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)

Tuesday, January 29, 2013

About interference fringes and modulation lanes in Io-B spectra

I am thinking and reading about interesting features in Jovian decametric spectra, sometimes seen in the Paris Observatory Nancay Station Archive. The following references may be of interest:


Imai Riihimaa Reyes Carr 2002:
"Measurement of Jupiter's decametric radio source parameters by the modulation lane method"

5 citations to this paper at:

"In previously published works we have developed a model to explain the production of modulation lanes in the dynamic spectra of Jupiter's decametric emission. In this paper we use the model with newly available data to test the model and to measure emission source and beam parameters. Some of the data were wideband, providing for the first time the opportunity to verify the accuracy of the model in fitting the considerable lane curvature exhibited in such a case. Relatively precise measurements of the cone half-angle of hollow-cone beam and other source and beam parameters of Io-B radiation were also made possible by the wideband data. Narrowband data enabled us to measure for the first time the beam cone half-angle for non-Io-A radiation. The measured cone half-angles for the two sources were both within ~2° or 3° of 60°. This measurement is consistent with the long-held idea that the sources Io-B, Io-A, and non-Io-A are due to the same rotating hollow-cone beam and that the only difference between the latter two is the intensification of Io-A radiation by the connection with Io in comparison with that of non-Io-A. We also measured the cone half-angle for S bursts and found it to be less than that of the much more common L bursts."

I display above a copy of Fig. 2 in this paper, and an image quoting a portion of Section 2, about interference fringes.


Imai Garcia Reyes Imai Thieman 2011:
"A Model of Jupiter's Decametric Radio Emissions as a Searchlight Beam"

"It has long been recognized that there is a marked long-term periodic variation in Jupiter's integrated radio occurrence probability. The period of the variation is on the order of a decade. Carr et al. [1970] showed that such variations are closely correlated with Jovicentric declination of the Earth (DE). The range of the smoothed variation of DE is from approximately +3.3 to -3.3 degrees. This DE effect was extensively studied and confirmed by Garcia [1996]. It shows that the occurrence probability of the non-Io-A source is clearly controlled by DE at 18, 20, and 22 MHz during the 1957-1994 apparitions. We propose a new model to explain the DE effect. This new model shows that the beam structure of Jupiter radio emissions, which has been thought of like a hollow-cone, has a narrow beam like a searchlight, which can be explained by assuming that the three dimensional shape of the radio source expands along the line of the magnetic field. If we consider the sizes of the radio coherent region are 1000 m along Jupiter's magnetic field line and 200 m along the latitudinal direction, the equivalent beam pattern is 1 degree wide along Jupiter's magnetic field line and 5 degrees in latitude. As the searchlight beam is fixed with Jupiter's magnetic field, the pure geometrical effect of DE can be explained by this searchlight beam model."

Sunday, January 27, 2013

No sunspots after 2017 ??

I refer to Penn and Livingston 2010:
"Long-term Evolution of Sunspot Magnetic Fields"


 From the abstract:
"...Independent of the normal solar cycle, a decrease in the sunspot magnetic field strength has been observed using the Zeeman-split 1564.8nm Fe I spectral line at the NSO Kitt Peak McMath-Pierce telescope. Corresponding changes in sunspot brightness and the strength of molecular absorption lines were also seen. This trend was seen to continue in observations of the first sunspots of the new solar Cycle 24, and extrapolating a linear fit to this trend would lead to only half the number of spots in Cycle 24 compared to Cycle 23, and imply virtually no sunspots in Cycle 25..."

13 citations to this paper at:


NOAA Space Weather Prediction Center lists ONE event on 130124 !! :


So far, the maximum monthly average sunspot number for cycle 24 occurred in November 2011: http://www.swpc.noaa.gov/SolarCycle/sunspot.gif

Sunday, January 20, 2013

Io-A opportunity for Mexico, on 2013 January 27 UTC

Good morning Students at the Planteles of the Escuela Preparatoria, Universidad Nacional Autonoma de Mexico, and All Radio JOVE Participants,

I am unable to guarantee this opportunity. Let us hope for the best.

I attach several Radio-Jupiter Pro 3 screen images plotted with this wonderful application written by Jim Sky:
Download link at:

 Io-A will begin at 00:10 and end at 02:40 Greewich Mean Time, equal to Universal Time Coordinated or Atomic Time minus exactly 35 seconds.

You may check UTC at the United States Naval Observatory page:

I have set the approximate UNAM coordinates to: 19.3 degrees north latitude, -99.2 degrees west longitude

Note the two maps of the sky showing Jupiter's trajectory.

Radio-Jupiter Pro 3 is FUN !!

Give my regards to Professor Alfonso Castillo Abrego and tell him I am a Basque American.
The Basque Nation is very small and very ancient, it is located in France and Spain :


I am a retired Radio Astronomer who worked for many years with the National Radio Astronomy Observatory in Virginia, West Virginia, Arizona, and New Mexico.

Muy cordiales saludos
Victor Herrero Arrieta


Thursday, January 17, 2013

The historic 25 meter Dwingeloo Telescope in the Netherlands


 "...The picture shows the telescope as it was in the beginning, with a tiny 21cm receiver supported by a single guyed pole. Over the ensuing decades, more sophisticated, and much heavier, cooled receivers had to be supported by three, and later four, sturdy legs. The telescope is now a National Monument..."

 Submitted by Peter Barthel

Sunday, January 6, 2013

Io-D arc on 130106 at Paris Observatory Nancay Station

Io-C and Io-D are radiated from the Jovian southern magnetic hemisphere and are generally left hand polarized.

Io-D is observed infrequently, it rarely reaches 20 MHz. Many of the modulations seen on the band of Io-D radiation are caused by the solar wind.

For 16 other Io-D related posts see:

For a method to use Jim Sky's wonderful Radio-Jupiter Pro 3 software to predict Io-D events see:



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

Many type III Solar bursts on 130106, at Paris Observatory Nancay Station

Many thanks to the Nancay Decametric Array Team at the Nancay Radio Astronomy Station of Paris Observatory