Unsupervised Generation of High Dynamic Range Solar Images: A Novel Algorithm for Self-calibration of Interferometry Data
by Surajit Mondal et al.*

2019-07-16 95 views

Imaging the sun at radio wavelengths with high fidelity is an intrinsically hard problem. This stems from: a) the large range of angular scales on which the emission is present; b) the huge difference in brightness temperature associated with the various emission mechanisms which are responsible for radio emission; and c) high variability of solar emission on small temporal (<1s) and spectral (~kHz) scales. These together imply that the uv […]

Detection of Spike-like structures near the front of Type II radio bursts
by S. Armatas et a.*

2019-07-02 377 views

Type II solar radio bursts are the result of energetic electrons accelerated by a shock. This kind of burst appears on dynamic spectra as lanes which drift slowly from high to lower frequencies. Often, we observe a fundamental – harmonic structure, which sometimes exhibits a division on each band called band-split.  Fine structures are emissions with short duration and bandwidth embedded within all types of radio bursts and constitute a […]

Scaling-laws of Radio Spike Bursts and Their Constraints on New Solar Radio Telescopes
by Baolin Tan et al.

2019-06-18 294 views

Radio observation is one of the most important methods in solar physics and space science. Sometimes, it is almost the sole approach to observing physical processes such as the acceleration, emission, and propagation of non-thermal energetic particles, etc. Long-term observation and study have revealed that a strong solar radio burst is always composed of many small bursts with different time-scales. Among them, a radio spike burst is the smallest one, […]

3D reconstruction of CME-driven shock-streamer interaction as a coronal magnetic field diagnostics
by S. Mancuso et al.*

2019-06-04 238 views

Coronal Mass Ejections (CMEs) expelled from the Sun can drive shocks that accelerate electrons which, in turn, produce electrostatic oscillations called Langmuir waves. These waves are then converted into escaping e.m. radiation, known as type II solar radio bursts, emitted near the fundamental and/or harmonic of the local electron plasma frequency. As shocks propagate outward from the Sun to regions of lower plasma density, type IIs appear in dynamic spectra […]

The effect of scattering on the apparent positions of solar radio sources observed by LOFAR
by Mykola Gordovskyy

2019-05-21 333 views

Radio sources observed in the decametric range during type II and type III solar radio bursts are believed to be produced by coherent plasma emission due to electrostatic plasma oscillations induced by propagating suprathermal electrons (e.g. Ginzburg & Zhelezniakov 1958). This type of emission is a valuable tool for observational diagnostics of the upper corona. Produced at the local plasma frequency, $f_{pe}\rm{[kHz]}= 8.93 (n_e\rm{[cm}^{-3}\rm{]})^{-1/2}$ or its harmonic, plasma emission can reveal […]

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

2019-05-07 245 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, […]

Variable Emission Mechanism of a Type IV Radio Burst
by D. Morosan et al.*

2019-04-23 249 views

Coronal mass ejections (CMEs) are sometimes accompanied by continuum emission at decimetric and metric wavelengths, called Type IV radio bursts. Of particular interest to determining CME properties are moving Type IV radio bursts, which are broadband radio sources moving outwards from the Sun. First studies suggested that moving Type IV bursts are emitted by synchrotron or gyro-synchrotron emitting electrons that are trapped inside CME loops (Dulk 1973). However, since their […]

Remote sensing the coronal magnetic field using solar S-bursts B. Clarke et al.*

2019-04-09 265 views

Solar activity is often accompanied by solar radio emission. At low frequencies, radio bursts with short durations of <1 s, known as solar S-bursts, have been identified. These intriguing, low frequency bursts were first identified by McConnell (1982) who named them solar S-bursts, owing to their similarity to Jovian S-bursts: the S stands for short or storm. S-bursts appear as narrow tracks on a dynamic spectrum that usually drift from […]

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