Observations and modelling of the wave mode evolution of an impulse-driven 3 mHz ULF wave

A combination of an HF Doppler sounder, a network of ground magnetometers, upstream solar wind monitors and a numerical model is used to examine the temporal evolution of an Ultra Low Frequency (ULF) wave. The event occurred on 16 April 1998 and followed a solar wind density and pressure increase seen in the upstream ACE spacecraft data. The magnetometer and HF Doppler sounder data show that the event develops into a low-<I>m</I> (&minus;6) field line resonance. HF signals that propagate via the ionosphere exhibit Doppler shifts due to a number of processes that give rise to a time-dependent phase path. The ULF electric and magnetic fields are calculated by a one-dimensional model which calculates the wave propagation from the magnetosphere, through the ionosphere to the ground with an oblique magnetic field. These values are then used to determine a model HF Doppler shift which is subsequently compared to HF Doppler observations. The ULF magnetic field at the ground and Doppler observations are then used to provide model inputs at various points throughout the event. We find evidence that the wave mode evolved from a mixture of fast and Alfvén modes at the beginning of the event to an almost purely shear Alfvénic mode after 6 wavecycles (33 min)

RESCALE: Review and Simulate Climate and Catchment Responses at Burrishoole

The climate of the Burrishoole catchment is projected to change significantly over the present century. Previous research of the catchment identified a scientific gap in knowledge in terms of understanding the implications of present and projected future changes in stream flow, water temperature, pH levels and DO concentrations on fish productivity in the catchment. To address this, a multidisciplinary team of scientists undertook an analysis of both present and likely future climate impacts on the catchment with a view to furthering the understanding of the inter-linkages between climate, climate change, and the freshwater ecosystem. The research findings outlined in the report provide climate change information at the catchment scale to assist catchment stakeholders in integrating climate change considerations into their decision-making processes. The report presents an in-depth assessment of the climate and environmental datasets from the catchment to establish if changes have occurred over the period of record. In order to assess the likely impacts of future changes in climate on the catchment, regional climate projections were developed and subsequently employed to simulate likely responses in stream flow and temperature, DOC and DO for the present century. The projected changes in both the climate and water-quality were then used to provide a basis for assessing impacts on fish growth and survival rates of salmonid and eel species in the catchment. The report provides a useful template for future studies, not just in the Burrishoole catchment but for other ecologically important catchments. The findings from the report are relevant to policy makers at the national scale; catchment managers at the regional scale; and, specifically, to stakeholders in the Burrishoole catchment, in developing adaptive responses to climate change.Funded under the Marine Research Sub-programme of the National Development Plan (2007-’13), as part of the Sea Change Strategy.Funder: Marine Institut

Ionospheric Signatures of Ultra Low Frequency Waves

Ultra Low Frequency (ULF) waves have been studied for many years and the observation and modelling of such phenomena reveals important information about the solar-terrestrial interaction. Being ubiquitous in the collisionless terrestrial space plasma environment, ULF waves represent important physical processes in the transfer of energy and momentum. This thesis comprises three distinct studies to observe, model and analyse ULF phenomena. The first two studies focus on ULF wave observations at high-latitudes in the terrestrial ionosphere using a collection of both space- and ground-based instruments. The first study provides a detailed analysis of the time evolution of a ULF wave using the characteristics of the observed ULF wave as input-parameters to a 1-D numerical model. As the wave signature evolves towards a Field Line Resonance (FLR) a change in the incident wave mode from a partially Alfvénic wave to a purely shear Alfvénic wave is observed. The second study presents statistics of 25 large spatial-scale ULF waves with observations from a high-latitude Doppler sounder and ground-based magnetometers, complemented by model results. The third and final study describes the implementation of a well established radar technique ("double-pulse"), which is new for the Super Dual Auroral Radar Network (SuperDARN), which aims to provide an unprecedented temporal resolution for ULF wave studies. The new pulse sequence increases the temporal resolution of SuperDARN by a factor of three. Preliminary findings suggest this technique yields impressive results for ionospheric scatter with steady phase values but that the method cannot be used for data when the phase is rapidly changing or if the data originates from slowly decorrelating plasma irregularities. The running of two independent pulse sequences on the stereo channels of the Hankasalmi radar has also enabled, for the first time, the observation of cross-contamination between the radar channels