Abstract The thesis is focused on the reconstruction of long-term cosmic ray variability using proxy data. The 11-year solar cycle in production/deposition rates of cosmogenic nuclides ¹⁰Be and ¹⁴C has been modelled for the conditions of grand minima and maxima of solar activity (namely, Maunder Minimum and Grand Modern Maximum). The result shows that contrary to the observed strongly suppressed amplitude of the solar cycle in sunspots during Maunder Minimum relatively to Grand Modern Maximum, the cosmic ray proxies have the comparable amplitudes during the two periods. This phenomenon is caused by the nonlinear relation between solar activity and production of cosmogenic nuclides. In addition to well-established proxies of cosmic rays, nitrate in polar ice has been recently proposed as a new proxy for the long-term variability of galactic cosmic rays. The thesis contains two tests of its applicability for this purpose with TALDICE and EPICA-Dome C ice core data from Central Antarctica. The results support the proposal for the multimillennial time scales. Lunar samples acquired during the Apollo missions are important data for estimating the averaged energy spectra of galactic cosmic rays and solar energetic particles at the Earth’s orbit. The development in modelling of the interaction between energetic particles and matter makes it necessary to revise the earlier results. Because of that, new production rates of ¹⁰Be and ¹⁴C in lunar samples by galactic cosmic rays and solar energetic particles have been computed. New accurate cosmic ray reconstructions from natural archives containing cosmogenic nuclides use sophisticated climatic models requiring yield functions of the nuclides with high altitude resolution. These functions have been computed for ⁷Be, ¹⁰Be, ¹⁴C, ²²Na, and ³⁶Cl in the Earth’s atmosphere. Overall, the major purpose of the studies presented in the thesis is to increase the quality of reconstructions of the long-term cosmic ray variability for better understanding of the solar and heliospheric physics. / Original papers The original publications are not included in the electronic version of the dissertation. Poluianov, S. V., Usoskin, I. G., & Kovaltsov, G. A. (2014). Cosmogenic Isotope Variability During the Maunder Minimum: Normal 11-year Cycles Are Expected. Solar Physics, 289(12), 4701–4709. https://doi.org/10.1007/s11207-014-0587-6 Poluianov, S., Traversi, R., & Usoskin, I. (2014). Cosmogenic production and climate contributions to nitrate record in the TALDICE Antarctic ice core. Journal of Atmospheric and Solar-Terrestrial Physics, 121, 50–58. https://doi.org/10.1016/j.jastp.2014.09.011 Poluianov, S., Artamonov, A., Kovaltsov, G., & Usoskin, I. (2015). Energetic particles in lunar rocks: Production of cosmogenic isotopes. Proceedings of Science, 30-July-2015, art. no. 051 . Traversi, R., Becagli, S., Poluianov, S., Severi, M., Solanki, S. K., Usoskin, I. G., & Udisti, R. (2016). The Laschamp geomagnetic excursion featured in nitrate record from EPICA-Dome C ice core. Scientific Reports, 6(1). https://doi.org/10.1038/srep20235 Poluianov, S. V., Kovaltsov, G. A., Mishev, A. L., & Usoskin, I. G. (2016). Production of cosmogenic isotopes 7Be, 10Be, 14C, 22Na, and 36Cl in the atmosphere: Altitudinal profiles of yield functions. Journal of Geophysical Research: Atmospheres, 121(13), 8125–8136. https://doi.org/10.1002/2016jd025034

O Sol e a Lua são os astros mais acessíveis à observação quer pelas suas frequentes aparições no céu, quer pelos seus tamanhos aparentes pronunciados. Por essas razões, constituem-se em astros disponíveis ao estudo, atendendo aos cuidados necessários no caso de observações solares. Apesar disso, pouca ou nenhuma atenção é dada a eles pelos professores dos ensinos fundamental e médio deixando de utilizar observações que podem contribuir muito para o aprendizado e, ainda, despertar o interesse dos alunos pela ciência. Em particular o Sol, permite a exemplificação e a compreensão de diversos fenômenos estudados na física, na biologia, na geografia, na química assim como permite aplicações práticas da matemática geometria e trigonometria ministradas em sala de aula. Escolhemos levar aos professores e aos estudantes universitários um curso sobre astronomia e física solar abordando questões sobre o Sol algumas pouco discutidas nos livros, mesmo os de Astronomia com a finalidade de proporcionar material de aprendizado, estudo e discussão de temas da astronomia moderna. Neste curso básico, serão abordados: como se concluiu que o Sol é uma estrela; como foram determinados seus principais parâmetros físicos e astronômicos tais como a sua distância, o seu tamanho, a sua massa, sua temperatura e composição química, e sua estrutura interna; e como o Sol produz energia. / The Moon and the Sun are the easiest celestial bodies to observe because their frequent appearance in the sky and their great apparent size. As a result, they are celestial bodies available to study, attending the essential cares regarding Sun observations. Nevertheless, teachers from elementary and high schools pay little or no attention to them and miss a great opportunity to use observations that might add a lot to the learning process and also to arouse students\' attention to science. The sun, specially, allows to illustrate and to understand several points that students learn in physics, biology, geography, and chemistry, and still can have practical applications in mathematics geometry and trigonometry taught in the classroom. We chose to bring to teachers and university students a course about astronomy and solar physics approaching issues of the Sun some of them very little discussed even in astronomy books for the purpose of provide learning material about modern astronomy topics. This basic course will develop: how was it concluded that the Sun is a star; how was it determined its main parameters, such as its distance, its size, its mass, its temperature and its chemical composition, and its internal structure; and how does the Sun produce energy.

Comprendre les variations de l’irradiance solaire, notamment dans le domaine UV, est essentiel pour les modèles climatiques. Les modèles d’irradiance sont précieux pour reconstruire l'irradiance solaire spectrale (SSI) en l'absence d'observations ou lorsque celles-ci manquent de stabilité. Cependant, ils font certaines hypothèses sur les structures solaires. Nous visons ici à contraindre ces hypothèses en caractérisant le contraste UV des structures solaires. Grâce aux données du satellite Solar Dynamic Observatory (SDO)entre 2010 et 2016, nous quantifions pour la première fois les contrastes dans l'UV. L'étude du contraste des structures solaires et de leur segmentation montre que des seuils photométriques sont nécessaires pour segmenter correctement les structures solaires, principalement en UV, en raison de la coexistence de structures sombres et brillantes pour la même valeur du champ magnétique. Certains pixels classés parmi le Soleil calme par le modèle SATIRE-S appartiennent en fait aux facules, mais ils sont trop peu nombreux pour avoir un impact sur les reconstructions de SSI. Nos résultats soulignent l'importance des observations multi-longueurs d'onde pour mieux contraindre l'identification des structures. Distinguer réseau et facule est essentiel pour reconstruire la SSI sur une longue période, et la prise en compte de la dépendance du contraste du réseau par rapport au champ magnétique améliore la reconstruction de la SSI. Enfin, nous ne trouvons aucun indice de variations du contraste durant le cycle solaire.Nous présentons aussi des résultats sur les corrélations entre les émissions Hα et Ca II des étoiles de type solaire. Nous montrons que l’hypothèse de Meunier et al., 2009 pour expliquer les anti-corrélations de certaines étoiles est confirmée par nos résultats. / Understanding solar irradiance variations,in particular in the ultraviolet wavelength range, is essential for climate modelling. Solar irradiance models are precious for reconstructing the spectral solar irradiance (SSI) in the absence of observations or when they lack stability. However, they come with their assumptions. Here we aim here to constrain these in the UV by characterising the contrast of solar magnetic features in the UV.From solar images taken by the Solar Dynamic Observatory (SDO) between 2010 and 2016, we quantify UV contrasts the first time. The study of the contrast of the solar structures and their segmentation shows that photometric thresholds are necessary to properly segment solar structures, mainly in the UV, because of the coexistence of both dark and bright structures for the same value of the magnetic field. Some pixels that are classified as quiet-Sun by the SATIRE-S model actually belong to faculae, but they are too few to have a significant impact on SSI reconstructions. Our results highlight the importance of multi-wavelength observations for better constraining the identification of structures. Distinguishing network and faculae is essential for such reconstructions over a long period, and using a network with magnetically variable contrast improves SSI reconstruction, Finally, we find no evidence of contrast variations during the solar cycle.We also present results on the correlations between Hα and Ca II emissions of Sun-like stars. We show that the hypothesis of Meunier et al., 2009 to explain the anti-correlations of certain stars corresponds to our observations.

O Sol e a Lua são os astros mais acessíveis à observação quer pelas suas frequentes aparições no céu, quer pelos seus tamanhos aparentes pronunciados. Por essas razões, constituem-se em astros disponíveis ao estudo, atendendo aos cuidados necessários no caso de observações solares. Apesar disso, pouca ou nenhuma atenção é dada a eles pelos professores dos ensinos fundamental e médio deixando de utilizar observações que podem contribuir muito para o aprendizado e, ainda, despertar o interesse dos alunos pela ciência. Em particular o Sol, permite a exemplificação e a compreensão de diversos fenômenos estudados na física, na biologia, na geografia, na química assim como permite aplicações práticas da matemática geometria e trigonometria ministradas em sala de aula. Escolhemos levar aos professores e aos estudantes universitários um curso sobre astronomia e física solar abordando questões sobre o Sol algumas pouco discutidas nos livros, mesmo os de Astronomia com a finalidade de proporcionar material de aprendizado, estudo e discussão de temas da astronomia moderna. Neste curso básico, serão abordados: como se concluiu que o Sol é uma estrela; como foram determinados seus principais parâmetros físicos e astronômicos tais como a sua distância, o seu tamanho, a sua massa, sua temperatura e composição química, e sua estrutura interna; e como o Sol produz energia. / The Moon and the Sun are the easiest celestial bodies to observe because their frequent appearance in the sky and their great apparent size. As a result, they are celestial bodies available to study, attending the essential cares regarding Sun observations. Nevertheless, teachers from elementary and high schools pay little or no attention to them and miss a great opportunity to use observations that might add a lot to the learning process and also to arouse students\' attention to science. The sun, specially, allows to illustrate and to understand several points that students learn in physics, biology, geography, and chemistry, and still can have practical applications in mathematics geometry and trigonometry taught in the classroom. We chose to bring to teachers and university students a course about astronomy and solar physics approaching issues of the Sun some of them very little discussed even in astronomy books for the purpose of provide learning material about modern astronomy topics. This basic course will develop: how was it concluded that the Sun is a star; how was it determined its main parameters, such as its distance, its size, its mass, its temperature and its chemical composition, and its internal structure; and how does the Sun produce energy.

Abstract This thesis examines magnetic reconnection in the solar corona. Magnetic reconnection is the only mechanism which allows the magnetic topology of magnetized plasmas to be changed. Many of the dynamic processes in the Sun's atmosphere are believed to be driven by magnetic reconnection and studying the behaviour of such phenomena is a key step to understanding the reconnection mechanism. In Chapters 1 to 3, we discuss the physical and mathematical framework on which current magnetohydrodynamic reconnection models are based. The aim of the thesis is to investigate theoretical models of magnetic reconnection using variety of analytic and numerical techniques within the theoretical frame work of magnetohydrodynamics (MHD). In Chapter 4 we use a line-tied X-point collapse model for compressible plasmas to investigate the role of viscosity on the energy release mechanism. This model also provides the basis for the investigation of Chapter 5 which explores the impact of Hall currents in the transient X-point energy dissipation. Chapter 6 is concerned with how reconnection is modified in the presence of generalized Ohm's law which includes both Hall current and electron inertia contributions. In contrast to the closed X-point collapse geometry adopted for compressible plasmas previously, we find it more convenient to explore this problem using an open incompressible geometry in which plasma is continually entering and exiting the reconnection region. Specially, we find the scaling of the Hall-MHD system size analytically, rather than numerically as in the X-point problem of Chapter 5. Chapter 7 summarizes the results of investigations in Chapters 4, 5 and 6.

Die effiziente Kompression von Daten wird eine wichtige Rolle für mehrere bevorste- hende und geplante Weltraummissionen spielen, die Helioseismologie betreiben werden, wie beispielsweise Solar Orbiter. Solar Orbiter ist die nächste Mission, die Helioseismologie beinhaltet, und soll im Oktober 2018 gestartet werden. Das Hauptmerkmal von Solar Orbiter ist der Orbit. Die Umlaufbahn des Satelliten wird zur Ekliptik geneigt sein, sodass der Satellit einen solaren Breitengrad von bis zu 33 Grad erreichen wird. Dies wird erstmals ermöglichen, die Pole der Sonne mit Hilfe von lokaler Helioseismologie zu studieren. Zusätzlich dazu können kombinierte Beobachtungen von Solar Orbiter und einem anderen Instrument dazu benutzt werden, die tiefen Schichten der Sonne mittels stereoskopischer Helioseismologie zu erforschen. Die Aufnahmen der Dopplergeschwindigkeit und der Kontinuumsintensität, die für Helioseismologie benötigt werden, werden vom Polarimetric and Helioseismic Imager (PHI) geliefert werden. Große Hindernisse für Helioseismologie mit Solar Orbiter sind die niedrige Datenüber- tragungsrate und die (wahrscheinlich) kurzen Beobachtungszeiten. Außerdem erfordert die Untersuchung der Pole der Sonne Beobachtungen in der Nähe des Sonnenrandes, sogar von dem geneigten Orbit von Solar Orbiter aus. Dies kann zu systematischen Fehlern führen. In dieser Doktorarbeit gebe ich eine erste Einschätzung ab, wie stark Helioseismologie von verlustbehafteter Datenkompression beeinflusst wird. Mein Schwerpunkt liegt dabei auf der Solar Orbiter Mission, die von mir erzielten Ergebnisse sind aber auch auf andere geplante Missionen übertragbar. Zunächst habe ich mit Hilfe synthetischer Daten die Eignung des PHI Instruments für Helioseismologie getestet. Diese basieren auf Simulationen der Konvektion nahe der Sonnenoberfläche und einem Modell von PHI. Ich habe eine sechs Stunden lange Zeitreihe synthetischer Daten erstellt, die die gleichen Eigenschaften wie die von PHI erwarteten Daten haben. Hierbei habe ich mich auf den Einfluss der Punktspreizfunktion, der Vibrationen des Satelliten und des Photonenrauschen konzentriert. Die von diesen Daten abgeleitete spektrale Leistungsdichte der solaren Oszillationen legt nahe, dass PHI für Helioseismologie geeignet sein wird. Aufgrund der niedrigen Datenübertragungsrate von Solar Orbiter müssen die von PHI für die Helioseismologie gewonnenen Daten stark komprimiert werden. Ich habe den Einfluss von Kompression mit Hilfe von Daten getestet, die vom Helioseismic and Magnetic Imager (HMI) stammen. HMI ist ein Instrument an Bord des Solar Dynam- ics Observatory Satelliten (SDO), der 2010 gestartet worden ist. HMI erstellt mit hoher zeitlicher Abfolge Karten der Kontinuumsintensität, der Dopplergeschwindigkeit und des kompletten Magnetfeldvektors für die komplette von der Erde aus sichtbare Hemispäre der Sonne. Mit Hilfe mit von HMI aufgenommenen Karten der Dopplergeschwindigkeit konnte ich zeigen, dass das Signal-zu-Rausch Verhältnis von Supergranulation in der Zeit-Entfernungs Helioseismologie nicht stark von Datenkompression beeinflusst wird. Außerdem habe ich nachgewiesen, dass die Genauigkeit und Präzision von Messungen der Sonnenrotation mittels Local Correlation Tracking von Granulation durch verlust- behaftete Datenkompression nicht wesentlich verschlechtert werden. Diese Ergebnisse deuten an, dass die niedrige Datenübertragungsrate von Solar Orbiter nicht unbedingt ein großes Hinderniss für Helioseismologie sein muss.

Kontext: Die Sonnenkorona wird seit 1932 mit Koronographen beobachtet. Nur wenige Jahre später war klar, dass die Korona viel heißer ist als die sichtbare Sonnenoberfläche; seit dem ist der Mechanismus der koronalen Heizung ungeklärt. Viele Mechanismen wurden vorgeschlagen, die genügend Energie zur Basis der Korona liefern, es hat sich aber kein vollständig selbstkonsitentes Bild des Energietransports und der koronalen Dissipation etabliert. Ziele: Wir möchten ein selbstkosistentes Modell aufstellen, welches Bewegungen auf der Sonnenoberfläche enthält, welche das Magnetfeld verbiegen und verflechten, wodurch in der Korona Ströme induziert und Ohm’sch dissipiert werden. Die Modellbeschreibung soll durch den Vergleich von synthetischen mit realen Beobachtungen untermauert werden. Methoden: Wir treiben das 3D MHD Model mit beobachteten photosphärischen Magnetfeldern und Horizontalbewegungen an. Durch Wärmeleitung entlang des Feldes sowie Strahlungsverluste wird die koronale Energiebilanz realistisch. Wir synthetisieren Spektren in verschiedenen Emissionslinien mit einer Atom-Datenbank und der berechneten koronalen Plasmatemperatur sowie -dichte. Diese vergleichen wir mit entsprechenden Beobachtungen der Korona über der aktiven Region, mit der wir die Simulation antreiben. Wir vergleichen extrahierte Modell-Feldlinien mit empirischen und theoretischen Skalengesetzen, die die koronale Heizung entlang von Bögen voraussagen. Resultate: Im Modell bilden sich heiße koronale Bögen mit Temperaturen deutlich über 1 MK. Ihre 3D-Struktur entspricht den beobachteten koronalen Bögen; Doppler-Karten lassen auf ähnliche Plasmaströmungen entlang der Bögen schließen. An die Modell-Daten passen wir ein Skalengesetz an, welches von der Bogenlänge und der magnetischen Flussdichte an den Fußpunkten abhängt. Schlussfolgerungen: Aus der substanziellen Übereinstimmung zwischen Modell und Beobachtung schließen wir, dass das Modell eine genügende Beschreibung der Heizung und Wärmeleitung entlang von koronalen Bögen darstellt, um die Beobachtungen zu erklären.

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京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18442号 / 理博第4002号 / 新制||理||1577(附属図書館) / 31320 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 一本 潔, 教授 嶺重 慎, 教授 柴田 一成 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

In this paper a search routine in MATLAB was developed in order to find and analyze oblique whistler waves in the data from the ESA and NASA spacecraft Solar Orbiter. Oblique whistler waves are a type of plasma wave which propagate at an angle with respect to the background magnetic field. They are efficient at scattering electrons in the solar wind but their role in interplanetary coronal mass ejections (ICMEs) is yet unknown. Magnetic field data from 1-31st of June 2022, as well as the 24th and 27-28th of January 2022 was examined. The search routine found six whistler waves in June and 12 for the dates in January. Among these, all found whistler waves were found in the sheath region of the ICMEs, and all had a plasma beta > 1. However due to instrumental artefacts the values of θk were found to be smaller than detected by the search routine, indicating less obliqueness than first expected. Some of the whistler waves seemed to have an obliqueness that changed with time and the bandwidth of the waves varied among the identified.