Charged particles constantly stream outward from the Sun to fill the solar system. These particles, consisting mainly of protons and electrons, form a plasma called the solar wind. The solar wind interacts with every celestial body in the solar system, giving rise to different phenomena, such as the auro- ras observed at high latitudes on Earth or disruption of the systems onboard artificial satellites.  The general structure of the solar wind has been established several decades ago, however we still do not fully understand how the solar wind properties, like temperature and velocity distribution, evolve as it propagates outward in the solar system. Observations of these properties cannot be explained from a conventional fluid description. In a system approximated as a fluid, particle collisions dictate its thermodynamic state. However, the solar wind is a weakly collisional plasma that deviates from thermodynamic equilibrium. Therefore, the radial evolution of the solar wind properties must be driven by different processes. In particular, wave-particle interactions are an important regulator of the solar wind properties, because of the strong connection between the electromagnetic fields and the charged particles.  In this thesis, we probe how the velocity distribution of solar wind par- ticles evolves as it travels from the Sun to the Earth. Specifically, we study the contribution of waves on the observed solar wind properties at different distances and how these waves can affect the interplanetary environment. We focus on two types of plasma waves frequently observed in the solar wind, Langmuir and ion-acoustic waves. We present their occurrence rates at differ- ent heliocentric distances and suggest wave generation mechanisms based on Solar Orbiter observations. We show that Langmuir waves in the unperturbed solar wind are more commonly observed in regions where the magnetic field magnitude is lower than the background value. Furthermore, we also find that the occurrence rate of ion-acoustic waves is increased in the ramp regions of interplanetary shocks observed at different heliocentric distances, compared to the ion-acoustic wave occurrence rate in the unperturbed solar wind.

Solar wind shocks and the intracluster medium comprise hot, low-density plasmas with few Coulomb collisions. Electrons there are not fluid and so gain and exchange energy by interaction with a variety of plasma waves. We explore two mechanisms for electron energization in such plasmas. In 2D kinetic simulations of solar wind shocks with low beta (magnetic pressure greater than thermal pressure), fast-mode / oblique-whistler waves accelerate electrons in bulk via proton-scale parallel electric fields; electrons’ bulk kinetic energy then converts to heat via magnetic field-aligned electrostatic wave scattering. We show and measure the heating for 2D shocks of varying magnetic obliquity and Mach number, and we qualitatively map the mechanism’s shock parameter regime. Next, consider the intracluster medium: a high-beta plasma (thermal pressure greater than magnetic pressure) in which Megaparsec-scale motions promptly trigger nanoparsec-scale plasma waves, which in turn can scatter 1–100 MeV cosmic ray electrons. Small-scale scattering combined with large-scale motion can heat electrons, and this process is called magnetic pumping. We use 1D simulations of plasma subjected to continuous bulk compression to measure the efficiency of magnetic pumping upon cosmic ray electrons. It is speculated that magnetic pumping may help re-accelerate MeV electrons to radio-emitting energies and so help explain the origin of diffuse, MHz–GHz radio halos enshrouding some clusters of galaxies.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography : leaves 72-73. / M.S.

The lunar space environment is shaped by the interaction between the Moon and the solar wind. In the present thesis, we investigate two aspects of this interaction, namely the interaction between solar wind protons and lunar crustal magnetic anomalies, and the interaction between solar wind protons and lunar regolith. We use particle sensors that were carried onboard the Chandrayaan-1 lunar orbiter to analyze solar wind protons that reflect from the Moon, including protons that capture an electron from the lunar regolith and reflect as energetic neutral atoms of hydrogen. We also employ computer simulations and use a hybrid plasma solver to expand on the results from the satellite measurements. The observations from Chandrayaan-1 reveal that the reflection of solar wind protons from magnetic anomalies is a common phenomenon on the Moon, occurring even at relatively small anomalies that have a lateral extent of less than 100 km. At the largest magnetic anomaly cluster (with a diameter of 1000 km), an average of ~10% of the incoming solar wind protons are reflected to space. Our computer simulations show that these reflected proton streams significantly modify the global lunar plasma environment. The reflected protons can enter the lunar wake and impact the lunar nightside surface. They can also reach far upstream of the Moon and disturb the solar wind flow. In the local environment at a 200 km-scale magnetic anomaly, our simulations show a heated and deflected plasma flow and the formation of regions with reduced or increased proton precipitation. We also observe solar wind protons reflected from the lunar regolith. These proton fluxes are generally lower than those from the magnetic anomalies. We find that the proton reflection efficiency from the regolith varies between ~0.01% and ~1%, in correlation with changes in the solar wind speed. We link this to a velocity dependent charge-exchange process occurring when the particles leave the lunar regolith. Further, we investigate how the properties of the reflected neutral hydrogen atoms depend on the solar wind temperature. We develop a model to describe this dependence, and use this model to study the plasma precipitation on the Moon when it is in the terrestrial magnetosheath. We then use the results from these and other studies, to model solar wind reflection from the surface of the planet Mercury. / Rymdmiljön runt månen formas av den växelverkan som sker mellan månen och solvinden. I den föreliggande avhandlingen undersöker vi två aspekter av denna växerverkan, nämligen växelverkan mellan solvindsprotoner och magnetiserade områden i månskorpan, och växelverkan mellan solvindsprotoner och månens ytdamm. Vi använder oss av partikelsensorer på månsatelliten Chandrayaan-1 för att analysera solvindsprotoner som reflekteras från månen, även de protoner som fångar upp en elektron från ytan och reflekteras som neutrala väteatomer. Vi använder oss också av datorsimuleringar för att bygga vidare på de uppmätta resultaten. Observationerna från Chandrayaan-1 visar att reflektion av solvindsprotoner från magnetiserade områden är ett vanligt förekommande fenomen på månen, som inträffar även vid magnetiseringar som är utbredda över mindre än 100 km. Vid det största magnetiserade området på månen (1000 km i diameter), reflekteras i genomsnitt ~10% av de infallande solvindsprotonerna. Våra datorsimuleringar visar att dessa protonflöden har globala effekter på månens plasmamiljö. De reflekterade protonerna kan nå månens nattsida. De kan också nå långt uppströms om månen och störa solvindsflödet. I den lokala plasmamiljön vid ett magnetiserat område av storleken 200 km visar våra simuleringar ett förändrat solvindsflöde, där det skapas områden som delvis skyddas från solvinden, likväl som områden som utsätts för mer solvind. Vi observerar även solvindsprotoner som reflekterats från ytdammet på månen. Dessa protonflöden är lägre än de från de magnetiska fälten. Reflektionen från ytan varierar mellan ~0.01% och 1% av solvindsflödet, i samband med förändringar i solvindshastigheten. Vi förklarar detta med att partiklarnas laddning bestäms av den hastighet de har när de lämnar måndammet. Vidare undersöker vi hur egenskaperna hos de reflekterade neutrala väteatomerna beror på solvindstemperaturen. Vi skapar en modell för att beskriva sambandet och använder sedan denna modell för att studera hur solvinden faller in mot månens yta när den befinner sig i jordens magnetoskikt, där jordens magnetfält orsakar en upphettning av solvindsflödet. Resultaten från dessa och andra studier använder vi sedan för att modellera solvindsreflektion från planeten Merkurius yta, för jämförelse med framtida observationer.

Renewable energy sources have received increasing attention in electric power systems around the world due to growing environmental concerns. Wind and solar are among the most promising alternatives to conventional energy generation. There has been a rapid growth of wind and solar energy integration in power systems in the last decade, and is expected to grow further in the years to come. The main concern with wind and solar energy sources is the uncertainty and the intermittency of power generation, which leads to problems in maintaining the overall system reliability. The impacts of these sources on bulk system reliability depend on a large number of factors. The strength of the wind or solar resource at the installation site, the existing renewable power penetration level in the system, the points of connection of these sources to the power grid, the correlation in resource availability between multiple installation sites, and the correlation between the load and the renewable power are key factors that are analyzed in this thesis. These factors are considered in evaluating the bulk system reliability and reliability benefits of wind and solar power sources, and the reliability worth to the electricity customers from the addition of these energy sources. The IEEE-RTS test system is utilized throughout the thesis to evaluate the effects of these factors on bulk system adequacy. Swift Current and Saskatoon wind resources are modeled and utilized in this thesis. The Swift Current area has a strong wind resource and provides better reliability benefit and reliability worth than the Saskatoon wind resource. The benefits from wind and solar power integration, however, also depend significantly on the location where it is connected to the grid network. Wind farms that are diversified in multiple regions with independent wind speed profiles provide superior reliability benefits and worth than wind farms located in one region. The incremental benefits of adding wind or solar power decreases as the renewable power penetration is increased in the power system. Wind power at practical locations provides higher reliability benefits than photovoltaics. However, the daytime contribution of photovoltaics to system reliability is relatively high. The reliability benefits and reliability worth of solar power are significantly different for different seasons. A comparison study on reliability benefit and worth between a wind integrated bulk system and a solar integrated bulk system is also done in this thesis in order to identify the best option for bulk system reliability.

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.

The tendency to use renewable energy resources has grown continuouslyover the past few decades, be it due to fear over warnings of globalwarming or because of the depletion and short life of fossil fuels or evenas a result of the interest which has developed among researchers doingscientific research into it. This work can be considered as joining any ofthese groups with an objective of giving electric light to the poorpopulation living in one of the poorest nations in the world.The aim of the work is to investigate supplying electric energy fromsolar-wind hybrid resources to remotely located communities detachedfrom the main grid line in Ethiopia. The communities in mind are one oftwo types; the first is the majority of the poor population residing in thecountryside; and the other is people relocated by the Government fromthe over used and dry regions to relatively productive and fertile ones inline with the long-term poverty reduction plan.The work was begun by investigating wind energy and solar energypotentials at four geographically different locations in Ethiopia bycompiling data from different sources and analyzing it using a softwaretool. The locations are Addis Ababa (09:02N, 038:42E), Mekele (13:33N,39:30E), Nazret (08:32N, 039:22E), and Debrezeit (8:44N, 39:02E).The results related to wind energy potential are given in terms of themonthly Average wind speed, the wind speed probability densityfunction (PDF), the wind speed cumulative density function (CDF), thewind speed duration curve (DC), and power density plots for all fourselected sites. According to the results obtained through the analysis, thewind energy potential, even if it is not exceptional, is irrefutably highenough to be exploited for generating electric energy.The solar energy potential, based on sunshine duration data collectedover a period of 7 - 11 years and radiation data obtained from differentsources, has been calculated using regression coefficients specific to thesites in question. Based on the sunshine duration data, the monthlyaverage daily sunshine amount for each of the places has also beencomputed and given in a form of plot. Through additional work on theresults of the calculations, the solar energy potential has been given inthe form of solar radiation plots for each of the selected sites. Asexpected, the results indicated an abundance of solar energy potential.It is based on the promising findings of these two energy resourcepotentials, wind and solar, that the feasibility study for a standalonesolar-wind hybrid energy supply system has proceeded, targeting thecommunity mentioned earlier. The hybrid system consisted of Windturbine, Photovoltaic panel, diesel generator and a bank of batteries, witha power conditioning converter included in the system.The hybrid standalone supply system is intended to provide electricity toa model community of 200 families with five to six family members ineach. The community is equipped with a primary load, a deferrable load,a community school and a health post. An electric load which includeslighting, water pumping, a radio receiver, and some clinical equipmenthas been suggested. Hybrid Optimization Model for ElectricRenewables, HOMER, software has been used for the analysis. Theaverage wind speed and average solar radiation calculated from the datafor all of the selected sites has been used to input into the software.The hybrid system design is approached in three different ways. The firstapproach is to include within the hybrid system those components whichare locally available, without giving special attention to their efficienciesand proceed with the design work. The second approach is tothoroughly search the market for the best and most efficienttechnological products and to select the best components for theanalysis. A third approach considered in an attempt of cost minimizationis to see if a self-contained type of design can be a better solution. Whatthis means is every household will have its own supply system that mayconsist of any combination of PV and wind turbine including converter,battery and charge controller.After running the simulations, lists of power supply systems have beengenerated, sorted according to their net present cost. Sensitivity variables,such as range of wind speeds, range of radiation levels and diesel pricehave been defined as inputs into the software and the optimizationprocess has been carried out repeatedly for the sensitivity variables andthe results have been refined accordingly. / QC 20100623

A time-dependent two-dimensional (2D) modulation model including drifts, the solar wind tennination shock (TS) with diffusive shock acceleration and a heliosheath based on the Parker (1965) transport equation is used to study the modulation of galactic cosmic rays (GCRs) and the anomalous component of cosmic rays (ACRs) in the heliosphere. In particular, the latitude dependence of the TS compression ratio and injection efficiency of the ACRs (source strength) based on the hydrodynamic modeling results of Scherer et al. (2006) is used for the first time in a modulation model. The subsequent effects on differential intensities for both GCRs and ACRs are illustrated, comparing them to the values without a latitude dependence for these parameters. It is found that the latitude dependence of these parameters is important and that it enables an improved description of the modulation of ACRs beyond the TS. With this modeling approach (without fitting observations) to the latitude dependence of the two parameters, it is possible to obtain a TS spectrum for ACRs at a polar angle of B = 55" that qualitatively approximates the main features of the Voyager 1 observations. This positive result has to be investigated further. Additionally, it is shown that the enhancement of the cosmic ray intensity just below the cut-off energy found for the ACR at the TS in an A < 0 magnetic polarity cycle in the equatorial plane with the latitude independent scenario, disappears in this region when the latitude dependence of the compression ratio and injection efficiency is assumed. Subsequent effects of these scenarios are illustrated on the global anisotropy vector of both GCRs and ACRs as the main theme of this work. For this purpose the radial and latitudinal gradients for GCRs and ACRs were accurately computed. The radial and latitudinal anisotropy components were then computed as a function of energy, radial distance and polar angle. It is also the first time that the anisotropy vector is comprehensively calculated in such a global approach to cosmic ray modeling in the heliosphere, in particular for ACRs. It is shown that the anisotropy vector inside (up-stream) and outside (down-stream) the TS behaves in a complicated way, so care must be taken in interpreting it. It is found that the latitude dependence of the two mentioned parameters can alter the direction (sign) of the anisotropy vector. Its behaviour beyond the TS is markedly different from inside the TS, mainly because of the slower solar wind velocity, with less dependence on the magnetic polarity cycles. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.

A time-dependent two-dimensional (2D) modulation model including drifts, the solar wind tennination shock (TS) with diffusive shock acceleration and a heliosheath based on the Parker (1965) transport equation is used to study the modulation of galactic cosmic rays (GCRs) and the anomalous component of cosmic rays (ACRs) in the heliosphere. In particular, the latitude dependence of the TS compression ratio and injection efficiency of the ACRs (source strength) based on the hydrodynamic modeling results of Scherer et al. (2006) is used for the first time in a modulation model. The subsequent effects on differential intensities for both GCRs and ACRs are illustrated, comparing them to the values without a latitude dependence for these parameters. It is found that the latitude dependence of these parameters is important and that it enables an improved description of the modulation of ACRs beyond the TS. With this modeling approach (without fitting observations) to the latitude dependence of the two parameters, it is possible to obtain a TS spectrum for ACRs at a polar angle of B = 55" that qualitatively approximates the main features of the Voyager 1 observations. This positive result has to be investigated further. Additionally, it is shown that the enhancement of the cosmic ray intensity just below the cut-off energy found for the ACR at the TS in an A < 0 magnetic polarity cycle in the equatorial plane with the latitude independent scenario, disappears in this region when the latitude dependence of the compression ratio and injection efficiency is assumed. Subsequent effects of these scenarios are illustrated on the global anisotropy vector of both GCRs and ACRs as the main theme of this work. For this purpose the radial and latitudinal gradients for GCRs and ACRs were accurately computed. The radial and latitudinal anisotropy components were then computed as a function of energy, radial distance and polar angle. It is also the first time that the anisotropy vector is comprehensively calculated in such a global approach to cosmic ray modeling in the heliosphere, in particular for ACRs. It is shown that the anisotropy vector inside (up-stream) and outside (down-stream) the TS behaves in a complicated way, so care must be taken in interpreting it. It is found that the latitude dependence of the two mentioned parameters can alter the direction (sign) of the anisotropy vector. Its behaviour beyond the TS is markedly different from inside the TS, mainly because of the slower solar wind velocity, with less dependence on the magnetic polarity cycles. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.

The three-dimensional (3D) steady-state electron modulation model of Ferreira (2002), based on Parker (1965) transport equation, is used to study the modulation of the 7 MeV galactic and Jovian electron anisotropies in the inner heliosphere. The Jovian electrons are produced in Jupiter's magnetosphere which is situated at ~ 5 AU in the ecliptic plane. The propagation of these particles is mainly described by the diffusion tensor applicable for the inner heliosphere. Some of the elements of the diffusion tensor are revisited in order to establish what contribution they make to the three-dimensional anisotropy vector and its components in the inner heliosphere. The 'drift' term is neglected since the focus of this study is on low-energy electrons. The effects on the electron anisotropy of different scenarios when changing the solar wind speed from minimum to maximum activity is illustrated. The effects on both the galactic and Jovian electron anisotropy of changing the polar perpendicular coefficient, in particular, are illustrated. It is shown that the computed Jovian electron anisotropy dominates the galactic anisotropy close to the Jovian electron source at ~5 AU, as expected, testifying to the validity of the3D-model. For the latitudinal anisotropy, the polar perpendicular diffusion plays a dominant role for Jovian electrons close to the source, with the polar gradient becoming the dominant factor away from the electron source. Of all three anisotropy components, the azimuthal anisotropy is dominant in the equatorial plane close to the source. It is found that there is a large azimuthal gradient close to the source because the low-energy electrons tend to follow the heliospheric magnetic field more closely than higher energy particles. The transition of the solar wind speed from minimum to intermediate to maximum solar activity condition was used to illustrate the modulation of the magnitude of the 7 MeV total anisotropy vector along the Ulysses trajectory. It was found that during the two encounters with the planet a maximum anisotropy of 38% was computed but with different anisotropy-timepeaks as the approach to Jupiter was different. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.