# What exactly is this VLA radio image of Jupiter showing?

This VLA image is beautiful, and instructive, but I don't understand it fully.

This version is from an article in Gizmodo where the credit reads: A radio image of Jupiter captured by the Very Large Array. Image: Imke de Pater, Michael H. Wong, Robert J. Sault and which cites the recent article in Science: Peering through Jupiter’s clouds with radio spectral imaging. However, that paper does not actually show this image.

Another version of the image can be found in Berkeley News: New radio map of Jupiter reveals what’s beneath colorful clouds and gives more information how the image was produced.

A radio image of Jupiter from the VLA at three wavelengths: 2 cm in blue, 3 cm in gold, and 6 cm in red. A uniform disk has been subtracted to better show the fine banded structure on the planet. The pink glow surrounding the planet is synchrotron radiation produced by spiraling electrons trapped in Jupiter’s magnetic field. Banded details on the planet’s disk probe depths of 30-90 km below the clouds. This image is averaged from 10 hours of VLA data, so the fine details seen in the other maps are smeared here by the planet’s rotation. Image by Imke de Pater, Michael H. Wong (UC Berkeley), Robert J. Sault (Univ. Melbourne).

I would like to know more about how the image was processed. What does it look like before the uniform disk is subtracted - is the radio emission from the region around the planet actually as strong as the planet disk itself, as this image suggests? If there is a reference for this image I'd also like to read it!

In the mean time, it really is beautiful!

The image is sometimes paired with the following image, taken here from Science News.

Since this image resolves lateral detail, I'm guessing it might be the same 10 hours of data, but processed with a moving frame and corrected for distortion as it wraps around during the rotation of the planet, while the global image above is smeared by rotation

A uniform disk has been subtracted to better show the fine banded structure on the planet.

This means the surface of the planet is far brighter (in the raw data) than the surrounding magnetosphere. The planet itself has been darkened considerably in the image, otherwise it would be a pale circle and show little or no detail.

The press release from the VLA's site itself doesn't even show the wide field image however; it concentrates on the image showing detail of the spot itself. It mentions:

an innovative data-reduction technique to "unsmear" the data from many hours of observing

There is an earlier 2006 paper by some of the same researchers showing earlier attempts, with a much more coarse radio map of Jupiter. This goes into more detail about the earlier image processing techniques though (requires good knowledge of Fourier analysis etc.)

(Note: I can't read the current Science paper in full, it's behind a paywall.)

• Hey the ArXiv paper and press release are good to have - thanks! But I guess you know I'm going to ask how much are "far brighter" and "darkened considerably" actually. 50%? $10^{12}$? Are these taken from somewhere that I can read? That's a problem with paywalls. So much research is funded by taxpayers who have to pay again to read about how their money was spent. Thus the importance of good outreach. Many University libraries and some public libraries make some journals available on-line within the library, but plenty of people don't even have those available locally. – uhoh Jun 6 '16 at 12:22
• By the way, if you look at the wide field image you can see just above the planet's "surface" the surrounding magnetosphere "dims" to a dark blue, I would guess this is the boundary where they applied the overall dimming to make the planet's detail visible. However even bits of the magnetosphere itself might be contrast stretched in some way too; so we probably can't even begin to guess the actual intensity at any point in the image. – Andy Jun 6 '16 at 12:41
• Could be attenuation in the upper atmosphere as well. Since these are radio images only, the "surface" is a slightly different thing. It's why "I would like to know more about how the image was processed." But I think there is a good chance you are right. Good eye - thanks for pointing that out! – uhoh Jun 6 '16 at 13:21