scholarly journals Radio imaging-spectroscopy observations of the Sun in decimetric and centimetric wavelengths

2012 ◽  
Vol 8 (S294) ◽  
pp. 489-494 ◽  
Author(s):  
Yihua Yan ◽  
Wei Wang ◽  
Fei Liu ◽  
Lihong Geng ◽  
Zhijun Chen ◽  
...  
Keyword(s):  
Radio Emission ◽  
Solar Flares ◽  
Inner Mongolia ◽  
Imaging Spectroscopy ◽  
Current Status ◽  
The Sun ◽  
Radio Imaging ◽  
Time Space ◽  
Decimetric Wave ◽  
Wave Range

AbstractTo address fundamental processes in the solar eruptive phenomena it is important to have imaging-spectroscopy over centimetric-decimetric wave range. The Chinese Spectral Radioheliograph (CSRH) in 0.4-15 GHz range with high time, space and frequency resolutions is being constructed to achieve this goal. The perspectives to open new observational windows on solar flares and CMEs will be achieved by mapping the radio emission from unstable electron populations during the basic processes of energy release. CSRH is located in a radio quiet region in Inner Mongolia of China. The array of CSRH-I in 0.4-2.0 GHz with 40 4.5m antennas has been established and starts test observations. The 60 2m antennas for array of CSRH-II in 2-15 GHz have been mounted and assembled. The progress and current status of CSRH are introduced.

scholarly journals Image Simulation for Mingantu Ultrawide Spectral Radioheliograph in the Decimetre Wave Range

2015 ◽  
Vol 32 ◽  
Author(s):  
Jing Du ◽  
Yihua Yan ◽  
Wei Wang ◽  
Donghao Liu
Keyword(s):  
Inner Mongolia ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Frequency Resolution ◽  
The Sun ◽  
Image Simulation ◽  
Time Space ◽  
Wide Range ◽  
Wave Range ◽  
Imaging Performance

AbstractThe MUSER is a solar-dedicated radio interferometric array, which will observe the Sun over a wide range of radio frequencies (0.4–15 GHz), and make high time, space and frequency resolution images of the Sun simultaneously. MUSER is located in Mingantu Station in Inner Mongolia of China, which is about 400 kilometres away from Beijing. MUSER consists of two arrays: MUSER-I and MUSER-II. MUSER-I contains 40 antennas with 4.5-m aperture operating at 400 MHz to 2 GHz. MUSER-II contains 60 antennas with 2-m aperture operating at 2 to 15 GHz. Currently, MUSER has already been established and entered into the stage of test observation. This work is focus on the imaging performance of MUSER-I. This paper introduces MUSER-I briefly, presents the analysis of the array configurations, and evaluates the image quality mainly using the dynamic range, fidelity index, and the peak signal-to-noise ratio, also make some actual solar model simulations with CASA, the results will be shown below.

Energetic electrons in solar flares: observational support for acceleration processes linked to magnetic reconnection

2021 ◽  
Author(s):  
Nicole Vilmer ◽  
Sophie Musset
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Imaging Spectroscopy ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
High Energy ◽  
X Rays ◽  
Energetic Electrons ◽  
Radio Imaging ◽  
Gyrosynchrotron Emission

<p>Efficient electron (and ion) acceleration is produced in association with solar flares. Energetic particles play a major role in the active Sun since they contain a large amount of the magnetic energy released during flares. Energetic electrons (and ions) interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic electrons also produce radio emission in a large frequency band through gyrosynchrotron emission processes in the magnetic fields of flaring active regions and conversion of plasma waves when e.g. propagating to the high corona towards the interplanetary medium. It is currently admitted that solar flares are powered by magnetic energy previously stored in the coronal magnetic field and that magnetic energy release is likely to occur on coronal currents sheets along regions of strong gradient of magnetic connectivity. However, understanding the connection between particle acceleration processes and the topology of the complex magnetic structures present in the corona is still a challenging issue. In this talk, we shall review some recent results derived from X-ray and radio imaging spectroscopy of solar flares bringing some new observational constraints on the localization of HXR/radio sources with respect to current sheets, termination shocks in the corona derived from EUV observations.</p>

Diagnosing coronal magnetic fields with radio imaging-spectroscopy technique

2019 ◽  
Vol 15 (S354) ◽  
pp. 17-23
Author(s):  
Yihua Yan ◽  
Baolin Tan ◽  
V. Melnikov ◽  
Xingyao Chen ◽  
Wei Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Imaging Spectroscopy ◽  
Wide Band ◽  
Electromagnetic Spectrum ◽  
The Sun ◽  
Spectroscopy Technique ◽  
Radio Imaging ◽  
Imaging Telescope ◽  
Coronal Magnetic Fields ◽  
Multiple Frequencies

AbstractMingantu Spectral Radioheliograph (MUSER) is an aperture-synthesis imaging telescope, dedicated to observe the Sun, operating on multiple frequencies in dm to cm range. The ability of MUSER to get images and measure Stokes I and V parameters simultaneously at many frequencies in a wide band is of fundamental importance. It allows one to approach/solve such important problems as measuring the strength, geometry and dynamics of magnetic field at coronal heights. Here we consider some of the recently developed radio physics methods to be used for solving the problems. These methods allow us to obtain information that is unattainable in other areas of the electromagnetic spectrum.

scholarly journals Synergy between solar and stellar flares: challenges and perspectives

2015 ◽  
Vol 11 (S320) ◽  
pp. 419-426
Author(s):  
Suzanne L. Hawley
Keyword(s):  
Solar Flares ◽  
Additional Data ◽  
Current Status ◽  
The Sun ◽  
Stellar Flare ◽  
Stellar Flares ◽  
Similarities And Differences

AbstractI will review the current status of stellar flare observations and models, highlight similarities and differences with solar flares, and plead for additional data and insight from the “Sun as a Star”.

scholarly journals Galactic tide and local stellar perturbations on the Oort cloud: creation of interstellar comets

2019 ◽  
Vol 629 ◽  
pp. A139 ◽  
Author(s):  
S. Torres ◽  
M. X. Cai ◽  
A. G. A. Brown ◽  
S. P. Zwart
Keyword(s):  
Dynamical Evolution ◽  
Cumulative Effect ◽  
Oort Cloud ◽  
Radial Velocities ◽  
Current Status ◽  
Interstellar Space ◽  
The Sun ◽  
Semi Major Axis ◽  
Software Environment ◽  
External Perturbations

Comets in the Oort cloud evolve under the influence of internal and external perturbations, such as giant planets, stellar passages, and the Galactic gravitational tidal field. We aim to study the dynamical evolution of the comets in the Oort cloud, accounting for the perturbation of the Galactic tidal field and passing stars. We base our study on three main approaches; analytic, observational, and numerical. We first construct an analytical model of stellar encounters. We find that individual perturbations do not modify the dynamics of the comets in the cloud unless very close (<0.5 pc) encounters occur. Using proper motions, parallaxes, and radial velocities from Gaia DR2 and combining them with the radial velocities from other surveys, we then construct an astrometric catalogue of the 14 659 stars that are within 50 pc of the Sun. For all these stars we calculate the time and distance of closest approach to the Sun. We find that the cumulative effect of relatively distant (≤1 pc) passing stars can perturb the comets in the Oort cloud. Finally, we study the dynamical evolution of the comets in the Oort cloud under the influence of multiple stellar encounters from stars that pass within 2.5 pc of the Sun and the Galactic tidal field over ±10 Myr. We use the Astrophysical Multipurpose Software Environment (AMUSE), and the GPU-accelerated direct N-body code ABIE. We considered two models for the Oort cloud, compact (a ≤ 0.25 pc) and extended (a ≤ 0.5 pc). We find that the cumulative effect of stellar encounters is the major perturber of the Oort cloud for a compact configuration while for the extended configuration the Galactic tidal field is the major perturber. In both cases the cumulative effect of distant stellar encounters together with the Galactic tidal field raises the semi-major axis of ~1.1% of the comets at the edge of the Oort cloud up to interstellar regions (a > 0.5 pc) over the 20 Myr period considered. This leads to the creation of transitional interstellar comets (TICs), which might become interstellar objects due to external perturbations. This raises the question of the formation, evolution, and current status of the Oort cloud as well as the existence of a “cloud” of objects in the interstellar space that might overlap with our Oort cloud, when considering that other planetary systems should undergo similar processes leading to the ejection of comets.

scholarly journals Hydrodynamic Models of Solar and Stellar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 289-298
Author(s):  
Giovanni Peres
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Light Curves ◽  
Physical Parameters ◽  
The Sun ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Stellar Flares

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.

The sun and solar flares

1982 ◽  
Vol 17 (4) ◽  
pp. 165-173
Author(s):  
S McKenna-Lawlor
Keyword(s):  
Solar Flares ◽  
The Sun

Decameter radio emission of the Sun

2010 ◽  
Author(s):  
V. N. Melnik ◽  
A. A. Konovalenko ◽  
V. V. Dorovskyy ◽  
E. P. Abranin ◽  
H. Rucker ◽  
...  
Keyword(s):  
Radio Emission ◽  
The Sun ◽  
Decameter Radio
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