Download or read book Solar Oscillations in Magnetic Regions written by Christopher Hanson and published by . This book was released on 2014 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the 50 years of helioseismology, we have gained an extensive understanding into the physical processes present within our sun. With the aid of high resolution observations and increased computational power, the current body of understanding is rapidly growing. However, there are still many questions left answered today. In this thesis, we will address two phenomena in order to shed light on their related open questions. In the first part, we will examine the scattering regimes that exist within bundles of thin magnetic flux tubes. In particular, we will address the question of how magnetic plage can absorb large amounts of wave energy and whether the resultant scattered wave field can be used to infer the magnetic field structure. The second phenomenon concerns the seismic sources that are situated within acoustic power halos and what role of the magnetic field has in enhancing these sources. In addressing the multiple scattering regime, a semi-analytical model was developed in order to model the scattering between numerous thin flux tubes situated within a stratified atmosphere. We have used a method originally designed for oceanic wave scattering, and applied it to a solar context. While to some extent this has been done in the past, we further develop the model to include the scattering of all possible modes between thin magnetic flux tubes. In doing so, we outline and address a mathematical error in the original formalism, that was not apparent until previous results were compared to recent numerical studies. Numerous case studies are then examined, ranging from the simple case of two interacting tubes, to large numbers of closely packed tubes. Various parameters are explored and the effect these have on the scattering regime is reported. Our results compare quite well with numerical and observational studies, and this model presents a significant step forward in understanding how the scattered wave field can be used to infer the internal constitution of a slender magnetic field structure.On addressing the second phenomenon, we employ the helioseismic holography technique to examine the enhanced seismic sources that are situated within the acoustic power halo that surrounds complex active regions. We examine three active regions using SDO data and apply strict statistical precautions in our analysis. The relationship between the seismic sources and the magnetic field is explored, with a strong correlation found between seismic enhancement and quasi-horizontal fields of intermediate strength. Additionally, the most intense seismic emitters (acoustic glories) were found to be located within fields very close to horizontal. The relationship between the seismic source halos and the commonly used local acoustic power maps is also explored, with large similarities reported. We found that the greatest difference between the two types of halos occurs within the high frequency (9 mHz) regime. The results of this observational study agree with other recent studies, however this study presents a significant advancement on previous holography studies.
Download or read book Study of Oscillations and Flows in Solar Magnetic Active Regions written by Hope Thackray and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Magnetoconvection written by N. O. Weiss and published by Cambridge University Press. This book was released on 2014-10-30 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt: Leading experts present the current state of knowledge of the subject of magnetoconvection from the viewpoint of applied mathematics.
Download or read book A Study of Oscillations in Solar Active Regions written by Ram Ajor Maurya and published by LAP Lambert Academic Publishing. This book was released on 2014-05-16 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar active regions (ARs) are three-dimensional magnetic structures extending from deep sub-photosphere to coronal heights. These ARs are responsible for producing most of the energetic transients, such as flares and CMEs. Energetic transients are expected to excite p-mode oscillations in ARs by imparting mechanical impulse associated with their thermal expansion on the photosphere. Flare productive ARs may have distinctly different sub-photospheric properties compared to dormant ARs. We have determined the characteristic properties of local oscillation modes by applying the local helioseismic technique to several ARs. Strong evidence of substantial increase in mode amplitude are found from comparison of the pre- to the post-flare phases of energetic flares. Our study has revealed strongly twisted, sheared flows in the interior of flaring ARs having complex magnetic fields. We discovered steep gradients in meridional velocity at depths ranging from 1.5 to 5 Mm in flare productive ARs. Our study of sub-photospheric flows and photospheric magnetic fields of several ARs showed that the sub-photospheric kinetic helicity and photospheric magnetic helicity are weakly correlated.
Download or read book Solar and Space Physics written by National Research Council and published by National Academies Press. This book was released on 2014-09-25 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2010, NASA and the National Science Foundation asked the National Research Council to assemble a committee of experts to develop an integrated national strategy that would guide agency investments in solar and space physics for the years 2013-2022. That strategy, the result of nearly 2 years of effort by the survey committee, which worked with more than 100 scientists and engineers on eight supporting study panels, is presented in the 2013 publication, Solar and Space Physics: A Science for a Technological Society. This booklet, designed to be accessible to a broader audience of policymakers and the interested public, summarizes the content of that report.
Download or read book Solar Surface Magnetism written by R. J. Rutten and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observations of the solar magnetic field are largely confined to the radiation emitted from the photosphere, the thin layer of the solar atmosphere which we call "the solar surface". It is from solar surface observations that we must infer the internal structure and the internal magnetohydrodynamic processes that lead to the multitude of fascinat ing phenomena of solar magnetic activity, and from solar surface observations we must also infer the interplay of convection and magnetism that regulates field dispersal, drives the heating of the outer-atmospheric plasma, and generates the solar wind. There is much to be learned from solar surface magnetism in physics and astrophysics; currently, there are rapid developments in this exciting field. The workshop of which this volume contains the proceedings aimed at a synthesis between observers and theorists, both with regard to the discrete elements that are the building blocks of solar magnetism and with regard to the larger-scale spatial and temporal patterns in which the magnetic elements emerge and disappear. The workshop was held during November 1-5, 1993 in Soesterberg, The Netherlands. The fifty participants took a very active part in making the workshop quite a lively one. The articles in these proceedings cover most of the oral and poster presentations, excepting a dozen soon to be published elsewhere.
Download or read book SCORe 96 Solar Convection and Oscillations and their Relationship written by F.P. Pijpers and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 311 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the reviews and poster papers presented at the workshop Solar Convection and Oscillations and their Relationship: SCORe '96, held in Arhus, Denmark, May 27 - 31, 1996. The aim of this workshop was to bring together experts in the fields of convection and helioseismology, and to stimulate collaborations and joint research. The participation to this workshop was purposely kept limited in order to provide optimal conditions for informal discussions. In autumn of 199,5 the long-awaited GONG network of solar telescopes became fully operational and the first data already show significant improvement over existing datasets on solar oscillations. Furthermore, in December of 1995 the satellite SOHO was launched which, together with GONG, provides a major step forward in both the quantity and the quality of available solar oscillation data. It is with this in mind that we decided to organize the workshop to prepare for the optimal use of this wealth of data, with which to deepen our understanding of solar structure and specifically, of one of the longest-standing problems in solar and stellar modelling: the treatment of convection.
Download or read book Solar System Magnetic Fields written by E.R. Priest and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: In September 1984 a Summer School on Solar System Plasmas was held at Imperial College with the support of the Science and Engineering Research Council. An excellent group of lecturers was assembled to give a series of basic talks on the various aspects of the subject, aimed at Ph. D. students or researchers from related areas wanting to learn about the plasma physics of the solar system. The students were so appreciative of the lectures that it was decided to write them up as the present book. Traditionally, different areas of solar system science, such as solar and magnetospheric physics, have been studied by separate communities with little contact. However, it has become clear that many common themes cut right across these distinct topics, such as magnetohydrodynamic instabilities and waves, magnetic reconnect ion , convection, dynamo activity and particle acceleration. The plasma parameters may well be quite different in the Sun's atmosphere, a cometary tailor Jupiter's magnetosphere, but many of the basic processes are similar and it is by studying them in different environments that we come to understand them more deeply. Furthermore, direct in situ measurements of plasma properties at one point in the solar wind or the magnetosphere complement the more global view by remote sensing of a similar phenomenon at the Sun.
Download or read book Physics of the Sun written by P.A. Sturrock and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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. It proved necessary to divide the chapters into three separate volumes that cover three different aspects of solar physics. Volumes II and III are concerned with 'The Solar Atmosphere' and with 'Astrophysics and Solar-Terrestrial Relations'. This volume is devoted to 'The Solar Interior', except that the volume begins with one chapter reviewing the contents of all three volumes. Our study of the solar interior includes a review of nuclear, atomic, radiative, hydrodynamic and hydromagnetic processes, together with reviews of three areas of active current investigation: the dynamo mechanism, internal rotation and magnetic fields, and oscillations. The last topic, in particular, has emerged in recent years as one of the most exciting areas of solar research.
Download or read book Solar and Stellar Magnetic Activity written by C. J. Schrijver and published by Cambridge University Press. This book was released on 2008-10-30 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: This timely volume provides the first comprehensive review and synthesis of current understanding of magnetic fields in the Sun and similar stars. Magnetic activity results in a wealth of phenomena - including starspots, non-radiatively heated outer atmospheres, activity cycles, deceleration of rotation rates, and even, in close binaries, stellar cannibalism - all of which are covered clearly and authoritatively. This book brings together for the first time recent results in solar studies and stellar studies. The result is an illuminating new view of stellar magnetic activity. Key topics include radiative transfer, convective simulations, dynamo theory, outer-atmospheric heating, stellar winds and angular momentum loss. Researchers are provided with a state-of-the-art review of this exciting field, and the pedagogical style and introductory material make the book an ideal and welcome introduction for graduate students.
Download or read book Solar Magnetic Fields written by Manfred Schüssler and published by Cambridge University Press. This book was released on 1994-06-16 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: How are large-scale magnetic fields generated in the Sun in self-excited dynamo processes? And how are magnetic structures spontaneously formed in the Sun and how do they interact with the convective flows, storage and release of magnetic energy? These are just several of the fundamental questions answered in this timely review of our understanding of solar magnetic fields. This volume collects together review articles and research papers from an international conference, held in Freiburg, Germany, dedicated to the study of magnetic fields in the Sun. From large-scale patterns and global dynamo action to tiny flux tubes, from the overshoot layer below the convection zone up to the corona, and from instrumental problems and theoretical methods to the latest ground-based and satellite observations, this volume provides an essential review of our knowledge to date for graduate students and researchers.
Download or read book Physics of Solar Variations written by Domingo and published by Springer Science & Business Media. This book was released on 2013-11-09 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: V. DOMINGO Space Science Department, ESTEC, Noordwijk, The Netherlands The XIVth ESLAB Symposium on 'Physics of Solar Variations' was held in Scheveningen (The Netherlands) on 16-19 September, 1980. The objective of the symposium was to discuss from an interdisciplinary point of view the different types of changing phenomena that occur in the Sun and the effects that such changes may have on the Earth environment with the aim that a global look at the varying phenomena may improve the understanding of the underlying physical processes. Solar physicists of different background, investigators in solar radiometry and atmospheric scientists gathered to review the progress that has been made in the study of the different areas of solar variations. The proceedings of this symposium constitute an up-to-date collection of information on the variations of the Sun. The first and largest section of the proceedings is devoted to the physics of the Sun. An overview of how the observed variations contribute to the development of the theory of the solar structure is followed by several papers on recent results on the study of solar oscillations, a unique probe of Sun's interior. Several papers then summarise the theoretical and experimental efforts in the study of the solar magnetic cycle and its consequences. Finally the expansion of the corona with the formation of the solar wind and some characteristics of solar wind variations are described.
Download or read book Structure and Development of Solar Active Regions written by K.O. Kiepenheuer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt: K. O. KIEPENHEUER ( Fraunhofer Institut, Freiburg i. Br., Germany) The present symposium, to my knowledge the largest ever held in the field of solar research (170 astronomers from 21 countries) was held in the building of the Hun garian Academy of Sciences in Budapest from September 4 to 8, 1967. It was the 35th symposium organized and sponsored by the International Astronomical Union. The majority of participants were financedfrom national sources. The Organizing Commit tee consisted of K. O. Kiepenheuer (Chairman), L. Davis, L. Dezso (Local Organizer), A.D. Fokker, R. Michard, A.B. Severny, H.J. Smith, Z. Svestka, and H. Tanaka. In order to ensure prompt publication, the manuscripts had to be supplied by the authors 1 month after the meeting. The discussions have been recorded on tape. Their reproduction in this book, however, is based almost completely on the contributors' writing down their comments and questions on the spot. Two special projects have been reported and discussed shortly during the sym posium: The world wide project 'Cooperative Study of Solar Active Regions' (CSSAR) organized by Dr. R. Michard, under the auspices of the IAU, which has put at the disposal of our solar community a precious observing material on Active Regions over a period of 6 months.
Download or read book Solar Magneto atmospheric Oscillations written by Marie Elizabeth Newington and published by . This book was released on 2013 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: Estimates of wave energy fluxes in the solar photosphere and chromosphere suggest that gravity waves carry more energy than co-spatial acoustic waves. This work presents an exploration of the upward propagation of gravity waves from the photosphere to the chromosphere, in a realistic model of the solar atmosphere. The purpose is to determine what happens to upward propagating gravity waves when they reach regions where the magnetic forces dominate. Wave motions are assumed linear and the atmosphere is static and horizontally invariant. Dispersion and ray diagrams provide insight into the mode con¬version mechanism. Numerical solution of the linear adiabatic wave equations quantify wave energy fluxes. The analysis shows that typically even weak magnetic fields cause the gravity wave to reflect back downwards as a slow magneto-acoustic wave well before the Alfven-acoustic equipartition level, and it fails to reach the chromosphere. However, highly inclined magnetic fields allow gravity waves to penetrate the equipartition level and experience substantial mode conversion to up-going Alfven waves, or field-guided acoustic waves. Wave energy fluxes are sensitive to the magnetic field orientation and short radiative damping times, but are insensitive to the magnetic field strengths over the range considered (lOG -100 G). The mode conversion pathways found in adiabatic analyses are preserved in the presence of damping. Mode conversion of gravity waves to Alfven waves is a possible pathway to the upper atmosphere for wave energy. The cause of the high frequency enhancement (the acoustic glory) in seismic power surrounding large active regions with complex field structures is not yet understood. This work presents an investigation of the properties of the seismic emission power and acoustic power of large active regions that have acoustic glories. Helioseismic holography is used to create seismic emission power maps for six large active regions with complex magnetic field structures. Acoustic glories are visible in high-frequency seismic emission power maps (5.0 mHz -7.0 mHz) for all active regions studied. The analysis of acoustic power about large active regions, in high and low frequency regimes, confirms behaviours that are consistent with the findings of previous analyses of smaller active regions. Several new properties of high frequency seismic emission power associated with large active regions are identified: The maximum enhancements in seismic emission and acoustic power occur at different spatial locations; acoustic glories are most prominent in seismic emission power maps in the 5.0 mHz -6.0 mHz bandwidth; the radius of the acoustic glory reduces as frequency increases; and the mean value of high frequency (above 5.0 mHz) seismic emission power for the active regions studied was enhanced at intermediate line-of-sight magnetic flux densities (50 G -300 G).
Download or read book Solar Dynamics and Magnetism from the Interior to the Atmosphere written by Nagi N. Mansour and published by Springer Science & Business Media. This book was released on 2013-12-03 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discusses recent advances and new problems in the exploration of the Sun's interior structure, solar dynamics and dynamo, mechanisms of sunspot and active regions formation, sources of solar irradiance variations and links between the subsurface dynamics, flaring and CME activity. NASA's Solar Dynamics Observatory (SDO) mission has provided a large amount of new data on solar dynamics and magnetic activities during the rising phase of the current and highly unusual solar cycle. These data are complemented by the continuing SOHO mission and by ground-based observatories that include the GONG helioseismology network and the New Solar Telescope. Also, the observations are supported by realistic numerical simulations on supercomputers. This unprecedented amount of data provides a unique opportunity for multi-instrument investigations that address fundamental problems of the origin of solar magnetic activity at various spatial and temporal scales. This book demonstrates that the synergy of high-resolution multi-wavelength observations and simulations is a key to uncovering the long-standing puzzles of solar magnetism and dynamics. This volume is aimed at researchers and graduate students active in solar physics and space science. Originally published in Solar Physics journal, Vol. 287/1-2, 2013.
Download or read book Solar Interior and Atmosphere written by Arthur N. Cox and published by University of Arizona Press. This book was released on 1991-12 with total page 1444 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observational data derived from the world's largest solar telescopes are correlated with theoretical discussions in nuclear and atomic physics by contributors representing a wide range of interests in solar research.
Download or read book Third Advances in Solar Physics Euroconference written by Brigitte Schmieder and published by . This book was released on 1999 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
