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Author: Oliver J. Brambles Publisher: ISBN: Category : Languages : en Pages : 354
Book Description
The ionosphere is an important source of plasma in the magnetosphere, especially during geomagnetic storms. While satellite data has confirmed this population of ions, their effect on the dynamics of the magnetosphere-ionosphere (MI) system is not well understood. Global simulations play an important role in the understanding of geospace and allow the response of the MI system to ionospheric ions to be systematically investigated. This thesis focuses on the effect of ionospheric outflow on the strength and mode of magnetospheric convection. Models for transversely accelerated O+ outflow are implemented into a multifluid adaptation of the Lyon-Fedder-Mobarry (LFM) global simulation using empirical relationships which relate downward electromagnetic and particle power to an upwards flux of O+ ions. The effect of a cusp O+ ouflow on the strength of magnetospheric convection, as measured by the cross polar cap potential (CPCP), is examined for a moderate geomagnetic storm. The response of the CPCP to the O+ outflow is found to depend upon two competing factors. The reduction in ionospheric conductance when outflow is present increases the CPCP and the inflation of the magnetosphere due to an O+-enhanced ring current decreases the CPCP. Through controlled global simulations of geopsace it is shown that ionospheric O+ ions can generate 2-4 hour, planetary-scale, sawtooth oscillations. If the outflow fluence is above a threshold, convection transitions from a quasi-steady mode to the quasi-periodic sawtooth mode. The O+ ions promote sawtooth oscillations by reducing the nightside reconnection potential, which results in the increase of open flux to an unstable level, and by generating an outward force balance in the plasma sheet, which stretches the nightside field lines and facilitates plasmoid formation. This behavior has not previously been captured by a global simulation and represents a major breakthrough in the understanding of the dynamics of convection in the magnetosphere.
Author: Oliver J. Brambles Publisher: ISBN: Category : Languages : en Pages : 354
Book Description
The ionosphere is an important source of plasma in the magnetosphere, especially during geomagnetic storms. While satellite data has confirmed this population of ions, their effect on the dynamics of the magnetosphere-ionosphere (MI) system is not well understood. Global simulations play an important role in the understanding of geospace and allow the response of the MI system to ionospheric ions to be systematically investigated. This thesis focuses on the effect of ionospheric outflow on the strength and mode of magnetospheric convection. Models for transversely accelerated O+ outflow are implemented into a multifluid adaptation of the Lyon-Fedder-Mobarry (LFM) global simulation using empirical relationships which relate downward electromagnetic and particle power to an upwards flux of O+ ions. The effect of a cusp O+ ouflow on the strength of magnetospheric convection, as measured by the cross polar cap potential (CPCP), is examined for a moderate geomagnetic storm. The response of the CPCP to the O+ outflow is found to depend upon two competing factors. The reduction in ionospheric conductance when outflow is present increases the CPCP and the inflation of the magnetosphere due to an O+-enhanced ring current decreases the CPCP. Through controlled global simulations of geopsace it is shown that ionospheric O+ ions can generate 2-4 hour, planetary-scale, sawtooth oscillations. If the outflow fluence is above a threshold, convection transitions from a quasi-steady mode to the quasi-periodic sawtooth mode. The O+ ions promote sawtooth oscillations by reducing the nightside reconnection potential, which results in the increase of open flux to an unstable level, and by generating an outward force balance in the plasma sheet, which stretches the nightside field lines and facilitates plasmoid formation. This behavior has not previously been captured by a global simulation and represents a major breakthrough in the understanding of the dynamics of convection in the magnetosphere.
Author: Chao Huang Publisher: John Wiley & Sons ISBN: 1119507553 Category : Science Languages : en Pages : 47
Book Description
A comprehensive review of global ionospheric research from the polar caps to equatorial regions It's more than a century since scientists first identified the ionosphere, the layer of the Earth’s upper atmosphere that is ionized by solar and cosmic radiation. Our understanding of this dynamic part of the near-Earth space environment has greatly advanced in recent years thanks to new observational technologies, improved numerical models, and powerful computing capabilities. Ionosphere Dynamics and Applications provides a comprehensive overview of historic developments, recent advances, and future directions in ionospheric research. Volume highlights include: Behavior of the ionosphere in different regions from the poles to the equator Distinct characteristics of the high-, mid-, and low-latitude ionosphere Observational results from ground- and space-based instruments Ionospheric impacts on radio signals and satellite operations How earthquakes and tsunamis on Earth cause disturbances in the ionosphere The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about the Space Physics and Aeronomy collection in this Q&A with the Editors in Chief
Author: Katherine Garcia-Sage Publisher: ISBN: Category : Languages : en Pages : 280
Book Description
Abstract: During geomagnetically active times, ionospheric O + can contribute a significant fraction of the magnetospheric mass and energy densities. The global response of Earth's magnetosphere to the presence of ionospheric oxygen is still largely unknown and impossible to examine fully with in situ , single point satellite measurements. Global magnetohydrodynamic (MHD) models provide a picture of this large-scale response to ionospheric outflow. The goal of this dissertation is to examine the behavior and effects of outflowing oxygen in a multi-fluid MHD model by determining (1) how O + outflow from different regions of the ionosphere contributes to plasma sheet populations and (2) the effect of these oxygen populations on convection and global magnetospheric structure. I implement two empirical outflow models at the inner boundary of the recently-developed Multi-Fluid Lyon-Fedder-Mobarry MHD code and examine the response of the model to various outflow conditions. A model based on data from the Akebono spacecraft (Ebihara et al. , 2006) provides a low-energy polar and auroral region outflow, whereas a model based on data from the FAST spacecraft (Strangeway et al. , 2005) provides higher-energy outflow confined to the auroral regions. Using the Akebono model outflow, I show that both centrifugal acceleration and pressure gradients accelerate thermal O+ along the magnetic field into the plasma sheet and downtail into the solar wind. I examine O+ and H + plasma sheet populations for different outflow and solar wind conditions. To account for observed densities, nightside outflows must be augmented by polar wind, cusp outflows, or both. O+ outflow in general, and nightside outflow in particular, loads the plasma sheet with O + , inflating the plasma sheet, increasing the width of the tail and distance to the tail x-line, and reducing cross polar cap potential (CPCP). These effects are shown to relate to the width of the magnetosheath, indicating that the reduction in CPCP may be due to changes in the bow shock and magnetosheath that divert the solar wind around the magnetosphere. Finally, I show that during a realistic substorm simulation, the timing and strength of substorms are changed by a global O + outflow.
Author: W. J. Raitt Publisher: ISBN: Category : Languages : en Pages : 88
Book Description
The report surveys theoretical and experimental studies of ionospheric dynamics made during the contract period. Two major aspects of this topic were studied; the outflow of He (+) from the earth's ionosphere, and the effect of magnetospheric convection on the high latitude ionosphere. Model programs were written to study the general characteristics of the outflow of He(+) and also to make quantitative estimates of the escape flux of this ion. An existing model program for studying the effect of convection electric field on the F-region was updated and the N(+) ion was included in the model. Initial work was started to incorporate realistic convection trajectories in the model program. Experimental data from the S3-2 satellite was used to compare with theoretical predictions of both the variation of plasma density with perpendicular electric field and the onset of light ion outflow at high latitudes. While the light ion outflow showed good agreement with theory, the effects of perpendicular electric fields did not and provided further stimulus to incorporate the effect of convection trajectories in our ionospheric models. (Author).
Author: Yukitoshi Nishimura Publisher: Elsevier ISBN: 0128213736 Category : Science Languages : en Pages : 566
Book Description
Cross-Scale Coupling and Energy Transfer in the Magnetosphere-Ionosphere-Thermosphere System provides a systematic understanding of Magnetosphere-Ionosphere-Thermosphere dynamics. Cross-scale coupling has become increasingly important in the Space Physics community. Although large-scale processes can specify the averaged state of the system reasonably well, they cannot accurately describe localized and rapidly varying structures in space in actual events. Such localized and variable structures can be as intense as the large-scale features. This book covers observations on quantifying coupling and energetics and simulation on evaluating impacts of cross-scale processes. It includes an in-depth review and summary of the current status of multi-scale coupling processes, fundamental physics, and concise illustrations and plots that are usable in tutorial presentations and classrooms. Organized by physical quantities in the system, Cross-Scale Coupling and Energy Transfer in the Magnetosphere-Ionosphere-Thermosphere System reviews recent advances in cross-scale coupling and energy transfer processes, making it an important resource for space physicists and researchers working on the magnetosphere, ionosphere, and thermosphere. Describes frontier science and major science around M-I-T coupling, allowing for foundational understanding of this emerging field in space physics Reviews recent and key findings in the cutting-edge of the science Discusses open questions and pathways for understanding how the field is evolving
Author: William J. Burke Publisher: ISBN: Category : Atmospheric models Languages : en Pages : 84
Book Description
This report provides an introductory overview of electrodynamic interactions between the magnetosphere and ionosphere. In the first half of the paper, the viscous interaction and magnetic merging models for driving convection are described. The notion of adiabatic heating as a natural consequence of convection is introduced, in conjunction with a quasi-empirical model for the magnetospheric potential. The second half of the paper concerns observations of electrodynamic quantities taken in the topside ionosphere in the polar cap and auroral oval.
Author: Michael Mendillo Publisher: ISBN: Category : AD0766426 (from http://www.dtic.mil) Languages : en Pages : 30
Book Description
A simplified approach is used to obtain analytical expressions for the ionospheric drifts in three dimensions which would result from a spatially uniform and temporally constant magnetospheric dawn-dusk electric field. The resultant vector product E x B convection velocities of F-region heights agree in general character with the few measurements available from Thomson scatter drift experiments carried out during geomagnetically disturbed conditions. (Author).
Author: Romain Maggiolo Publisher: John Wiley & Sons ISBN: 1119507529 Category : Science Languages : de Pages : 61
Book Description
An overview of current knowledge and future research directions in magnetospheric physics In the six decades since the term 'magnetosphere' was first introduced, much has been theorized and discovered about the magnetized space surrounding each of the bodies in our solar system. Each magnetosphere is unique yet behaves according to universal physical processes. Magnetospheres in the Solar System brings together contributions from experimentalists, theoreticians, and numerical modelers to present an overview of diverse magnetospheres, from the mini-magnetospheres of Mercury to the giant planetary magnetospheres of Jupiter and Saturn. Volume highlights include: Concise history of magnetospheres, basic principles, and equations Overview of the fundamental processes that govern magnetospheric physics Tools and techniques used to investigate magnetospheric processes Special focus on Earth’s magnetosphere and its dynamics Coverage of planetary magnetic fields and magnetospheres throughout the solar system Identification of future research directions in magnetospheric physics The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about the Space Physics and Aeronomy collection in this Q&A with the Editors in Chief
Author: Mioara Mandea Publisher: Cambridge University Press ISBN: 1108418481 Category : Science Languages : en Pages : 347
Book Description
An interdisciplinary review of research in geomagnetism, aeronomy and space weather, written by eminent researchers from these fields.
Author: National Research Council Publisher: National Academies Press ISBN: 0309313953 Category : Science Languages : en Pages : 37
Book Description
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.
Author: Oliver J. Brambles
Author: Oliver J. Brambles
Author: Chao Huang
Author: Katherine Garcia-Sage
Author: W. J. Raitt
Author: Yukitoshi Nishimura
Author: William J. Burke
Author: Michael Mendillo
Author: Romain Maggiolo
Author: Mioara Mandea
Author: National Research Council