Are Solar Energetic Particle Events and Type II Bursts Associated with Fast and Narrow Coronal Mass Ejections?
by S. W. Kahler et al.*

2019-12-10 197 views

Gradual solar energetic (E > 10 MeV) particle (SEP) events, lasting several days, are produced in coronal/interplanetary shocks driven by fast (VCME ≥ 900 kms−1) coronal mass ejections (CMEs) associated with type II radio bursts.  The basic paradigm is that CMEs with VCME > Vf, the plasma fast-mode speed, drive shocks that can accelerate seed particles to the high energies observed as SEP events in space as well as electrons […]

Anisotropic radio-wave scattering in the solar corona
Nicolina Chrysaphi et al.*

2019-11-26 431 views

Solar radio emission is produced in the turbulent medium of the solar atmosphere, and its observed properties (source position, size, time profile, polarization, etc.) are significantly affected by the propagation of the radio waves from the emitter to the observer. Scattering of radio waves on random density irregularities has long been recognized as an important process for the interpretation of radio source sizes (e.g., Steinberg et al. 1971), positions (e.g., […]

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

2019-08-13 540 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 […]

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 0 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 al.*

2019-07-02 543 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 […]

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

2019-05-21 445 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 […]

Coronal Mass Ejection-driven Type II solar radio burst structure with LOFAR and radio-wave scattering
by Nicolina Chrysaphi et al.*

2019-01-29 576 views

Coronal Mass Ejections (CMEs) are often viewed as the major drivers of space weather disturbances in the Sun-Earth system. Shocks driven by CMEs can excite radio emissions characterised by a slow frequency drift across dynamic spectra. These radio emissions are known as Type II solar radio bursts and can consist of two bands with a frequency ratio of 1:2. Each of these bands can split into two thinner sub-bands, a […]

Coronal mass ejections associated to a super-active region
by H. Cremades et al.*

2018-12-18 588 views

During its transit through central meridian, and along four consecutive days, from 13 to 16 February 2011, NOAA active region (AR) 11158 generated coronal mass ejections (CMEs) in association with waves observed in the extreme ultraviolet (EUV) low corona, and even with a Moreton wave. On those dates, the spacecraft of the STEREO mission were located in quadrature with SOHO and SDO, enabling the exceptional observation of this series of […]

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