No description available.

No description available.

”Auroral Structure and Kinetics” (ASK) is a multispectral auroral imager,developed and built by University of Southampton, UK, and Royal Institute ofTechnology, Sweden. The scientific objective of the instrument include characterisationof both high and low energy electron precipitation in aurora with highspatial and temporal resolution, and direct observation of plasma drifts in theionosphere. ASK consists of three cameras taking images in different spectrallines. One part of this thesis deals with the development of the data acquisitionsystem for the instrument. This included the hardware part (computers controllingthe cameras)and the software for operation of ASK. ASK was installedon Svalbard in November 2005, and examples of first data are presented. Thesecond part of the thesis treats the problem of estimation of motions from theauroral sequences. Robust optical flow estimation algorithm has been applied toauroral sequences, and new formulations specific to the imaging of metastableions (carried out by ASK) are suggested.

Data from an ionospheric heating experiment in Tromsø have beenanalyzed. The experiment was carried out during auroral conditions inOctober 2006. Beside data from the EISCAT UHF radar also opticaldata were recorded with the ASK (auroral structure and kinetics) instrumentand enhancements of backscattered power from the E-regionwere studied. Two simultaneous layers of instability with an altitudeseparation of 5 km are observed at an altitude of 120 km. Thetwo layers differ in their spectral characteristics and show different timeevolution. For one heating cycle it was also found that auroral processescorrelate to the strength of enhancements and the characteristics of theion line spectra.

No description available.

No description available.

Fluctuations in the solar wind characteristics such as speed, temperature, magnetic strength and density are associated with pulsations in the magnetosphere. Coherent magnetohydrodynamic waves in the solar wind may sometimes be a direct source of periodic pulsations in the frequency interval 1 to 7 mHz in the magnetosphere. In studies of the solar wind and the way its variation affects the magnetosphere, the significance of different frequency components and their signal fonn are of interest. Spectral analysis and signal reconstruction are important tools in these studies and in this report the MultiTaper Method (MTM) of spectral analysis is compared to the "classic" method, using the Hanning window and Fourier transformation. The MTM-SSA toolkit, developed by Department of Atmospheric Science at the University of California, is used to ascertain whether the MTM might be suitable. The advantages of the MTM are reduced information loss in analysed data sequences and statistical support in the analysis. Besides the compared methods of spectral analysis, an attempt has been made to test the validity of the adiabatic law, assumed as the relation between the thermal pressure and the density in the solar wind plasma. It was unfortunately difficult to estimate the gamma parameter of this relation, possibly due to the turbulent behaviour of the solar wind.

A study of ACE solar wind data at lAU, for the period from 1998 to early 2005, was conducted. This was done in order to find sudden solar wind pressure enhancements accounting for plasma transfer through the magnetopause. In order to get information about the extent and orientation of the structures found, a correlation of found events to data from the Wind satellite was done. The enhancements considered are those with a relative increase exceeding unity. These are found by applying a 1-hour box-car average to the data set. A part of the event distribution was found to vary at periodicities of 11 years, 140 days, and 29 days. Most of the pressure enhancements found were due to a corresponding increase in plasma density. The transverse extent of most of the structures found was rather large, i.e., of the order of 100 Earth radii and the mean orientation of the plasma fronts  were found  to lie between the radial direction and that of  the Archimedean spiral. The duration of most of the structures was shorter than 1 hour. An investigation of the direction of the GSE Z-component of the magnetic field of the events, showed that there was no predominant orientation.

The newest station in the South African National Antarctic Expedition, the SANAE IV, hostsnumerous research programmes. One is AMIGO which aims to establish the correlationbetween the solar wind and the magnetosphere. A magnetometer, located at a geographicposition of2.83°W, 71.67°S, consisting of two perpendicular coil sensors is installed to detectgeomagnetic field motions, also known as pulsations, in the North-South and East-Westdirections. ([7])The data, treated in this report, cover the years 2003 and 2004 with the exception of the 20first days in January 2003 and another randomly scattered 22 dates during both 2003 and2004 when the data are corrupt or simply just nonexistent.The data consist of detected pulses that are recorded as a voltage, unit m V, which aretransformed into corresponding magnetic flux density amplitudes. The interesting pulsationfrequencies are extracted from the respective powerspectra for certain time intervals. Toconduct this operation a MA TLAB-program that extracts these frequencies is later used toproduce statistics to provide a graspable view of the frequency distribution.The statistics show that the pulsations within the Pc4 range, and specifically the ones close toPc5, are most represented in the data, closely followed by the Pc5 and with a small but yetsignificant representation of frequencies from the Pc3 range. Pc 1 and Pc2 frequencies aredetected sporadically but their existence is negligible at the whole.It is also established that the daytime pulsations are scattered over a wider frequency spectrumthan during evening or morning, with the widest spectrum somewhere around noon ± 2 hours.Some of the results are in acceptable correlation with the theoretical assumptions such aswhere and when the different sources set up the pulsations.

A whistler wave is a Very Low frequency (VLF) trace that obtains its characteristics from dispersive propagation in the magnetosphere. Field-aligned ducts of enhanced plasma density ensure the propagation from one hemisphere to the other. The origin of these signals is lightning strikes that emit radiation which spans the entire spectrum with the bulk being in the VLF band. The VLF portion can travel great distances within the Earth-ionosphere waveguide (EIWG) before penetrating through the ionosphere, and exciting a duct. The relative location, compared to the duct, of those strikes that cause whistlers is unknown. It is of interest to examine where the whistlers that have been observed at Tihany, Hungary, and Dunedin, Nerv Zealand, originate. This is one tool to gain further understanding of the properties, especially the plasma density structure, of the ionosphere and the magnetosphere. Therefore time series with observed whistlers from these stations has been correlated with lightning data obtained from the World Wide Lightning Location Network (WWLLN). The results show that whistlers observed at Tihany mainly originate from lightning in an area surrounding the magnetic conjugate point which is situated in the ocean just off East London, South Africa. This area, called the source region, has a radius slightly less than 1000 km. Whistlers also originate from lightning activity over the rest of Southern Africa and the northern parts of South America. A clear diurnal distinction is seen in that the correlation is maximized when the whistler station and the source region are covered in darkness. This is believed to relate to the diurnal variation of the ionospheric profile, which becomes more transparent to VLF waves at night. A similar diurnal correlation pattern for Dunedin was also obtained. The general correlation results for Dunedin were very sporadic. Whistler statistics for the two stations and lightning statistics for the Tihany's magnetic conjugate point are also presented. It reveals a general diurnal maximum in received whistlers in dark hours for Tihany with absolute maximum at 1 UTC and for Dunedin, the maximum occurs in the afternoon with absolute maximum at 15 UTC. It also reveals a seasonal maximum when the conjugate point is in the summer season. The lightning statistics for Tihany's magnetic conjugate point reveals a diurnal maximurn ranging from the afternoon until a couple of hour after midnight. Something worth noting is the delay between the peaks of lightning activity and whistler registration at Tihany. The lightning activity peaks around 18 UTC. The explanation is once again believed to relate to the behavior of the ionosphere in darkness.