This study investigates if the descent of odd nitrogen, generated in the thermosphere and the upper mesosphere by energetic particle precipitation (EPP-NOx), has a detectable impact on stratospheric wind and temperature in late winter and spring presumably through the loss of ozone and reduction of absorption of solar UV. In both hemispheres, similar downward propagating geomagnetic signals in the extratropical stratosphere are found in spring for those years when no stratospheric sudden warming occurred in mid-winter. Anomalous easterly winds and warmer polar regions are found when the 4-month averaged winter Ap index (Ap) is high, and the signals become clearer when solar F10.7 is low. In May, significant geomagnetic signals are obtained in the Northern Hemisphere when the data are grouped according to the phase of the stratospheric equatorial QBO. The magnitudes of changes in spring stratospheric wind and temperatures associated with Ap signals are in the range of 10–20 m s−1 and 5–10 K, which are comparable with those of the 11-yr SC signals typically found in late winter. The spring Ap signals show the opposite sign to that expected due to in situ cooling effects caused by catalytic destruction of stratospheric ozone by descending EPP-NOx. Thus it is unlikely that the in situ chemical effect of descending EPP-NOx on stratospheric ozone would have a dominant influence on stratospheric circulation. Instead, we suggest that the detected Ap signals in the extratropical spring stratosphere may be an indirect consequence of geomagnetic and solar activity, dynamically induced by changes in wave ducting conditions.

Incoherent scatter radars are powerful ground based instruments for ionospheric measurements. By analysis of the Doppler shifted backscatter spectrum, containing the signature of electrostatic plasma waves, plasma bulk properties are estimated. At high latitudes the backscattered radar power is occasionally enhanced several orders of magnitude above the thermal backscatter level. These enhancements occur during geomagnetic disturbed conditions and are referred to as naturally enhanced ion acoustic echoes (NEIALs). NEIALs are linked to auroral activity with optical auroral emission observed in the vicinity of the radar measurement volume simultaneously to NEIALs. The backscatter enhancements are thought to be caused by wave activity above thermal level due to instability. A number of theories have been put forward including streaming instabilities and Langmuir turbulence to explain NEIAL observations. NEIALs occur in two classes distinct by their Doppler features. Observations of the first type, which has been studied more extensively, are generally modelled well by the Langmuir turbulence model. The difficulty in trying to understand the driving mechanism of the instability is the limited spatial resolution of the radar measurements. Observations of the second type, reported on more recently, have been interpreted as evidence for naturally occurring strong Langmuir turbulence by means of their Doppler features. Aperture synthesis is a technique to increase the spatial resolution of the radar measurements to below beam width of the single receiver antennas. The technique is employed to investigate the structure of NEIALs in the plane perpendicular to the magnetic field at sub-degree scale corresponding to hundreds of meters to a few kilometres at ionospheric altitudes. Calibration of the radar interferometer is necessary and a calibration technique is presented in paper I. Interferometry observations of a NEIAL event with receivers deployed at the EISCAT incoherent scatter radar on Svalbard are presented in paper II. The size of the enhanced backscatter region is found to be limited to 900 x 500m in the plane perpendicular to the geomagnetic field. These observations constitute the first unambiguous measurements giving evidence for the limited size of the enhanced backscatter region. In paper III observations of strong Langmuir turbulence signatures are presented. The apparent turbulent region in these observations is limited to two narrow altitude regions, 2km extent, and electron density irregularities caused by the turbulence are thought to reach down to decimeter scale length. The turbulence observations were obtained during energetic electron precipitation thereby differing from other observations during which a low energy component in the electron precipitation is reported. In paper IV a statistical study of strong Langmuir turbulence radar signatures is presented. The study reveals differing local time distributions for these signatures from type I NEIALs indicating di_ering driving conditions for the two types of NEIALs. It is found that strong Langmuir turbulence signatures are predominantly observed in the pre-midnight sector where auroral break-up aurora prevails. / <p>QC 20150303</p>

The Sun’s corona expands outward, populating the solar system with plasma. This plasma is known as the solar wind. The solar wind carries with it the Sun’s magnetic field, which is also known as the interplanetary magnetic field (IMF). The resulting configuration of the IMF creates a current sheet at solar equatorial latitudes, which the Earth crosses as it orbits the Sun. When the Earth is on one side of the current sheet it is in a sector where the IMF is directed largely away from or toward the Sun. On the other side of the current sheet the IMF is in opposite direction. The crossing of the current sheet is known as a sector boundary crossing (SBC). The solar wind and IMF properties change significantly near the current sheet, and this affects the Earth’s ionosphere. The Super Dual Auroral Radar Network (SuperDARN) high frequency (HF) radar data rates from 2001-2011 were examined using several techniques: a superposed epoch analysis, a fast fourier transform (FFT) analysis, and a cross–correlation analysis. Data from multiple instruments were analyzed in this study. These include the solar wind and IMF data from spacecraft, observations of charged particles precipitating into the Earth’s ionosphere, echoes from ground–based SuperDARN radars, and data from gound–based neutron monitors that detect galactic cosmic rays. Solar wind and IMF properties change significantly across a sector boundary. An increase in the IMF magnitude of about 30% occurs on the day of the SBC, and the IMF returns to pre–crossing values over the next two days. There is a decrease in the solar wind speed of about 15% the day before and the day of the SBC, and the solar wind density doubles at the time of the SBC. The polarity of the SBC does not appear to affect the solar wind and IMF. A peak in the data rate of SuperDARN echoes from both the ionosphere and ground occurs within one day of the SBC, though the variability of these data is quite large. The hemispherical power, which is an estimation of the electron energy flux precipitating into the ionosphere derived from satellite observations, increases following a SBC. Satellite particle data also revealed that the equatorward auroral oval boundary moves equatorward following a SBC. The cosmic ray counts at the Earth’s surface appear to be unaffected by the SBC. The solar wind and ionosphere data sets exhibited strong periodicities, and these were harmonics of the synodic rotational period of the Sun (approximately 27 days). Common periodicities observed were 27 days, 13.5 days, 9 days, 6.75 days and 5.4 days. There was a dominant 9–day periodicity observed in the solar wind and ionospheric data from 2005–2008, but was not observed in the solar 10.7 cm wavelength electromagnetic flux. The 9-day periodicity in the solar wind during this period has been linked to three persistent features on the Sun that produced corotating high–speed streams, or areas of fast solar wind. The parameters whose change did not depend on the polarity of the SBC had periodicities that were half that of the SBCs. From the cross–correlation analysis some relationships between the data sets became evident. For periods of high solar wind speed there were low SuperDARN data rates, and vice versa. The solar wind speed and hemispherical power were found to be well correlated, while the hemispherical power and the SuperDARN scatter occurrence were found to be anticorrelated. The solar wind changes appear to be affecting the state of the ionosphere, likely through particle precipitation. The SuperDARN scatter occurrence has been shown in past studies to be most greatly affected by changes in the electron density profile of the ionosphere, which can be influenced by changes in particle precipitation. These results demonstrate a link between the solar wind and the state of the ionosphere.

This project is a feasibility study for Hydro Extrusion Sweden AB, a company that produces extruded aluminium profiles. The main purpose of this project was to analyse the difference of Mg2Si particle sizes in aluminium alloys when varying parameters, such as cooling rate and composition, in aluminium extrusion, particularly the EN AW 6082 alloy. The Mg2Si particles have a great impact on the product’s mechanical properties. This was done in order to investigate whether real-time process parameter control is possible or not. The main software used was Thermo-Calc and the add-on module DICTRA. Thermo-Calc was used to do equilibrium calculations and gather data for the alloy and its phases. Based on this information and data from Hydro, simulations in DICTRA could be performed. The results were then plotted with respect to time and radius. The findings indicate that the cooling rate significantly influences the particle size. As the process becomes more intricate and involves a greater number of trace elements, adjusting the cooling rate could potentially be employed as a means to address this issue. The results also showed that trace elements had a minimal effect on the particle size. However, this probably does not match the reality since other phases affect and block the growth of Mg2Si.The overall results indicate a positive outcome for using DICTRA in determining particle sizes. However, further research needs to be done in correlation with more experiments before this could be a viable research method for Hydro. / Det här projektet är en förstudie för företaget Hydro Extrusion Sweden AB som producerar extruderade aluminiumprofiler. Det huvudsakliga syftet med projektet var att analysera skillnaden på Mg2Si-partiklarnas storlek i aluminiumlegeringar när olika parametrar som kylhastighet och sammansättning användes vid aluminiumextrudering, mer specifikt legeringen EN AW 6082. Mg2Si partiklarna har stor betydelse för produktens mekaniska egenskaper. Syftet med detta var att undersöka huruvida det är möjligt att styra process parametrarna i realtid. Mjukvaran som användes var Thermo-Calc och tilläggsmodulen DICTRA. Thermo-Calc användes för att göra jämviktsberäkningar och samla in data för legeringen samt dess faser. Baserat på denna information och data från Hydro kunde simuleringar i DICTRA utföras. Resultaten plottades sedan med avseende på tid och radie. Partikelstorleken påverkas avsevärt av kylningshastigheten enligt resultaten. I framtiden, när processen blir mer avancerad med fler spårämnen, kan det vara möjligt att justera kylningshastigheten för att hantera detta. Resultaten visade också att spårämnen hade en mycket liten effekt på partikelstorleken. Detta stämmer dock förmodligen inte med verkligheten eftersom andra faser påverkar och blockerar tillväxten av Mg2Si. De övergripande resultaten pekar på ett positivt resultat för att använda DICTRA för att bestämma partikelstorlekar. Ytterligare forskning måste göras i samband med fler experiment innan detta kan vara en genomförbar forskningsmetod för Hydro.

Abstract This thesis studies the long-term relation between the solar wind driven energetic particle forcing into the atmosphere and the tropospheric circulation in the Northern Hemisphere winter. The work covers the period of more than one hundred years since the turn of the 20th century to present. The thesis makes a statistical analysis of satellite measurements of precipitating energetic electrons, sunspot number data and geomagnetic activity, and compares them with temperature and pressure measurements made at the Earth's surface. Recent results, both observational and from chemistry climate models, have indicated significant effects in the Earth's middle atmosphere due to the energetic electrons precipitating from the magnetosphere. These effects include the formation of reactive hydrogen and nitrogen oxides in the high latitude mesosphere and the depletion of ozone caused by them. Ozone is a radiatively active and important gas, which affects the thermal structure and dynamics of the middle atmosphere. Accordingly, the depletion of ozone can intensify the large scale stratospheric circulation pattern called the polar vortex. Winter weather conditions on the surface have been shown to be dependent on the polar vortex strength. This thesis shows that there is a significant relation between the average fluxes of medium energy (ten to hundred keVs) precipitating electrons and surface temperatures in parts of the Northern Hemisphere in winter time. Temperatures are positively correlated with electron fluxes in North Eurasia and negatively correlated in Greenland during the period 1980-2010 which is covered by direct satellite observations of precipitating particles. This difference is especially notable when major sudden stratospheric warmings and the quasi-biennial oscillation (QBO), which both are known to affect the polar vortex strength, are taken into account. When extended to the late 19th century, the analysis shows that a similar temperature pattern is predominated during the declining phase of the sunspot cycle. The high speed solar wind streams and energetic particle precipitation typically maximize also at the declining phase of the solar cycle. This specific temperature pattern is related to the variability of the northern annular mode (NAM), which is the most significant circulation pattern in the Northern Hemisphere winter. Before the space era, geomagnetic activity measured by ground observations can be used as a proxy for energetic particle precipitation. Earlier studies have found a significant positive correlation between geomagnetic activity and NAM since the 1960s. We find that, when the QBO measured at 30 hPa height is in the easterly phase, a positive correlation is extended to the beginning of 1900s. We also show that high geomagnetic activity causes a stronger effect in the Northern Hemisphere winter than high sunspot activity, especially in the Atlantic and Eurasia. A comprehensive knowledge of the Earth's climate system and all its drivers is crucial for the future projection of climate. Solar variability effects have been estimated to produce only a small factor to the global climate change. However, there is increasing evidence, including the results presented in this thesis, that the different forms of solar variability can have a substantial effect to regional and seasonal climate variability. With this new evidence, the solar wind related particle effects in the atmosphere are now gaining increasing attention. These effects will soon be included in the next coupled model inter comparison project (CMIP6) as an additional solar related climate effect. This emphasizes the relevance of this thesis.

The goal of this thesis is to improve our knowledge on energetic particle precipitation into the Earth’s atmosphere from the thermosphere to the surface. The particles origin from the Sun or from temporarily trapped populations inside the magnetosphere. The best documented influence of solar (high-) energetic particles on the atmosphere is the Ozone depletion in high latitudes, attributed to the generation of HOx and NOx by precipitating particles (Crutzen et al., 1975; Solomon et al., 1981; Reid et al., 1991). In addition Callis et al. (1996b, 2001) and Randall et al. (2005, 2006) point out the importance of low-energetic precipitating particles of magnetospheric origin, creating NOx in the lower thermosphere, which may be transported downwards where it also contributes to Ozone depletion. The incoming particle flux is dramatically changing as a function of auroral/geomagnetical activity and in particular during solar particle events. As a result, the degree of ionization and the chemical composition of the atmosphere are substantially affected by the state of the Sun. Therefore the direct energetic or dynamical influences of ions on the upper atmosphere depend on solar variability at different time scales. Influences on chemistry have been considered so far with simplified precipitation patterns, limited energy range and restrictions to certain particle species, see e.g. Jackman et al. (2000); Sinnhuber et al. (2003b, for solar energetic protons and no spatial differentiation), and Callis et al. (1996b, 2001, for magnetospheric electrons only). A comprehensive atmospheric ionization model with spatially resolved particle precipitation including a wide energy range and all main particle species as well as a dynamic magnetosphere was missing. In the scope of this work, a 3-D precipitation model of solar and magnetospheric particles has been developed. Temporal as well as spatial ionization patterns will be discussed. Apart from that, the ionization data are used in different climate models, allowing (a) simulations of NOx and HOx formation and transport, (b) comparisons to incoherent scatter radar measurements and (c) inter-comparison of the chemistry part in different models and comparison of model results to MIPAS observations. In a bigger scope the ionization data may be used to better constrain the natural sources of climate change or consequences for atmospheric dynamics due to local temperature changes by precipitating particles and their implications for chemistry. Thus the influence of precipitating energetic particles on the composition and dynamics of the atmosphere is a challenging issue in climate modeling. The ionization data is available online and can be adopted automatically to any user specific model grid.