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No description available.

The central theme of the research presented in this thesis is an investigation of the stability of a symmetrically restricted four-body problem called the Caledonian Symmetric Four-Body Problem (CSFBP) (Steves and Roy, 2001) using a newly developed numerical integration scheme which enables the numerical exploration of the systems as they pass through two-body close encounters. A study of the hierarchical stability of the CSFBP system is made, followed by an empirical stability analysis of hierarchically stable regions in the phase space of the CSFBP. The study of the dynamics and stability of four-body systems like CSFBP is relevant in order to determine stable hierarchical arrangements which will be capable of hosting exoplanetary systems. A comprehensive literature review of the key features of the CSFBP is presented. The collision manifold of the phase space of the CSFBP is explored for a whole range of CSFBP systems and the fundamentallimitatioDs of the existing numerical integration scheme (cf. Szell, Steves and Erdi (2004a); Szell, Erdi: Sandor and Steves (2004)) have been analysed. It was found that, neglecting the collision orbits in the phase space of the CSFBP is a major limitation in the numerical exploration of the global stability features of the CSFBP. A review of regularisation theory is given, highlighting the key stages needed to develop a regularisation method for a gravitational few-body problem. A global regularisation method (cf. Heggie (1974)) is then derived to handle various two-body close encounters. An algebraic optimisation algorithm (Gruntz and Waldvogel, 1997) is adapted for numerically implementing the regularisation scheme. The numerical accuracy and the computational performance of the developed integration scheme were tested for a broad range of CSFBP orbits. Regardless of the nature of the orbits, it was found that the regularised integration scheme outperformed the standard non-regularised integration schemes in terms of computational performance and improved numerical accuracy characterized by stable energy profiles. The hierarchical stability of the CSFBP is investigated using the developed integration schemes. Numerical simulations were conducted for a comprehensive set of CSFBP orbits. It was found that the analytical hierarchical stability criteria was satisfied even after the inclusion of orbits with two-body close encounters. An empirical stability investigation was also made and it identified regions of hierarchical stability in the phase space of the CSFBP for any value of Co < Ccrit.

We present a Curtis Schmidt CCD survey of two strips of the sky overlapping with the NGC and SGC 2dFGRS fields. When this survey is used in conjunction with data from the APM Galaxy Survey, DUKST, 2dFGRS and 2MASS, we find that there is a hole in the SGC distribution of galaxies of 100 x60 in angular extent which extends to z~0.1. The magnitude of this galaxy number deficiency is 30% . The two-point correlation function for our CTIO data is calculated and we find that there is excess power in our SGC function with the break occurring on larger angular scales relative to that in the NGC. When we take into account the effect of the integral constraint we find that a power law form of the two-point correlation function extending beyond ~100h(^-1) Mpc cannot be ruled out, and we show that this kind of pure power law behaviour is an example of what might be needed to explain the hole we claim exists in the SGC distribution of galaxies. We also find evidence of bias from the fact that the galaxy number deficiency in the 2dF SGC n(z) is greater when more instrinsically luminous galaxies are sampled. We also investigate the clustering properties of a sample of faint blue galaxies at z=l-2 and are able to use our CTIO clustering results in order to constrain the galaxy correlation length in the local Universe where we find that r(_0)=4.7h(^-1)Mpc. By parametrising the clustering evolution using the clustering growth parameter ϵ, we find that our faint blue galaxies are consistent with an ϵ=0.1 model, which corresponds to a scenario where clustering is approximately fixed in proper coordinates. Finally, we investigate whether the presence of dust in such faint blue galaxies could have an impact in the sub-mm wave-band. We show that by using either a 1/ƛ or Calzetti absorption law for the dust and re-distributing the evolved spiral galaxy ultraviolet (UV) radiation into the far infrared (FIR), we can account for all of the 'faint'(≤ ImJy) 850μm galaxy counts and a significant proportion of the sub-mm extra-galactic background.

This thesis discusses new observations made of large scale solar wind structure during solar minimum conditions. The phenomena of interplanetary radio scintillation (IPS) is exploited and used in conjunction with white light observations from the Heliospheric Imager instruments on the STEREO spacecraft. Methodologies for combining the two techniques are developed and then used in two case studies. The first case study is an observation and analysis of complex solar wind features in the presence of a co-rotating interaction region. The second is an observation and analysis of coronal mass ejections and their associated effects. In both studies, observations were supported by in situ data from the Venus Express spacecraft. Both cases represent the first time that such phenomena have been observed at interplanetary distances using these techniques. Extremely long baseline IPS observations were also made in order to address the hypothesis that the fast solar wind flow is radial. Observations made over several years, at different times in the solar cycle and over both hemispheres demonstrate that, down to the level of sensitivity for this technique, the hypothesis still stands. Off radial flow characteristics were observed using this technique during the passage of non-ambient solar wind features across the raypath. These results demonstrate that this technique can detect off radial flow when it is present and hence reveal aspects of the behaviour of the interplanetary magnetic field under different solar wind conditions.

A major mission driver for space exploration is to maximise science data return whilst minimising ground-based human intervention and hence associated operations costs. Future robotic exploration such as the ESA ExoMars mission (launch 2018), and the eventual Mars Sample Return (MSR) mission will require rovers to travel further and faster than has been achieved to date. In order to make this possible it is essential that currently earth bound decisions be transferred to the exploration platform wherever possible. In line with this, this Thesis presents a new solution which requires a combined on-Earth and on-board rover approach. The on-board element utilises autonomy and basic image processing techniques to image a predefined number of potential targets. The Earth-based element uses a more complex knowledge based system approach which has been primed by a human Planetary Geology Expert. This Earth based approach, which is used to process the autonomously captured images, is presented as a precursor to a future onboard solution. Both solution elements represent significant advances in the current state of the art. This Thesis provides details of the design, implementation and experimentation undertaken to validate the performance of both the on-board and on-Earth solution elements.

The solar wind is a highly supersonic outflow of coronal plasma flowing in a close to radial direction out from the Sun. Generally, there are two modes of outflow, a fast stream mode with velocities in the range of 750 kms−1 to 800 kms−1, and a slow stream mode with velocities in the range of 350 kms−1 to 400 kms−1. The method of interplanetary scintillation (IPS) is used to obtain solar wind velocity estimates by observing the “twinkling” of radio waves from distant compact sources caused by density variations in the solar wind. The Aberystwyth IPS group has been conducting IPS observations using the European Incoherent SCATter radar (EISCAT) in northern Scandinavia since 1993 and more recently using the Multi-Element Radio-Linked Interferometer Network (MERLIN) radio telescopes in the United Kingdom. This thesis investigates the large-scale structure of the solar wind using IPS observations in conjunction with white-light, extreme ultra-violet (EUV) and X-ray Carrington rotation maps from ground-based: Mauna Loa; and space-based: SOlar and Heliospheric Observatory (SOHO) and Yohkoh; as well as in-situ spacecraft observations of solar wind velocity from Wind and Ulysses. A complete study of EISCAT IPS data from 1994 to 2003 is undertaken looking for detections of interaction in terms of shear layers and co-rotating interaction regions (CIRs) by ballistically mapping the IPS observations out to in-situ distances to see how interaction develops. From this, an investigation was carried out with solar minimum (1994-1997) EISCAT IPS data investigating a possible bi-modal fast solar wind structure. In addition, the technique of extremely long-baseline IPS measurements (developed from 2002) was used to look at the finer structure of solar wind velocity. This technique was also used to investigate the direction of flow which included observations of fast and slow wind, interaction regions, and the passage of a magnetic cloud.

Charge exchange is investigated as a source of magnetospheric He+ . Ionic data from the Magnetospheric Ion Composition Spectrometer (MICS) on the Combined Release and Radiation Effects Satellite (CRRES) are investigated during storm and quiet periods. A He+ /He++ maximum is observed at Ring Current altitudes, where particle trapping is relatively stable. A study of ionic number density across the main and recovery phases of geomagnetic storms provides evidence of a recovery phase source of He+ that does not include the other species. It is suggested that charge exchange of trapped He++ ions with exospheric neutral hydrogen is the source of this He + . Cross sections are obtained for the He++ He+ charge exchange reaction. A new population of He+ ions is observed within the drift echo of an injection which occurred during orbit 497 of CRRES, at E/q values not present in the injection. The possibility of this new He+ population having arisen due to charge exchange is discussed, and charge exchange cross sections are calculated for the reaction. The cross sections calculated for these data are larger than those found by previous work, and it is concluded that the observed effect cannot be explained entirely by charge exchange. Solar wind precursors to pseudobreakups are compared to those of substorms. [Tsurutani et al., 2003] gave examples of stormtime periods which did not contain substorm expansion phases. These are investigated for evidence of electron injections at geosynchronous altitude. It is shown that injections did occur during these periods, though generally at lower energy than those with expansions. The injections are attributed to pseudobreakup activity rather than full substorms. Solar wind parameters are compared to injection energy for storms with expansions and without. It is shown that the occurrence of expansions is associated with spikes in solar wind density, though a time lag of up to 20 minutes is required. This is explained in relation to the pressure catastrophe ([Erickson and Wolf, 1980]), whereby some time is required for magnetospheric convection.