Radar studies of small-scale e-region plasma irregularities

Coherent scatter radars are extensively employed in the study of important geophysical processes in the Earth’s upper atmosphere and magnetosphere. The science relies on the ability of coherent scatter radars to detect plasma irregularities in the E arth’s ionosphere and relate their properties to the geophysical process under consideration. This thesis is concerned with the physical characteristics of the plasma irregularities deduced from coherent scatter radar observations. Data from three coherent scatter radar systems, PACE, SABRE and COSCAT, each sensitive to a different hregularity wavelength, are analysed. Statistics for the backscatter power, phase speed and spectral width at each wavelength are calculated and compared. Furthermore, the functional dependence of the irregularity parameters on each other has been investigated. Strong relationships between the spectral width and irregularity phase speed and the spectral width and backscatter power are identified. The spectral widths tend to exhibit a minimum at phase speeds close to the ion-acoustic speed. There is a decrease in the average backscatter power as the spectral width increases. A new measurement of the dependence of the spectral width on the irregularity wave number is deduced. These results have important significance for the general interpretation of coherent scatter radar measurements. Special experimental campaigns with SABRE and COSCAT in conjunction with EISCAT have been undertaken to enable the irregularity phase speed and the plasma drift speed to be compared. This is a very important relationship since the plasma drift speed is routinely estimated from the in-egularity phase speed. The analysis confirms the non-linear behaviour of the relationship between these two parameters. Similar results are obtained for COSCAT and SABRE. Differences can be attributed to the expected variations with wave number and to variations in the height of the observed irregularities, consistent with the kinetic theory of Robinson and Honary (1990). A cknow ledgem ents For making this thesis possible and for sustaining me throughout its construction thanks are given to: Professor Tudor Jones for his stewardship as head of the Ionospheric Physics Group and his constructive remarks regarding the final manuscript. Dr. Terry Robinson for his supervision and an eternal supply of good suggestions. Dr. Alan Rodger for his supervision and asking me the most pertinent questions. British Antarctic Survey (BAS) for results from the PACE radar. For their geophysical knowledge Dr. Mark Lester and Dr. Tim Yeoman. A plethora of scientists for their helpful discussions; Dr. Ian McCrea for COSCAT and ion-energy balance, Nick Mattin for PACE data and irregularities. Dr. Mike Pinnock for specti’al widths and radar systems. Nigel Wade, Dr. Chris Thomas, Andrew ‘Grit’ Stone, Alistair Kershaw and Mehbub Ashraf for help with computing of all types. Generations of the workshop for building radars, their wry observations, wit and encouragement; Peter Chapman, Warren Smith, Mick Parsons, Stuart Crooks, Lynda Forsyth and Martin Hollingshead. Everyone else who I had the fortune to work with or just know in the ionospheric physics group, including: Martin Popple (irrepressible), Paul Rylah (space). Dr. Alan Stocker (samosas). Dr. Farideh Honary (kinetic chocolate). Dr. Bob Cherry (think about the future), Dr. Eric Bradshaw (lungs on legs). Dr. Stuart Kelly (space), Steve Milan (maximum information in minimum space) Jackie Davies (EISCAT help), John Taylor (cultural pipeline). Dr. Awni Abdulahad (unstoppable), Julian Thornhill (digital guru), Kathleen (all those fiddly forms). Dr. Thomas Smid for always opening ones mind from a new side, countless denizens of RSL (once RPL never forgotten), the new vanguard: Brian Shand(man), Mark II Ransom, Dr. Richard ‘Mongoose’ Beard, Dr. Neil ‘The Terminator’ Arnold, Zou Li, Darren Wright and all those to come. The SERC who funded this work with a CASE research studentship in collaboration with BAS (NERC), the Max Planck Institut fur Aeronomie and Uppsala ionospheric Observatory for the operation of the Swedish radar of SABRE, Dr. K. Schlegel and Dr. T. Nygrén for their collaboration in the COSCAT experiment and the EISCAT scientific association for EISCAT.