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Michel, F. C.

Publications and source records attributed to Michel, F. C..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Magnetopause shapes - General solutions

The problem of determining the shape of a magnetopause, namely, the tangential discontinuity separating (typically) the magnetic field of a source from external plasma, is reduced to solving an integral equation. No symmetry assumptions whatsoever are used in the derivation, consequently, realistic problems such as model shapes for the earth's magnetosphere (tilted dipole, flowing plasma, etc.) can in principle be treated. Moreover, the magnetic field source itself need not be a simple dipole. A variational method is suggested whereby the optimum parameters for any finite term trial shape are obtained.

Michel, F. C.↗
NASA NTRS1977

Accretion magnetosphere stability. II - Polar cap 'drip'

The entry of plasma past the shielding magnetic field of a collapsed object is examined. It is concluded that a plausible entry mode is simply a 'dripping' motion of the polar caps of the magnetopause, owing to radiation of the hot compressed plasma there. The plasma 'drips' would hit the object's surface either near the magnetic poles or in a ring-shaped 'auroral' zone around the poles. Insofar as this entry mode is concerned, no special role is played by finite plasma resistivity since the plasma can reach the stellar object even if the conductivity is infinite.

Michel, F. C.↗
NASA NTRS1976

Heavy ions from the Galilean satellites and the centrifugal distortion of the Jovian magnetosphere

The Galilean satellites constitute a potentially significant source of plasma to the Jovian atmosphere. The paper examines the distortion of the Jovian magnetosphere that would result from injection of ions at the Galilean satellites. The magnetic distortion produced is a localized perturbation near the equatorial plane, in contrast to the large-scale distortion produced by Jovian atmospheric ions. The study estimates the relative perturbation currents resulting from the two sources in terms of the unknown ion production rate at the satellites. It is found that the two perturbations would be of comparable magnitudes if the ion source flux at all of the Galilean satellites were comparable to the photo-ion escape flux from Jupiter's atmosphere. More specifically, ions produced by the Galilean satellites should be confined near the equatorial plane of Jupiter's magnetosphere in a sheet whose thickness is determined by a centrifugal scale height given essentially by the ion thermal speed divided by the corotation frequency.

Hill, T. W.↗
NASA NTRS1975

Planetary magnetospheres

Space-probe observations of planetary magnetospheres are discussed. Three different categories of planetary magnetospheres are identified (intrinsic slowly rotating, intrinsic rapidly rotating, and induced), and the characteristics of each type are outlined. The structure and physical processes of the magnetospheres of Mercury, Mars, and Jupiter are described, and possible configurations are presented for the Martian and Jovian ones. Expected magnetic moments are derived for Saturn, Uranus, and Neptune. Models are constructed for possible induced magnetospheres of the moon, Mercury, Venus, Mars, and Io.

Hill, T. W.↗
NASA NTRS1975

On the interpretation of low-energy particle access to the polar caps

Neither particle access to the polar caps by motion along magnetospheric field lines connected to the interplanetary field (in the 'open' model) nor particle access to the polar caps by combined diffusive and convective motion across magnetospheric field lines (in the 'closed' model) adequately explains the available data. The fact that data exist that are difficult to interpret with one model does not automatically confirm the other model.

Michel, F. C.↗
NASA NTRS1974

Centrifugal instability of the Jovian magnetosphere and its interaction with the solar wind

The outer regions (r greater than 2.3 Jupiter radii) of the magnetosphere of Jupiter will systematically accumulate plasma. If sufficient plasma accumulates, the field lines must open to allow the plasma to escape. Available energy sources appear able to supply plasma at a high enough rate to keep the field lines constantly open beyond about 60 Jupiter radii. It is suggested that the solar wind interaction with Jupiter may be essentially different from that with the earth, with the Jovian magnetosphere opening up to form a planetary wind.

Michel, F. C.↗
NASA NTRS1974

Configuration of the Jovian magnetosphere

A model is presented in which the Jovian magnetosphere is severely inflated by the centrifugal stress of partially corotating plasma streaming out along field lines from the ionosphere. The model is consistent with observations reported from the Pioneer 10 encounter, including the disk-like field configuration, the diurnal modulation of trapped-particle fluxes, and the inferred departure from rigid corotation in the outer magnetosphere. The field configuration is closed on the dayside, but on the nightside the plasma can force the magnetic field open to form a planetary wind flowing in the antisolar direction.

Hill, T. W.↗
NASA NTRS1973

The Viking parachute qualification test technique.

The parachute system for NASA's Viking '75 Mars lander was flight qualified in four high-altitude flight tests at the White Sands Missile range (WSMR). A balloon system lifted a full-scale simulated Viking spacecraft to an altitude where a varying number of rocket motors were used to propel the high drag, lifting test vehicle to test conditions which would simulate the range of entry conditions expected at Mars. A ground-commanded cold gas pointing system located on the balloon system provided powered vehicle azimuth control to insure that the flight trajectory remained within the WSMR boundaries. A unique ground-based computer-radar system was employed to monitor inflight performance of the powered vehicle and insure that command ignition of the parachute mortar occurred at the required test conditions of Mach number and dynamic pressure. Performance data were obtained from cameras, telemetry, and radar.

Raper, J. L.↗
NASA NTRS1973

Balloon launched Viking decelerator test program

Four BLDT flights were conducted during the summer of 1972. The purpose of these tests was to qualify the Viking parachute system behind the full-scale Viking entry vehicle over the maximum range of entry conditions anticipated in the Viking '75 soft landing on Mars. A summary of the test series is presented. Test conditions ranged from a Mach number of 2.0 to 0.5 and dynamic pressure from 11.7 to 4.4 psf. This range of conditions covers the uncertainty in entry conditions at Mars due to atmospheric and entry performance uncertainties. Emphasis is placed on parachute performance and simulated Mars entry vehicle motions as influenced by the parachute performance. Conclusions are presented regarding the ability of the parachute to perform within the operational parameters required for a successful soft Martian landing. A list of references which covers all reports in the qualification test program is included.

Moog, R. D.↗
NASA NTRS1973

Lunar ion flux and energy

The dynamics of the lunar ionosphere and resulting flux of lunar ions to the lunar surface are reviewed. In the Lunar rest frame, ions formed from the neutral lunar atmosphere are accelerated by the interplanetary electric and magnetic fields. The trajectories of heavier ions are primarily along the electric field; the ion flux is in a direction perpendicular to the solar wind flow, correlated to the orientation of the interplanetary magnetic field, and impacts the surface with energies of tens of electron volts to a few keV. Thus we predict a relatively energetic (compared to thermal energies), highly directional, lunar ion flux but with the possibility that light ions such as hydrogen can execute orbits that return them to portions of the lunar surface not directly exposed to the solar wind. The effects of surface electric and magnetic fields are discussed, as is the ion energy spectrum. We calculate the trapping of atmospheric ions which impact the surface and from this the density of neutral Ar 40 in the lunar atmosphere. We show that using the acceleration model, the lunar atmosphere total neutral number density can be calculated from ion detector data.

Manka, R. H.↗
NASA NTRS1973

Lunar ion energy spectra and surface potential

The acceleration model for lunar ions and the resulting ionosphere dynamics are reviewed briefly. An application is made to lunar atmosphere trapped in the surface fines, and the enhancement in the Ar-40/Ar-36 ratio in samples from the Apennine Front compared to the adjacent mare is calculated to be about 2.0. The predicted lunar ion energy spectra is shown and found to agree well with Suprathermal Ion Detector measurements; from this spectra, the neutral atmosphere scale height can be studied and the neutral atmosphere number density is found to be 100,000 to 300,000 per cu cm at the sunrise and sunset terminators. The lunar surface potential is calculated and is found to be several volts positive over much of the sunlit face of the moon but to go tens of volts negative at the terminator.

Manka, R. H.↗
NASA NTRS1970

Alignment of oblique rotators

Pulsar slowdown by radiation field torques indicated by alignment torque in magnetized oblique sphere rotating in vacuum

Goldwire, H. C., Jr.↗
NASA NTRS1970

Pulsar planetary systems

Pulsar formation effect on orbits of preexisting planets and postformation planets effects on pulsar period and phase residuals

Michel, F. C.↗
NASA NTRS1969

Relativistic stellar-wind torques

Solar wind-induced torque calculated considering special and general relativistic effects, extending method to pulsar rotational model

Michel, F. C.↗