Download or read book Solar Flares As Natural Particle Accelerators written by Wei Liu and published by . This book was released on 2008-07-01 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar flares, which have significant space weather consequences, are natural particle accelerators and one of the most spectacular phenomena of solar activity. RHESSI is the most advanced solar X-ray and gamma-ray mission ever flown and has opened a new era in solar flare research following its launch in 2002. This book offers a glimpse of this active research area from a high-energy perspective and contains a comprehensive guideline for RHESSI data analysis. Its main theme is the investigation of particle acceleration and transport in solar flares. The strength of this book lies in its well-balanced account of the latest X-ray observations and theoretical models. The observational focus is on the morphology and spectra of imaged X-ray sources produced by nonthermal electrons or hot plasma. The modeling takes the novel approach of combining the Fokker-Planck treatment of the accelerated particles with the hydrodynamic treatment of the heated atmosphere. Applications of this modeling technique reach beyond the Sun to other exotic environments in the universe, such as extrasolar planetary auroras, stellar flares, and flares on accretion disks around neutron stars and black holes.
Download or read book Particle kinematics in solar flares observations and theory written by Marina Battaglia and published by Cuvillier Verlag. This book was released on 2009-02-05 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is devoted to the study of particle acceleration and propagation processes in solar flares. Solar flares are amongst the most powerful and energetic activity phenomena our Sun exhibits. They release energy of the order of 1032 erg in seconds to minutes. In the process, electrons and protons are accelerated to relativistic energies, making flares very efficient particle accelerators. The most compelling observational signatures of flares can be found in X-rays and extreme ultra-violet wavelengths. Due to atmospheric absorption, those wavelengths can only be studied from space. Since the beginning of the space age, countless flares have been observed by satellites. The present work is largely based on observations by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), an X-ray satellite which has been observing the Sun since February 2002. It is a NASA mission with substantial Swiss hardware and software contribution. Using RHESSI observations of flares of different intensity, a deeper understanding of the particle transport and energy transport processes in flare loops, as well as the acceleration site and acceleration mechanism is sought. The time evolution of images and spectra is studied along with the quantitative relations between X-ray sources observed in the corona (coronal sources) and from the chromosphere (footpoints). The spectral relations found between coronal sources and footpoints are compared to the so-called ``intermediate thin-thick target model'', which was based on observations by the satellite Yohkoh. We show that the spectral relations between coronal sources and footpoints observed with RHESSI cannot be explained by the intermediate thin-thick target model. In a next step, return currents in the flare loop were considered. With this extension to the existing model, the spectra of the coronal source and the footpoints, as well as the relations between them can be explained, indicating the importance of return currents in flare loops. In a second part, observations of so-called ``pre-flares'' are presented. This earliest phase of a flare cannot be explained by the standard flare model of chromospheric evaporation which involves energy transport and deposition in the chromosphere by beams of accelerated electrons. In pre-flares, an increase in density and emission measure is observed, indicating that chromospheric evaporation is occurring. However, no observational signatures of fast electrons are found. We show that if energy is transported by means of thermal conduction instead of an electron beam, the observations can explained.
Download or read book Observations and Simulations of Particle Acceleration in Solar Flares written by Peter Messmer and published by . This book was released on 2001 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Particle Acceleration and Kinematics in Solar Flares written by Markus Aschwanden and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Particle Acceleration and Trapping in Solar Flares written by G. Trottet and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: These are the Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares. The Workshop was held on June 23-26,1986, at the city hall of Aubigny-sur-Nere (France), near Bourges and near the Nan
Download or read book Stochastic Acceleration of Electrons by Turbulence in Solar Flares written by Qingrong Chen and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar flares are among the most powerful explosions and most efficient particle accelerators in the solar system. The model of stochastic acceleration by plasma turbulence has been very instrumental in explaining the observed high-energy radiations and particles from solar flares. In this thesis, we aim to better constrain the electron acceleration and scattering processes by turbulence from hard X-ray imaging spectroscopic observations of solar flares. By utilizing the leaky box Fokker-Planck equation and the thick target equation describing particle acceleration and transport, we derive analytical formulas for the stochastic acceleration model quantities directly in terms of the accelerated and escaping particle spectra. Based on the hard X-ray radiating electron flux spectral images via regularized inversion, we determine the timescales for electron escape, pitch angle scattering, energy diffusion, and direct acceleration in two intense solar flares with a high-energy loop-top coronal source observed by the RHESSI mission. The existence of distinct coronal hard X-ray sources up to 100-150 keV in the impulsive phase indicates efficient confinement of high-energy electrons in the corona. The results that the electron escape time increases with energy and the acceleration time and scattering time exhibit very different energy dependences contradict existing predictions for stochastic acceleration due to wave-particle resonant interactions. The discrepancy between the observations and the acceleration model could be alleviated if the turbulence spectrum is much steeper than commonly assumed. A more plausible explanation for such events is that the escape of electrons from the loop-top acceleration region is not diffusive in nature due to scattering, but is affected by magnetic mirroring.
Download or read book Physical Processes in Solar Flares written by B.V. Somov and published by Springer Science & Business Media. This book was released on 1991-12-31 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Solar Flares and Space Research written by Cornelis de Jager and published by . This book was released on 1969 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Particle Acceleration in Solar Flares written by Stanford University. Institute for Plasma Research and published by . This book was released on 1973 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Particle Acceleration and Kinematics in Solar Flares written by and published by . This book was released on 2002 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aspects of Particle Acceleration in Solar Flares written by Yuri E. Litvinenko and published by . This book was released on 1996 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Progress in Solar Physics written by C. de Jager and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 617 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Role of Particle Acceleration in Solar Flares written by and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Antarctic Journal of the United States written by and published by . This book was released on 1992 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the National Symposium on Natural and Manmade Radiation in Space written by E. A. Warman and published by . This book was released on 1972 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cosmic Ray Astrophysics written by Reinhard Schlickeiser and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 521 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the first part, the book gives an up-to-date summary of the observational data. In the second part, it deals with the kinetic description of cosmic ray plasma. The underlying diffusion-convection transport equation, which governs the coupling between cosmic rays and the background plasma, is derived and analyzed in detail. In the third part, several applications of the solutions of the transport equation are presented and how key observations in cosmic ray physics can be accounted for is demonstrated.
Download or read book Fundamental Problems in Solar Activity written by COSPAR. Plenary Meeting and published by Elsevier Science & Technology. This book was released on 1993 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reviews the state-of-the-art in the understanding of solar active phenomena in the areas of: key structures producing solar activity; initiation and development of transient activity; non-thermal phenomena in the sun and the interplanetary medium; flare prediction and long-term solar visibility.
