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, August 8, 2014

Definition: solar type Zebra - Spatially and Spectrally Resolved Observations

I refer to Chen Bastian Gary and Ju Jing 2011:


"Spatially and Spectrally Resolved Observations of a Zebra Pattern in a Solar Decimetric Radio Burst"

Abstract: "We present the first interferometric observation of a zebra-pattern radio burst with simultaneous high spectral (≈1 MHz) and high time (20 ms) resolution. The Frequency-Agile Solar Radiotelescope Subsystem Testbed (FST) and the Owens Valley Solar Array (OVSA) were used in parallel to observe the X1.5 flare on 2006 December 14. By using OVSA to calibrate the FST, the source position of the zebra pattern can be located on the solar disk. With the help of multi-wavelength observations and a nonlinear force-free field extrapolation, the zebra source is explored in relation to the magnetic field configuration. New constraints are placed on the source size and position as a function of frequency and time. We conclude that the zebra burst is consistent with a double-plasma resonance model in which the radio emission occurs in resonance layers where the upper-hybrid frequency is harmonically related to the electron cyclotron frequency in a coronal magnetic loop."

"...ZP [zebra patterns] bursts appear in radio dynamic spectra as closely-spaced, quasi-parallel bands of emission, typically ranging from ~ 5−20 in number
but sometimes showing as many as 70...They have been observed at meter wavelengths for decades..."

Wednesday, August 6, 2014

Periodic bursts of Jovian non-Io decametric radio emission strongly correlated with solar wind ram pressure

Periodic bursts of Jovian non-Io decametric radio emission strongly correlated with solar wind ram pressure

Panchenko, M.; Rucker, H. O.; Farrell, W. M. [ AA(Space Research Institute AAS, Graz, Austria), AB(Space Research Institute AAS, Graz, Austria), AC(NASA Goddard Space Flight Center, Greenbelt, MD, USA)] 2013


With many thanks to Tom Ashcraft, who brought it to my attention, I provide the link to this very interesting paper (free 2 MB pdf):


 Abstract: "During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period ≈1.5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ˜25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind."

Saturday, August 2, 2014

Sun Earth Jupiter 2014 August

Many thanks to: STEREO and WIND Teams, Taxpayers of France, Nancay Decametric Array Team at 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 SDO HMI Magnetograph Team, Lockheed Martin Solar Laboratory