Radio bursts in the 2017 September 6, X9.3 flare
by M. Karlicky and J. Rybak

2020-11-17 273 views

Radio bursts and their fine structures are an integral part of solar flares. Although many of them are known as e.g. type II, III, V, J, U, and IV, still some unique bursts and fine structures, not observed so far, can be detected. This is the case of the X9.3 flare observed on September 6, 2017, where we found not only several unique bursts and fine structures, but also their […]

Microwave Spectral Imaging of an Erupting Magnetic Flux Rope During a Large Solar Flare
by B. Chen et al.*

2020-09-22 410 views

Magnetic flux ropes are believed to be the centerpiece of the three-part structure of coronal mass ejections. In the standard model of eruptive solar flares, flux rope eruption also induces the impulsive flare energy release through magnetic reconnection. Signatures of flare-associated flux ropes in the low solar corona have been frequently reported in extreme ultraviolet (EUV) wavelengths, particularly the so-called EUV “hot channel” structures (see, e.g., Cheng et al. 2017 […]

Split-Band Feature of a Solar Flare Termination Shock
by Chen et al

2019-11-12 278 views

In many space and astrophysical plasma contexts, shocks are considered as one of the most important mechanisms for accelerating charged particles up to relativistic speeds. Different types of shocks are present on the Sun. One of the most well-known types is shocks driven by coronal mass ejections (see, e.g., Morosan et al. 2019, and recent CESRA Nuggets by Mancuso et al., Chrysaphi et al., Zucca et al.). There is another […]

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

2019-05-07 458 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, […]

Short-period Waves in Flare Loops: Possible Vehicle for Flare Energy Transport
by Sijie Yu et al

2019-03-26 402 views

Solar flares involve the sudden release of magnetic energy in the solar corona. Accelerated nonthermal electrons have been often invoked as the primary means for transporting the bulk of the released energy to the lower solar atmosphere. However, significant challenges remain for this scenario, especially in accounting for the large number of accelerated electrons inferred from observations. Propagating magnetohydrodynamics (MHD) waves, particularly those with subsecond/second-scale periods, have been proposed as […]

Large area solar flare ribbons as the model to explain puzzling millimeter emission
by G.G. Motorina et al.*

2019-03-12 424 views

Solar flares are sudden explosive processes, that convert the energy of the magnetic field into the kinetic energy of electrons and ions. Since the beginning of the century, millimeter observations of solar flares became routinely possible at a few frequencies with limited spatial resolution (see Kaufmann 2012, as a review). One of the most puzzling aspects of the observations at millimeter wavelengths (200-400 GHz) is the presence, in some flares, […]

Flare SOL2012-07-06: on the origin of the circular polarization reversal between 17 GHz and 34 GHz
by Altyntsev et al.*

2017-10-24 773 views

The new generations of multiwavelength radioheliographs with high spatial resolution will employ microwave imaging spectropolarimetry to recover flare topology and plasma parameters in the flare sources and along the wave propagation paths. The recorded polarization depends on the emission mechanism and emission regime (optically thick or thin), the emitting particle properties, and propagation effects.

Observations of a radio-quiet solar preflare
by A. Benz et al.*

2017-10-17 645 views

A substantial fraction of the flare energy (as observed e.g. in bolometric luminosity) first appears in non-thermal electrons and ions (Emslie et al. 2012). It implies that the particles are efficiently accelerated to a non-Maxwellian velocity distribution. Most of the non-thermal electrons have energies in the 10 – 30 keV range, but some are accelerated beyond 100 keV and radiate gyro-synchrotron radio emission. Nearly all of the flare energy is […]

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