scholarly journals FIRST SPECTROSCOPIC IMAGING OBSERVATIONS OF THE SUN AT LOW RADIO FREQUENCIES WITH THE MURCHISON WIDEFIELD ARRAY PROTOTYPE

2011 ◽  
Vol 728 (2) ◽  
pp. L27 ◽  
Author(s):  
Divya Oberoi ◽  
Lynn D. Matthews ◽  
Iver H. Cairns ◽  
David Emrich ◽  
Vasili Lobzin ◽  
...  
Keyword(s):  
Spectroscopic Imaging ◽  
The Sun ◽  
Radio Frequencies ◽  
Murchison Widefield Array

Waves and Quasi-Periodic-Pulsations in Weak Active Solar Emissions

2021 ◽  
Author(s):  
Divya Oberoi ◽  
Atul Mohan ◽  
Surajit Mondal
Keyword(s):  
Type I ◽  
The Sun ◽  
X Rays ◽  
Noise Storm ◽  
Physical Conditions ◽  
Spatially Resolved ◽  
Science Area ◽  
Radio Frequencies ◽  
Murchison Widefield Array ◽  
Release Processes

<p>The presence of Quasi-periodic pulsations (QPPs) is found to be a common feature of flaring energy release processes on the Sun. They are observed all across the EM range from hard X-rays to radio and provide insights into the physical conditions in the coronal plasma and the processes involved in the generation of these waves and oscillations. There have been numerous observations of spatially resolved QPPs at higher energies, though there are fewer examples at radio frequencies. Spatially resolved observations of these phenomena are particularly rare at low radio frequencies and there are none which are associated with the weaker episodes of active emissions which are much more numerous and frequent. The key reason limiting such studies has been the lack of availability of spectroscopic snapshot images of sufficient quality to detect and characterise the low level changes in the morphology of the sources of active emissions. Together, the data from the Murchison Widefield Array (MWA), a SKA precursor, and an imaging pipeline developed to meet the specific needs of solar imaging, now meet this challenge and enable us to explore this rich and interesting science area. Our work has led to the discovery of several previously unknown phenomena - second-scale QPPs in the size and orientation of a type III source, with simultaneous QPPs in intensity; 30 s QPPs in the radio light curve of a type I emission source associated with active region loop hosting a transient brightening; and intermittent presence of an anti-correlation in the size and intensity of a type I noise storm source along with QPPs. In this presentation we will briefly summarise these recent results and discuss their implications.</p>

High-resolution spectroscopic imaging of the Sun with a universal birefringent filter and a Fabry-Perot Interferometer

1992 ◽  
Vol 15 (5) ◽  
pp. 509-518 ◽  
Author(s):  
F. Cavallini ◽  
G. Ceppatelli ◽  
A. Righini ◽  
F. Berrilli ◽  
B. Caccin ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Imaging ◽  
The Sun ◽  
Birefringent Filter ◽  
Fabry Perot

First results from Automated Imaging Routine for Compact Arrays for Radio Sun

2018 ◽  
Vol 13 (S340) ◽  
pp. 159-160 ◽  
Author(s):  
Surajit Mondal ◽  
Atul Mohan ◽  
Divya Oberoi ◽  
Leonid Benkevitch ◽  
Colin J. Lonsdale ◽  
...  
Keyword(s):  
Solar Corona ◽  
Spectral Resolution ◽  
Complex Dynamics ◽  
Imaging Studies ◽  
Automated Imaging ◽  
First Results ◽  
Radio Frequencies ◽  
Murchison Widefield Array ◽  
New Instruments

At low radio frequencies the solar corona is very dynamic in both spectral and temporal domains. To capture the fine details of this complex dynamics, imaging studies at high temporal and spectral resolution are necessary. The advent of the new instruments like the Murchison Widefield Array (MWA; Tingay et al. 2013, Bowman et al. 2013), is now making this possible.

scholarly journals The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies

2013 ◽  
Vol 30 ◽  
Author(s):  
S. J. Tingay ◽  
R. Goeke ◽  
J. D. Bowman ◽  
D. Emrich ◽  
S. M. Ord ◽  
...  
Keyword(s):  
Signal Processing ◽  
System Level ◽  
Radio Frequency Interference ◽  
Astronomy Observatory ◽  
Square Kilometre Array ◽  
Expected Performance ◽  
Low Levels ◽  
Radio Frequencies ◽  
Murchison Widefield Array ◽  
Aperture Arrays

AbstractThe Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80–300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised.

scholarly journals Searching for dark matter signals from local dwarf spheroidal galaxies at low radio frequencies in the GLEAM survey

2020 ◽  
Vol 494 (1) ◽  
pp. 135-145 ◽  
Author(s):  
R H W Cook ◽  
N Seymour ◽  
K Spekkens ◽  
N Hurley-Walker ◽  
P J Hancock ◽  
...  
Keyword(s):  
Dark Matter ◽  
Massive Particle ◽  
Low Frequency ◽  
Electromagnetic Spectrum ◽  
Radio Sources ◽  
Synchrotron Emission ◽  
Dark Matter Annihilation ◽  
Astrophysical Objects ◽  
Radio Frequencies ◽  
Murchison Widefield Array

ABSTRACT The search for emission from weakly interacting massive particle (WIMP) dark matter annihilation and decay has become a multipronged area of research not only targeting a diverse selection of astrophysical objects, but also taking advantage of the entire electromagnetic spectrum. The decay of WIMP particles into standard model particles has been suggested as a possible channel for synchrotron emission to be detected at low radio frequencies. Here, we present the stacking analysis of a sample of 33 dwarf spheroidal (dSph) galaxies with low-frequency (72–231 MHz) radio images from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. We produce radial surface brightness profiles of images centred upon each dSph galaxy with background radio sources masked. We remove 10 fields from the stacking due to contamination from either poorly subtracted, bright radio sources or strong background gradients across the field. The remaining 23 dSph galaxies are stacked in an attempt to obtain a statistical detection of any WIMP-induced synchrotron emission in these systems. We find that the stacked radial brightness profile does not exhibit a statistically significant detection above the 95 per cent confidence level of ∼1.5 mJy beam−1. This novel technique shows the potential of using low-frequency radio images to constrain fundamental properties of particle dark matter.

The Noise-like Character of Solar Radiation at Metre Wavelengths

1949 ◽  
Vol 2 (2) ◽  
pp. 228
Author(s):  
R Payne-Scott
Keyword(s):  
Solar Radiation ◽  
Thermal Radiation ◽  
Radio Receiver ◽  
The Sun ◽  
Receiver Noise ◽  
Thermal Origin ◽  
Fluctuation Noise ◽  
Radio Frequencies ◽  
Variable Bias

Thermal radiation received from the sun at radio frequencies is indistinguishable from fluctuation noise in the radio receiver. However, the enhanced radiation often encountered at metre wavelengths is unlikely to have a thermal origin and hence may not be noise-like in character. This paper describes an experiment in which enhanced solar radiation on 85 and 60 Mc/s. was compared with receiver noise and with a C.W. signal by comparing the outputs from a diode with variable bias. This should detect any marked difference in the distribution of amplitudes of the fluctuations in solar and receiver noise. It was found that the enhanced solar radiation was indistinguishable from receiver noise.

scholarly journals Solar radiation at radio frequencies and its relation to sunspots

1947 ◽  
Vol 190 (1022) ◽  
pp. 357-375 ◽  
Keyword(s):  
Solar Radiation ◽  
Thermal Radiation ◽  
Sunspot Group ◽  
Experimental Studies ◽  
The Sun ◽  
Electrical Discharges ◽  
Interference Phenomenon ◽  
Radio Frequencies

Experimental studies of solar radiation on a frequency of 200 Mcyc./sec. are described. This radiation has characteristics similar to those of thermal radiation but is always hundreds of times greater than the thermal radiation anticipated from the photosphere and sometimes greater by a factor of 10 4 . The day-to-day intensity variations over a period of 6 months confirm a correlation with simspots. The received intensity of radiation is subject to rapid fluctuations; sudden in­creases, or ‘bursts’, of duration from a fraction of a second to a minute are characteristic. These rapid fluctuations are similar at widely-spaced receiving points, and it is concluded that most of them are extraterrestrial, and presumably solar, in origin. Directional observations, based on the interference phenomenon as the sun rises over the sea, indicate that the radiation originates not uniformly over the sun’s disk but in restricted areas in the immediate vicinity of a sunspot group. Values of received intensity are at times too great to be accounted for in terms of thermal radiation, so that another mechanism producing radiation must exist. Radiation from gross electrical discharges is suggested.

Murchison Widefield Array: Tracing solar disturbances from the Sun to the Earth

2011 ◽  
Author(s):  
D. Oberoi ◽  
C. J. Lonsdale ◽  
L. Benkevitch ◽  
I. H. Cairns ◽  
A. J. Coster ◽  
...  
Keyword(s):  
The Sun ◽  
The Earth ◽  
Murchison Widefield Array ◽  
Solar Disturbances

scholarly journals 52. Brightness distribution of the sun at 1·45 metres

1957 ◽  
Vol 4 ◽  
pp. 294-297
Author(s):  
J. Firor
Keyword(s):  
Electron Density ◽  
Brightness Distribution ◽  
Optical Observations ◽  
The Sun ◽  
Quiet Sun ◽  
Electron Density And Temperature ◽  
Radio Frequencies

The brightness distribution of the quiet sun at radio frequencies is of importance in determining the electron density and temperature in the chromosphere and the corona. Calculations made by Smerd, based on parameters derived from optical observations of the sun, indicate that the brightness distributions for wave-lengths near 1·5 metres are sensitive to the assumed coronal conditions and hence are well suited to checking these parameters.

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