Download or read book Coupling the Photospheric and Coronal Magnetic Field Observations and Analysis written by Brian Neal Handy and published by . This book was released on 1999 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coupling the Photospheric and Coronal Magnetic Fields written by Brian Neal Handy and published by . This book was released on 1998 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Atlas of Photospheric Magnetic Field Observations and Computed Coronal Magnetic Fields 1976 1985 written by J. Todd Hoeksema and published by . This book was released on 1986 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Daily magnetogram observations of the large scale photospheric magnetic field have been made. These measurements provide a homogeneous record of the changing solar field through most of Solar Cycle 21. Using the photospheric data, the configuration of the coronal and heliospheric fields can be calculated using a Potential Field -- Source Surface model. This provides a 3 dimensional picture of the heliospheric field evolution during the solar cycle. This note announces the publication of UAG Report 94, an Atlas containing the complete set of synoptic charts of the measured photospheric magnetic field, the computed field at the source surface, and the coefficients of the multipole expansion of the coronal field. The general underlying structures of the solar and heliospheric fields, which determine the environment for solar terrestrial relations and provide the context within which solar activity related events occur, can be approximated from these data. The provision of a homogeneous dataset of the solar magnetic field over nearly an entire sunspot cycle in a convenient, inclusive package will stimulate the studies of the large scale structures of the solar and heliospheric magnetic field, encourage others to consider the relationship of the large scale, ambient field structures to activity on short time scales and smaller spatial scales, and enable the inclusion of the heliospheric field in analyses of solar terrestrial relations.
Download or read book Study of Photospheric Magnetic Field and Coronal Emission from Active Regions written by Jordan Armando Guerra Aguilera and published by . This book was released on 2016 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar explosive phenomena (flares and Coronal Mass Ejections, CMEs) are examples of how the most dynamical processes within the heliosphere are interconnected and powered by the Sun. Solar flares originate in active regions (AR) -- areas of strong magnetic field on the solar surface. The electromagnetic (EM) energy released during flares, along with the often-seen CMEs, propagate through the heliosphere. In the Earth's vicinity, EM radiation and charged particles have the potential to produce unfavorable conditions for humans and technology in space. From many points of view (scientific, operational, economical) it is thus important to understand and try to predict when solar flares and associated eruptive phenomena will occur. This dissertation explores how to best leverage the available observational data to provide predictive information about the future flaring activity. This dissertation consists of two main components: 1) investigation of the photosphere-corona coupling by analyzing photospheric magnetic field and coronal data in search for signals or behaviors that precede eruptions; and 2) the combination of existing flare prediction methods in order to develop a novel ensemble prediction. For the first part, the data employed correspond to line-of-sight (LOS) magnetograms from the Helioseismic and Magnetic Imager (HMI) and EUV intensity maps from the Atmospheric Imaging Assembly (AIA), both instruments onboard NASA's Solar Dynamics Observatory (SDO) satellite. Photospheric magnetic field and coronal EUV emissions were characterized by measuring the power-law decay of their spatio-temporal spectra and the data statistical associations (auto- and cross-correlations). These measures, calculated with high spatio-temporal resolution, appeared to characterize the AR evolution, provide information about the state of the photospheric plasma, reveal insights into the photospheric conditions for flares, and expose the potential of combining coronal and photospheric data for flare prediction. On the other hand, the construction of an ensemble forecast for major flares (M and X classes) was carried out by assigning a statistical weight to each ensemble member -- calculated from their track history and then linearly combining the forecasts. The performed linear combination resulted in the improvement of both probabilistic and categorical forecast by carefully choosing the performance metric to optimize. The performance of the ensemble forecasting method could be further improved by expanding the training sample of forecasts and observations. In conclusion, the combination of high-quality observational data with advanced statistical analysis techniques holds the key for understanding the photosphere-corona coupling and release of magnetic energy in solar flares. It is possible to enhance the quality of the existing flare forecasts by using smart ways to combine information from a set of different methods.
Download or read book Large scale Configuration of the Coronal and Interplanetary Magnetic Field written by Kenneth Howard Schatten and published by . This book was released on 1968 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: A physical model that is consistent with many of the properties observed in the corona and in interplanetary space has been developed. The model allows the large-scale magnetic field configuration above the photosphere to be computed from photospheric magnetic field observations using Green's function solution to Maxwell's equations. Sources for the magnetic field are related to the observed photospheric field and to the field computed at a 'source' surface about 0.6 solar radii above the photosphere. The model is able to explain the shape of rays and streamers in the inner corona. (Author).
Download or read book Rotation of the Coronal Magnetic Field written by J. T. Hoeksema and published by . This book was released on 1986 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The coronal magnetic field rotates differently than photosphere. The field configuration of the corona can be calculated from the observed photospheric field using a potential field model. Correlation of the field patterns at different latitudes with a lag near one solar rotation shows much less differential rotation than observed in the photospheric field; however, the peak is very broad and determines the rotation rate rather poorly. Consideration of longer lags reveals a more complex rotational structure and indicates different rotation rates in the northern and southern hemispheres. Spectral analysis of the equatorial dipole component of the coronal field reveals an organization into just a few discrete rotation frequencies which are apparently present simultaneously. Spectral analysis of the field at different latitudes shows that the frequencies are present simultaneously. Spectral analysis of the field at different latitudes shows that the frequencies are present simultaneously, but in different hemispheres, and that the southern hemisphere fields rotate more slowly than those in the north in solar cycle 21.
Download or read book Magnetic Coupling between the Interior and Atmosphere of the Sun written by S.S. Hasan and published by Springer Science & Business Media. This book was released on 2010-03-10 with total page 561 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar physics in India has a tradition that can be traced to the setting up of the Kodaikanal Observatory in 1899 when the Madras Observatory was relocated to a high altitude site with a view to initiate observations of the sun. This conference on Magnetic Coupling between the Interior and the Atmosphere of the Sun during 2–5 December 2008 was planned to coincide with centenary of the Evershed effect discovery at Kodaikanal in 1909. The aim of this meeting was to bring to a critical focus a comprehensive - derstanding of the important issues pertaining to solar magnetism with particular emphasis on the various MHD processes that operate in the solar atmosphere. The current status of magnetic eld measurements and their implications in the light of recenttheoriesandnumericalmodelingthataddressthe fundamentalscalesandp- cessesinthehighlymagnetizedturbulentplasmawerereviewedduringthismeeting. The meeting was timely for the following reasons: Space observations such as from SOHO and TRACE have provided a wealth of multiwavelength observations onprocessesoccurringinregionsofthe atmosphereextendingfromthe photosphere up to the outer corona. With the launch of Hinode and STEREO in 2006 and of SDO (Solar Dynamics Observatory) shortly, this conference provided a platform for in-depth discussions on new results from various space missions as well as a comparison with ground-based observing facilities such as the Swedish 1-m Solar Telescope. Using sophisticated image processing techniques, such telescopes r- tinelygenerateobservationswitharesolutionbetterthan0. 1arcsec,therebyyielding more informative diagnostics for instance of the microstructure of ux tubes.
Download or read book The Magnetic Solar Photosphere and Corona written by Xudong Sun and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Sun's magnetic field drives the dynamic behavior of its atmosphere and modulates the space weather conditions that we experience at the Earth. This dissertation focuses on the recent advances in understanding magnetic field measurements, static-state modeling of the corona, and their applications in space weather forecasting. We revisit the full-Sun line-of-sight magnetic field data archive from the Michelson Doppler Imager (MDI). Using the Wang-Sheeley-Arge (WSA) model coupled with the potential field source surface (PFSS) model, we retrospectively optimize the space weather forecasting scheme for the MDI data. We evaluate the long-term performance of the model: the solar wind speed prediction near the Earth yields a 16% error over solar cycle 23, and the interplanetary magnetic field polarity is correctly predicted 81% of time. The prediction accuracy is strongly correlated with the activity cycle phase. We design a new interpolation scheme to estimate the unobserved magnetic field in the polar region which improves the solar wind speed prediction. Making use of the PFSS model and the MDI data, we characterize the global-scale coronal and heliospheric magnetic field structure and its evolution during cycle 23. The modeled features agree reasonably well with remote-sensing and in-situ observations. The recent cycle displayed an extended minimum activity period, whose peculiar heliospheric consequences can be partly explained by a reduction of the polar magnetic field strength. The PFSS model may need to adopt a smaller source surface radius to better fit some observations. We use a series of vector magnetograms from the Heliospheric and Magnetic Imager (HMI) to study the magnetic field and energy evolution of NOAA active region (AR) 11158. With the aid of a non-linear force-free field (NLFFF) extrapolation, we find substantial electric current and magnetic free energy increase during early flux emergence. The computed free energy is enough to power the ensuing X-class flare. We find a step-wise energy decrease during the flare, but the value is likely underestimated. The new observations confirm the rapid and irreversible change of the photospheric field during a major flare. The horizontal field was enhanced, with the field becoming more inclined and more parallel to the polarity inversion line. Such change is consistent with the conjectured coronal field "implosion". Observation and modeling of this AR also illustrates the important role of magnetic topology. A small bipole emerged in the sunspot complex, subsequently created a quadrupolar flux system, and induced a series of eruptions with highly inclined trajectory. Field extrapolation suggests complicated magnetic connectivity with a coronal null point, which is supported by coronal observations. Owing to the asymmetrical photospheric flux distribution, the confining magnetic pressure decreases much faster horizontally than upward, and thus likely guided the non-radial eruption during its initial stage.
Download or read book Multi Wavelength Observations of Coronal Structure and Dynamics written by Penny Martens and published by Elsevier. This book was released on 2002-10-21 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: These are the Proceedings of the Yohkoh 10th Anniversary Meeting, a COSPAR Colloquium held in Kona, Hawaii, USA, on January 20-24, 2002. The title of the meeting was Multi-Wavelength Observations of Coronal Structure and Dynamics. In these proceedings the many and varied advances of the dynamics solar atmosphere in the past ten years of observations by Yohkoh have been reviewed.
Download or read book The Solar Dynamics Observatory written by Phillip Chamberlin and published by Springer Science & Business Media. This book was released on 2012-05-05 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is dedicated to the Solar Dynamics Observatory (SDO), which was launched 11 February 2010. The articles focus on the spacecraft and its instruments: the Atmospheric Imaging Assembly (AIA), the Extreme Ultraviolet Variability Experiment (EVE), and the Helioseismic and Magnetic Imager (HMI). Articles within also describe calibration results and data processing pipelines that are critical to understanding the data and products, concluding with a description of the successful Education and Public Outreach activities. This book is geared towards anyone interested in using the unprecedented data from SDO, whether for fundamental heliophysics research, space weather modeling and forecasting, or educational purposes. Previously published in Solar Physics journal, Vol. 275/1-2, 2012. Selected articles in this book are published open access under a CC BY-NC 2.5 license at link.springer.com. For further details, please see the license information in the chapters.
Download or read book Structure and Dynamics of the Coronal Magnetic Field written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-11 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last few years have seen a marked increase in the sophistication of models of the solar corona. This has been brought about by a confluence of three key elements. First, the collection of high-resolution observations of the Sun, both in space and time, has grown tremendously. The SOHO (Solar Heliospheric Observatory) mission is providing additional correlated high-resolution magnetic, white-light and spectroscopic observations. Second, the power and availability of supercomputers has made two- and three-dimensional modeling routine. Third, the sophistication of the models themselves, both in their geometrical realism and in the detailed physics that has been included, has improved significantly. The support from our current Space Physics Theory grant has allowed us to exploit this confluence of capabilities. We have carried out direct comparisons between observations and models of the solar corona. The agreement between simulated coronal structure and observations has verified that the models are mature enough for detailed analysis, as we will describe. The development of this capability is especially timely, since observations obtained from three space missions that are underway (Ulysses, WIND and SOHO) offer an opportunity for significant advances in our understanding of the corona and heliosphere. Through this interplay of observations and theory we can improve our understanding of the Sun. Our achievements thus far include progress modeling the large-scale structure of the solar corona, three-dimensional models of active region fields, development of emerging flux and current, formation and evolution of coronal loops, and coronal heating by current filaments. VanHoven, Gerard and Schnack, Dalton D. Goddard Space Flight Center NAG5-2257...
Download or read book Solar Flare Magnetic Fields and Plasmas written by Yuhong Fan and published by Springer Science & Business Media. This book was released on 2012-03-28 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is devoted to the dynamics and diagnostics of solar magnetic fields and plasmas in the Sun’s atmosphere. Five broad areas of current research in Solar Physics are presented: (1) New techniques for incorporating radiation transfer effects into three-dimensional magnetohydrodynamic models of the solar interior and atmosphere, (2) The connection between observed radiation processes occurring during flares and the underlying flare energy release and transport mechanisms, (3) The global balance of forces and momenta that occur during flares, (4) The data-analysis and theoretical tools needed to understand and assimilate vector magnetogram observations and (5) Connecting flare and CME phenomena to the topological properties of the magnetic field in the Solar Atmosphere. The role of the Sun’s magnetic field is a major emphasis of this book, which was inspired by a workshop honoring Richard C. (Dick) Canfield. Dick has been making profound contributions to these areas of research over a long and productive scientific career. Many of the articles in this topical issue were first presented as talks during this workshop and represent substantial original work. The workshop was held 9 – 11 August 2010, at the Center Green campus of the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. This volume is aimed at researchers and graduate students active in solar physics, solar-terrestrial physics and magneto-hydrodynamics. Previously published in Solar Physics journal, Vol. 277/1, 2012.
Download or read book A Study of the Cyclical Variations of Coronal Holes and Their Relation to Open Magnetic Fields written by John M. Davis and published by . This book was released on 1984 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: This contract was a study of possible variations in the observed flux from coronal holes over a solar cycle and their relationship to solar magnetic fields. The variation of X-ray emission from coronal holes was measured and compared with data on photospheric magnetic field strength and models of open field structures from holes. The data set consisted of reduced X-ray images from AS & E rocket flights and digitized photospheric magnetic field strength data from Mt. Wilson and Kitt peak observatories over the period 1974 to 1981. The results are as follows. We found that soft X-ray emission from coronal holes could be detected in the rocket data, confirming earlier Skylab results. Also, this emission appeared to vary systematically over an 8-year period, from a minimum in mid-1974 to a maximum about one year after sunspot activity maximum. This conclusion is strengthened by three other observations: (1) HeI 10830 A coronal holes exhibited decreased contrast during this same period; (2) the particular holes that we measured were typical of those at each phase of the cycle in terms of their evolutionary and interplanetary characteristics; and (3) the X-ray hole emission followed a similar trend in Harvey et al.'s (1982) data whereby the photospheric field strength of near-equatorial holes increased systematically by a factor of three between 1975 and 1980. Further, our own measurements of field strengths within the X-ray hole boundaries were sparse but generally in agreement with the Harvey et al. trend. Keywords include: Coronal Holes; Solar cycle variations; Solar X-ray; Coronal images.
Download or read book Physics of the Inner Heliosphere II written by Rainer Schwenn and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Download or read book Rotation of the Photospheric Magnetic Fields A North South Asymmetry written by E. Antonucci and published by . This book was released on 1989 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: During most of solar cycle 21 the large-scale photospheric field rotated more rapidly in the northern hemisphere than in the southern. the large-scale northern field rotated with a 26.9 day period (synodic), was centered at 15 degress N, and covered a latitude zone about 24 degrees wide. The large-scale southern field rotated with a periodicity of 28.1 days, was centered at 26 degrees s, and covered a latitude zone about 32 degrees wide. Our analysis showed rotational power at only a few discrete latitudes and frequencies in each hemisphere. The center of each peak lies near the sunspot differential rotation curve. The largest scale field contributes to the configuration of the coronal and interplanetary magnetic field (IMF). The strength of the first harmonic of the northern field suggests that this structure may be related to the 4-sector pattern observed in the IMF polarity. The southern field had much lower power at the first harmonic of the solar rotation rate and so would contribute only to a 2-sector structure in the IMF. These results were discovered in Fourier analysis of photospheric synoptic charts obtained at the Wilcox Solar Observatory from 1976 - 1986 and confirmed a higher resolution maps from the National Solar Observatory. Mt. Wilson magnetic field measurements from solar cycle 20 show a similar north-south asymmetry. Keywords: Solar rotation; Solar magnetic field; Solar asymmetry. (JHD).
Download or read book Coronal Holes and Solar Wind Acceleration written by John L. Kohl and published by Springer Science & Business Media. This book was released on 2013-11-09 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: The SOHO-7 Workshop was held from 28 September through 1 October 1998 at the Asticou Inn in Northeast Harbor, Maine. The primary topic of this Workshop was the impact of SOHO observations on our understanding of the nature and evolution of coronal holes and the acceleration and composition of the solar wind. The presentations and discussions occasionally went beyond this topic to include the impact of the reported research on other solar structures and the heliosphere. SOHO (the Solar and Heliospheric Observatory), a project of international cooperation between ESA and NASA, was launched in December 1995 and began its science operations during the first few months of 1996. To many solar and space physicists, it was a great advantage that SOHO began itscomprehensive look at the Sun during the 1996 solar minimum. The qualitatively simple two-phase corona, with polar coronal holes expanding into the high-speed solar wind, and a steady equatorial streamer belt related somehow to the stochastic slow-speed solar wind, allowed various SOHO diagnostics to be initiated with a reasonably well understoodcircumsolar geometry. The analysis of subsequentSOHO measurements made during the rising phase of solar cycle 23 will continue to benefit from what has been learned from the first two years of data.
Download or read book Solar Prominences written by Jean-Claude Vial and published by Springer. This book was released on 2014-11-24 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the latest research results on solar prominences, including new developments on e.g. chirality, fine structure, magnetism, diagnostic tools and relevant solar plasma physics. In 1875 solar prominences, as seen out of the solar limb, were described by P.A. Secchi in his book Le Soleil as "gigantic pink or peach-flower coloured flames". The development of spectroscopy, coronagraphy and polarimetry brought tremendous observational advances in the twentieth century. The authors present and discuss exciting new challenges (resulting from observations made by space and ground-based telescopes in the 1990s and the first decade of the 21st century) concerning the diagnostics of prominences, their formation, their life time and their eruption along with their impact in the heliosphere (including the Earth). The book starts with a general introduction of the prominence “object” with some historical background on observations and instrumentation. In the next chapter, the various forms of prominences are described with a thorough attempt of classification. Their thermodynamic (and velocity) properties are then derived with emphasis on the methods (and their limits) used. This goes from the simplest optically thin case to the heavy radiative treatment of plasmas out of local thermodynamic equilibrium. The following chapters are devoted to the magnetic field measurements and indirect derivation. A new branch of diagnostic tools, the seismology, is presented along with some MHD basics. This allows to better understand the propagation of waves, the energy and force equilibria. Both small-scale and large-scale studies and their relationship are presented. The importance of the newly discovered cavities is stressed in the context of prominence destabilization. The issues of prominence formation and eruption, their connection with flares and Coronal Mass Ejections and their impact on the Earth are addressed on the basis of the latest results. Finally, an exciting new area of research is unveiled with the newly discovered evidence of similar manifestations in the Universe and their possible impact on the habitability of exoplanets. References to the basic physics (where necessary) are provided and the proposed web sites addresses will allow the reader to load exciting movies. The book is aimed at advanced students in astrophysics, post-graduates, solar physicists and more generally astrophysicists. Amateurs will enjoy the many new images which go with the text.
