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)

Monday, December 31, 2012

Wednesday, December 26, 2012

Jansky Very Large Array observations of decimetric type III bursts and electron beam trajectories - Chen et al. 2012

Wonderful paper !! :

http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1211.3058    with link to a free pdf

Abstract:

"We report observations of type III radio bursts at decimeter wavelengths (type IIIdm bursts) -- signatures of suprathermal electron beams propagating in the low corona -- using the new technique of radio dynamic imaging spectroscopy provided by the recently upgraded Karl G. Jansky Very Large Array (VLA). For the first time, type IIIdm bursts were imaged with high time and frequency resolution over a broad frequency band, allowing electron beam trajectories in the corona to be deduced. Together with simultaneous hard X-ray (HXR) and extreme ultraviolet (EUV) observations, we show these beams emanate from an energy release site located in the low corona at a height below ~15 Mm, and propagate along a bundle of discrete magnetic loops upward into the corona. Our observations enable direct measurements of the plasma density along the magnetic loops, and allow us to constrain the diameter of these loops to be less than 100 km. These over-dense and ultra-thin loops reveal the fundamentally fibrous structure of the Sun's corona. The impulsive nature of the electron beams, their accessibility to different magnetic field lines, and the detailed structure of the magnetic release site revealed by the radio observations indicate that the localized energy release is highly fragmentary in time and space, supporting a bursty reconnection model that involves secondary magnetic structures for magnetic energy release and particle acceleration."






ALMA continuum and spectral line observations of the young Brown Dwarf rho-Oph 102 at about 0.89 mm and 3.2 mm - Ricci et al. 2012

"...Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have for the first time found that the outer region of a dusty disk encircling a brown dwarf contains millimeter-sized solid grains like those found in denser disks around newborn stars. The surprising finding challenges theories of how rocky, Earth-scale planets form, and suggests that rocky planets may be even more common in the Universe than expected..."

 http://adsabs.harvard.edu/abs/2012ApJ...761L..20R 

http://www.nrao.edu/pr/2012/browndisks/ 

Artistic impression of a Brown Dwarf above

Abstract:
"We present ALMA continuum and spectral line observations of the young brown dwarf ρ-Oph 102 at about 0.89 mm and 3.2 mm. We detect dust emission from the disk at these wavelengths and derive an upper limit on the radius of the dusty disk of ~40 AU. The derived variation of the dust opacity with frequency in the millimeter (mm) provides evidence for the presence of mm-sized grains in the disk's outer regions. This result demonstrates that mm-sized grains are found even in the low-density environments of brown dwarf disks and challenges our current understanding of dust evolution in disks. The CO map at 345 GHz clearly reveals molecular gas emission at the location of the brown dwarf, indicating a gas-rich disk as typically found for disks surrounding young pre-main-sequence stars. We derive a disk mass of ~0.3%-1% of the mass of the central brown dwarf, similar to the typical values found for disks around more massive young stars."



Monday, December 24, 2012

Square Kilometer Array Antennas at night - Peter McFarlane




http://www.skatelescope.org/wp-content/gallery/precursors-pathfinders-design-studies-page/thumbs/thumbs_kat-7-at-night-credit-peter-mcfarlane.jpg

Saturday, December 22, 2012

About modulations of ionospheric origin, in the Nancay Jovian Decametric Spectra, that are not due to Faraday rotation

I review an interesting paper by Genova, Aubier, and Lecacheux, 1981:

http://adsabs.harvard.edu/abs/1981A%26A...104..229G

(with link to a free pdf)

 Abstract: "A study of wideband Jovian decametric spectra observed in France makes it possible to clearly distinguish three kinds of lane-like structures, each with definite spectral characteristics. It is noted that one is of terrestrial ionospheric origin. The others, the well known 'modulation lanes' and a new class of modulations referred to zero as 'high frequency lanes' are of Jovian origin. A tentative interpretation by propagation effects either in the terrestrial ionosphere F-zone or in the Jovian plasma torus is given."

In Section III, the Authors discuss modulations of Terrestrial Ionospheric origin. I quote in part:






From Section VI, Conclusions, I quote in part:


Final North American ALMA antenna delivered

Friday, December 21, 2012

Solar cycle progression - November 2012

I refer to the NOAA Space Weather Prediction Center "Solar Cycle Progression" report :

http://www.swpc.noaa.gov/SolarCycle/

 "...the panel has agreed that solar minimum occurred in December, 2008... Given the predicted date of solar minimum and the predicted maximum intensity, solar maximum is now expected to occur in May, 2013. Note, this is a consensus opinion, not a unanimous decision. A supermajority of the panel did agree to this prediction."

 The maximum Sunspot Number Monthly Value for Cycle 24 MAY have already occurred in October 2011, with a value of about 95.

Friday, November 9, 2012

LOFAR images and spectra of type III bursts, in the 122 to 162 MHz band, on 111013



I review the ASTRON (Netherlands Institute for Radio Astronomy) and JIVE (Joint Institute for VLBI in Europe) Daily Image for 121031:
http://www.astron.nl/dailyimage/index.html?main.php?date=20121031

by Gottfried Mann, Christian Vocks, and Frank Breitling.

 "...On October 13, 2011 the Sun was observed by LOFAR in the framework of its key science project "Solar Physics and Space Weather with LOFAR". The results are presented on this slide:

At the bottom the dynamic radio spectrum is shown in the frequency range of 122 - 162 MHz. It shows four so-called type III radio bursts. They appear as stripes of enhanced radio emission rapidly drifting from high to low frequencies. They are signatures of beams of energetic electrons generated by a flare on the Sun. If they travel along open magnetic field lines through the corona, they excite along their path radio radiation manifesting as type III bursts.

On top the corresponding radio images at 133 MHz are show before (left), during (middle), and after (right) the occurrence of the type III burst at 10:27:18 UT. The white circle indicates the limb of the visible disc of the Sun.

The radio images are produced by means of the solar imaging pipeline developed at the Leibniz-Institut fur Astrophysik Potsdam (AIP). The brightening of the radio source during the type III burst is seen at the South-East limb of the Sun. This observation impressively demonstrates that LOFAR can really work as a dynamic spectroscopic radio imager of the Sun..."

Friday, October 26, 2012

Interesting Non-Io dependent Jovian events, with multiple arcs, on 121023 and 121026, at Paris Observatory






Many thanks to the Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory, and Professor Imai Laboratory at Kochi National College of Technology in Japan

Friday, October 5, 2012

Io-A central pass with modulation lanes, on 121004, at Paris Observatory







Many thanks to the Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory, and Professor Imai Laboratory at Kochi National College of Technology in Japan

Friday, September 21, 2012

Rare Io-D, on 120921, at Paris Observatory







Many thanks to the Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory, and Professor Imai Laboratory at Kochi National College of Technology in Japan

Sunday, August 26, 2012

Io-A on 120826, at Paris Observatory






Many thanks to the Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory, and Professor Imai Laboratory at Kochi National College of Technology in Japan

Sunday, August 19, 2012

Io-A with an arc and some interesting modulation lanes, on 120819, at Paris Observatory









Many thanks to the Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory, and Professor Imai Laboratory at Kochi National College of Technology in Japan