Coherent nonlinear effects on electromagnetic wave-particle interactions

In many particle simulations and space experiments, the knowledge of nonlinear characteristics of both waves and particles in plasmas is very helpful in the data analysis phase. Such knowledge is needed even more in the designing phase of appropriate diagnostics and probings in both simulations and space experiments. In this tutorial lecture, I will attempt to provide a basic introduction to the fundamental features of coherent nonlinear wave-particle and wave-wave interactions in magnetized plasmas. The present lecture covers only some of the important and basic characteristics in the coherent nonlinear interactions. The main subjects are: (1) trapping dynamics in the electrostatic wave, (2) nonlinear phase trapping and phase bunching in electromagnetic wave both in homogeneous and inhomogeneous plasmas, and (3) coherent three wave interactions.     

Theory of magnetic pulsations

We present theory of long period (pc 3 to pc 5) magnetic pulsations. It consists of two parts; one (we call type A) deals with a resonant Alfvén wave excitation at a local field line by a monochromatic wave generated at the magnetopause, and the other (we call type B) deals with an excitation of a surface eigenmode by an externally applied impulse at a location with a rapid spatial change of plasma parameter(s).For the type A pulsations, the theory gives the frequency, the sense and the ellipticity of the polarization and the orientation angle of the major axis as a function of the magnetospheric parameters. In particular, it is shown that the orientation angle of the major axis of the polarization ellipse is a sensitive function of the direction of the wave propagation in longitude and the change of the number density and the magnetic flux density in the radial direction, hence it can be used as an important diagnostic parameter.In the type B pulsations, the theory gives the excitation frequency and the damping rate of the pulsations using the derived surface eigenmode. Example of an application to the observed magnetic field oscillations at the plasmapause is presented in which the observed frequency and the damping rate are used to estimate the plasmapause density and its radial density gradient.     

Augmented Empirical Models of Plasmaspheric Density and Electric Field Using IMAGE and CLUSTER Data

Empirical models for the plasma densities in the inner magnetosphere, including plasmasphere and polar magnetosphere, have been in the past derived from in situ measurements. Such empirical models, however, are still in their initial phase compared to magnetospheric magnetic field models. Recent studies using data from CRRES, Polar, and Image have significantly improved empirical models for inner-magnetospheric plasma and mass densities. Comprehensive electric field models in the magnetosphere have been developed using radar and in situ observations at low altitude orbits. To use these models at high altitudes one needs to rely strongly on the assumption of equipotential magnetic field lines. Direct measurements of the electric field by the Cluster mission have been used to derive an equatorial electric field model in which reliance on the equipotential assumption is less. In this paper we review the recent progress in developing empirical models of plasma densities and electric fields in the inner magnetosphere with emphasis on the achievements from the Image and Cluster missions. Recent results from other satellites are also discussed when they are relevant.     

The Japanese Experiment Module

This paper describes Japanese Experiment Module (JEM) which is a Japanese contribution to International Space Station (SS) Program. First half of phase B study of JEM was completed last March successfully. JEM primary function and basic configuration has been established. JEM consists of a Pressurized Module (PM), an Exposed Facility (EF), a scientific/equipment airlock, a local remote manipulator, and an Experimental Logistic Module (ELM). With all those hardware elements, JEM will accommodate general scientific and technology development research (some of which are to utilize the advantage of microgravity environment), and also accommodate control panels for the Space Station Mobile Remote Manipulator System and attached payloads.     

Changes in mood status and neurotic levels during a 20-day bed rest

This study evaluated changes of mood status and depressive and neurotic levels in nine young male subjects during a 20-day 6 degrees head-down tilting bed rest and examined whether exercise training modified these changes. Participants were asked to complete psychometrical inventories on before, during, and after the bed rest experiment. Depressive and neurotic levels were enhanced during bed rest period according to the Japanese version of Zung's Self-rating Depression Scale and the Japanese version of the General Health Questionnaire. Mood state "vigor" was impaired and "confusion" was increased during bed rest and recumbent control periods compared to pre-bed rest and ambulatory control periods according to the Japanese version of Profiles of Mood State, whereas the mood "tension-anxiety", "depression-dejection", "anger-hostility" and "fatigue" were relatively stable during experiment. Isometric exercise training did not modify these results. Microgravity, along with confinement to bed and isolation from familiar environments, induced impairment of mental status.     

Dust Properties in the Local Interstellar Medium

Ulysses measurements yield reliable in-situdetection of large dust particles which stem from the interstellar medium (ISM) and which are not observed in interstellar extinction data. Both current models of large grains in the ISM: core-mantle grains as well as composite grains, are in agreement with dust properties implied by the Ulysses results. However, the size of particles detected by Ulysses still exceeds the size of the large grains that are predicted for the ISM. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cross-Scale Coupling Within Rolled-Up MHD-Scale Vortices and Its Effect on Large Scale Plasma Mixing Across the Magnetospheric Boundary

Kelvin-Helmholtz Instability (KHI) is an MHD-scale instability that grows in a velocity shear layer such as the low-latitude boundary layer of the magnetosphere. KHI is driven unstable when a velocity shear is strong enough to overcome the stabilization effect of magnetic field. When the shear is significantly strong, vortices in the nonlinear stage of KHI is so rolled-up as to situate magnetospheric plasma outward of the magnetosheath plasma and vice versa. The big question is if such highly rolled-up vortices contribute significantly to the plasma transport across the boundary and to the filling of the plasma sheet by cool magnetosheath component, which is observed under northward Interplanetary Magnetic Field (IMF) condition. Here we review our recent results from two-fluid simulations of MHD-scale KHI with finite electron inertia taken into account. The results indicate that there is coupling between the MHD-scale dynamics and electron-scale dynamics in the rolled-up stage of the vortices. While the details differ depending on the initial magnetic geometry, the general conclusion is that there is significant modification of the MHD-scale vortex flow pattern via coupling to the micro-physics. The kick-back from the parasitic micro-physics enhances highly the potential for large-scale plasma mixing of the parent MHD-scale vortices, which is prohibited by definition in ideal-MHD. We also review our recent 3-D MHD simulation results indicating that KHI vortex can indeed roll-up in the magnetotail-flank situation despite the strong stabilization by the lobe magnetic field. These results encouraged us to search for evidence of rolled-up vortices in the Cluster formation flying observations. As reviewed in this paper, a nice event was found during northward IMF interval. This interval is when the plasma transport via large scale reconnection becomes less efficient. The finding supports the argument that KHI is playing some role in transporting solar wind into the magnetosphere when the normal mode of transport cannot dominate.     

Search for primordial antiparticles with BESS

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) has been carried out to search for primordial antiparticles in cosmic rays. In ten flights from 1993 to 2004, it measured the cosmic-ray antiproton spectrum in the energy range 0.1–4.2 GeV at various solar activity conditions. It also searched for antideuterons and antihelium nuclei, and it made precise measurement of cosmic-ray particle spectra. The BESS program has been extended to long duration balloon (LDB) flights in Antarctica (BESS-Polar) with the goal of achieving unprecedented sensitivity in the search for primordial antiparticles. This report describes recent results from BESS and progress of the BESS-Polar program.     

Pointing control of spacecraft using two SGCMGs via LPV control theory

In this paper, we consider a pointing control of a spacecraft using two single-gimbal control moment gyros (SGCMGs). Our pointing control problem is to make the line-of-sight of a camera or an antenna that is fixed on a body axis aim along a desired direction. To solve this problem, we first state the control objective for the pointing control through the angular momentum conservation principle. Then, we develop a gain-scheduled (GS) controller via linear parameter-varying (LPV) control theory. Finally, the feasibility of the proposed control method is shown by a numerical simulation.     

Estimating the High-Resolution Mean Sea-Surface Velocity Field by Combined Use of Altimeter and Drifter Data for Geoid Model Improvement

The mean sea-surface height obtained from satellite altimeters is different from the geoid by the amount of mean sea-surface dynamic topography associated with ocean currents. Assuming geostrophy at the sea surface, the mean sea-surface dynamic topography can be obtained from the mean sea-surface velocity field. This field is derived by combining anomalies (i.e., deviations from the mean) of sea-surface velocity obtained from altimeter data and in situ surface velocities estimated from trajectories of surface drifting-buoys (hereafter, drifters). Where a drifter measured the surface velocity, the temporal mean velocity can be estimated by subtracting the altimeter-derived velocity anomaly at that time from the drifter-measured surface velocity. The method is applied to the surface flow field of the North Pacific, using TOPEX/POSEIDON and ERS-1/2 altimeter data, and WOCE-TOGA surface drifter data obtained from October 1992 through December 2000. The temporal mean velocity field is estimated with a resolution of quarter degrees in both latitude and longitude. The obtained mean velocity field clearly shows the Kuroshio and Kuroshio Extension, which are narrower and stronger than the climatological mean features derived from historical hydrographic data averaged over several decades. Instantaneous velocities are estimated by summing up these temporal mean velocities and anomalies, every ten days during the eight years. They compare well with in situ velocities measured by the surface drifters. The instantaneous velocity field shows energetic fluctuation of the Kuroshio Extension vividly. This revised version was published online in August 2006 with corrections to the Cover Date.