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


"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..."



Artistic impression of a Brown Dwarf above

"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


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:


(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 :


 "...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.