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The topics addressed are: (1) generalized semikinetic models; (2) collision-collisionless transition model; (3) observation of O+ outflows; (4) equatorial transitions; (5) inner plasmasphere-ionosphere coupling; (6) plasma wave physical processes; (7) ULF wave ray-tracing; and (8) nighttime anomalous electron heating events.
Episodic overturn of the south polar terrain on Enceladus would convey radio lytic oxidants from surface irradiation by Saturn's inner magnetospheric electrons to the putative underlying polar sea and contribute to CO2 and other gas production driving the visibly active cryovolcanism. Low duty cycle of active episodes below 1 - 10 percent would raise the relative importance of the continuous radiolytic chemical energy input for mass and heat outflow, e.g. as compared to heating by gravitational tides. The "Pac-Man" thermal anomaly on Mimas most likely arises from leading-trailing asymmetry of electron irradiation and resultant radio lytic processing of the moon ice to a few centimeters of depth. The Mimas thermal anomaly distribution suggests a relatively stable surface unmodified by Enceladus-like geologic overturn or cryovolcanic activity. In both cases, the heavily irradiated skin depth corresponds to the sensible thermal layer probed by Cassini infrared measurements. Neutral gas and dust emissions from Enceladus limit energetic ion and plasma electron fluxes in the inner magnetosphere, thereby governing the irradiation of Mimas and other Saturn moons.
As a result of natural processes, plasma clouds are often injected into the magnetosphere. These chemical releases can be used to study many aspects of such injections. When a dense plasma is injected into the inner magnetosphere, it is expected to take up the motion of the ambient plasma. However, it has been observed in previous releases at moderate altitudes that the cloud preserved its momentum for some time following the release and that parts of the cloud peeled off from the main cloud presumable due to the action of an instability. As one moves outward into the magnetosphere, the mirror force becomes less dominant and the initial conditions following a release are dominated by the formation of a diamagnetic cavity since the initial plasma pressure from the injected Ba ions is greater than the magnetic field energy density. A previous high-altitude release (31,300 km) showed this to be the case initially, but at later times there was evidence for acceleration of the Ba plasma to velocities corresponding to 60,000 K. This effect is not explained. This series of experiments is therefore designed to inject plasma clouds into the magnetosphere under widely varying conditions of magnetic field strength and ambient plasma density. In this way the coupling of injected clouds to the ambient plasma and magnetic field, the formation of striations due to instabilities, and possible heating and acceleration of the injected Ba plasma can be studied over a wide range of magnetosphere parameters. Adding to the scientific yield will be the availability of measurements for the DOD/SPACERAD instruments which can monitor plasma parameters, electric and magnetic fields, and waves before, during and after the releases.
The Geotail satellite mission is a cooperative venture of NASA and ISAS of Japan for exploration of the magnetotail region of the earth's magnetosphere. Geotail will deepen understanding into fundamental processes, such as those of energy transfer from the solar wind to the magnetosphere, magnetotail particle acceleration, tail energy release onset, the transport of particles between the tail and the inner magnetosphere, the bow shock, and wave-particle interactions. Attention is given to both Geotail spacecraft and mission design.
Through the analysis of a combination of CRRES satellite measurements and ground-based measurements, an empirical scenario was developed for the onset of substorms. The process develops from ripples at the inner edge of the plasma sheet associated with dusk to dawn excursions of the electric field, prior to the beginning of dipolarization. The importance of Poynting flux is considered. Substorms develop when significant amounts of energy flow in both directions with the second cycle stronger than the initial cycle. Pseudobreakups occur when the energy flowing in both directions is weak or out of phase. The observations indicate that the dusk to dawn excursions of the cross-tail electric field correlate with changes in currents and particle energies observed by CRRES, and with ultra low frequency wave activity observed on the ground. Magnetic signatures of field aligned current filaments, associated with the substorm current wedge were observed to be initiated by the process.
Ionospheric outflow plays an important role in coupling the ionosphere with the solar wind-magnetosphere system. Previous multi-fluid MHD studies explored the global influence of oxygen ions of ionospheric origin (O+) on magnetospheric dynamics. A detailed exploration of the interaction of ionospheric ions with the magnetotail requires kinetic treatment for ions. We perform a self-consistent investigation of these processes with a three-dimensional space-time adaptive hybrid code, HYPERS, powered by an intelligent Event-driven Multi-Agent Planning System (EMAPS). By comparing simulations with and without outflow we conclude that oxygen ions, flowing from the ionosphere through the lobes into the tail or directly entering the inner magnetosphere, are able to significantly modify the magnetotail configuration and induce X-points and current sheet structures at locations where magnetic reconnection does not occur in a simulation without outflow, potentially very close to the Earth. This finding may have implications for interpreting substorms and magnetotail reconnection events observed for southward magnetic field simultaneously with significant contents of oxygen ions of ionospheric origin.
During geomagnetic storms and substorms, the magnetosphere and ionosphere are strongly coupled by precipitating magnetospheric electrons from the Earth's plasma sheet and driven by both magnetospheric and ionospheric processes. Magnetospheric wave activity initiates electron precipitation, and the ionosphere and upper atmosphere further facilitate this process by enhancing the value of precipitated energy uxes via connection of two magnetically conjugate regions and multiple atmospheric reections. This paper focuses on the resulting electron energy uxes and afliated heightintegrated Pedersen and Hall conductances in the auroral regions produced by multiple atmospheric reections during the 17 March 2013 geomagnetic storm and their effects on the inner magnetospheric electric eld and ring current. Our study is based on the magnetically and electrically selfconsistent Rice ConvectionModelEquilibrium of the inner magnetosphere with SuperThermal Electron Transport modied electron energy uxes that take into account the electron energy interplay between the two magnetically conjugate ionospheres. SuperThermal Electron Transportmodied energy ux in the Rice ConvectionModelEquilibrium leads to a signicant difference in the global conductance pattern, ionospheric electric eld formation, Birkeland current structure, ring current energization and its energy content, subauroral polarization drifts intensications and their spatial locations, interchange instability redistribution, and overall energy interplay on the global scale.
The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than 0.63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O(+) flux and a large part of the H(+) flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.
The transport of ions from the polar ionosphere to the inner magnetosphere during storm time conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the rate of energization of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than .63 eV) the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4-8), with measurements made with the ISEE 1 satellite during a storm. This O(+) flux and a large part of the H(+) flux appear to be consistent with the DE-1 and DE-2 satellite measurements of the polar ionospheric outflow during disturbed times.
This document is a final report on research activities and accomplishments that occurred during the funding period of 10-1-90 through 1-30-94. The focus of our interdisciplinary investigation during the Dynamics Explorer Mission was on the complex coupling processes that tap the magnetic-storm energy, stored in the ring current particle reservoir, and transport this energy into the subauroral, midlatitude and even equatorial ionospheric regions. The transport of energy through the inner magnetosphere and into the underlying ionospheric regions is a critical element in our understanding of the impact of solar and magnetic disturbances on upper atmospheric and ionospheric regions equatorward of the auroral zone.
An overview is presented of the hot plasmas and energetic (not less than 20 keV) particles observed in the vicinity of Neptune by the Low Energy Charged Particle (LECP) experiment aboard the Voyager 2 spacecraft. The LECP findings are presented on the shock, the magnetosheath, the magnetopause, and the cusp of the Neptune's magnetosphere; the middle magnetosphere; the inner magnetosphere and material interactions; the magnetotail and the substorms; and the characteristics of Triton's plasma. It is shown that, in sharp contrast to the Uranian magnetotail, the Neptunian magnetotail shows no evidence of substorm processes.
A description is presented of theory and models, taking into account magnetospheric dynamo processes, magnetospheric topology of fields and currents, a new theory of sources of Birkeland currents, dielectric and permeability effects in collisionless plasmas, field-aligned current sheets as tangential and rotational discontinuities, electrodynamics of convection in the inner magnetosphere, coupling of Birkeland current rings, region one Birkeland currents connecting to sunward convecting flux tubes, and corrected geomagnetic coordinates for epoch 1980. Other topics explored are related to early history, an introduction to magnetospheric currents, surface observations, near-space observations, distant space observations, ionospheric effects, plasma instabilities, and current systems in other magnetospheres. Attention is given to the dynamics of field-aligned current sources at earth and Jupiter, fundamentals of current description, polar cap current systems, electric fields and currents associated with active aurora, and the role of currents in plasma redistribution.
Laboratory data and models of sputter-induced erosion and chemical alterations in ice films are reviewed and the results are applied to icy grains and satellites exposed to magnetospheric ion bombardment. It is shown that the source of the plasma in the inner magnetosphere of Saturn is likely to be the sputter erosion of the icy objects in this region and the sputter erosion and possible stabilization of the E-ring are considered. Ion-induced polymerization is discussed as a source of the darkened rings of Uranus.
Geotail was launched on 24 July 1992 as the first new spacecraft of the International Solar Terrestrial Physics Program (ISTP). A primary objective of the Geotail mission is the acquisition of particles and fields measurements in the tail region of the magnetosphere. Some of the specific scientific objectives of the Geotail mission are; (1) assessment of the relative importance of solar-wind and ionospheric sources to the plasmas of the magnetotail, (2) a search for plasmoids and flux ropes, (3) direct observation of the effects of plasma acceleration and heating in the current sheet, and (4) measurements of currents and convective flows carried by magnetotail plasmas. The Comprehensive Plasma Instrumentation (CPI) aboard the Geotail spacecraft provides observations of the charged particles that comprise the plasma populations of the magnetosphere and the solar wind. In many cases the physical processes that contribute to the flow of energy and mass through the Solar-Terrestrial plasma system can be understood only through a detailed examination and analysis of the distribution of the particle velocities in the ambient plasmas. The CPI provides detailed measurements of these distributions. It employs three plasma analyzers: (1) the Hot Plasma analyzer (CPI-HP) for hot electrons and ions found in the plasma sheet and the inner magnetosphere; (2) a Solar Wind analyzer (CPI-SW) for cool plasmas with high bulk speeds such as those found in the solar wind and magnetosheath; and (3) an Ion Composition analyzer (CPI-IC) for identification of ion species such as H(+), He(+), He(++), and O(+). Along with measurements from other fields and particles instrumentation on Geotail, the CPI measurements provide a fundamental experimental base for investigations of solar-terrestrial plasmas and fields.
The Echo program's use of large sounding rockets to inject electron beams into the outer trapping region where the earth's plasma sheet interacts with the inner magnetosphere is discussed. The beams pass through the plasma sheet and the trapping region, reflect at the southern hemisphere conjugate point and return to the vicinity of the rocket where they are detected and analyzed for acceleration and diffusion processes which may also be responsible for the radiation belts. The motion of electron beams in the magnetosphere is discussed from the standpoint of single particle motion, and the trajectories of electrons injected with known energy, known angle between the electron velocity vector and the local magnetic field vector, and known position are examined. The interaction between the rocket motion and the electron drift motion is described, and the advantages and drawbacks of beam detection by optical methods and by throwaway detectors are compared. Planned Echo experiments using the Space Shuttle are discussed
Coupling of source, transport, and sink processes produces a fairly accurate model for the macroscopic structure and dynamics of magnetospheric electrons. Auroral electrons are controlled by convective transport from a plasma sheet source coupled with a precipitation loss due to whistler and electrostatic plasma turbulence. Outer and inner zone electrons are governed by radial diffusion transport from convection and acceleration sources external to the plasmapause and by parasitic precipitation losses arising from cyclotron and Landau interactions with whistler and ion cyclotron turbulence.
Magnetosphere-Ionosphere (MI) coupling and associated with this process electron and ion energization processes have interested scientists for decades and, in spite of experimental and theoretical research efforts, are still ones of the least well known dynamic processes in space plasma physics. The reason for this is that the numerous physical processes associated with MI coupling occur over multiple spatial lengths and temporal scales. One typical example of MI coupling is large scale ring current (RC) electrodynamic coupling that includes calculation of the magnetospheric electric field that is consistent with the ring current (RC) distribution. A general scheme for numerical simulation of such large-scale magnetosphere-ionosphere coupling processes has been presented earlier in many works. The mathematical formulation of these models are based on "modified frozen-in flux theorem" for an ensemble of adiabatically drifting particles in the magnetosphere. By tracking the flow of particles through the inner magnetosphere, the bounce-averaged phase space density of the hot ions and electrons can be reconstructed and the magnetospheric electric field can be calculated such that it is consistent with the particle distribution in the magnetosphere. The new a self-consistent ring current model has been developed that couples electron and ion magnetospheric dynamics with calculation of electric field. Two new features were taken into account in addition to the RC ions, we solve an electron kinetic equation in our model, self-consistently including these results in the solution. Second, using different analytical relationships, we calculate the height integrated ionospheric conductances as the function of precipitated high energy magnetospheric electrons and ions as produced by our model. This results in fundamental changes to the electric potential pattern in the inner magnetosphere, with a smaller Alfven boundary than previous potential formulations would predict but one consistent with recent satellite observations. This leads to deeper penetration of the plasma sheet ions and electrons into the inner magnetosphere and more effective ring current ions and electron energization.
This grant funded several studies of magnetospheric substorms and their effect on the dynamics of the earth's geomagnetic tail. We completed an extensive study of plasmoids, plasma/magnetic field structures that travel rapidly down the tail, using data from the ISEE 3 and IMP 8 spacecraft. This study formed the PhD thesis of Mark Moldwin. We found that magnetically plasmoids are better described as flux-ropes (twisted magnetic flux tubes) rather than plasma bubbles, as had been generally regarded up to that point (Moldwin and Hughes, 1990; 1991). We published several examples of plasmoids observed first in the near tail by IMP 8 and later in the distant tail by ISEE 3, confirming their velocities down tail. We showed how the passage of plasmoids distorts the plasma sheet. We completed the first extensive statistical survey of plasmoids that showed how plasmoids evolve as they move down tail from their formation around 30 RE to ISEE 3 apogee at 240 RE. We established a one-to-one correspondence between the observation of plasmoids in the distant tail and substorm onsets at earth or in the near tail. And we showed that there is a class of plasmoid-like structures that move slowly earthward, especially following weak substorms during northward IMF. Collectively this work constituted the most extensive study of plasmoids prior to the work that has now been done with the GEOTAIL spacecraft. Following our work on plasmoids, we turned our attention to signatures of substorm onset observed in the inner magnetosphere near geosynchronous orbit, especially signatures observed by the CRRES satellite. Using data from the magnetometer, electric field probe, plasma wave instrument, and low energy plasma instrument on CRRES we were able to better document substorm onsets in the inner magnetosphere than had been possible previously. Detailed calculation of the Poynting flux showed energy exchange between the magnetosphere and ionosphere, and a short burst of tailward convective flow just prior to onset, suggesting the active role of the ionosphere in the onset process, and adding credibility to the ballooning instability theory of substorm onset. This grant also supported a number of other substorm studies and reviews. These are represented by the list of publications and meeting presentations resulting out of this grant.