Substorms in the inner plasma sheet

Thin Current Sheets (TCS) are regularly formed prior to substorm breakup, even in the near-Earth plasma sheet, as close as the geostationary orbit. A self-consistent kinetic theory describing the response of the plasma sheet to an electromagnetic perturbation is given. This perturbation corresponds to an external forcing, for instance caused by the solar wind (not an internal instability). The equilibrium of the configuration of this TCS in the presence of a time varying perturbation is shown to produce a strong parallel thermal anisotropy (T T) of energetic electrons and ions (E>50keV) as well as an enhanced diamagnetic current carried by low energy ions (E<50keV). Both currents tend to enhance the confinement of this current sheet near the magnetic equator. These results are compared with data gathered by GEOS-2 at the geostationary orbit, where the magnetic signatures of TCS, and parallel anisotropics are regularly observed prior to breakup. By ensuring quasi-neutrality everywhere we find, when low frequency electromagnetic perturbations are applied, that although the magnetic field line remains an equipotential to the lowest order in T_e/T_i, a field-aligned potential drop exists to the next order in (T_e/T_i). Thus the development of a TCS implies the formation of a field-aligned potential drop ( few hundred volts) to ensure the quasi-neutrality everywhere. For an earthward directed pressure gradient, a field-aligned electric field, directed towards the ionosphere, is obtained, on the western edge of the perturbation (i.e. western edge of the current sheet). Thus field aligned beams of electrons are expected to flow towards the equatorial region on the western edge of the current sheet. We study the stability of these electron beams and show that they are unstable to “High Frequency” (HF) waves. These “HF” waves are regularly observed at frequencies of the order of the proton gyrofrequency (f_H+) just before, or at breakup. The amplitude of these HF waves is so large that they can produce a strong pitch-angle diffusion of energetic ions and a spatial diffusion that leads to a reduction of the diamagnetic current. The signature of a fast ion diffusion is indeed regularly observed during the early breakup; it coincides with the sudden development of large amplitude transient fluctuations, ballooning modes, observed at much lower frequencies (fH+). These results suggest that the HF waves, generated by field-aligned electron beams, provide the dissipation which is necessary to destabilize low frequency (ballooning) modes.     

Radio plasma imager simulations and measurements

The Radio Plasma Imager (RPI) will be the first-of-its kind instrument designed to use radio wave sounding techniques to perform repetitive remote sensing measurements of electron number density (N _e) structures and the dynamics of the magnetosphere and plasmasphere. RPI will fly on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission to be launched early in the year 2000. The design of the RPI is based on recent advances in radio transmitter and receiver design and modern digital processing techniques perfected for ground-based ionospheric sounding over the last two decades. Free-space electromagnetic waves transmitted by the RPI located in the low-density magnetospheric cavity will be reflected at distant plasma cutoffs. The location and characteristics of the plasma at those remote reflection points can then be derived from measurements of the echo amplitude, phase, delay time, frequency, polarization, Doppler shift, and echo direction. The 500 m tip-to-tip X and Y (spin plane) antennas and 20 m Z axis antenna on RPI will be used to measures echoes coming from distances of several R _E. RPI will operate at frequencies between 3 kHz to 3 MHz and will provide quantitative N _e values from 10^–1 to 10⁵ cm^–3. Ray tracing calculations, combined with specific radio imager instrument characteristics, enables simulations of RPI measurements. These simulations have been performed throughout an IMAGE orbit and under different model magnetospheric conditions. They dramatically show that radio sounding can be used quite successfully to measure a wealth of magnetospheric phenomena such as magnetopause boundary motions and plasmapause dynamics. The radio imaging technique will provide a truly exciting opportunity to study global magnetospheric dynamics in a way that was never before possible.     

The Radio Plasma Imager investigation on the IMAGE spacecraft

Radio plasma imaging uses total reflection of electromagnetic waves from plasmas whose plasma frequencies equal the radio sounding frequency and whose electron density gradients are parallel to the wave normals. The Radio Plasma Imager (RPI) has two orthogonal 500-m long dipole antennas in the spin plane for near omni-directional transmission. The third antenna is a 20-m dipole along the spin axis. Echoes from the magnetopause, plasmasphere and cusp will be received with the three orthogonal antennas, allowing the determination of their angle-of-arrival. Thus it will be possible to create image fragments of the reflecting density structures. The instrument can execute a large variety of programmable measuring options at frequencies between 3 kHz and 3 MHz. Tuning of the transmit antennas provides optimum power transfer from the 10 W transmitter to the antennas. The instrument can operate in three active sounding modes: (1) remote sounding to probe magnetospheric boundaries, (2) local (relaxation) sounding to probe the local plasma frequency and scalar magnetic field, and (3) whistler stimulation sounding. In addition, there is a passive mode to record natural emissions, and to determine the local electron density, the scalar magnetic field, and temperature by using a thermal noise spectroscopy technique.     

Super rogue wave catalysis in Titan’s ionosphere

Super rogue ion-acoustic waves are proposed as a physical catalyst for the heavy hydrocarbon ions formation in the Titan ionosphere. We justified that analytically and numerically by probing a Titan referenced plasma system, consists of the most abundant positive ions and superthermal electrons. A solution of the nonlinear Schrödinger equation (NLSE) has provided us by the plasma (un) stable regions at altitude 900–1200 km from the Titan surface with superthermal parameter values, relative ion to electron densities, and temperature ratio variations. Our results are not only agreed with the Cassini data but also predict a chemistry independent approach for the heavy hydrocarbons’ formation conditions.     

Dynamics of the Nightside Boundaries of the Auroral Oval during Magnetic Storm on May 27–29, 2017

Cosmic Research - Using the Meteor M2 low-orbit satellite, the dynamics of the boundaries of the auroral oval on the nightside during the magnetic storm observed from May 27 to 29, 2017, was...     

Tethered propellant resupply technique for space stations

Interim results of a study on use of the tethered propellant resupply technique on the space station are summarized. The acceleration produced by a gravity-gradient-stabilized tether can predictably settle propellants and thereby simplify propellant resupply of vehicles when compared to zero-g techniques. Separation of the gas and liquid phases by settling enables performance of liquid acquisition and gas venting without special hardware in the propellant tanks and without special procedures. The primary requirement for propellant transfer is control of liquid sloshing to maintain liquid over the supply tank outlet and gas over the receiver tank vent. Ultimately, the decision to use this technique on the space station may depend upon the capability to adjust depot logistic operations to a tether.     

A Three-Dimensional Simulation of Collisional-Interchange-Instability in the Equatorial-Low-Latitude Ionosphere

We present a three-dimensional simulation of collisional-interchange-instability in the equatorial-low-latitude F region of ionosphere. The instability is responsible for the generation of large plasma density depletion or bubble. General 3D potential and continuity equations are derived to simulate the phenomena. To understand the linear aspect of the instability, the general 3D linear growth rate is derived using 3D potential equation. The linear growth characteristics are compared with earlier field-aligned-integrated growth analyses. The numerical simulation of bubble in the 3D spherical polar geometry is finally presented. Distinct evolution characteristics of bubble in 3D and 2D simulation are further discussed.     

Detection of suprathermal ionospheric O+ ions inside the plasmasphere

The plasma diagnostic experiments on the AUREOL-3 satellite have revealed flows of low energy 0⁺ ions deep inside the night plasmasphere during a large substorm. Flux gradients of the 0⁺ ions were accompanied by enhancements of ELF electric field noise. The appearance of suprathermal ions at $\text{L ? 2.5 – 3}$ is interpreted within the framework of electrostatic ion-cyclotron acceleration of ionospheric ions in the diffuse auroral zone /12/ followed by a radial displacement of these ions inside the plasmasphere driven by azimuthal electric fields during substorm activity. Electrostatic oscillations observed inside the plasmasphere are apparently associated with gradient instability at the sharp boundaries of suprathermal ion flows.     

Project Trinidad

The first intercontinental satellite communication link, which involved the NASA Echo I balloon, a transmitting station on the Island of Trinidad, and a receiving station at Floyd, NY, is discussed. Rome Air Development Center (RADC) experimental stations were set up using a great deal of ingenuity and makeshift equipment and on a very small budget. Much of the equipment was salvaged from unrelated systems, while some was hand-built for this project. The implementation of the system, the testing of the system using moon bounce, the first orbital launch of the Echo I balloon, and the early difficulties encountered in the project are reviewed     

A pure-Cartesian formulation for tracking filters

A pure-Cartesian formulation is presented for angle-only and angle-plus-range tracking filters. Unlike conventional angle-only filters, which use target elevation and bearing as measurements, the filter expresses the sensor measurements in Cartesian coordinates. Consequently, the filter performs equally well for any line-of-sight (LOS) geometry, even when target elevation approaches or is equal to ±90°