Download or read book Empirical Modeling of 3D Plasma Pressure and Magnetic Field Structures in the Earth s Plasma Sheet written by Chao Yue and published by . This book was released on 2015 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ions and electrons in the nightside magnetosphere, driven by the dawn-to-dusk convection electric field, flow earthward and are energized. As a result, plasma pressure is enhanced and magnetic field configuration becomes more stretched, forming the necessary conditions for the development of substorms. Determining the physical processes leading to the changes of the plasma and magnetic field configurations, as well as the processes resulting from the configuration variations, is thus crucial to understanding substorms. Accurate evaluation of these processes, including formation of field-aligned currents (FACs), isotropization by current sheet scattering, and some localized instabilities that may responsible for substorm onset, relies on knowing the realistic 3 dimensional (3D) magnetic field configurations, which cannot be provided by current available empirical models with sufficient accuracy or as a function of growth phase development. Therefore, we have developed a 3D force-balanced empirical substorm growth phase magnetic field model, which allows us to investigate the evolution of these configurations during the substorm growth phase and evaluate the physical processes governing the configuration changes. Here, we first statistically analyzed the growth phase pressures using Geotail and THEMIS data, and identified three primary factors causing the growth phase pressure change: solar wind dynamic pressure (PSW), energy loading, and sunspot number. We then constructed a 2D equatorial empirical pressure model and an error model in the near Earth plasma sheet (r 20 RE) using the Support Vector Regression Machine (SVRM) with the three factors as input. The model predicts the plasma sheet pressure accurately with median errors of 5%, and the predicted pressure gradients agree reasonably well with observed gradients obtained from two-probe measurements. The model shows that pressure increases linearly as PSW increases, while the pressure responses to energy loading and sunspot number are nonlinear. From these model pressure distributions, we were able to establish a realistic 3D growth phase magnetic field configurations that satisfy the physical constraint of force balance with the plasma pressures using a 3D magnetic field model [Zaharia, 2008]. The force-balanced magnetic field configuration shows that Bz decreases in the near Earth region and increases in the tail due to an increasing perpendicular current peaking at the earthward edge of the plasma sheet. The current peak moves towards the Earth as energy loading increases, indicating earthward penetrating of the plasma sheet. Meanwhile, positive dBz/dz is found to develop late in the growth phase, but a Bz minimum at the equator does not form, unlike the prediction by Saito et al. [2010]. The perpendicular current peaks off the equator plane and its peak moves towards the equatorial plane as the growth phase evolves, indicating the thinning of current sheet. In addition, there are typical Region-1 FACs around 12 to 20 RE at the beginning of substorm growth phase and they gradually evolve to Region-2 FACs in the late growth phase with their earthward boundary moving to smaller r. The model magnetic fields agree quantitatively well with observed fields. The magnetic field is substantially more stretched under higher PSW while the dependence on sunspot number is non-linear and less substantial. The excellent agreements between the model results and observations give us confidence that the realistic model can be used at the first time to understand the pressure and magnetic field changes observed during a substorm event by providing accurate evaluations of the effects of energy loading and PSW, as well as the temporal and spatial effects along a spacecraft trajectory. By applying our modeling to a substorm event, we found that the equatorward moving of proton aurora during the growth phase is mainly due to continuous stretching of magnetic field lines, and the ballooning instability is more favorable at late growth phase around midnight tail where there is a localized plasma beta peak. Furthermore, the equatorial mapping of the breakup auroral arc is X ~ -14 RE near midnight, coinciding with the location of the maximum growth rate for ballooning instability.
Download or read book Simulating the Interplay Between Plasma Transport Electric Field and Magnetic Field in the Near Earth Nightside Magnetosphere written by Malamati Gkioulidou and published by . This book was released on 2012 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: The convection electric field resulting from the coupling of the Earth's magnetosphere with the solar wind and interplanetary magnetic field (IMF) drives plasma in the tail plasma sheet earthward. This transport and the resulting energy storage in the near Earth plasma sheet are important for setting up the conditions that lead to major space weather disturbances, such as storms and substorms. Penetration of plasma sheet particles into the near-Earth magnetosphere in response to enhanced convection is crucial to the development of the Region 2 field-aligned current system and large-scale magnetosphere-ionosphere (M-I) coupling, which results in the shielding of the convection electric field. In addition to the electric field, plasma transport is also strongly affected by the magnetic field, which is distinctly different from dipole field in the inner plasma sheet and changes with plasma pressure in maintaining force balance. The goal of this dissertation is to investigate how the plasma transport into the inner magnetosphere is affected by the interplay between plasma, electric field and magnetic field. For this purpose, we conduct simulations using the Rice Convection Model (RCM), which self-consistently calculates the electric field resulting from M-I coupling. In order to quantitatively evaluate the interplay, we improved the RCM simulations by establishing realistic plasma sheet particle sources, by incorporating it with a modified Dungey force balance magnetic field solver (RCM-Dungey runs), and by adopting more realistic electron loss rates. We found that plasma sheet particle sources strongly affect the shielding of the convection electric field, with a hotter and more tenuous plasma sheet resulting in less shielding than a colder and denser one and thus in more earthward penetration of the plasma sheet. The Harang reversal, which is closely associated with the shielding of the convection electric field and the earthward penetration of low-energy protons, is found to be located at lower latitudes and extend more dawnward for a hotter and more tenuous plasma sheet. In comparison with simulation runs under an empirical but not force balance magnetic field from the Tsyganenko 96 model, the simulation results show that transport under force-balanced magnetic field results in weaker pressure gradients and thus weaker R2 FAC in the near-earth region, weaker shielding of the penetration electric field and, as a result, more earthward penetration of plasma sheet protons and electrons with their inner edges being closer together and more azimuthally symmetric. To evaluate the effect of electron loss rate on ionospheric conductivity, a major contributing factor to M-I coupling, we run RCM-Dungey with a more realistic, MLT dependent electron loss rate established from observed wave activity. Comparing our results with those using a strong diffusion everywhere rate, we found that under the MLT dependent loss rate, the dawn-dusk asymmetry in the precipitating electron energy fluxes agrees better with statistical DMSP observations. The more realistic loss rate is much weaker than the strong diffusion limit in the inner magnetosphere. This allows high-energy electrons in the inner magnetosphere to remain much longer and produce substantial conductivity at lower latitudes. The higher conductivity at lower latitudes under the MLT dependent loss rate results in less efficient shielding in response to an enhanced convection electric field, and thus to deeper penetration of the ion plasma sheet into the inner magnetosphere than under the strong diffusion everywhere rate.
Download or read book A Model of the Plasma Sheet in the Earth s Magnetosphere written by David Wallace Forslund and published by . This book was released on 1969 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Earth s Plasmasphere written by Fabien Darrouzet and published by Springer Science & Business Media. This book was released on 2009-08-21 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt: James L. Burch·C. Philippe Escoubet Originally published in the journal Space Science Reviews, Volume 145, Nos 1–2, 1–2. DOI: 10. 1007/s11214-009-9532-7 © Springer Science+Business Media B. V. 2009 The IMAGE and CLUSTER spacecraft have revolutionized our understanding of the inner magnetosphere and in particular the plasmasphere. Before launch, the plasmasphere was not a prime objective of the CLUSTER mission. In fact, CLUSTER might not have ever observed this region because a few years before the CLUSTER launch (at the beginning of the 1990s), it was proposed to raise the perigee of the orbit to 8 Earth radii to make multipoint measu- ments in the current disruption region in the tail. Because of ground segment constraints, this proposal did not materialize. In view of the great depth and breadth of plasmaspheric research and numerous papers published on the plasmasphere since the CLUSTER launch, this choice certainly was a judicious one. The fact that the plasmasphere was one of the prime targets in the inner magnetosphere for IMAGE provided a unique opportunity to make great strides using the new and comp- mentary measurements of the two missions. IMAGE, with sensitive EUV cameras, could for the rst time make global images of the plasmasphere and show its great variability d- ing storm-time. CLUSTER, with four-spacecraft, could analyze in situ spatial and temporal structures at the plasmapause that are particularly important in such a dynamic system.
Download or read book Physical Limitations of Empirical Field Models written by Sorin Gabriel Zaharia and published by . This book was released on 2002 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Mosaic Structure of Plasma Bulk Flows in the Earth s Magnetotail written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-13 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Moments of plasma distributions observed in the magnetotail vary with different time scales. In this paper we attempt to explain the observed variability on intermediate timescales of approximately 10-20 min that result from the simultaneous energization and spatial structuring of solar wind plasma in the distant magnetotail. These processes stimulate the formation of a system of spatially disjointed. highly accelerated filaments (beamlets) in the tail. We use the results from large-scale kinetic modeling of magnetotail formation from a plasma mantle source to calculate moments of ion distribution functions throughout the tail. Statistical restrictions related to the limited number of particles in our system naturally reduce the spatial resolution of our results, but we show that our model is valid on intermediate spatial scales Delta(x) x Delta(z) equal to approximately 1 R(sub E) x 1000 km. For these spatial scales the resulting pattern, which resembles a mosaic, appears to be quite variable. The complexity of the pattern is related to the spatial interference between beamlets accelerated at various locations within the distant tail which mirror in the strong near-Earth magnetic field. Global motion of the magnetotail results in the displacement of spacecraft with respect to this mosaic pattern and can produce variations in all of the moments (especially the x-component of the bulk velocity) on intermediate timescales. The results obtained enable us to view the magnetotail plasma as consisting of two different populations: a tailward-Earthward system of highly accelerated beamlets interfering with each other, and an energized quasithermal population which gradually builds as the Earth is approached. In the near-Earth tail, these populations merge into a hot quasi-isotropic ion population typical of the near-Earth plasma sheet. The transformation of plasma sheet boundary layer (PSBL) beam energy into central plasma sheet (CPS) quasi-thermal energy occurs in the abs...
Download or read book Modeling Magnetospheric Plasma Processes written by Gordon R. Wilson and published by American Geophysical Union. This book was released on 1991-01-08 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 62. The ultimate goal of modeling of the plasma in Earth's environment is an understanding of the magnetosphere and ionosphere as a coupled global system. To achieve this goal requires a coordinated effort between models applied to different spatial scales. The desire to model this system on a global scale is leading to models which encompass larger and larger regions. The ever-increasing availability of computing resources has allowed models to expand to 2 and 3 dimensions. At the other extreme are the micro-scale processes which transfer energy to individual particles within the global system. As more detailed observations become available the necessity for accurately including such processes in the global models becomes more apparent. Then it becomes a question of how to incorporate the necessary physical processes from all scale sizes into a model of a global system. It now seems clear that such multi-scale scenarios exist where micro-scale processes provide energy to the plasma which flows outward from Earth into the distant magnetotail before returning to the near-Earth regions. The challenge of incorporating all relevant processes into a model of this entire plasma path is a formidable one. The existence of separate models of the separate steps along this pathway leads directly to efforts to fuse models with different scales into a single, self-consistent treatment.
Download or read book 3 D Force balanced Magnetospheric Configurations written by Sorin Gabriel Zaharia and published by . This book was released on 2003 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Hybrid Multiscale Simulation Technology written by Alexander S. Lipatov and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive description of hybrid plasma simulation models providing a very useful summary and guide to the vast literature on this topic.
Download or read book Comparative Studies of Multi scale Convective Transport Through the Earth s Plasma Sheet written by Timothy Bryan Guild and published by . This book was released on 2007 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In this dissertation we explore multi-scale, convective transport through the Earth's plasma sheet using in situ observations and global terrestrial magnetospheric simulations. We statistically test the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model with observations from the Geotail spacecraft at a variety of spatial and temporal scales within the plasma sheet. These comparisons, in addition to quantifying the LFM range of validity, illuminate model shortcomings and highlight the additional physics necessary to resolve data/model discrepancies. First, we perform the first ever comprehensive validation of the LFM in the plasma sheet. We show that the LFM largely reproduces global, long-term average plasma sheet properties and variability, but we also identify and characterize its systematic deficiencies. We find that the LFM overestimates the average plasma sheet velocity, and show that a portion of this overestimate is reflected in excessive LFM ionospheric transpolar potential (15%), and a portion of it is due to insufficient simulation resolution (15%). By characterizing the LFM plasma sheet velocity distribution as a function of simulation resolution, we find that increased resolution inherently changes the nature of the dynamics and transport within the LFM plasma sheet, bringing it into closer agreement with magnetotail observations containing fast, localized bulk flows. To perform the data/model comparisons described thus far, we construct one of the largest central plasma sheet data set of Geotail observations to date. Using this comprehensive data set, we investigate the equatorial distributions of fast, convective flows and infer that the Earthward extent of the average neutral line, the most likely location of near-Earth reconnection, is convex relative to the Earth and offset toward dusk. Due to the importance of these fast flows to mass, momentum, and energy transport in both the observed and simulated plasma sheets, we use the LFM to establish that locally-reconnecting magnetic lobe field lines initiate simulated "flow channels", explore the instability governing their subsequent evolution, and examine their similarity to observations of bursty bulk flows. This dissertation demonstrates the fruitful augmentation of sparse, statistical plasma sheet data sets with global MHD models, thereby enabling further exploration of the multi-scale nature of convective transport within the global, time-dependent plasma sheet.
Download or read book Plasma Behavior in a Romac Magnetic Field written by L. S. Combes and published by . This book was released on 1962 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A PLASMA CONTAINMENT DEVICE ENTITLED ROMAC (ROTATED MAGNETIC CUSP) WASCONSTRUCTED. AN ATTEMPT WAS MADE TO COMBINE THE BASIC STABILITY ADVANTAGES OF FOUR-POLE LINE CUSP WITH THE LOW LOSS RATE OF A MORROR FIELD. THE MAGNETIC FIELD FOR ROMAC WAS PRODUCED BY ADDING A MIRROR FIELD ORTHONGONALLY TO THE CUSP FIELD. USING PULSE TECHNIQUES AN IONIZED GAS WAS CREATED WITHIN A BICONICAL CHAMBER AND THE ROMAC MAGNETIC FIELD PRODUCED TRANSIENTLY WITH THE MIRROR FIELD ALONG THE AXIS OF THE CHAMBER(Z AXIS) AND THE CUSP FIELD IN THE X-Y PLANE. MEASUREMENTS WITH MAGNETIC PROBES AND LIGHT PIPES SHOW THAT A DISTURBANCE IN THE MAGNETIC FIELD, ACCOMPANIED BY AN INCREASE IN LIGHT INTENSITY, STARTED AT THE PERIPHERY OF THE PLASMA CHAMBER AND WAS PROPAGATED INWARD AT TWO VELOCITIES TO THE CENTRAL AXIS. DETAILED MEASUREMENTS WERE MADE ON THE MAGNETIC FIELD CONFIGURATION. THESE INDICATE THAT, AT THE TIME THE SECOND WAVE ARRIVED AT THE AXIS, THE MIRROR HIELD HAD BEEN TO A LARGE EXTENT SEPARATED FROM THE CUSP FIELD SO THAT MOSTLY MIRROR FIELD EXISTED THROUGHOUT THE CENTRAL REGION, WHILE MOSTLY CUSP FIELD EXISTED IN THE OUTER REGION. THE INTENSITY OF THE FIELD AT THIS TIME IN THE CENTRAL REGION INDICATES THAT THE CUSP FIELD WAS COMPRESSING THE PLASMA AND MIRRORFIELD IN THIS REGION WERE EVEN LARGER THAN THE MAXIMUM INTENSITY OF THE APPLIED MIRROR FIELD.
Download or read book Frontiers in Magnetospheric Plasma Physics written by and published by Elsevier. This book was released on 2004-12-14 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: This COSPAR Colloquium Series deals with the main achievements that were accomplished through the collaborative efforts among ISTP participants; the plasma dynamics of magnetic reconnection in a thin plasma sheet, the action of the solar wind on the plasma population in the plasma sheet and around the magnetotail boundary layer, the relationship between the substrom expansion region and the X-line formation in the magnetotail, and the temporal evolution of the dipolarization from from the near-Earth to the distant tail.
Download or read book Particle Dynamics in the Plasma Sheet written by John S. Wagner and published by . This book was released on 1978 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract.
Download or read book Modeling the Inner Plasma Sheet Protons and the Magnetic Field written by Chih-Ping Wang and published by . This book was released on 2002 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of the Compression of Magnetized Plasma and Magnetic Flux written by Dimitry Mikitchuk and published by Springer. This book was released on 2019-06-28 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present research studies the fundamental physics occurring during the magnetic flux and magnetized plasma compression by plasma implosion. This subject is relevant to numerous studies in laboratory and space plasmas. Recently, it has attracted particular interest due to the advances in producing high-energy-density plasmas in fusion-oriented experiments, based on the approach of magnetized plasma compression. The studied configuration consists of a cylindrical gas-puff shell with pre-embedded axial magnetic field that pre-fills the anode-cathode gap. Subsequently, axial pulsed current is driven through the plasma generating an azimuthal magnetic field that compresses the plasma and the axial magnetic field embedded in it. A key parameter for the understanding of the physics occurring during the magnetized plasma compression is the evolution and distribution of the axial and azimuthal magnetic fields. Here, for the first time ever, both fields are measured simultaneously employing non-invasive spectroscopic methods that are based on the polarization properties of the Zeeman effect. These measurements reveal unexpected results of the current distribution and the nature of the equilibrium between the axial and azimuthal fields. These observations show that a large part of the current does not flow in the imploding plasma, rather it flows through a low-density plasma residing at large radii. The development of a force-free current configuration is suggested to explain this phenomenon. Previously unpredicted observations in higher-power imploding-magnetized-plasma experiments, including recent unexplained structures observed in the Magnetized Liner Inertial Fusion experiment, may be connected to the present discovery.
Download or read book Energy Transfer and Dissipation in Plasma Turbulence written by Yan Yang and published by Springer. This book was released on 2019-05-02 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book revisits the long-standing puzzle of cross-scale energy transfer and dissipation in plasma turbulence and introduces new perspectives based on both magnetohydrodynamic (MHD) and Vlasov models. The classical energy cascade scenario is key in explaining the heating of corona and solar wind. By employing a high-resolution hybrid (compact finite difference & WENO) scheme, the book studies the features of compressible MHD cascade in detail, for example, in order to approximate a real plasma cascade as “Kolmogorov-like” and to understand features that go beyond the usual simplified theories based on incompressible models. When approaching kinetic scales where plasma effects must be considered, it uses an elementary analysis of the Vlasov–Maxwell equations to help identify the channels through which energy transfer must be dissipated. In addition, it shows that the pressure–strain interaction is of great significance in producing internal energy. This analysis, in contrast to many other recent studies, does not make assumptions about wave-modes, instability or other specific mechanisms responsible for the dynamics – the results are direct consequences of the Vlasov–Maxwell system of equations. This is an important step toward understanding dissipation in turbulent collisionless plasma in space and astrophysics.
