Job and PhD Vacancies

New Lecturer in Planetary Physics

Ref: APL02

This job has now been filled...





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Post-doctoral positions

Two Research Assistant posts in Atmospheric Physics at UCL

ref: APL04

These posts now filled..

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Ph.D. Studentships

The new Scanning Doppler Imager (SCANDI) for meso-scale studies of thermospheric energetics and dynamics

The APL uses state-of-the-art Fabry-Perot Interferometers (FPIS) to observe airglow and the aurora. The observations allow measurement of the behaviour of the thermosphere at altitudes above 100km. The FPIs are located close to the EISCAT incoherent scatter radars which measure the ionosphere. The Scandinavian region is also well covered by a variety of instrumentation, such as riometers, magnetometers, meridian scanning photometers, all-sky cameras. There are also satellite instruments making many overpasses, which all together provide a comprehensive set of tools for studying and understanding the complex inter-relation between the thermosphere, ionosphere and magnetosphere. This is a mature field in which the large-scale behaviour of the Earth.s upper atmosphere (on scales of thousands of kilometres and hours) is now adequately understood. The new frontier is meso-scale (i.e., tens of kilometres and tens of minutes) and smaller. Among other unresolved issues, there is a large discrepancy (with a factor of around 2) between models and observations for energy dissipation and momentum transfer. These issues require investigation of perturbations and variability at smaller scales. The new Scanning Doppler Imager (SCANDI) is an all-sky version of the FPI. The PhD will involve the student in the construction and calibration of the SCANDI and its deployment on the island of Svalbard in the winter of 2006-2007. Subsequently data collection and analysis will be used for meso-scale studies of thermospheric energetics and dynamics. The project will be suitable for a 4 year PhD.

Contact: Dr Anasuya Aruliah

Thermosphere-Mesosphere Coupling Study

The Atmospheric Physics Laboratory has a network of Fabry-Perot Interferometers in northern Scandinavia to study the upper atmosphere in the region of auroral activity called the auroral oval. This is a highly dynamic region of the upper atmosphere since it is directly coupled with the solar wind from the Sun, via the Earth's magnetosphere. Our major experimental work has been with the dominant red and green line auroral and airglow emissions of the thermosphere, which cover an altitude region of between 100-300km. We are proposing an investigation of the coupling of the energetics between the thermosphere and mesosphere regions by simultaneous observations of auroral and airglow emissions from around 90km, 110km and 240km. The transfer of energy is very complex, involving winds, tides, gravity waves, turbulence, radiative processes and chemistry. Coupling between the middle and upper atmosphere is new territory and the experimental work will be augmented by theoretical models that are also part of the expertise of the APL.

Contact: Dr Anasuya Aruliah

Energetics of the High-Latitude Magnetosphere-Ionosphere-Thermosphere System

The ionosphere responds almost immediately to changes in the electric field near the north and south poles. These changes can be highly dynamic and derive from the way that the solar wind interacts with the Earth's magnetic field. However, the neutral atmosphere, which is the vast bulk of the upper atmospheric composition, can take a few hours before such changes feed through to the large- scale motion via ion-neutral interactions. This inertia has major consequences for the ionosphere-thermosphere system, in particular the currents and energy dissipation. Studies of the energetics of the upper atmosphere at high- latitudes may be achieved through a combination of ground- based observations by Fabry-Perot Interferometers (built by this group), coherent/incoherent scatter radars, ionospheric tomography and satellite measurements. These are then compared with model simulations, in particular with the UCL/Sheffield/SEL three-dimensional Coupled Thermosphere-Ionosphere- Plasmasphere model. There is plenty of scope here for an instrumental PhD through to a modelling PhD and any combination in-between.

Contact: Dr Anasuya Aruliah, for ground-based instrumentation;
Dr. Alan Aylward, for modelling of the earth's upper atmosphere

Small Scale Structure of the Aurorae: Space Weather Studies

The Atmospheric Physics Laboratory has built and deployed an instrument platform on the island of Svalbard in the Arctic Ocean. The platform (operated in collaboration with Southampton University) contains a high resolution (0.2 nm in wavelength) spectrograph, two high-speed photometers and an auroral imaging TV. These instruments are used primarily to study the emissions from the polar cap aurorae. The aurorae change from day to night and with geomagnetic activity, amongst other effects. When the Earth encounters a Coronal Mass Ejection and the auroral and magnetic activity increases, Svalbard is one of the key areas for understanding the interactions, as it is often connected directly to the field lines that are most affected by particle intrusion and particle acceleration mechanisms. This is part of the field of study known recently as "Space Weather". The spectrograph and photometers have changeable filters, and can thus be used to study a range of ions and neutral species emitting as the result of particle precipitation. A number of studies are ongoing into Space Weather, small-scale structure in the aurorae and its causes, so-called "black aurorae" and other topics.

Contact: Dr Ian Furniss

Solar Variability and Climate-Change-Linked Studies

In recent years more and more evidence has accumulated that there is a link between solar variability (in the sense of changes in the solar cycle/sunspots and radiative output) and climate change. This is controversial because the effects that are seen to change cyclically on the Sun represent a tiny fraction of the Sun's output, and most of the energy that reaches the Earth from the varying phenomena is expected to be "soaked up" by the minute fraction of the Earth's atmosphere that borders interplanetary space. However, correlations show there appears to be linkage of some kind. A number of theories have been developed to explain this. One is that intergalactic cosmic rays seed rain clouds and the flux of cosmic rays goes inversely with sunspot number. Another idea is that the sun has varying amounts of open magnetic flux at different times, and this produces different types of coupling at the earth's magnetopause. Yet other theories suggest it is rather the releasing of trapped oscillations (tides and so-called planetary waves) in the earth's lower atmosphere that is the cause of the apparent correlation. All these effects are mitigated by the middle atmosphere – the region between the thermosphere which borders space, and the troposphere where our weather occurs. The Atmospheric Physics Laboratory has developed a model of the Earths upper atmosphere that implicitly includes the middle atmosphere, and it is using this in a number of studies of the possible mechanisms that could explain how our weather might be controlled on long time-scales by the variability of the Sun.

Contact: Dr. Alan Aylward

Comparative Thermospheres of the Terrestrial Planets

The Atmospheric Physics Laboratory has working numerical models of the thermospheres of the Earth, Mars and Titan. Venus and Triton are under development. In developing models of the other planets, often one discovers, by contrast, interesting new things about ones own. A number of projects are ongoing in this area of comparative planetology. Apart from finishing the development of the Venus and Triton models, there is ongoing work to understand the way the solar wind interacts with the different bodies – all but one of which (the earth) are devoid of substantial protective magnetic fields. There is also a need to understand the ways climate is controlled on the different bodies and what determines water and gas loss. As more space probes arrive at Mars with every suitable conjunction, there is more data on the Martian atmosphere to try to understand, and from 2004 for several years the Cassini probe will be dipping occasionally into the Titan upper atmosphere: a real test for our Titan thermosphere model!

Contact: A.D,.Aylward (A.Aylward@ucl.ac.uk)

Comparative Thermospheres of the Gas Giants

The Atmospheric Physics Laboratory has developed models of the thermospheres and ionospheres of Jupiter and Saturn. It is hoping soon to add Uranus and Neptune, in a simplified way, to this group. Already involved in trying to understand data on the jovian upper atmosphere from the Galileo mission, there will soon be data from Cassini in the Saturnian system to give a comparison between planets which look superficially similar but between which there are significant differences. These models will be used to try to understand the upper atmospheres of the planets, how they interact with the magnetospheres, how they depend on solar wind strength, and how they depend on what happens deep in the atmospheres of the gas giants. Much is still not properly understood about these planets – like the basic fact that their thermospheres are several times hotter than simple calculations of solar energy in vs. thermal conductive cooling would suggest. The research programme is already looking at some of these basic questions, but we expect them to take a whole new turn when data starts arriving from Cassini, ground-based and HST observations.

Contact: Prof S.Miller

Extrasolar Planets: Modelling the Unseeable

There has been a lot of interest lately generated by the detection of planets around other stars. Most of these planets it can be deduced are around Jovian size, but much nearer to their host star. Work at the Atmospheric Physics Lab with a model of such an extrasolar planet (based on our model of Jupiter, "moved in " towards the star) has already given insights in to how stable these planets would be, what sort of emissions they might be expected to produce, and what the morphologies of their upper atmospheres might be. APL also has models of the terrestrial planets' atmospheres, and these similarly could be adapted to try to predict what extra-solar terrestrial sized planets might be like. NASA and ESA both plan missions to try to look for such planets and one of their key questions at this stage is "what should we be looking for?". Modelling of the planets and their atmospheres may help to answer such questions, as well as give insights in to what controls temperatures, and compositions of such bodies, questions critical to those trying to understand the prevalence or otherwise of life throughout the universe.

Contact Dr. Alan Aylward