Modeling of Solar Atmosphere Parameters Above Sunspots Using RATAN-600 Microwave Observations
by A.G. Stupishin et al.*

2018-05-15 326 views

Models of the upper transition region of sunspots have been derived based on the observed radio spectrum between 3 and 18 GHz from Radio Astronomical Telescope of the Academy of Sciences 600 (RATAN-600) observations. Our objective is to match the spectrum to show that, within the limits of the one-dimensional observations and modeling, we have obtained a reasonable description of the upper transition-region structure of sunspots. We have developed a diagnostic […]

LOFAR observations of Fine Fundamental and Harmonic Structures in Solar Radio Bursts
by Xingyao Chen et al*

2018-05-01 442 views

Type III solar radio bursts are believed to be the most sensitive signatures of near-relativistic electron beam propagation in the corona. These intense bursts of solar radio emissions sometimes appear in the dynamic spectrum as a chain of several elementary bursts, which are known as striae, so an individual burst is composed of myriad of such stria (de La Noe & Boischot, 1972). Although there are several generation mechanisms of […]

Solar Type-IIIb Radio Bursts as Tracers for Electron Density Fluctuations in the Corona
by V. Mugundhan et al.*

2018-04-17 216 views

Type III bursts are generated when an electron accelerated close to speed of light excite the layers of coronal plasma they encounter when travelling away from the sun. These bursts are seen in a time-frequency-intensity image (called dynamic spectrum, as the time variation of the spectrum is visualized by it) as a bright patch, drifting from high to low frequencies on short time-scales ($\approx$ few-seconds). At times, along the path […]

New evidence for a coronal mass ejection driven fast drifting type II radio burst
by K. Anshu et al.

2018-04-03 550 views

Type II solar radio bursts are considered to originate from plasma waves excited by magnetohydrodynamic (MHD) shocks and converted into radio waves at the local plasma frequency and its harmonics. Type II radio bursts are mostly associated with coronal mass ejections (CMEs) and flares Nindos et al. (2008). We studied a seldom occurring high frequency type II burst on 4th Novemeber 2015, which had both fundamental and harmonic components. The […]

Association of radio polar cap brightening with bright patches and coronal holes
by C. L. Selhorst et al.*

2018-03-20 296 views

The purpose of this work is to model the emission of 17 GHz polar bright patches, which are frequently observed by the Nobeyama Radioheliograph (NoRH) in association with coronal holes. Although these bright regions have been observed for a few decades, their nature remains unclear. Our simulations were based on the temperature and density profiles from the SSC atmospheric model (Selhorst et al., 2005), with modifications to include a coronal […]

Dressing the Coronal Magnetic Extrapolations of Active Regions with a Parameterized Thermal Structure
by Gelu M. Nita et al.

2018-03-06 357 views

The study of time-dependent solar active region morphology and its relation to eruptive events requires analysis of imaging data obtained in multiple wavelength domains with differing spatial and time resolutions, ideally in combination with 3D physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based simulation tool, GX Simulator, originally developed for modeling microwave and X-ray emission from flaring loops (Nita et al. 2015), to […]

Solar ALMA observations: constraining the chromosphere above sunspots
by M. Loukitcheva et al.*

2018-02-20 584 views

Our understanding of sunspots is far from complete despite intensive research over hundreds of years. Radiation at submillimeter and millimeter wavelengths is formed in local thermodynamic equilibrium (LTE) in the low to mid chromosphere, and its intensity depends linearly on the ambient temperature of the medium. Observations at these wavelengths thus provide important diagnostics of sunspot chromospheres (Loukitcheva et al. 2014). The largest radio telescope in the world, the Atacama […]

Synergy of stochastic and systematic energization of plasmas during turbulent reconnection
by Th. Pisokas, L. Vlahos and H. Isliker

2018-02-06 448 views

In the current literature the acceleration of particles during solar flares is attributed to either weak turbulence or to large scale Unstable Current Sheet (UCS). The way UCS drive weak turbulence in a separated volume on the loop top or inside the loops below the UCS was never been presented in detail. During the last thirty years the plasma physics community developed the concept of turbulent reconnection. This concept went unnoticed […]

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