Hercules A

Hercules A
Radio-Optical View of the Galaxy Hercules A - Many thanks to: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Friday, June 26, 2015

Structure of solar radio noise 150 to 432 MHz - combined observations of 4 storms with the Nancay Radioheliograph and the Giant Meterwave Radio Telescope

With many thanks I refer to:

Mercier Subramanian Chambe Janardhan 2014

"The structure of solar radio noise storms"



27 References at:

Abstract: "Context. The Nançay Radioheliograph (NRH) routinely produces snapshot images of the full sun (field of view ~3 R&sun;) at 6 or 10 frequencies between 150 and 450 MHz, with typical resolution 3 arcmin and time cadence 0.2 s. Combining visibilities from the NRH and from the Giant Meterwave Radio Telescope (GMRT) allows us to produce images of the sun at 236 or 327 MHz, with the same field as the NRH, a resolution as low as 20 arcsec, and a time cadence 2 s.

Aims: We seek to investigate the structure of noise storms (the most common non-thermal solar radio emission) which is yet poorly known. We focus on the relation of position and altitude of noise storms with the observing frequency and on the lower limit of their sizes.

Methods: We use an improved version of a previously used method for combining NRH and GMRT visibilities to get high-resolution composite images and to investigate the fine structure of noise storms. We also use the NRH data over several consecutive days around the common observation days to derive the altitude of storms at different frequencies.

Results: We present results for noise storms on four days. Noise storms consist of an extended halo and of one or several compact cores with relative intensity changing over a few seconds. We found that core sizes can be almost stable over one hour, with a minimum in the range 31-35 arcsec (less than previously reported). The heliocentric distances of noise storms are ~1.20 and 1.35 R&sun; at 432 and 150 MHz, respectively. Regions where storms originate are thus much denser than the ambient corona and their vertical extent is found to be less than expected from hydrostatic equilibrium.

Conclusions: The smallest observed sizes impose upper limits on broadening effects due to scattering on density inhomogeneities in the low and medium corona and constrain the level of density turbulence in the solar corona. It is possible that scatter broadening has been overestimated in the past, and that the observed sizes cannot only be attributed to scattering. The vertical structure of the noise storms is difficult to reconcile with the classical columnar model."


Sunday, June 21, 2015

About the United States Air Force Solar Observatories Radio Event Reports

The Space Weather Prediction Center of the USA National Oceanic and Atmospheric Administration  relays the radio event data provided to them by the USAF Solar Observatories:



The USAF Solar Observatories are interested principally on strong events that might possibly affect the combat readiness of the United States Air Force. Their reports very frequently do not mention many relatively weak events of much scientific interest.

Wednesday, June 3, 2015

Murchison Widefield Array - 3D movies of plasma tubes in the Earths's magnetosphere

I refer to Loi et al. 2015:



http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015arXiv150406470L&refs=REFERENCES&db_key=PRE          32 References





Abstract: "Ionization of the Earth's atmosphere by sunlight forms a complex, multi-layered plasma environment within the Earth's magnetosphere, the innermost layers being the ionosphere and plasmasphere. The plasmasphere is believed to be embedded with cylindrical density structures (ducts) aligned along the Earth's magnetic field, but direct evidence for these remains scarce. Here we report the first direct wide-angle observation of an extensive array of field-aligned ducts bridging the upper ionosphere and inner plasmasphere, using a novel ground-based imaging technique. We establish their heights and motions by feature-tracking and parallax analysis. The structures are strikingly organized, appearing as regularly-spaced, alternating tubes of overdensities and underdensities strongly aligned with the Earth's magnetic field. These findings represent the first direct visual evidence for the existence of such structures."

CAASTRO Press release: real-time, 3D movies of plasma tubes

"...By creatively using a radio telescope to see in 3D, astronomers have detected the existence of tubular plasma structures in the inner layers of the magnetosphere surrounding the Earth. For over 60 years, scientists believed these structures existed but by imaging them for the first time, we’ve provided visual evidence that they are really there," said Cleo Loi of CAASTRO at the University of Sydney.

Ms Loi is the lead author on this research, undertaken as part of her award-winning undergraduate thesis and published in Geophysical Research Letters today. In collaboration with international colleagues, she identified the structures.

"The discovery of the structures is important because they cause unwanted signal distortions that could, as one example, affect our civilian and military satellite-based navigation systems. So we need to understand them," Ms Loi said.

"The region of space around the Earth occupied by its magnetic field, called the magnetosphere, is filled with plasma that is created by the atmosphere being ionised by sunlight. The innermost layer of the magnetosphere is the ionosphere, and above that is the plasmasphere. They are embedded with a variety of strangely shaped plasma structures including, as has now been revealed, the tubes. We measured their position to be about 600 kilometres above the ground, in the upper ionosphere, and they appear to be continuing upwards into the plasmasphere. This is around where the neutral atmosphere ends, and we are transitioning to the plasma of outer space," explained Ms Loi.

Using the Murchison Widefield Array (MWA), a radio telescope located in the Western Australian desert, Ms Loi found that she could map large patches of the sky and even exploit the MWA’s rapid snapshot capabilities to create a movie – effectively capturing the real-time motions of the plasma.

"We saw a striking pattern in the sky where stripes of high-density plasma neatly alternated with stripes of low-density plasma. This pattern drifted slowly and aligned beautifully with the Earth’s magnetic field lines, like aurorae," Ms Loi said.

"We realised we may be onto something big and things got even better when we invented a new way of using the MWA."

The MWA consists of 128 antenna ‘tiles’ spread over an area roughly three by three kilometres that work together as one instrument – but by separating the signals from tiles in the east from the ones in the west, the astronomers gave the MWA the power to see in 3D.

"This is like turning the telescope into a pair of eyes, and by that we were able to probe the 3D nature of these structures and watch them move around," said Ms Loi.

"We were able to measure the spacing between them, their height above the ground and their steep inclination. This has never been possible before and is a very exciting new technique."

This ability adds yet another accolade to the MWA’s name after it had already proven its worth as a powerful precursor instrument to the Square Kilometre Array (SKA), and now the MWA‘s 3D vision has the potential to provide many more in-depth analyses of the formation of plasma structures.

It is to Cleo’s great credit that she not only discovered this but also convinced the rest of the scientific community. As an undergraduate student with no prior background in this, that is an impressive achievement," said Ms Loi’s supervisor Dr Tara Murphy, also of CAASTRO at the University of Sydney.

When they first saw the data, many of her senior collaborators thought the results were literally ‘too good to be true’ and that the observation process had somehow corrupted the findings, but over the next few months, Cleo managed to convince them that they were both real and scientifically interesting."

Ms Loi has been awarded the 2015 Bok Prize of the Astronomical Society of Australia for her work...."


Shyeh Tjing Loi - Lead Author

Plama tubes visualization

Murchison Widefield Array antenna tiles

Tuesday, June 2, 2015

Sun Earth Jupiter 2015 June

Many thanks to: STEREO and WIND Teams, Taxpayers of France, French Air Force, Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory, Prof. Dr. Kazumasa Imai Kochi National College of Technology Kochi Japan, Trinity College Dublin Ireland Astrophysics Group, United States NOAA SWPC, NASA Solar Dynamics Observatory Teams, Lockheed Martin Solar Laboratory

The events of 150618 shown above, are most likely due to solar activity received by the sidelobes of the Nancay Decametric Array. I thank Laurent Denis for his analysis.

150622 Sun - Eruptive M6.5 Flare with Earth directed CME

150622 1653 to 150623 1319 UT, animation of M6.5 flare and post flare activity affecting a huge solar region, ultraviolet composite at 171 211 and 304 nano meter

150625 Sun, animation of M7.9 flare in AR 2371, 171 nm ultraviolet