Search results for: physical-processes-in-solar-flares

Physical Processes in Solar Flares

Author : B.V. Somov
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Solar flares are very complex electromagnetic phenomena of a cataclysmic nature. Particles are accelerated to very high velocities and a variety of physical processes happen inside and outside flares. These processes can be studied by a large number of techniques from Earth and from space. The aim is to discover the physics behind solar flares. This goal is complicated because information about the flare mechanism can be obtained only in an indirect way by studying the secondary effects. This book provides three stages in the solution of the solar flare problem. Chapter one describes the connection between observational data and theoretical concepts, where it is stressed that next to investigating flares, the related non-stationary large-scale phenomena must be studied as well. The second chapter deals with secondary physical processes, in particular the study of high-temperature plasma dynamics during impulsive heating. The last chapter presents a model built on the knowledge of the two previous chapters and it constructs a theory of non-neutral turbulent current sheets. The author believes that this model will help to solve the problem of solar flares. For solar physicists, plasma physicists, high-energy particle physicists.

Solar Flare Mechanism Based on Magnetic Arcade Reconnection and Island Merging

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The authors propose a model describing physical processes of solar flares based on resistive reconnection of magnetic field subject to continuous increase of magnetic shear in the arcade. The individual flaring process consists of magnetic reconnection of arcade field lines, generation of magnetic islands in the magnetic arcade, and coalescence of magnetic islands. When a magnetic arcade is sheared (either by foot point motion or by flux emergence), a current sheet is formed and magnetic reconnection can take place to form a magnetic island. A continuing increase of magnetic shear can trigger a new reconnection process and create a new island in the under lying arcade below the magnetic island. The new born island rises faster than the preceding island and merges with it to form one island. Before completing the island merging process, the new born island exhibits two phases of rising motion: a first phase with a slower rising speed and a second phase with a faster rising speed. The flare plasma heating occurs mainly due to magnetic reconnection in the current sheet under the new born island. The new born island represents the X-ray plasma ejecta which shows two phases of rising motion observed by Yohkoh [Ohyama and Shibata (1997)]. The first phase with slower new born island rising speed corresponds to the early phase of reconnection of line-tied field in the underlying current sheet and is considered as the preflare phase. In the second phase, the island coalescence takes place, and the underlying current sheet is elongated so that the line-tied arcade field reconnection rate is enhanced. This phase is interpreted as the impulsive phase or the flash phase of flares. The obtained reconnection electric field is large enough to accelerate electrons to an energy level higher than 10 keV, which is necessary for observed hard X-ray emissions. After merging of the islands is completed, magnetic reconnection continues in the current sheet under the integrated island for a longer period, which is considered as the main phase of flares. The sequence of all these processes is repeated with some time interval while a shear-increasing motion continues. The authors propose that these repetitive flaring processes constitute a set of homologous flares.

Highly Energetic Physical Processes and Mechanisms for Emission from Astrophysical Plasmas

Author : International Astronomical Union. Symposium
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Particle Acceleration and Kinematics in Solar Flares

Author : Markus Aschwanden
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Over the last decade we entered a new exploration phase of solar flare physics, equipped with powerful spacecraft such as Yohkoh, SoHO, and TRACE that pro vide us detail-rich and high-resolution images of solar flares in soft X-rays, hard X -rays, and extreme-ultraviolet wavelengths. Moreover, the large-area and high sensitivity detectors on the Compton GRO spacecraft recorded an unprecedented number of high-energy photons from solar flares that surpasses all detected high energy sources taken together from the rest of the universe, for which CGRO was mainly designed to explore. However, morphological descriptions of these beau tiful pictures and statistical catalogs of these huge archives of solar data would not convey us much understanding of the underlying physics, if we would not set out to quantify physical parameters from these data and would not subject these measurements to theoretical models. Historically, there has always been an unsatisfactory gap between traditional astronomy that dutifully describes the mor phology of observations, and the newer approach of astrophysics, which starts with physical concepts from first principles and analyzes astronomical data with the goal to confirm or disprove theoretical models. In this review we attempt to bridge this yawning gap and aim to present the recent developments in solar flare high-energy physics from a physical point of view, structuring the observations and analysis results according to physical processes, such as particle acceleration, propagation, energy loss, kinematics, and radiation signatures.

Heliophysics Space Storms and Radiation Causes and Effects

Author : George L. Siscoe
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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. Over the past few centuries, our understanding of how the Sun drives space weather and climate on the Earth and other planets has advanced at an ever increasing rate. 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 volume, the second in a series of three heliophysics texts, integrates the many aspects of space storms and the energetic radiation associated with them -from their causes on the Sun to their 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 of the space weather responses in geospace. Historical space weather observations, in-situ particle measurement techniques, radiative emissions from energetic particles, and impacts of space weather on people and technology in space are also reviewed. In addition to its utility as a textbook, it constitutes a foundational reference for researchers in the fields of heliophysics, astrophysics, plasma physics, space physics, solar physics, aeronomy, space weather, planetary science, and climate science. Additional online resources, including lecture presentations and other teaching materials, can be accessed

High Energy Aspects of Solar Flares

Author : A. Gordon Emslie
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This edited volume describes many aspects of current research on solar flares, emphasizing recent progress in understanding their X-ray and gamma-ray emissions. Several of the chapters deal comprehensively with the problems of particle acceleration, conversion of particle energy into various forms of radiation, and the inference of physical processes from observations. Other chapters deal with the full breadth and richness of flare observations, including microflares and nanoflares. This volume is aimed at graduate students and researchers in solar physics and space science. Previously published in Space Science Reviews journal, Vol. 159/1-4, 2011.

Solar Maximum Analysis

Author : Vladimir Evgenʹevich Stepanov
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These proceedings contain the review and contributed papers given at the SMY--SMA Workshop held in Irkutsk (USSR), 17--24 June 1985. The main themes of the Workshop were plasma physics and magnetohydrodynamics with applications to processes occurring in solar flares. The papers published in this volume are organized around the following topics: -- the reconnection of coronal magnetic fields as a source of flare energy -- the acceleration of particles to high energies -- the dynamics of interplanetary clouds and shocks

Heliophysical Processes

Author : Natchimuthuk Gopalswamy
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An outgrowth of the first Asia-Pacific Regional School on the International Heliophysical Year (IHY), this volume contains a collection of review articles describing the universal physical processes in the heliospace influenced by solar electromagnetic and mass emissions. The Sun affects the heliosphere in the short term (space weather) and in the long term (space climate) through numerous physical processes that exhibit similarities in various spatial domains of the heliosphere. The articles take into account various aspects of the Sun-heliosphere connection under a systems approach. This volume will serve as a ready reference work for research in the emerging field of heliophysics, which describes the physical processes taking place in the physical space controlled by the Sun out to the local interstellar medium.

Physics of the Sun

Author : P.A. Sturrock
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This volume, together with its two companion volumes, originated in a study commis sioned by the United States National Academy of Sciences on behalf of the National Aeronautics and Space Administration. A committee composed of Tom Holzer, Dimitri Mihalas, Roger Ulrich and myself was asked to prepare a comprehensive review of current knowledge concerning the physics of the sun. We were fortunate in being able to persuade many distinguished scientists to gather their forces for the preparation of 21 separate chapters covering not only. solar physics but also relevant areas of astrophysics and solar-terrestrial relations. In proved necessary to divide the chapters into three separate volumes that cover three different aspects of solar physics. Volumes I and III are concerned with "The Solar Interior" and with "Astrophysics and Solar-Terrestrial Relations." This volume, devoted to "The Solar Atmosphere," covers not only the chromosphere and corona but also the principal phenomena usually referred to as "solar activity." The emphasis is on identifying and analyzing the relevant physical processes, but each chapter also contains a great deal of descriptive material.

First Ten Years of Hinode Solar On Orbit Observatory

Author : Toshifumi Shimizu
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This book provides the latest scientific understanding of the Sun, sharing insights gleaned from the international solar physics project Hinode. The authors (who are the main project contributors) review, from the various viewpoints, the discoveries and advances made by the on-orbit operations of the Hinode spacecraft in its first decade. Further, they present a wealth of scientifically important photographs and data from Hinode. Launched in September 2006, Hinode is the third Japanese solar observatory on orbit, and employs three highly advanced telescopes jointly developed and operated with international partners. The book describes the background of these research topics, how the Hinode telescopes have tackled various challenges, and the scientific achievements and impacts in the first 10 years. Furthermore, it explores future perspective of researches in Japan. The book will benefit undergraduate students interested in recent advance in the solar research, as well as graduate students and researchers working in solar physics, the space sciences, astronomy, and plasma physics.