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Reiff, P. H.

Publications and source records attributed to Reiff, P. H..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Sunward convection in both polar caps

The storm of July 29, 1977 was chosen as an object of study for the Coordinated Data Analysis Workshop (CDAW), a part of the International Magnetospheric Study (IMS). The purpose of CDAW was to synthesize many diverse data sets in order to understand as fully as possible the magnetosphere's response to a variety of inputs, including a strong interplanetary shock, a time of strongly southward interplanetary magnetic field (IMF), and a time of strongly northward IMF. The July 29 event was particularly interesting because it contained effects of storm time compressions and of strongly southward and strongly northward IMF'S. The convection data appear to indicate reversed (sunward) convection in the polar cap in both the northern and southern hemispheres, although conjugacy cannot be established because the northern and southern passes were at different locations and different times

Reiff, P. H.↗
NASA NTRS1981

Dependence of polar cap potential drop on interplanetary parameters

The convection potential drop across the polar cap is computed from data obtained on high-inclination low-altitude satellites. Potential measurements are correlated with various combinations of parameters measured simultaneously in the upstream solar wind. Most of the potential drop is successfully predicted by merging theory, although a significant background potential drop of 35 kV does not depend on IMF parameters and is attributed to a process other than merging. Results indicate that small values of the IMF are amplified by a factor of 5-10 at the dayside magnetopause, which, when taken into account, improves correlations between IMF parameters and polar cap potential drop. Potential drop is better correlated with IMF parameters than with geomagnetic indices, due to nonlinear response of the magnetosphere affecting geomagnetic activity indices.

Reiff, P. H.↗
NASA NTRS1981

Quantitative simulation of a magnetospheric substorm. I - Model logic and overview

Results of a comprehensive computer simulation of the behavior of the earth's inner magnetosphere during a substorm-type event are reported. It is pointed out that the computer model self-consistently computes electric fields, currents, and plasma distributions and velocities in the inner-magnetosphere/ionosphere system; parallel electric fields and ionospheric neutral winds, however, are not included. The basic equations of the model are derived, and the inputs are described. An overview of the results is also given. The first appendix contains derivations of general, useful laws of bounce-averaged gradient, curvature, and E x B drifts in a plasma with isotropic pitch angle distribution. The second appendix gives a description of the numerical method used in the simulation.

Harel, M.↗
NASA NTRS1981

Quantitative simulation of a magnetospheric substorm. II - Comparison with observations

Results of the computer simulation of the behavior of the inner magnetosphere during the substorm-type event of September 19, 1976, are discussed. The computed electric fields are found to compare satisfactorily with electric fields measured from S3-2, although there are detailed differences. The three general features on which the model and observations are in good agreement are (1) the magnitude and direction of the high-latitude electric field, (2) the degree to which the low-latitude ionosphere is shielded from the high-latitude convection electric field, and (3) the fact that the poleward electric field on the duskside is significantly larger, on the average, than the equatorward electric field on the dawnside. Simple formulas are presented that give rough estimates of global Joule heating rates from observable parameters.

Harel, M.↗
NASA NTRS1981

Quantitative simulation of a magnetospheric substorm. III - Plasmaspheric electric fields and evolution of the plasmapause

Results of a substorm simulation are used to investigate the penetration of substorm-associated electric fields into the plasmasphere. Near 4 earth radii in the equatorial plane, the time-dependent electric field model is characterized by eastward components in the dusk-midnight local time sector and westward components after midnight. With the exception of a small region just before dusk, the model predicts eastward electric field components throughout the daytime sector. The characteristic radial component is directed inward at all local times with the exception of a small region just after dawn. It is noted that these results compare favorably with available whistler and incoherent-scatter radar measurements obtained during magnetically disturbed periods. By assuming an initial plasmapause shape and by following the computed E x B drift trajectories of plasma flux tubes from that initial boundary, the short-term evolution of the plasmapause during the substorm-like event of September 19, 1976, is examined.

Spiro, R. W.↗
NASA NTRS1981

Cusp region particle precipitation and ion convection for northward interplanetary magnetic field

Data from Atmosphere Explorer D for periods of strong northward interplanetary magnetic field are discussed. In the dayside magnetospheric cusp region energy time spectrograms of suprathermal positive ion fluxes exhibit a characteristic 'V' pattern as the spacecraft moves toward higher latitudes; that is, with the peak in the energy spectrum falling in energy and then rising again. Convection velocities follow this pattern closely with strong eastwest flows (with antisunward components) occurring in the equatorward half of the 'V' and significant sunward flows occurring in the poleward half of the 'V'. These patterns can be understood qualitatively in terms of a model of ionospheric electric potential produced by the known dependence of Birkeland current densities on magnetic activity.

Burch, J. L.↗
NASA NTRS1980

Cusp proton signatures and the interplanetary magnetic field

The variation of proton average energy with latitude in the cusp has been suggested as an indicator of the means of particle entry. If magnetic merging is the principal means of particle entry, the proton average energy should fall with increasing latitude; if diffusion is the principal means, the average energy should first fall and then briefly rise as a function of latitude, showing a 'V' signature. In the present work, 60 selected cusp passes of the AE-D satellite for which IMP-J interplanetary or magnetosheath magnetic-field data were available were examined. About one-third of these passes showed clear or likely merging-type energy dispersions; a third showed clear or likely V-type energy dispersions, and a third showed unclear or no energy dispersions. The results are strongly correlated with the IMF - the merging signatures are associated with southward IMF and the V signatures with northward IMF. Unclear cases are associated with unsteady or weakly northward IMF.

Reiff, P. H.↗
NASA NTRS1980

Cusp region particle precipitation and ion convection for northward interplanetary magnetic field

Data from Atmosphere Explorer D for periods of strong northward interplanetary magnetic field show the following characteristic behavior in the dayside magnetospheric cusp region: energy-time spectrograms of suprathermal positive ion fluxes exhibit a characteristic 'V' pattern as the spacecraft moves toward higher latitudes; that is, with the peak in the energy spectrum falling in energy and then rising again. Convection velocities follow this pattern closely with strong east-west flows (with antisunward components) occurring in the equatorward half of the 'V' and significant sunward flows occurring in the poleward half of the 'V'. These patterns can be understood qualitatively in terms of a model of ionospheric electric potential produced by the known dependence of Birkeland current densities on magnetic activity.

Burch, J. L.↗
NASA NTRS1980

Plasma-sheet dynamics and magnetospheric substorms

A conceptual model of the formation of the plasma sheet and of its dynamical behavior in association with magnetospheric substorms is proposed. The two essential assumptions of the model are that (1) the plasma mantle is the primary source of plasma-sheet particles and (2) the momentum tends to inhibit the rate of magnetic field annihilation (merging) in the tail current sheet. It is found that there exists no steady state configuration for the plasma sheet, which must instead shrink continuously in thickness until the near-earth portion of the current sheet is disrupted by the formation of a magnetic neutral line. The thinning of the plasma sheet and the resulting current-sheet disruption are proposed to be the direct causes of the growth phase and expansion phase, respectively, of substorms.

Hill, T. W.↗
NASA NTRS1980

On the cause of plasma-sheet thinning during magnetospheric substorms

It is proposed that the thinning of the plasma sheet during magnetospheric substorms is caused by an earthward gradient of the rate of magnetic merging (field annihilation) in the tail current sheet, which is in turn caused by the velocity-dependent access of plasma mantle particles to the current sheet. A simple model calculation based on this effect predicts a thinning time constant of the order of 1 hour, consistent with observations. The mechanism is also consistent with the observed correlation between plasma-sheet thinning and southward-directed magnetic field components in the solar wind.

Hill, T. W.↗
NASA NTRS1980

Environmental protection of the solar power satellite

This paper examines theoretically several features of the interactions of the Solar Power Satellite (SPS) with its space environment. The leakage currents through the kapton and sapphire solar cell blankets are calculated. At geosynchronous orbit, this parasitic power loss is only 0.7%, and is easily compensated by oversizing. At low-earth orbit, the power loss is potentially much larger (3%), and anomalous arcing is expected for the high-voltage negative surfaces. Preliminary results of a three-dimensional self-consistent plasma and electric field computer program are presented, confirming the validity of the predictions made from the one-dimensional models. Lastly, the paper proposes magnetic shielding of the satellite, to reduce the power drain and to protect the solar cells from energetic electron and plasma ion bombardment. It is concluded that minor modifications from the baseline SPS design can allow the SPS to operate safely and efficiently in its space environment.

Reiff, P. H.↗
NASA NTRS1979

Low-altitude signatures of the boundary layers

Low altitude measurements reveal two distinct types of dayside boundary-layer plasmas. The first type is characterized by a proton distribution whose average energy decreases with increasing latitude and generally shows cool, unaccelerated electron fluxes. This type is observed only near noon and is correlated with southward interplanetary magnetic field (IMF). The second type is characterized by a 'V' signature in which the proton average energy first decreases then briefly increases as a function of latitude. The electron distribution in the latter case is hotter and often shows evidence of small scale acceleration regions. This type can be seen at all local times in the dayside and at noon is correlated with a northward IMF. It is suggested that the type 1 plasma is the low altitude signature of the plasma mantle and the type 2 plasma is the low altitude signature of the low latitude boundary layer.

Reiff, P. H.↗
NASA NTRS1979

Earth and Jupiter: Comparison of magnetopause structure

Using published data from the Jovian magnetopause crossings of Pioneers 10 and 11, the apparent crossing times as determined from the solar wind plasma detector and from the vector magnetometer are comapred. There were 13 published crossings for which both plasma and magnetic-field signatures were clearly defined. The occurrence distribution of these 13 crossings with respect to the relative timing of plasma and field signatures is shown. Results indicate that Jupiter's magnetopause is more turbulent than the Earth's possibly as the result of the large velocity shear between the magnetosheath and the partially corotating Jovian plasma. However, it is noted that the data set considered is too small to justify a definitive interpretation.

Reiff, P. H.↗
NASA NTRS1979

Electrostatic protection of the Solar Power Satellite and rectenna

Several features of the interactions of the solar power satellite (SPS) with its space environment were examined theoretically. The voltages produced at various surfaces due to space plasmas and the plasma leakage currents through the kapton and sapphire solar cell blankets were calculated. At geosynchronous orbit, this parasitic power loss is only 0.7%, and is easily compensated by oversizing. At low-Earth orbit, the power loss is potentially much larger (3%), and anomalous arcing is expected for the EOTV high voltage negative surfaces. Preliminary results of a three dimensional self-consistent plasma and electric field computer program are presented, confirming the validity of the predictions made from the one dimensional models. Magnetic shielding of the satellite, to reduce the power drain and to protect the solar cells from energetic electron and plasma ion bombardment is considered. It is concluded that minor modifications can allow the SPS to operate safely and efficiently in its space environment. The SPS design employed in this study is the 1978 MSFC baseline design utilizing GaAs solar cells at CR-2 and an aluminum structure.

Freeman, J. W.↗
NASA NTRS1979

Computer modeling of events in the inner magnetosphere

The first effort at computer simulating the behavior of the inner magnetosphere during a substorm-type event on 19 September 1976 was completed. The computer model simulates many aspects of the behavior of the closed-field-line portion of the earth's magnetosphere, and the auroral and subauroral ionosphere. For these regions, the program self-consistently computes electric fields, electric currents, hot-plasma densities, plasma flow velocities and other parameters. Highlights of the results of our event simulation are presented. Predicted electric fields for several times during the event agree reasonably well with corresponding data from satellite S3-2. Detailed discussion is presented for a case of rapid subauroral flow that was observed on one S3-2 pass and is predicted by the computer runs. The computed global distribution of Birkeland current agrees reasonably well with the observations of Iijima and Potemra.

Harel, M.↗
NASA NTRS1978

Dayside auroral arcs and convection

Recent Defense Meteorological Satellite Program and International Satellite for Ionospheric Studies dayside auroral observations show two striking features: a lack of visible auroral arcs near noon and occasional fan shaped arcs radiating away from noon on both the morning and afternoon sides of the auroral oval. A simple model which includes these two features is developed by reference to the dayside convection pattern of Heelis et al. (1976). The model may be testable in the near future with simultaneous convection, current and auroral light data.

Reiff, P. H.↗