Solar chromospheric temperature diagnostics: A joint Hα – ALMA analysis
by K. Reardon et al

2019-10-01 309 views

There are many challenges in inferring the spatially and temporally varying temperatures of the dynamic solar chromosphere. The principal problem has been the complex formation of the spectral lines in the UV, visible, and infrared that have been the prime diagnostics to probe this region of the atmosphere. The Atacama Large Millimeter Array (ALMA), which became available for solar observations in 2016, promises to help address this issue by observing […]

Third harmonic electromagnetic radiation observed in Interplanetary Type III radio bursts by
M. Reiner et al.*

2019-09-17 498 views

Type III solar radio bursts, which appear as characteristic frequency-drifting features on radio dynamic spectra, are generated by energetic beams of electrons originating in solar active regions and propagating through the interplanetary medium. The remotely observed type III radiation consists of fundamental and harmonic components. Second harmonic electromagnetic radiation in type III solar radio bursts is well established at both high frequencies (metric and decametric wavelengths) and at low frequencies […]

Direct Observations of Traveling Ionospheric Disturbances as 
Focusers of Solar Radiation: Spectral Caustics
by A. Koval et al*

2019-08-27 268 views

The solar radiation focusing effect is related to the specific phenomenon of propagation of the Sun-emitted HF and VHF waves through the terrestrial ionosphere. This natural effect is observed with ground-based radio instruments running within the 10-200 MHz range, as distinctive patterns – the Spectral Caustics (SCs) – on the solar dynamic spectra. On the spectrograms they exhibit unusual morphology and specific time-frequency features (CESRA nugget by Koval et al., […]

Solar Physics with the Square Kilometre Array
by A. Nindos et al.*

2019-08-13 475 views

Although solar physics is one of the most mature branches of astrophysics, the Sun confronts us with a large number of outstanding problems that are fundamental in nature.  These problems include the determination of the structure and dynamics of the solar atmosphere, the magnetic field evolution in the chromosphere and corona, coronal heating, the physics of impulsive energy release, energetic particle acceleration and transport, the physics of coronal mass ejections […]

High‐Frequency Communications Response to Solar Activity in September 2017 as Observed by Amateur Radio Networks
by Nathaniel A. Frissell

2019-05-07 287 views

Long before satellite communications, high frequency (HF, 3–30 MHz) radio was the primary method for long distance, over-the-horizon wireless communications. HF signals are able to travel long distances by refracting off of the ionosphere in what is known as “skip” or “skywave” propagation. Aside from a transmitter and receiver, no additional technological infrastructure is needed. Because of this, even in the modern age of space‐borne relays and widely distributed Internet availability, […]

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

2018-10-02 241 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 […]

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

2017-08-29 4,365 views

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.*

2017-08-15 643 views

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 […]

1 2 3