Current collection by a highly positive body moving in the ionospheric plasma

In this paper we derive an interesting feature of the space charge region surrounding a positively charged body moving in a magnetoplasma and, precisely, the fact that, for potentials of the body in excess of a certain value, at least in an inner region close to the body, the electron collection (and the structure of the self-consistent potential) is isotropic. This is used to derive current-voltage characteristics for such a situation. These theoretical characteristics are then convincingly compared with those obtained from the analysis of the data obtained during the recently flown TSS-1R mission

Investigation of electrodynamic stabilization and control of long orbiting tethers

The possibility of using electrodynamic forces to control pendular oscillations during the retrieval of a subsatellite is investigated. The use of the tether for transferring payloads between orbits is studied

Electron collection by a charged satellite in the ionospheric plasma

The space charge region surrounding a highly charged, electron collecting, spacecraft moving in the ionospheric plasma, can be divided into an inner zone (close to the spacecraft), where electron collection is isotropic with respect to the magnetic-field direction, and an outer zone where the electrons are mainly collected along magnetic field lines. In this paper we outline a theory to obtain the current voltage characteristic of such a positive satellite. It is shown that the theoretical results compare very favorably with the experimental data obtained by the TSS-1R mission

Electrodynamic deorbiting of LEO satellites

In this paper we present realistic calculations of deorbiting times for a LEO satellite through the use of electrodynamic tethers. We refer to two possible tether systems (a bare and a conducting insulated tether) both equipped with an inflatable conducting balloon at the upper end. The calculations take into account average ionospheric properties and the electrical interaction of the wire with the ionosphere. Furthermore, they have been done for several inclination orbits and include also the deviation of the tether from the vertical direction under the combined action of the gravity gradient and the electrodynamic forces. The results obtained for the decay times, for typical constellation satellite, indicate that such tether systems are definitely of interest for the deorbiting application

Postmitotic Expression of SOD1G93A Gene Affects the Identity of Myogenic Cells and Inhibits Myoblasts Differentiation

To determine the role of mutant SOD1 gene (SOD1G93A) on muscle cell differentiation, we derived C2C12 muscle cell lines carrying a stably transfected SOD1G93A gene under the control of a myosin light chain (MLC) promoter-enhancer cassette. Expression of MLC/SOD1G93A in C2C12 cells resulted in dramatic inhibition of myoblast differentiation. Transfected SOD1G93A gene expression in postmitotic skeletal myocytes downregulated the expression of relevant markers of committed and differentiated myoblasts such as MyoD, Myogenin, MRF4, and the muscle specific miRNA expression. The inhibitory effects of SOD1G93A gene on myogenic program perturbed Akt/p70 and MAPK signaling pathways which promote differentiation cascade. Of note, the inhibition of the myogenic program, by transfected SOD1G93A gene expression, impinged also the identity of myogenic cells. Expression of MLC/SOD1G93A in C2C12 myogenic cells promoted a fibro-adipogenic progenitors (FAPs) phenotype, upregulating HDAC4 protein and preventing the myogenic commitment complex BAF60C-SWI/SNF. We thus identified potential molecular mediators of the inhibitory effects of SOD1G93A on myogenic program and disclosed potential signaling, activated by SOD1G93A, that affect the identity of the myogenic cell population

The TSS-1 mission: Results on satellite charging

In the present paper we first give a short account of the mission TSS-1 flown on the Shuttle sts-46 in August 1992 and its basic electrical configurations. We then show some results obtained from the experiment RETE on board the satellite which are relevant for the issue of satellite charging

Current collection to long conductors with wide geometries for bare electrodynamic tether applications - A laboratory update

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77101/1/AIAA-2002-1123-228.pd

Constraining Low-Frequency Alfvenic Turbulence in the Solar Wind Using Density Fluctuation Measurements

One proposed mechanism for heating the solar wind, from close to the sun to beyond 10 AU, invokes low-frequency, oblique, Alfven-wave turbulence. Because small-scale oblique Alfven waves (kinetic Alfven waves) are compressive, the measured density fluctuations in the solar wind place an upper limit on the amplitude of kinetic Alfven waves and hence an upper limit on the rate at which the solar wind can be heated by low-frequency, Alfvenic turbulence. We evaluate this upper limit for both coronal holes at 5 solar radii and in the near-Earth solar wind. At both radii, the upper limit we find is consistent with models in which the solar wind is heated by low-frequency Alfvenic turbulence. At 1 AU, the upper limit on the turbulent heating rate derived from the measured density fluctuations is within a factor of 2 of the measured solar wind heating rate. Thus if low-frequency Alfvenic turbulence contributes to heating the near-Earth solar wind, kinetic Alfven waves must be one of the dominant sources of solar wind density fluctuations at frequencies of order 1 Hz. We also present a simple argument for why density fluctuation measurements do appear to rule out models in which the solar wind is heated by non-turbulent high-frequency waves ``sweeping'' through the ion-cyclotron resonance, but are compatible with heating by low-frequency Alfvenic turbulence.Comment: 8 pages, 3 figures, submitted to Ap

Shuttle charging by tether controlled electron beam

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95327/1/grl10600.pd

Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere

The dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy