### 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 […]

### 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 […]

### 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, […]

### Comparison of alternative zebra-structure models in solar radio emission by G.P. Chernov et al.*

2017-05-16

Discussion about the nature of zebra-structure (ZS) in type IV radio bursts continues, despite the ten proposed models. First of all, this is due to the wide variety of stripes in each new phenomenon, making the explanation of all the fine details by any one mechanism becomes impossible. The most widespread explanation is the emission at different levels of double plasma resonance (DPR), sequential on the height surfaces in the magnetic […]

### How Electron Beams Produce Continuous Coherent Plasma Emission by H. Che, M. Goldstein, P. Diamond, and R. Sagdeev

2017-04-11

It is commonly accepted that energetic electron beams can produce drift frequency radio emission or Type III bursts since Ginzburg and Zhelezniakov first proposed the idea in 1958. However, the electron two-stream instability time (see reference 2) in the corona is fraction of a second, while the duration of coronal Type III bursts lasts several orders of magnitude longer. This problem is called the “Sturrock Dilemma” and remains a subject […]

### Emission of radiation by plasmas with counter-streaming electron beams by L. F. Ziebell et al.*

2017-01-31

The phenomena of emission of radiation by the Sun, which are known as type II and type III solar radio bursts, have been known and investigated for more than sixty years. The bursts of radiation occur at a frequency corresponding to the plasma frequency at the source region, and harmonics are frequently observed. It is commonly accepted that the radiation is generated by a nonlinear mechanism, proposed by Ginzburg and […]

### Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves by C. R. Goddard et al.*

2017-01-03

Flaring activity on the Sun triggers waves and oscillations in the solar corona. The study of these waves and oscillations allows comparisons to magnetohydrodynamic (MHD) theory and modelling to be made, and seismological inversions based on this comparison allow local plasma parameters to be measured indirectly (e.g. De Moortel & Nakariakov 2012). Simultaneous EUV imaging and radio observations make it possible to study how these waves and oscillations can produce […]

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