A programme of simultaneous photographic and radio echo observations of meteors is described. The author has been mainly concerned with the photographic aspects of the programme and a detailed description of the problems involved in the operation of meniscus Schmidt cameras is included. In particular, a new method of sensitising the steeply curved focal surface, characteristic of these instruments, is described. A critical analysis of the sensitivity of the photographic system is given. An angular measuring instrument and microphotometer have been designed and constructed in order that the spherically curved photographic plates may be measured directly. These instruments result in a considerable saving in analysis time when compared with the American technique of copying the plates onto a flat surface for measurement in conventional instruments. The techniques developed for the computation of the position of a meteor trail, and the velocity and brightness of a meteor, are described. Observations have been carried out over a period of zt years and a total of 75 meteors have been photographed. 18 of these meteors have radio echoes assooiated with them. One of the correlated observations, of a bright Geminld meteor, has enabled the attachment coefficient of eleotrons to neutral oxygen molecules to be determined. It has been found to be an order of magnitude greater than the theoretical estimate which has been the only value available until now. An attachment coefficient of this order is shown to explain the departures of radio echo observations of meteors from the simple diffusion theory. For example, it is shown that an attachment coefficient of this order will limit the maximum possible echo duration from a meteor trail to a few hundred seconds, instead of several hours which might be expected on diffusion theory. It will confine the echoing region on a meteor trail to a narrow height range and cause a departure of radio echo observations from the A duration law. These are well established observational facts. 53 colour indices have been derived from the observations. A dependence both on velocity and magnitude is found, the latter being the greater. The results are in agreement with those obtained with the American Super Schmidt cameras but the interpretation is questioned. The variation in colour index is explained qualitatively in terms of observational effects due to the visual magnitude estimates and to real changes in the meteor spectrum. In view of the observational effects on visual estimates of brightness it is suggested that the photographic magnitude scale should be made the standard to which observations are related. A relationship between the absolute photographic magnitude and the luminous intensity in the photographic spectral range is derived. The dependence of the ratio of luminosity to ionisation upon brightness and velocity is investigated. No significant brightness dependence is found. The velocity dependence of the ratio of luminous intensity to electron line density is established. The velocity dependence of the luminous and ionising efficiencies, and of the probability of ionisation, are found. The relative values of the efficiencies have been derived from the present data although it is not possible to determine their absolute values. A relationship between the absolute photographic magnitude and the electron line density is determined. The relationship involves a velocity index and this is tabulated with the estimated uncertainty in its value. Some suggestions for future observations are included.

No description available.

This thesis investigates energy transfer between solar wind (SW)-magnetosphere-ionosphere systems during geomagnetic storms that could pose a significant threat to terrestrial technology. A superposed epoch analysis (SEA) of 143 storms from the last solar cycle (1997-2008) was completed. The average geomagnetic storm was investigated via SW data and the global SYM-H index. A new dual trend was observed when comparing storm size to main phase duration which reduced for storms with SYM-H minima <-150 nT, opposite to the findings of Yokoyama and Kamide [1997]. This suggests ring current enhancement dominates recovery, meaning intense storms can occur on the same timescales as weak; important for space weather prediction. One of the first global SEA studies of storm time ionospheric convection using HF SuperDARN radars and map potential technique was completed. Latitude-Time-Velocity plots were developed to best observe the average convection response to storm driving compared to quiet periods and Gillies et al. [2011]. A case study was presented comparing the SEA results to two recent storms, showing remarkable agreement, suggesting the SEA average convection could be used in future predictions. An SEA of global UV auroral images from the IMAGE and Polar spacecraft produced expected auroral responses to geomagnetic storm driving (e.g. Milan et al. [2009]). Open-closed field line boundaries, identified using the method of Boakes et al. [2008], were compared to convection reversal boundaries derived from the SuperDARN analysis. Consistent statistical boundary o_sets suggested a small 'viscous-like' interaction between the SW and magnetosphere was present, estimated to produce an additional ∽4-11 kV potential during quiet and storm periods; an important, small addition to the usual reconnection driven convection. These studies increase our understanding of storm time SW-magnetosphere-ionosphere coupling, raising interesting questions for future work. The combination of datasets makes this one of the largest statistical studies of storms.

The Sun is at the centre of our solar system and it is constantly ejecting a flow of plasma outward into interplanetary space. This flow can take the form of two primary types; the fast solar wind; and the slow solar wind. The Sun may also eject plasma with more dynamic events which cause high density clouds of plasma to travel alongside the solar wind. In the modern world, a number of different techniques have been developed to study the solar wind from the Earth and also in interplanetary space. Interplanetary scintillation (IPS) is a technique that has been applied at Aberystwyth University to observe the continual density variations in the solar wind by observing a distant astronomical radio source and the scintillation of its radio waves as they pass through the solar wind. To perform this, a number of radio sites around the world have been used such as the European Incoherent SCATter radar (EISCAT) in northern Scandinavia, and the ever growing LOw Frequency ARray (LOFAR) based in the Netherlands. The IPS technique has also proved to be highly complementary with Heliospheric Imagers (HIs) onboard the Solar TErrestrial RElations Observatory (STEREO) spacecraft which detect the white light which has been scattered by the solar wind particles. This thesis investigates the solar wind using a wide variety of techniques to observe the small- and large-scale structures which form in the solar wind. A study of IPS in 2007 and 2008 detected numerous events of rapid velocity variations which occurred in the slow solar wind. This showed evidence that the slow solar wind may have a ?blobular? nature formed of many small-scale transients as well as the large-scale transients which are already well known to us. In November 2011 LOFAR observed its first coronal mass ejection (CME) while observing IPS. This event proved to become of interest as it was successfully detected by a number of different techniques and could modeled and tracked accurately as it propagated outward to Earth?s orbit and even interacted with the Earth?s magnetosphere. A technique which could be applied to coronagraph observation separated the dynamic and quiescent solar wind structures from the images. The quiescent component became the basis for the development of a new solar wind model which could quickly and accurately map the background quiescent solar wind free from any of the complexities cause by CMEs.

No description available.

The discovery of large accumulations of meteorites in Antarctica is comparably recent, with annual collection expeditions beginning in 1974. Since then, over 50,000 meteorites have been recovered from the icefields of Antarctica. Many of those meteorites have had long residence times of up to 2 Ma mostly encased in ice; during which many of the meteorites have undergone considerable alteration. Understanding the paths of alteration allows reconstruction of original features, but additionally it gives a unique opportunity to examine a natural laboratory of cold, water-restricted alteration environments similar to those on Mars today and in its history. To fully understand the weathering of meteorites in these environments, six L6 chondrites in a variety of weathering states have been examined and characterised petrologically, chemically, and magnetically. Chemical analyses undertaken are major and trace elements measured in bulk and in spatially resolved analysis and bulk oxygen isotopes. Petrology has proven to control the weathering patterns and alteration state of the meteorite. A chemical weathering index has been developed to characterise the state of weathering using bulk chemical data, which also links with the petrological findings. This is especially evident in micro features created by shock, which promote rapid mineral breakdown and acidification of alteration fluids, which, fundamentally changes the nature and speed of the alteration. Shock generated features have created increased vulnerability to weathering and so areas that have undergone significant shock on Mars are more vulnerable to weathering and breakdown. However, the heterogeneity that is inherent to alteration environments of low water to rock ratios results in short transport distances for elements, resulting in little bulk chemical change with significant mineralogical alteration.

This thesis studies the large-scale dynamics in the Earth's magnetosphere due to solar wind driving. When the interplanetary magnetic field (IMF) is orientated southward, reconnection on the dayside magnetopause opens magnetic flux, which eventually reconnects in the magnetotail. When dayside reconnection is dominant, the polar cap, the area where open magnetic flux meets the Earth's surface, increases. Similarly, when nightside reconnection is dominant, the polar cap decreases in size. This framework is known as the expanding and contracting polar cap paradigm (ECPC). Part of this thesis considers the ionospheric flows, a part of the ECPC, which relates global auroral imagery of the size of the polar cap through a physics-based model of the ECPC, and compares the calculated ionospheric flow velocities to satellite, and ground-based measurements of plasma drift. The comparison also discusses the known limitations of the model and the observations. In the following chapters, specific events within the ECPC, or magnetospheric modes, are put into the context of solar wind driving and the auroral response. Substorms are a sporadic magnetospheric response mode, where the polar cap expands at first, followed by a distinct nightside brightening of the aurora and a decrease in polar cap flux. Steady magnetospheric convection events (SMCs) are times when the day and nightside reconnection rates are balanced, such that the polar cap flux stays constant. By considering dayside reconnection rates and the magnetospheric response during these events, it is established that the majority of SMCs are part of the substorm cycle. Sawtooth events (SEs) appear as a quasi-periodic version of substorms, but occur under more extreme solar wind driving. It is shown that the aurora behaves according to the ECPC in terms of latitudinal expansions and contractions, but the temporal behaviour is significantly different from substorms.

This thesis studies the spatiotemporal variability of phenomena within the Martian plasma environment arising from the interaction of the interplanetary solar environment with the Martian upper atmosphere and ionosphere. In particular, two phenomena have been studied including, (1) rapid reductions in the superthermal electron plasma population, or ‘electron holes’, within the illuminated Martian induced magnetosphere (IM), and (2) the outermost interface of the Martian plasma environment to the solar wind, the Martian bow shock. I have used ~ 11 years (2004 to 2015) of plasma observations at Mars by the Mars Express (MEX) mission to investigate aspects of these phenomena that no previous study has been able to explore. Bespoke automated algorithms have been devised to identify both the electron holes and the Martian bow shock over this time period. I have identified that the electron holes are a common occurrence within the illuminated Martian IM, with 56% of the MEX orbits over the period containing at least one event. I have verified that the spatial distribution of these phenomena are colocated with the intense crustal magnetic fields, and demonstrated that their altitudinal distribution is dependent on the relative intensity of the crustal magnetic fields. Using the long timescale MEX bow shock observations, I have computed statistically robust models of the Martian bow shock shape and location, and consequently studied its spatial variability over time. For the first time, I have demonstrated that average bow shock position varies by 10% throughout Mars’ elliptical orbit of the Sun. I have used complimentary datasets to describe this variation in terms of the solar wind dynamic pressure, EUV flux, and the crustal magnetic fields. This newfound knowledge has then allowed me to discover that the Martian bow shock’s average altitude varies by 5 - 10% over the period of the ~ 11 year solar cycle.

Meteorites are ejected from random areas of the lunar surface and therefore provide geological information about the Moon far from areas sampled during the Apollo and Luna programs. However, unlike those samples, the exact launch locations and geological setting of lunar meteorites are unknown, limiting greatly the knowledge we can obtain from them. During this project the launch location of lunar meteorites were studied using both laboratory analytical techniques and remote sensing instruments. This approach enabled me to provide meteorites with a geological context, increasing the geological knowledge it is possible to obtain from them. The lunar feldspathic meteorites Miller Range (MIL) 90036 and MIL 090070 bulk-rock compositions and mineral chemistries were studied. MIL 090036 is a feldspathic immature regolith breccia (26.72 wt.% Al2O3, 5.27 wt.% FeO) that exhibits a Th-enrichment (1.89 ppm Th). This could be related to a high alkali component that has been observed in impact melt breccia clasts in this meteorite, but also it could be related to a KREEP component that, although it was not observed in the particular sample studied, it can be present in the bulk meteorite. Most of the provenance results show that the regolith from the surroundings of the Procellarum KREEP Terrane (PKT) in the nearside are the most similar to the composition of this meteorite and therefore the likely source location for MIL 090036. MIL 090070 is a feldspathic immature regolith breccia with bulk-rock compositions of 30.72 wt.% Al2O3, 3.77 wt.% FeO and a low Th abundance (0.44 ppm). The geochemistry of MIL 090070 may be formed by a mixture of ferroan and magnesian anorthositic rocks, although other possible explanation could be that they were all essentially ferroan-derived and that this rock types are more related to high-magnesium suite that previously thought. MIL 090070 was probably launched from the farside of the Moon as suggested by its compositional differences when compared to Apollo 16 regolith breccias, including the lack of KREEP. The present work has studied the possible launch locations of 37 lunar meteorites (67 individual stones) using bulk-rock FeO, TiO2 and Th compositions and the 2-degree LP-GRS dataset from Prettyman et al. 2006. My method compares the composition of both the analytical and the remote sensing measurements. The outcome is a shapefile that allows for a correct visualization in ArcGIS™. Results obtained suggest that differences in KREEP components between the PKT and other areas of the Moon are not the only indicator of a heterogeneous mantle. This study also indicates that ferroan anorthosites are widely distributed with patches occurring within the central farside highlands. The large number of feldspathic meteorites that contain both magnesian and ferroan anorthosites compared to those that contain only one or the other, could indicate that these rock types are genetically related and that the wide Mg# distribution in FAN and MAN could be produced by serial magmatism. If this is correct, some of the ferroan anorthositic lithologies observed within lunar samples would not be the direct product of the magma ocean crystallization.

When investigating solar wind-magnetosphere-ionosphere coupling, it is important to understand how the solar wind, and the interplanetary magnetic field (IMF) frozen into it, behaves as it reaches the Earth. Magnetic reconnection, for example, is a phenomenon whose morphology is governed by the IMF orientation and wields a large influence over many of the processes occurring within the magnetosphere. Exploiting nearly a decade of spacecraft data, primarily from ESA's Cluster mission and NASA's ACE mission, the three studies presented in this thesis aim to help improve the specification of the IMF at the magnetopause.