagation effects in the terrestrial ionosphere. Particularly, low-frequency solar radiation passing through the ionosphere could be subject to different influences […]

Wavelet-based characterization of small-scale solar emission features at low radio frequencies
by A. Suresh et al.*

2017-08-15

The improved sensitivity provided by new-generation radio arrays has unveiled an enormous diversity of previously under-appreciated solar radio bursts. Observations in the 100-240 MHz band using the Murchison Widefield Array (MWA) have highlighted the presence of a myriad of weak, short-lived, narrow-band solar emission features (Fig. 1), even during calm solar periods. Their appearance in the MWA solar dynamic spectrum (DS) comes closest to miniature versions of type-III bursts with […]

Probing the Temperature Structure of the Solar Chromosphere with ALMA
by C. Alissandrakis et al.*

2017-08-01

Determining the detailed temperature structure of the solar atmosphere from observations is a basic means of constructing and testing atmospheric models. One avenue to address this problem is based on measuring the center-to-limb variation of the intensity in various spectral regions. Observations in the radio domain are particularly suited for such a task since they don’t suffer from a set of complications (e.g., departures from the ionization and local thermodynamic […]

Oscillation of solar radio emission at coronal acoustic cut-off frequency
by T. Zaqarashvili et al.

2017-07-25

Recent SECCHI COR2 observations on board the STEREO-A spacecraft have detected density structures at a distance of 2.5-15 R$_{\odot}$ propagating with periodicity of about 90 minutes (Viall and Vourlidas 2015). The authors suggested that the density structures probably formed in the lower corona. We analyzed radio emission at the frequencies of 8–32 MHz, which correspond to a distance of about 1.5–2.5 R$_{\odot}$ according to the Baumbach-Allen model of coronal electron […]

Siberian Radioheliograph: First Results
by S.V. Lesovoi et al.*

2017-07-11

Regular observations of the Sun have started at the first stage of the multiwave Siberian Radioheliograph (SRH). It is a T-shaped interferometer currently consisting of 48 antennas observing in a 4-8 GHz operating frequency range with a 10 MHz instantaneous receiving band. The SRH’s antennas are installed on the central antenna posts of the Siberian Solar Radio Telescope (SSRT: Grechnev et al., 2003). The maximum baseline is currently 107.4 m […]

The 30 cm solar radio flux: a new proxy for upper atmosphere specification
by Thierry Dudok de Wit and Sean Bruinsma

2017-06-27

The 10.7 cm solar radio flux is a widely (if not the most widely) used proxy for solar activity. However, other centimetric wavelengths have also been monitored, some routinely and for several decades. Such observations provide unique records of long-term solar variability. We find that the radio flux at 30 cm receives relatively stronger contributions from Bremsstrahlung vs gyro-resonance emissions (as compared to the 10.7 cm flux); as a consequence, […]

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