Critical Fluctuations in Beam-Plasma Systems and Solar Type III Radio Bursts
by G. Thejappa and R. J. MacDowall

2017-12-05 406 views

The type III radio bursts are the most intense radio emissions from the sun. In Figure 1, we present a typical type III burst observed by the STEREO spacecraft. Ginzburg and Zheleznyakov (1958) were the first to suggest that Langmuir waves excited by the solar flare accelerated electrons are the source of these bursts. The in situ detection of electron beams and Langmuir waves in association with type III bursts […]

Observations of solar radio burst fine structures with LOFAR
by E. Kontar et al.*

2017-11-28 1,106 views

During solar flares, electrons are accelerated up to relativistic speeds. As they propagate upwards through the solar corona, they produce so-called type III radio bursts. These type III bursts often demonstrate fine structure, with their spectra consisting of multiple narrowband “striae”; most likely, these structures are caused by small-scale density inhomogeneities of the coronal plasma so that the subsequent fundamental plasma processes that produce the radio bursts is produced in […]

VLA Measurements of Faraday Rotation through Coronal Mass Ejections
by Jason E. Kooi et al*

2017-11-21 344 views

Coronal mass ejections (CMEs) are large-scale eruptions of ionized gas (or plasma) from the Sun. The ejected material of a CME is associated with strong magnetic fields, which can cause substantial geomagnetic storms at Earth that enhance the radiation space environment and affect global communications and geolocation. Remote-sensing techniques such as Faraday rotation (FR), the rotation of the plane of polarization of linearly polarized radiation as it propagates through a […]

Solar Prominence Modelling at ALMA Wavelengths
by A. Rodger and N. Labrosse

2017-11-14 405 views

The small-scale temperature structure of prominences remains an outstanding question in solar physics. Theoretical models provide scenarios for how cool prominence plasma can be formed and maintained within the extreme conditions of the corona. However, knowledge of the detailed temperature structure of the prominence plasma and its evolution at small spatial and temporal scales is still lacking. The Atacama Large Millimeter/sub-millimeter Array (ALMA) provides a novel method for high spatial […]

Small electron acceleration episodes in the solar corona
by T. James et al.

2017-11-07 658 views

Large solar flares are well known sites of prodigious particle acceleration. While these have deservedly attracted considerable attention, small episodes of electron acceleration and heating have been lately recognized as possible candidates for heating the quiet solar corona. We study the number, power and energy carried by nonthermal electrons produced by instances of small scale electron acceleration in the solar corona. Our primary focus is on small electron acceleration events […]

Acceleration and Storage of Energetic Electrons in Magnetic Loops in the Course of Electric Current Oscillations
by V.V. Zaitsev and A.V. Stepanov

2017-10-31 512 views

There are long-lived radio events on the Sun and stars like in type IV solar radio bursts with sudden reductions and pulsating type III bursts (Slottje, 1972; Huang et al. 2016) as well as intriguing intense radio emission from ultracool stars that lasts for several rotation periods (Hallinan et al. 2007). This can be the result of the multiple injections of accelerated electrons into the coronal magnetic loops. The idea […]

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

2017-10-24 701 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.*

2017-10-17 572 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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