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The transport of solar energetic particles (SEPs) in the inner heliosphere is a very important issue which can affect our daily life. For example, large SEP events can lead to the failure of power grids, interrupt communications, and may participate in global climate change. The SEPS also can harm humans in space and destroy the instruments on board spacecraft. Studying the transport of SEPs also helps us understand remote regions of space which are not visible to us because there are not enough photons in those places. The interplanetary magnetic field is the medium in which solar energetic particles travel. The Parker Model of the solar wind and its successor, the Weber and Davis model, have been the dominant models of the solar wind and the interplanetary magnetic field since 1960s. In this thesis, I have reviewed these models and applied an important correction to the Weber and Davis model. Various solar wind models and their limitations are presented. Different models can affect the calculation of magnetic field direction at 1ÃU by as much as about 30\%. Analysis of the onset of SEP events could be used to infer the release time of solar energetic particles and to differentiate between models of particle acceleration near the Sun. It is demonstrated that because of the nature of the stochastic heliospheric magnetic field, the path length measured along the lineof force can be shorter than that of the nominal Parker spiral. These results help to explain recent observations. A two dimensional model and a fully three dimensional numerical model for the transport of SEPs has been developed based on Parker's transport equation for the first time. R̀̀eservoir'' phenomenon, which means the inner heliosphere works like a reservoir for SEPs during large SEP events, and multi-spacecraft observation of peak intensities are explained by this numerical model.
In this dissertation, I explore the relationship between solar energetic particles (SEPs) and the interplanetary magnetic field, and I use observations of SEPs to probe the region of space between the Sun and the Earth. After an introduction of major concepts in heliospheric physics, describing some of the history of energetic particles and defining the data sets used in the work, the rest of this dissertation is organized around three major concepts related to energetic particle transport: magnetic field-line length, interplanetary turbulence, and particle scattering and diffusion. In Chapter 2, I discuss how energetic particles can be used to measure the lengths of field lines and how particle scattering complicates the interpretation of these measurements. I then propose applying these measurements to a particular open problem: the origin and properties of heliospheric current sheets. In the next chapter, I move from the large to small scale and apply energetic particle measurements to important problems in interplanetary turbulence. I introduce two energetic-particle features, one of which I discovered in the course of this work, which have size scales roughly that of the correlation scale of the turbulence (the largest scale over which observations are expected to be similar). I discuss how multi-spacecraft measurements of these energetic particle features can provide a measure of the correlation scale independent of the magnetic field measurements. Finally, I consider interplanetary scattering and diffusion in detail. I describe new observations of particle diffusion in the direction perpendicular to the average magnetic field, showing that particles only scatter a few times between their injection at the Sun and observation at the Earth. I also provide numerical simulation results of diffusion parallel to the field which can be used to correct for the effects of transport on the particles. These corrections allow inferences to be made about the particle energies at injection from observations of the event-integrated fluences at 1 AU. By carefully including scattering, cooling, field line meandering and turbulence effects, solar-energetic particles become a powerful tool for studying the inner heliosphere.
Heliophysics is a fast-developing scientific discipline that integrates studies of the Sun's variability, the surrounding heliosphere, and the environment and climate of planets. The Sun is a magnetically variable star and for planets with intrinsic magnetic fields, planets with atmospheres, or planets like Earth with both, there are profound consequences. This 2010 volume, the second in this series of three heliophysics texts, integrates the many aspects of space storms and the energetic radiation associated with them - from causes on the Sun to effects in planetary environments. It reviews the physical processes in solar flares and coronal mass ejections, interplanetary shocks, and particle acceleration and transport, and considers many space weather responses in geospace. In addition to its utility as a textbook, it also constitutes a foundational reference for researchers in fields from heliophysics to climate science. Additional online resources, including lecture presentations and other teaching materials, are available at www.cambridge.org/9780521760515.
All papers have been peer-reviewed. Our star is a very effective particle accelerator. Energies up to GeVs have been observed in Solar energetic particle events. These events are often associated with solar flares and/or Coronal Mass Ejections. Understanding how particles are accelerated in these phenomena has been an outstanding problem in space plasma physics for a long time. Part of the reason is its practical (e.g. Space weather) and fundamental (cosmic ray origin) importance. In this conference we review recent progresses on this problem, with a balance between observations, theories and numerical simulations. Specific topics include 1) particle acceleration at flare site, 2) turbulence properties of the solar wind, 3) particle acceleration and transport in the inner heliosphere, 4) particle acceleration at the termination shock and heliosheath, and 5) particle acceleration at supernova remnant shocks.
This concise primer introduces the non-specialist reader to the physics of solar energetic particles (SEP) and systematically reviews the evidence for the two main mechanisms which lead to the so-called impulsive and gradual SEP events. More specifically, the timing of the onsets, the longitude distributions, the high-energy spectral shapes, the correlations with other solar phenomena (e.g. coronal mass ejections), as well as the all-important elemental and isotopic abundances of SEPs are investigated. Impulsive SEP events are related to magnetic reconnection in solar flares and jets. The concept of shock acceleration by scattering on self-amplified Alfvén waves is introduced, as is the evidence of reacceleration of impulsive-SEP material in the seed population accessed by the shocks in gradual events. The text then develops processes of transport of ions out to an observer. Finally, a new technique to determine the source plasma temperature in both impulsive and gradual events is demonstrated. Last but not least the role of SEP events as a radiation hazard in space is mentioned and a short discussion of the nature of the main particle telescope designs that have contributed to most of the SEP measurements is given.
Physics of the Inner Heliosphere gives for the first time a comprehensive and complete summary of our knowledge of the inner solar system. Using data collected over more than 11 years by the HELIOS twin solar probes, one of the most successful ventures in unmanned space exploration, the authors have compiled six extensive reviews of the physical processes of the inner heliosphere and their relation to the solar atmosphere. Researchers and advanced students in space and plasma physics, astronomy, and solar physics will be surprised to see just how closely the heliosphere is tied to, and how sensitively it depends on, the sun. Volume 2 deals with particles, waves, and turbulence, with chapters on: - magnetic clouds - interplanetary clouds - the solar wind plasma and MHD turbulence - waves and instabilities - energetic particles in the inner solar system
Solar energetic particles (SEPs) emitted from the Sun are a major space weather hazard motivating the development of predictive capabilities. This book presents the results and findings of the HESPERIA (High Energy Solar Particle Events forecasting and Analysis) project of the EU HORIZON 2020 programme. It discusses the forecasting operational tools developed within the project, and presents progress to SEP research contributed by HESPERIA both from the observational as well as the SEP modelling perspective. Using multi-frequency observational data and simulations HESPERIA investigated the chain of processes from particle acceleration in the corona, particle transport in the magnetically complex corona and interplanetary space, to the detection near 1 AU. The book also elaborates on the unique software that has been constructed for inverting observations of relativistic SEPs to physical parameters that can be compared with space-borne measurements at lower energies. Introductory and pedagogical material included in the book make it accessible to students at graduate level and will be useful as background material for Space Physics and Space Weather courses with emphasis on Solar Energetic Particle Event Forecasting and Analysis. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.
If charged particles move through the interplanetary or interstellar medium, they interact with a large-scale magnetic ?eld such as the magnetic ?eld of the Sun or the Galactic magnetic ?eld. As these background ?elds are usually nearly constant in time and space, they can be approximated by a homogeneous ?eld. If there are no additional ?elds, the particle trajectory is a perfect helix along which the par- cle moves at a constant speed. In reality, however, there are turbulent electric and magnetic?elds dueto the interstellaror solar wind plasma. These ?elds lead to sc- tering of the cosmic rays parallel and perpendicular to the background ?eld. These scattering effects, which usually are of diffusive nature, can be described by s- tial diffusion coef?cients or, alternatively, by mean free paths. The knowledge of these parameters is essential for describing cosmic ray propagation as well as d- fusive shock acceleration. The latter process is responsible for the high cosmic ray energies that have been observed. The layout of this book is as follows. In Chap. 1, the general physical scenario is presented. We discuss fundamental processes such as cosmic ray propagation and acceleration in different systems such as the solar system or the interst- lar space. These processes are a consequence of the interaction between charged cosmic particles and an astrophysical plasma (turbulence). The properties of such plasmas are therefore the subject of Chap. 2.