Electromagnetic waves are crucial for energy transfer in the nearly collision- less plasma of the Earth's inner magnetosphere. The waves in the frequency range 1-8 kHz whose visualisation in the form of frequency-time spectrograms reveals a harmonic frequency modulation of the wave intensity are called magnetospheric line radiation (MLR). Waves characterized by a nearly periodic time modulation of the wave intensity observed at frequencies between about 0.5 and 4 kHz are called quasiperiodic (QP) emissions. Although both types of the events were re- peatedly observed by ground-based instruments and low-altitude satellites, their origin remains still unclear. Between 2004 and 2010 these wave events were me- asured by the DEMETER spacecraft (almost Sun-synchronous orbit, altitude of about 700 km). This thesis presents a systematic study of the properties of the observed events, a comparison of the observations by the spacecraft and ground- based instruments, and an investigation of a relation to solar wind parameters.

Present-day Mars is a cold and dry planet with a thin CO2-dominated atmosphere comprising only a few ­­­mbar pressure at low altitudes. However, the Martian surface is marked with valley networks, hydrated mineral clays, carbonates and the remains of deltas and meandering rivers, i.e. traces of an active hydrological cycle present early in the planet's geological history. A strong greenhouse effect, and thus a thicker atmosphere, would have been required to sustain a sufficiently warm environment, particularly under the weaker luminosity of the early Sun. The fate of this early atmosphere is currently unknown. While several mechanisms can remove atmospheric mass over time, a prominent hypothesis suggests that the lack of an intrinsic Earth-like global magnetic dipole has allowed the solar wind to erode the early Martian atmosphere by imparting energy to the planet's ionosphere which subsequently flows out as ion escape, over time depleting the greenhouse gasses and collapsing the ancient hydrological cycle. Previous studies have found insignificant ion escape rates under present-day conditions, however, the young Sun emitted significantly stronger solar wind and photoionizing radiation flux compared to the present. The geological record establishes the time of collapse of the hydrological cycle, estimated to have occurred in the mid-late Hesperian period (~3.3 billion years ago) at latest. To constrain the amount of atmosphere lost through ion escape since, we use the extensive database of ion flux measurements from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) particles package on the Mars Express orbiter (2004-present) to quantify the ion escape rate dependence on upstream solar wind and solar radiation conditions. The Martian ion escape rate is shown to be insensitive to solar wind parameters with a weak inverse dependence on solar wind dynamic pressure, and linearly dependent on solar ionizing photon flux, indicating efficient screening of the bulk ionosphere by the induced magnetic fields. The impact of an extreme coronal mass ejection is studied and found to have no significant effect on the ion escape rate. Instead, intense solar wind is shown to only increase the escaping energy flux, i.e. total power of escaping ions, without increasing the rate by accelerating already escaping ions. The orientation of the strongest magnetized crustal fields are shown to modulate the ion escape rate, though to have no significant time-averaged effect. We also study the influence of solar wind and solar radiation on the major Martian plasma boundaries and discuss factors that might limit the ion escape rate, including solar wind-ion escape coupling, which is found to be ≲1% and decreasing with increased solar wind dynamic pressure. The significant escape rate dependencies found are extrapolated back in time, considering the evolution of solar wind and ionizing radiation, and shown to account for only 4.8 ± 1.1 mbar equivalent surface pressure loss since the time of collapse of the Martian hydrosphere in the Hesperian, with ~6 mbar as an upper estimate. Extended to the late Noachian period (3.9 billion years ago), the found dependencies can only account for ≲10 mbar removed through ion escape, an insignificant amount compared to the ≳1 bar surface pressure required to sustain a warm climate on early Mars.

Abstract The Cassini/Huygens mission is a collaborative mission of NASA and ESA to study the Saturnian system. Cassini Plasma Spectrometer (CAPS)is one of the scientific investigations onboard the Cassini orbiter. It consists of three separate spectrometers: Electron Spectrometer (ELS), Ion Mass Spectrometer (IMS) and Ion Beam Spectrometer (IBS). The University of Oulu has a co-investigator status in the CAPS project, and been mainly involved in simulating the structure and scientific performance of the IBS instrument. IBS is a high resolution hemispherical electrostatic analyser aimed to study the solar wind ions. This thesis contains an Introduction and five original papers. Papers I–III contain a detailed description of the simulation process of the IBS instrument and related results. In Paper I the manufacturing tolerances were calculated in order to verify that the high resolution requirements can be achieved using available manufacturing processes. In Paper II the simulations have been further developed and the instrument properties have been studied in more detail. In Paper III the simulation model is used to help the analysis and interpretation of the laboratory calibrations of the IBS flight model. Papers IV and V study the long-term fluctuations in solar wind and interplanetary magnetic field in the period range of 1–2 years (so called mid-term quasi periodicities, MTQP), using the wavelet transformation method to produce dynamic power spectra. In paper IV the MTQP structure in solar wind speed at 1 AU was studied using the longest available series of geomagnetic activity. It was shown that the long-term occurrence MTQP fluctuations roughly follows the long-term solar activity, suggesting that MTQP fluctuations are closely connected with the solar dynamo activity. Moreover, it was also noted that MTQP activity may offer a possibility for a precursory signal which could be used to predict significant changes in long-term solar activity. While Paper IV presents the temporally longest study of MTQP fluctuations, Paper V gives the spatially widest treatment of the same phenomenon. Paper V studies MTQP fluctuations in solar wind and interplanetary magnetic field measured by four probes in the outer heliosphere. It is shown that two MTQP fluctuations of different periods (1.3 and 1.7 years)co existed during solar cycle 22, while during solar cycle 21 only the 1.7-year band existed. This suggests that the solar dynamo acts differently during even and odd cycles. It is also shown that the two MTQP fluctuations during solar cycle 22 are organized latitudinally. While the 1.3-year periodicity originates from equatorial regions, the 1.7-year fluctuations arise at mid-latitudes. / Original papers Original papers are not included in the electronic version of the dissertation. Vilppola, J. H., Keisala, J. T., Tanskanen, P. J., & Huomo, H. (1993). Optimization of hemispherical electrostatic analyzer manufacturing with respect to resolution requirements. Review of Scientific Instruments, 64(8), 2190–2194. https://doi.org/10.1063/1.1143958 Vilppola, J. H., Tanskanen, P. J., Huomo, H., & Barraclough, B. L. (1996). Simulations of the response function of a plasma ion beam spectrometer for the Cassini mission to Saturn. Review of Scientific Instruments, 67(4), 1494–1501. https://doi.org/10.1063/1.1146881 Vilppola, J. H., Tanskanen, P. J., Barraclough, B. L., & McComas, D. J. (2001). Comparison between simulations and calibrations of a high resolution electrostatic analyzer. Review of Scientific Instruments, 72(9), 3662–3669. https://doi.org/10.1063/1.1392337 Mursula, K., Zieger, B., & Vilppola, J. H. (2003). Mid-term quasi-periodicities in geomagnetic activity during last 15 solar cycles: Connection to solar dynamo strength. Solar Physics, 212(1), 201–207. https://doi.org/10.1023/a:1022980029618 Mursula, K., & Vilppola, J. H. (2004). Fluctuations of the Solar Dynamo Observed in the Solar Wind and Interplanetary Magnetic Field at 1 AU and in the Outer Heliosphere. Solar Physics, 221(2), 337–349. https://doi.org/10.1023/b:sola.0000035053.17913.26

1 Title: MHD discontinuities in the solar wind and their relation to processes in the Earth magnetosphere Author: Oleksandr Goncharov Department / Institute: Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University Supervisor of the doctoral thesis: Prof. RNDr. Jana Safrankova, DrSc Abstract: Collisionless shocks are ubiquitous in the heliosphere from the outer corona to the termination shock. They play an important role in the interaction of the solar wind with the planets because they efficiently convert the energy of the directed ion flow into the energy of heated ions and electrons, the energy of the enhanced magnetic field, and the energy of the accelerated particles. The leading idea of the thesis is to investigate evolution of distinct solar wind features, predominantly interplanetary shocks, within the solar wind, their interaction with the outer magnetospheric boundaries (magnetopause and bow shock), and to follow a path of resulting discontinuities through the magnetosphere up to its far tail. The methodology is based on the statistical evaluation of multispacecraft observations as well as on case studies of particular events. Some experimental investigations are supported with computer modeling. Moreover, an application of fast plasma measurements of the...

Solar wind, a stream of supersonic plasma emanating from the solar corona, serves as an ideal laboratory for a study of high Reynolds number plasma flows. Turbulent processes that govern the dynamics of the so-called inertial range, i.e., the spatial scales smaller than energy injection scales but larger than the scales where the dissipation processes set in, have been studied for decades. At present, it is believed that the large-scale free energy in a form of kinetic and magnetic fluctuations is transferred via turbulent cascade into smaller scales, where kinetic effects become dominant and heating takes place. In order to understand dissipation processes, high-cadence measurements of solar wind parameters are necessary. The bright monitor of the solar wind (BMSW) instrument on board the Spektr-R spacecraft provides such data, and in tandem with high-cadence measurements of the magnetic field from the Wind spacecraft, we are able address the nature of the sub-ion scale fluctuations. The thesis focus on three interconnected topics, (a) what changes are induced by the passage of a collisionless IP shock in the framework of turbulence, (b) study of a decay of the turbulent energy downstream an IP shock, and (c) identifying the dominant mode of the sub-ion scale fluctuations.

The heliosphere and solar magnetic field play an important role in protecting the solar system from harmful, high-energy Galactic radiation. Until recently, the magnetic field had been assumed to be passive, carried outwards by the solar wind. The influence of the solar magnetic field on the plasma has just begun to be understood. Among the consequences, the magnetic field could cause the heliotail to be short, collimating the flow into two lobes instead of the classical long, comet-like tail. In this dissertation, I investigate the role certain aspects of the magnetic field have on the heliosphere and detail how interstellar neutral particles alter its effect on the environment. From the observation by Voyager 1 (V1) and Voyager 2 (V2), it is clear that the plasma environment in the outer heliosphere is not fully understood. I present the first time-dependent model of the outer heliosphere that includes solar-cycle variations of the magnetic field strength. I find that the model can accurately predict the plasma environment at V2 but cannot describe all features observed at V1, suggesting additional processes are present. The effect of including the heliospheric current sheet (HCS) on large-scale modeling of the heliosphere is also studied. The inherent numerical dissipation in the HCS reduces the magnetic field strength in the heliosheath; however, the two-lobe structure of the heliotail remains. Neutral hydrogen has also been shown to greatly affect the location of the heliospheric boundaries. The large mean free path of these neutrals requires them to be described kinetically. To understand how the neutrals affect the influence of the solar magnetic field, I developed the Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics (SHIELD) model, a kinetic-magnetohydrodynamic model of the outer heliosphere. The model couples a 3D Monte-Carlo model to the magnetohydrodynamic solver. SHIELD reproduces the results of similar models, namely a higher filtration of neutrals into the heliosphere when compared to a fluid description of the atoms. When SHIELD is applied to the heliotail, the two-lobe structure persists even with kinetic neutrals. These results show that the solar magnetic field plays a crucial role in determining the heliospheric structure.

Magnetic reconnection is a fundamental process that changes magnetic field configuration and converts a magnetic energy to flow energy and plasma heating. It can be found in a plasma with frozen magnetic field lines at boundaries where different magnetic field topologies encounter each other and thin current sheets are created as it is typical in the solar wind. In the thesis, we have used spacecraft measurements of solar wind plasma and magnetic field to found magnetic reconnection exhausts. We analyze and compare them with theoretical predictions. The results of the statistical analysis oriented on re-distribution of the magnetic energy in reconnection showed that both a portion of the energy deposited into heat as well as the energy spent on an acceleration of the exhaust plasma increase with the magnetic shear angle in accord with the increase of the magnetic flux available for reconnection. Moreover, we identify unusual events in the solar wind; we found magnetic reconnection exhausts accompanied by one or two side jets and explained their possible causes.

Spectral indices and flatness scaling exponents corresponding to solar wind plasma measurements before, during and after a coronal mass ejection (CME) detected by NASA's Wind spacecraft on September 2014 have been obtained. The Politano-Pouquet (PP) law for isotropic and incompressible magnetohydrodynamic (MHD) turbulence has been validated over a series of selected time intervals. The performed analysis showed that turbulence was well established within most of such intervals and several mean energy transfer rates were computed. Furthermore, the results detailed in this essay suggest possible correlations between the aforementioned energy transfer rates and the spectral indices and flatness scaling exponents, and also between enhanced intermittencies and large values of the mean energy transfer rates.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20375号 / 工博第4312号 / 新制||工||1668(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 山川 宏, 教授 引原 隆士, 准教授 海老原 祐輔 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21069号 / 工博第4433号 / 新制||工||1689(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 山川 宏, 教授 松尾 哲司, 准教授 海老原 祐輔 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM