Jupiter research paper pick of the bunch
14 March 2008
A research paper from the UCL Centre for Planetary Physics is featured in the New Journal of Physics' tenth-anniversary collection of highlights.
The journal's website also features and interview with the paper's lead author, Dr Nick Achilleos (UCL Physics & Astronomy).
To mark the journal's tenth birthday, the editorial board and publishing staff have compiled a shortlist of some of their article highlights from across physics that have been published in NJP, an Institute of Physics journal, since 1998.
The paper 'A dynamical model of Jupiter's auroral electrojet' - originally published in 2001 - discusses the dual personality of Jupiter's atmosphere.
The upper atmosphere of Jupiter - a region known as the thermosphere - contains hydrogen gas. Some of this gas is ionised as it absorbs energy from sunlight - this forms the ionosphere. The auroral rings or ovals surrounding Jupiter's magnetic poles receive a continual 'rain' of energetic charged particles which heats and ionises the hydrogen, causing beautiful displays of light similar to the Earth's northern and southern lights.
Dr Achilleos explained: "The thermosphere of Jupiter reaches temperatures of up to 1000K, and sunlight alone cannot be attributed to such high temperature levels. We attempted to answer this question by using a computer model of Jupiter's thermosphere and ionosphere regions. The results were surprising. Instead of a constant outflow of energy from the auroral regions to the rest of the planet, it was found that the wind systems on Jupiter tend to be controlled by the planet's rapid rotation (period 10 hours) and giant size (10 Earth radii = 1 Jupiter radius).
"Hydrogen flowing into the auroral ovals is slowed down in its rotation by the 'auroral rain', he added. "The resulting balance between centrifugal force (very strong at Jupiter), gravity and pressure forces then acts to accelerate this hot gas towards the poles, confining it to high latitudes. At higher altitudes, the flow of gas looks very different but cannot carry the enormous heat energy required. Thus, the search for the mysterious 'extra heat' continues, but we have learned much about the influence of giant planets' aurorae on their wind systems, and how this compares with the situation for the Earth. "
To find out more, use the links at the top of this article
Image: Dr Achileos