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Atmospheric Physics

This page lists all the PhD projects offered by Atmospheric Physics group.



Modelling the Terrestrial Atmosphere


The Atmospheric Physics Laboratory has developed a comprehensive model of the Earth's upper and middle atmospheres (15 km to 600km altitude). This is being used for a number of studies, including comparisons with satellite data, and ground-based instruments. One particularly important strand of our work is the look at how effects in the lower atmosphere - the troposphere where we have the weather and climate that affects us - may be linked to what happens on the Sun or in near-Earth space. This covers the fields of 'Space Weather', where, for example, we see how the effects of solar flares can penetrate to the ground, and the way solar variability might affect the climate.

In recent years 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, including some control of clouds by cosmic rays, varying mechanisms for particle entry through the Earth's magnetic shield, and the release of trapped wave energy from the lower atmosphere by small modifications to the critical mesopause layer of the atmosphere.

Apart from our own model studying these effects we have a collaboration with the Met Office where we are looking at issues to do with coupling their tropospheric model to our upper atmosphere model. One recent project we have started is to look at how the 'Global Electric Circuit' might affect the coupling to the magnetosphere and beyond. This Circuit is driven by thunderstorms charging up the ionosphere above 100km height to 250-300KV with respect to the ground. There is a "Fair Weather" current back down from the ionosphere over the rest of the Earth. We are trying to understand how this might affect the dynamics, chemistry and thermodynamics of the atmosphere.

Contact: Prof. Alan Aylward (a.aylward AT ucl.ac.uk); Dr Anasuya Aruliah (a.aruliah AT ucl.ac.uk)

Planetary Aurorae and Magnetosphere-Ionosphere Coupling


The beautiful auroral displays of magnetised planets (such as the Earth, Jupiter and Saturn) are the result of powerful global systems of electrical current which flow between their ionospheres and magnetospheres. At the giant planets, rapid rotation plays an important role in the formation of auroral ovals. The Atmospheric Physics Laboratory group at UCL have a wealth of experience in both observations and modelling of the auroral physics and the global atmospheric flows which arise via the electrodynamic coupling of the planet and its space environment. We have analysed enormous datasets of ground-based spectroscopic observations of giant planetary aurorae, taken in infrared light, which reveal the emissions from the ion H3+. Such data have enabled us to confirm the primary role of this ion in the heating and dynamics of the hydrogen-rich auroral regions of the gas giants. Planned future work includes ongoing mapping of the H3+ emissions in order to build a more comprehensive picture of the physical conditions in the ionospheres of the gas giants.

On the modelling side, we have built global models of the thermospheres and ionospheres of Jupiter, Saturn and Uranus. These have been used in pioneering studies of the effects of auroral precipitation on upper atmospheric flows and planetwide heating processes. Such studies are important for identifying the types of energy inputs required to explain the unusually high temperatures in the upper atmospheres. Planned future work includes more studies of how time variability of the aurora and the magnetospheric conditions affect the atmospheric flows and heating: a key question here is the timescale associated with the atmosphere's response to changes in magnetospheric conditions. We have recently collaborated with the team who manage the magnetometer aboard the Cassini spacecraft on studies of Saturn's magnetospheric structure, and we envisage that this experience with spacecraft data will provide valuable future inputs and constraints for our own planetary models.

Magnetospheric Projects: Since 2009, our 'Atmospheric Physics' group has extended our modelling expertise out into the magnetospheric region and constructed models of the disc-like, rapidly rotating magnetospheres of Jupiter and Saturn. We have published several studies comparing the Saturn model with observations from the Cassini spacecraft of the planet's magnetic field and plasma environment. Further comparative studies of this nature are needed. On the more theoretical side, we also wish to build a more 'complete' magnetospheric model for Saturn by including the effect of the solar wind interaction, which for example 'distorts' the planet's plasma sheet from an equatorial disc into a 'bowl-like' shape. Thus for someone interested in plasma / magnetospheric physics, there is a variety of options for postgraduate work.

Contacts: Dr Nick Achilleos (nick AT apl.ucl.ac.uk); Prof. Steve Miller (s.miller AT ucl.ac.uk)

Magnetospheric Turbulence at Saturn

This project would suit a student interested in the analysis of magnetic data from the Cassini spacecraft. It focuses in particular on the nature of the fluctuations in the magnetic field, how those fluctuations characterise different plasma regimes in the magnetosphere of Saturn, and in particular how the spectrum of the fluctuations across different scales can give information about turbulence in the system. The student would be working closely with Dr. Patrick Guio and Dr. Nicholas Achilleos, both of whom have expertise in tools for this type of data analysis.


Structure and Energetics of the high-latitude MIT system


We have a network of Fabry-Perot Interferometers (FPIs) in northern Scandinavia, within the Arctic Circle, used to study the Earth's upper atmosphere: the magnetosphere-ionosphere-thermosphere (MIT) system. This study is achieved by measuring airglow and auroral emissions, more commonly known as the Northern Lights. The upper atmosphere near the magnetic poles is highly dynamic due to direct coupling with the turbulent solar wind, via the Earth's magnetosphere. The project will involve instrumental fieldwork with the FPIs, and collaboration with other instruments such as the EISCAT radar and magnetometers, which provide complementary observations of the ionosphere, as well as comparison with the APL atmospheric model. The investigation will be into the small-scale structure and the energetics of the interaction between the neutral and charged particles of the upper atmosphere.

Contact: Dr Anasuya Aruliah (a.aruliah AT ucl.ac.uk

Investigating the difference between satellite and ground magnetometer measurements of the Earth's magnetic field

The three Swarm satellites were launched by the European Space Agency last November 2013. They will measure the Earth's magnetic field and its structure to an unprecedented level of precision, Earth scientists and atmospheric scientists will use the observations to separate out the magnetic field generated by the Earth's core and mantle, from that generated by the ionosphere and magnetosphere.

It has been discovered that the magnetic field measured by magnetometers on the ground give different measurements from magnetometers on satellites. The aim of the project is to identify the cause of this difference.

It is proposed that the altitude distribution of electric currents in the ionosphere may be a primary source of difference. The UCL Coupled Middle Atmosphere and Thermosphere model will be used to test the hypothesis. The model simulations will be compared with magnetic measurements from the Swarm satellite and ground magnetometers. 

Contact: Dr Anasuya Aruliah (a.aruliah AT ucl.ac.uk)

Probing the Atmosphere of Jupiter and Saturn in the Far Infrared


Probing the Atmosphere of Jupiter and Saturn in the Far Infrared The wavelengths beyond 50 microns contain the spectroscopic signatures of many molecules at temperatures and under environmental conditions that cannot be easily accessed in other wavelength regions. These far infrared wavelengths can only be observed using observatories placed beyond the Earth's atmosphere as they are blocked from reaching the ground even at the highest terrestrial observatories. One of the space based observatories that UCL has been involved in building was the European Space Agency's Infrared Space Observatory (ISO) which operated from 1995 until 1998. Although almost all of the data from this facility has now been published, significant and unique data sets taken on the planetary atmospheres of Jupiter and Saturn have not see the light of day. With the exciting new observations from the latest infrared satellite (Herschel) now being released it is now time to revisit the ISO observations and, together with the atmospheric modelling expertise present in the Astronomy group, to build a new detailed model of the planetary atmospheres of the gas giants to look in detail at the chemistry and structure of their atmospheres and what these unique data can reveal in conjunction with the latest observations.



                                         

Contact: Prof Bruce Swinyard (bruce.swinyard@stfc.ac.uk) and Prof Steve Miller (s.miller@ucl.ac.uk)



                                         


 


                                        

    
    
    
	
		

Page last modified on 26 sep 14 16:37 by Serena Viti