LOFAR tied-array imaging and spectroscopy of solar S bursts

With many thanks I refer to Morosan et al. 2015

http://arxiv.org/abs/1507.07496

29 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015arXiv150707496M&refs=REFERENCES&db_key=PREhttp://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015arXiv150707496M&refs=REFERENCES&db_key=PRE

"Context. The Sun is an active source of radio emission that is often associated with energetic phenomena ranging from nanoflares to coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), numerous millisecond duration radio bursts have been reported, such as radio spikes or solar S bursts (where S stands for short). To date, these have neither been studied extensively nor imaged because of the instrumental limitations of previous radio telescopes. Aims. Here, Low Frequency Array (LOFAR) observations were used to study the spectral and spatial characteristics of a multitude of S bursts, as well as their origin and possible emission mechanisms. Methods. We used 170 simultaneous tied-array beams for spectroscopy and imaging of S bursts. Since S bursts have short timescales and fine frequency structures, high cadence (~50 ms) tied-array images were used instead of standard interferometric imaging, that is currently limited to one image per second. Results. On 9 July 2013, over 3000 S bursts were observed over a time period of ~8 hours. S bursts were found to appear as groups of short-lived (<1 s) and narrow-bandwidth (~2.5 MHz) features, the majority drifting at ~3.5 MHz/s and a wide range of circular polarisation degrees (2-8 times more polarised than the accompanying Type III bursts). Extrapolation of the photospheric magnetic field using the potential field source surface (PFSS) model suggests that S bursts are associated with a trans-equatorial loop system that connects an active region in the southern hemisphere to a bipolar region of plage in the northern hemisphere. Conclusions. We have identified polarised, short-lived solar radio bursts that have never been imaged before. They are observed at a height and frequency range where plasma emission is the dominant emission mechanism, however they possess some of the characteristics of electron-cyclotron maser emission."

...

Observations of Crab giant pulses with 34 meter antenna, 8 GHz bandwidth

 With many thanks, I refer to:

Glenn Jones 2015, "Observations of Radio Giant Pulses with GAVRT"

http://arxiv.org/abs/1507.03864

10 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2011AIPC.1357..281J&amp;refs=REFERENCES&amp;db_key=AST

Abstract: "Radio giant pulses provide a unique opportunity to study the pulsar radio emission mechanism in exquisite detail. Previous studies have revealed a wide range of properties and phenomena, including extraordinarily high brightness temperatures, sub-nanosecond emission features, and banded dynamic spectra. New measurements of giant pulse characteristics can help guide and test theoretical emission models. To this end, an extensive observation campaign has begun which will provide more than 500 hours on the Crab with a 34-meter antenna located in California, USA. The observations are being done as part of an educational outreach program called the Goldstone-Apple Valley Radio Telescope (GAVRT). This antenna has a novel wide bandwidth receiver which provides up to 8 GHz of instantaneous bandwidth in the range of 2.5 to 14 GHz. These observations will provide detailed information about the variability, amplitude distribution, and detailed frequency structure of radio giant pulses. In addition, a database of pulses from these observations and others of the Crab pulsar is being created which will simplify multiwavelength correlation analysis."

Diminishing solar activity may bring new Ice Age by 2030

"...The arrival of intense cold similar to the one that raged during the “Little Ice Age”, which froze the world during the 17th century and in the beginning of the 18th century, is expected in the years 2030—2040. These conclusions were presented by Professor V. Zharkova (Northumbria University) during the National Astronomy Meeting in Llandudno in Wales by the international group of scientists, which also includes Dr Helen Popova of the Skobeltsyn Institute of Nuclear Physics and of the Faculty of Physics of the Lomonosov Moscow State University, Professor Simon Shepherd of Bradford University and Dr Sergei Zharkov of Hull University..."

"...In the current study published in 3 peer-reviewed papers the researchers analysed a total background magnetic field from full disk magnetograms for three cycles of solar activity (21-23) by applying the so-called “principal component analysis”, which allows to reduce the data dimensionality and noise and to identify waves with the largest contribution to the observational data. This method can be compared with the decomposition of white light on the rainbow prism detecting the waves of different frequencies. As a result, the researchers developed a new method of analysis, which helped to uncover that the magnetic waves in the Sun are generated in pairs, with the main pair covering 40% of variance of the data (Zharkova et al, 2012, MNRAS). The principal component pair is responsible for the variations of a dipole field of the Sun, which is changing its polarity from pole to pole during 11-year solar activity..."

http://astronomynow.com/2015/07/17/diminishing-solar-activity-may-bring-new-ice-age-by-2030/

 

Royal Astronomical Society National Astronomy Meeting 2015 Llandudno Wales :

http://nam2015.org/

http://nam2015.org/index.php/science-programme/parallel-sessions/list/2

Interferometric study of PSR B0329+54 and the interstellar medium, at 324 MHz, with maximum baselines near 1 light second

With many thanks, I refer to:

"PSR B0329+54: Substructure in the scatter-broadened image discovered with RadioAstron on baselines of up to 235,000 km"
   
Popov, M. V.; Andrianov, A. S.; Bartel, N.; Gwinn, C. R.; Johnson, M. D.; Joshi, B. C.; Kardashev, N. S.; Karuppusamy, R.; Kovalev, Y. Y.; Kramer, M.; Rudnitskii, A. G.; Safutdinov, E. R.; Shishov, V. I.; Smirnova, T. V.; Soglasnov, V. A.; Zensus, J. A.; Zhuravlev, V. I.

http://arxiv.org/abs/1501.04449

25 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015arXiv150104449P&amp;refs=REFERENCES&amp;db_key=PRE

Abstract: "We studied scattering properties of the pulsar PSR B0329+54 with a ground-space radio interferometer RadioAstron which included the 10-m Space Radio Telescope, the 110-m Green Bank Telescope, the 14x25-m Westerbork Synthesis Radio Telescope, and the 64-m Kalyazin Radio Telescope. The observations were performed at 324 MHz on baselines of up to 235,000 km in November 2012 and January 2014. At short ground-space baselines of less than about 20,000 km, the visibility amplitude decreases with the projected baseline length, providing a direct measurement of the diameter of the scattering disk of 4.7±0.9 mas. The size of the diffraction spot near Earth is 15,000±3,000 km. At longer baselines of up to 235,000 km, where no interferometric detection of the scattering disk would be expected, significant visibilities were observed with amplitudes scattered around a constant value. These detections result in a discovery of a substructure in the completely resolved scatter-broadened image of the pointlike source, PSR B0329+54. They fully attribute to properties of the interstellar medium. The visibility function at the longest ground-space baselines in the delay domain consists of many isolated unresolved spikes, in agreement with the amplitude-modulated noise model. Within the assumption of turbulent as well as large-scale irregularities in the plasma of the interstellar medium, we estimate that the effective scattering screen lies 0.35±0.10 of the distance from Earth toward the pulsar."

More on RadioAstron at:

http://herrero-radio-astronomy.blogspot.com/2013/07/the-radioastron-1-light-second-baseline.html

http://herrero-radio-astronomy.blogspot.com/2011/07/10-meter-radioastron-russian-space.html

http://www.asc.rssi.ru/radioastron/

Publications of RadioAstron :
http://www.asc.rssi.ru/radioastron/publications/publ.html

Wikipedia article:
https://en.wikipedia.org/wiki/Spektr-R

"...Spektr-R[2] (or RadioAstron) is a Russian scientific satellite with a 10 m (33 ft) radio telescope on board. It was launched on 18 July 2011,[3] by Zenit-3F launcher, from Baikonur Cosmodrome to perform research on the structure and dynamics of radio sources within and beyond our galaxy. Together with some of the largest ground-based radio telescopes, this telescope forms interferometric baselines extending up to 350,000 km (220,000 mi)..."

...o...

The Ooty Radio Telescope PONDER real time software for pulsar and scintillation observations

With many thanks I refer to:

Arun Naidu, B.C Joshi, P.K Manoharan, M.A Krishnakumar 2015

http://arxiv.org/abs/1503.01405

31 references:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015ExA....39..319N&amp;refs=REFERENCES&amp;db_key=AST

Abastract: "This paper describes a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time-stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a bandwidth of about four times larger (16 MHz) than that of the legacy system as well as its fluctuation spectrum with high temporal and frequency resolutions. The key point is that all the above modes operate in real time. This paper presents the design aspects of PONDER and outlines the design methodology for future similar backends. It also explains the principal operations of PONDER, illustrates its capabilities for a variety of pulsar and IPS observations and demonstrates its usefulness for a variety of astrophysical studies using the high sensitivity of the ORT"

 ...o... 

Solar Type Examples

Pulsar Profiles 2015 July

=======================================================================

...NEUTRON STARS...

Unprecedented sudden 36% increase in spin down rate of pulsar B0540-69

This unusual behavior may teach us much about neutron stars.

I refer to Marshall Guillemot Harding Martin Smith 2015:
http://arxiv.org/abs/1506.05765

http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1506.05765

29 references in the paper:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015arXiv150605765M&amp;refs=REFERENCES&amp;db_key=PRE

Abstract: "We report the discovery of a large, sudden, and persistent increase in the spin-down rate of B0540-69, a young pulsar in the Large Magellanic Cloud, using observations from the Swift and RXTE satellites. The relative increase in the spin-down rate of 36% is unprecedented for B0540-69. No accompanying change in the spin rate is seen, and no change is seen in the pulsed X-ray emission from B0540-69 following the change in the spin-down rate. Such large relative changes in the spin-down rate are seen in the recently discovered class of 'intermittent pulsars', and we compare the properties of B0540-69 to such pulsars. We consider possible changes in the magnetosphere of the pulsar that could cause such a large change in the spin-down rate."

...o...

An introduction to the Instituto Argentino de Radioastronomia IAR

With many thanks, I refer to:

Instituto Argentino de Radioastronomia IAR:
http://www.iar.unlp.edu.ar/

Publications:
http://www.iar.unlp.edu.ar/publicaciones/public-gral14.htm

Public outreach:
http://www.iar.unlp.edu.ar/art-difu.htm

Bulletin:
http://www.iar.unlp.edu.ar/boletin/bol-mar07.htm

....

.ooo.

Sun Earth Jupiter 2015 July

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

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.Sun Earth Jupiter.