Engineering topics
Publications and source records attributed to Mozer, F. S..
The spherical double-probe electric-field experiment on the ISEE-1 spacecraft is described. It is shown that the instrument measures magnetospheric, magetosheath, and solar wind electric fields with a sensitivity well below one mV/m. Design features and diagnostic experiments performed in orbit to understand the instrument operation are discussed.
Rocket borne measurements employing a double probe technique were used to gather evidence for the existence of electric fields in the auroral ionosphere having components parallel to the magnetic field direction. An analysis of possible experimental errors leads to the conclusion that no known uncertainties can account for the roughly 10 mV/m parallel electric fields that are observed.
DC electric fields and solar electrons were simultaneously measured by the Apollo 15 subsatellite in the earth's magnetotail at lunar orbital distance and by rocket and balloon experiments in the polar ionosphere. The magnetotail and polar ionosphere transverse electric fields are found generally to agree in magnitude and direction. The electron spectra from 0.5 to 200 keV are essentially identical, indicating that the potential difference due to parallel electric fields between the magnetotail and the rocket located in the polar ionosphere did not exceed approximately 500 V during the time of the measurements.
A computer program simulated the spectrum which resulted when a radar signal was transmitted into the ionosphere for a finite time and received for an equal finite interval. The spectrum derived from this signal is statistical in nature because the signal is scattered from the ionosphere, which is statistical in nature. Many estimates of any property of the ionosphere can be made. Their average value will approach the average property of the ionosphere which is being measured. Due to the statistical nature of the spectrum itself, the estimators will vary about this average. The square root of the variance about this average is called the standard deviation, an estimate of the error which exists in any particular radar measurement. In order to determine the feasibility of the space shuttle radar, the magnitude of these errors for measurements of physical interest must be understood.
For abstract, see N77-10397.
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An investigation is conducted concerning the conditions encountered during a Javelin sounding rocket experiment conducted on Apr. 3, 1970 at Fort Churchill, Canada. Evidence is presented that near the equatorward edge of the auroral arc an intense beam of cold plasma ions was flowing parallel to the earth's magnetic field. The beam was associated with intense narrow band electric field oscillations near the local ion gyrofrequency. The data support the hypothesis that intense electrostatic ion cyclotron waves were driven unstable by field-aligned currents.
Observations have been made of electric field oscillations near the local ion gyro frequency and of an intense beam of plasma ions at the edge of an auroral arc. The observations are in good agreement with ion heating as the saturation mechanism for electrostatic ion cyclotron waves.
A Nike Tomahawk sounding rocket was launched into a 400-gamma auroral substorm from Esrange, Kiruna, Sweden. The rocket instrumentation included a split Langmuir-probe plasma-velocity detector and a double-probe electric-field detector. Above 140-km altitude, the electric field deduced from the ion-flow velocity measurement and the electric field measured by the double probe agree to an accuracy within the uncertainties of the two measurements. The difference between the two measurements at altitudes below 140 km provides an in situ measurement of current density and conductivity. Alternatively, if values for the conductivity are assumed, the neutral-wind velocity can be deduced. The height-integrated current was 0.11 A/m flowing at an azimuth angle of 276 deg. The neutral winds were strong, exhibited substantial altitude variation in the east-west component, and were predominantly southward.
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Simultaneous measurements have been made of the ionospheric electric field at altitudes above 100 km (with rockets and radar) and of the atmospheric electric field at an altitude of about 30 km (with balloons). These results show that the horizontal components of the electric field at 30 km were essentially equal to the ionospheric electric field, as has been argued previously on theoretical grounds.
A quantitative three-dimensional model is proposed for the electric potential arising from magnetopause reconnection, in which several approximations are made concerning configuration of the magnetosheath flow, limitations on the magnitude of the reconnection speed, and the geometry of the problem. These approximations are such that the model yields an upper limit for the potential. The magnitude of the polar cap ionospheric electric field computed from this model is larger than that measured on balloons by an average factor of about 3, and the model reproduces the temporal variations of the experimental data. It is concluded that magnetopause reconnection is a highly efficient process that is probably the dominant mechanism driving polar cap convection and supplying energy to the magnetosphere. It seems that the most efficient way for the solar wind to pass the magnetospheric obstacle is by magnetopause reconnection.
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Energetic protons and electrons introduced into the vicinity of the synchronous orbit by geomagnetic substorms and observed on ATS 5 at various local times have been analyzed for velocity dispersion effects associated with their longitudinal drift. Particles with energies between about 30 and 200 keV are shown to be produced simultaneously within tens of minutes at local times between about 0000 and 0400 near 6.6 earth radii during substorm activity. Those with energies not less than approximately 75 keV move in longitude in the direction and with the magnitude expected from gradient B drifts. Lower-energy protons and electrons appear at the satellite sooner than expected from their gradient B drifts, as though the observed particles of such energies were not those originally accelerated but were newly produced from or by the higher-energy drifting component.
The electric field in the ionosphere and the magnetic field at the earth's surface in the mid-latitude region were both measured during a sudden impulse. Ionospheric conductivities deduced from this data were consistent with expectations, thus suggesting that the fluctuations in the magnetic field at the earth's surface were caused by overhead ionospheric currents that were driven by an electric field associated with the sudden impulse.
Four hundred and seventy-eight hours of electric field data obtained by the flight of 32 balloons between L = 5.4 and L = 8.2 have been averaged to determine mean properties of the auroral zone electric field. The results are understood in terms of a model in which the two-cell convection pattern is rotated about the sun-earth line by an amount that depends on the sign and magnitude of the y component of the interplanetary magnetic field. This model and the data suggest either that important parallel potential drops exist along auroral zone magnetic field lines or that simple conjugacy between the two hemispheres does not exist along such field lines.
Space measurements of electric fields have provided instrumentation for measuring atmospheric parameters and a better basis for understanding the electrical coupling between the magnetosphere and the atmosphere. Applications of an incoherent scatter radar (developed for ionospheric electric field research) to the measurement of atmospheric winds and turbulence and of Langmuir double probes (also developed for space research) for measurement of atmospheric electric fields are described. The increased knowledge of magnetospheric electric fields has focused attention on the electrical coupling between the magnetosphere and the atmosphere with conclusions that should considerably modify previous physical concepts in both domains.