Download or read book Development and Application of a Global Magnetic Field Evolution Model for the Solar Corona written by Anthony Robinson Yeates and published by . This book was released on 2008 with total page 225 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Magnetohydrodynamic Modeling of the Solar Corona and Heliosphere written by Xueshang Feng and published by Springer. This book was released on 2019-08-01 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book covers intimately all the topics necessary for the development of a robust magnetohydrodynamic (MHD) code within the framework of the cell-centered finite volume method (FVM) and its applications in space weather study. First, it presents a brief review of existing MHD models in studying solar corona and the heliosphere. Then it introduces the cell-centered FVM in three-dimensional computational domain. Finally, the book presents some applications of FVM to the MHD codes on spherical coordinates in various research fields of space weather, focusing on the development of the 3D Solar-InterPlanetary space-time Conservation Element and Solution Element (SIP-CESE) MHD model and its applications to space weather studies in various aspects. The book is written for senior undergraduates, graduate students, lecturers, engineers and researchers in solar-terrestrial physics, space weather theory, modeling, and prediction, computational fluid dynamics, and MHD simulations. It helps readers to fully understand and implement a robust and versatile MHD code based on the cell-centered FVM.
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 Global Evolution of Magnetic Fields in the Photosphere of the Sun During Cycles 20 23 written by Reto Knaack and published by Cuvillier Verlag. This book was released on 2005 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Global Evolution of Magnetic Fields in the Photsphere of the Sun During Cycles 20 23 written by and published by Cuvillier Verlag. This book was released on 2005-07-05 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Systematische tagliche Messungen des Magnetfeldes der Sonne werden mittels des Zeeman-Effekts seit 1966 am Mount Wilson Observatorium (UCLA, University of California, Los Angeles) und seit 1974 am Kitt Peak Observatorium (NSO, National Solar Observatory, Arizona) durchgeführt. Die resultierenden Magnetfeldkarten (oder "Magnetogramme") zeigen ein sehr komplexes magnetisches Muster, das sich über alle räumlichen Skalen erstreckt. Während die verschiedenen Komponenten dieses Musters (einschliesslich der Sonnenflecken) unterschiedliche, begrenzte Lebensdauern haben, entwickelt sich das globale Muster in einer komplexen und nicht zufällige Art mit dem 22-jahrigen magnetischen Zyklus, welcher durch Dynamo-Prozesse im Innern der Sonne erzeugt wird.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1990 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coronal Magnetometry written by Sarah E. Gibson and published by Frontiers Media SA. This book was released on 2017-07-11 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetism defines the complex and dynamic solar corona. It determines the magnetic loop structure that dominates images of the corona, and stores the energy necessary to drive coronal eruptive phenomena and flare explosions. At great heights the corona transitions into the ever-outflowing solar wind, whose speed and three-dimensional morphology are controlled by the global coronal magnetic field. Coronal magnetism is thus at the heart of any understanding of the nature of the corona, and essential for predictive capability of how the Sun affects the Earth. Coronal magnetometry is a subject that requires a concerted effort to draw together the different strands of research happening around the world. Each method provides some information about the field, but none of them can be used to determine the full 3D field structure in the full volume of the corona. Thus, we need to combine them to understand the full picture. The purpose of this Frontiers Research Topic on Coronal Magnetometry is to provide a forum for comparing and coordinating these research methods, and for discussing future opportunities.
Download or read book Evolution of Coronal Magnetic Fields written by Julia Katharina Thalmann and published by . This book was released on 2010 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Sun to the Earth and Beyond written by National Research Council and published by National Academies Press. This book was released on 2003-12-17 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume, The Sun to the Earth-and Beyond: Panel Reports, is a compilation of the reports from five National Research Council (NRC) panels convened as part of a survey in solar and space physics for the period 2003-2013. The NRC's Space Studies Board and its Committee on Solar and Space Physics organized the study. Overall direction for the survey was provided by the Solar and Space Physics Survey Committee, whose report, The Sun to the Earth-and Beyond: A Decadal Research Strategy in Solar and Space Physics, was delivered to the study sponsors in prepublication format in August 2002. The final version of that report was published in June 2003. The panel reports provide both a detailed rationale for the survey committee's recommendations and an expansive view of the numerous opportunities that exist for a robust program of exploration in solar and space physics.
Download or read book The Evolution of Modeled Coronal Mass Ejection in the Lower Corona written by Rebekah Minnel Evans Frolov and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coronal mass ejections (CMEs) and their associated shocks are major sources of space weather. In order to forecast their impact at Earth, it is crucial to accurately model their propagation in interplanetary space. The only tool capable of treating the large scales of CME evolution is global magnetohydrodynamics (MHD) modeling. However, this approach cannot resolve the small scales on which important processes occur (such as the acceleration of the solar wind and coronal heating). The solar wind solution depends on which method is utilized to mimic these processes. And because the evolution of a CME depends crucially on its interaction with the solar wind, the CME evolution will also be connected to the heating mechanisms and drivers utilized in an MHD model. In the first part of the thesis, we show that the ad hoc approaches to coronal heating used in global MHD models leads to unphysical conditions for CME-driven shock formation in the lower corona (1-10 solar radii). We present this argument in two steps. First, we present a CME simulation in which the solar wind was accelerated and heated by reducing the value of the polytropic index (to less than the adiabatic value) in the lower corona. As it is not well understood, we do not model the CME initiation process - we utilize an out-of-equilibrium Titov-Demoulin flux rope to begin the eruption. We analyze several aspects of the CME, such as its kinematics and energy evolution, the shock formation and evolution, the plasma flows in the CME-sheath and their connection to the CME magnetic field vector, and the plasma pile-up at the front of the CME. We find that some characteristics are inconsistent with the observed properties of CMEs, and we connect these to the ad hoc treatment of the solar wind heating. Second, we use data of CME shock-accelerated solar energetic particle events to constrain the profile of the Alfven speed in the lower corona. We show that the Alfven speed profile from global MHD models with ad hoc heating is not aligned with these observations, but that local (one dimensional) models with physically-motivated Alfven wave dissipation as a heating mechanism were in agreement. In the second part of the thesis, we study the resonant absorption of surface Alfven waves (SAW), a process which heats the solar wind. It is driven by a transverse gradient in the local Alfven speed (in relation to the magnetic field direction). In the solar corona, we expect this mechanism to occur at the boundaries of open and closed magnetic fields. We make the first estimation of SAW energy dissipation in the solar corona and find that it is comparable to the ad hoc heating a polytropic model at the boundary of open and closed magnetic fields and in subpolar open field regions. Next, we implemented the SAW damping mechanism into the new solar corona component of the Space Weather Modeling Framework, in which Alfven wave energy transport is self-consistently coupled to the MHD equations. The model already included wave dissipation along open magnetic field lines, mimicking turbulence. We demonstrate that including SAW dissipation in the model improved agreement with observations of coronal temperature both near the Sun and in the inner heliosphere by comparing with data from Ulysses and the Solar Terrestrial Relations Observatory (STEREO). Also, the inclusion of SAW dissipation steepened the Alfven speed profile in the lower corona, aligning the Alfven profile better with observational constraints of shock formation. In the final part of the thesis, we modeled a CME in this newly developed solar wind background, and studied the interaction between the CME and the wind. We generate the eruption with a flux rope. We constrain the parameters of the flux rope with data from the 13 May 2005 eruption, including H-alpha images of the pre-eruption magnetic field, coronagraph images of the CME's shape and velocity. Because the flux rope traveled faster than the local magnetosonic speed, it acted as a piston and drove a shock wave ahead of it. The CME-driven shock had a strong impact on the solar wind environment through which it propagates: it altered the wave energy by concentrating it in the sheath through advection, and also increasing its value through momentum transfer. This simulation demonstrated how Alfven waves are focused into the sheaths of ICMEs. The wave energy is then dissipated at the shock due to SAW damping. The shock heating accounted for 10% of the total change in thermal energy of the CME. The resulting temperature distribution of the CME is more aligned with observations than from a CME modeled in a polytropic solar wind. This thesis has improved our understanding of the interaction between a CME and the solar wind through which it propagates. Our picture of CME-evolution in the lower corona will be tested by future missions Solar Probe (which will sample this region directly) and the Solar Orbiter.
Download or read book The Solar Corona written by Leon Golub and published by Cambridge University Press. This book was released on 2010 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: Second edition graduate level textbook giving an up-to-date treatment of our understanding of the solar corona.
Download or read book The Origin and Dynamics of Solar Magnetism written by M.J. Thompson and published by Springer Science & Business Media. This book was released on 2009-05-01 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting in 1995 numerical modeling of the Earth’s dynamo has ourished with remarkable success. Direct numerical simulation of convection-driven MHD- ow in a rotating spherical shell show magnetic elds that resemble the geomagnetic eld in many respects: they are dominated by the axial dipole of approximately the right strength, they show spatial power spectra similar to that of Earth, and the magnetic eld morphology and the temporal var- tion of the eld resembles that of the geomagnetic eld (Christensen and Wicht 2007). Some models show stochastic dipole reversals whose details agree with what has been inferred from paleomagnetic data (Glatzmaier and Roberts 1995; Kutzner and Christensen 2002; Wicht 2005). While these models represent direct numerical simulations of the fundamental MHD equations without parameterized induction effects, they do not match actual pla- tary conditions in a number of respects. Speci cally, they rotate too slowly, are much less turbulent, and use a viscosity and thermal diffusivity that is far too large in comparison to magnetic diffusivity. Because of these discrepancies, the success of geodynamo models may seem surprising. In order to better understand the extent to which the models are applicable to planetary dynamos, scaling laws that relate basic properties of the dynamo to the fundamental control parameters play an important role. In recent years rst attempts have been made to derive such scaling laws from a set of numerical simulations that span the accessible parameter space (Christensen and Tilgner 2004; Christensen and Aubert 2006).
Download or read book Global Solar Magnetic Fields written by and published by . This book was released on 1991 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The global solar magnetic field greatly affects the corona, heliosphere, and terrestrial environment as well as revealing much about the Sun itself. It may be useful to think of the global field in two ways: as an aggregate of many small scale processes and as an entity. When considering the origin and evolution of the global field, one immediately focuses on the smaller-scale features and processes that it comprises. These include the emergence of active regions, the interaction of new and existing flux patterns, the distortion and dispersal of flux over the surface by convective motions, the phenomena that produce the emergence of patterns with various periods, and the influence of convection and rotation at various depths on flux tubes. When contemplating the effects of the global field, one often focuses on it as an entity or on its large-scale features. Examples are the reversal of the polar fields, the asymmetry between the north and south hemispheres, the dipole or quadrupole structure of the coronal field and its observation at the Earth as 2 or 4 polarity sectors, and the rigid rotation seen in coronal holes. Both views help us appreciate the significance of the global field.
Download or read book Modelling Solar Coronal Magnetic Field Evolution written by Erin Elizabeth Goldstraw and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Magnetic Structures and Their Role in The Evolution of Coronal Mass Ejections written by Qiang Hu and published by Frontiers Media SA. This book was released on 2022-02-09 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:
