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Brace, L. H.

Publications and source records attributed to Brace, L. H..

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Is the red arc a good indicator of ionosphere-magnetosphere conditions

Weak red arcs were observed on the two consecutive nights of July 12-13 and July 13-14, 1969, at Richland, Washington, whereas no red arcs were detectable on the nights preceding and following the observations. Satellite (Ogo 6) data of electron temperature and density, low-frequency ac electric field, and suprathermal electron flux corresponding to the conjugate region of Richland show no significant variations during these days. The data show elevated electron temperatures and enhanced low-frequency ac noise levels at the expected red arc position in the neighborhood of the density trough, as indicated by previous observations. The data appear to indicate that the optical criterion of red arc occurrence would lead to the conclusion of significantly different ionosphere-magnetosphere conditions during these four nights, whereas the more detailed in situ data show that the conditions were very similar.

Nagy, A. F.↗
NASA NTRS1974

The behavior of the plasmapause at mid-latitudes - Isis 1 Langmuir probe measurements

Observations of the electron concentration and the temperature from the electrostatic probes on the Isis 1 satellite were used to examine the location and behavior of the plasmapause at about 3000-km altitude in the vicinity of L = 4. At these altitudes the electron concentration measurements are equivalent to measurements of H(+), since the satellite is well into the protonosphere. The plasmapause is evident as a sharp drop in electron concentration by a factor of 100 as the satellite passes into the polar cap, and a corresponding increase is observed as it enters the plasmasphere on the opposite side of the earth. An enhancement of temperature is also observed at the plasmapause, an effect that is most visible at night, when the temperatures at latitudes above and below the plasmapause are usually very low. The position of the plasmapause decreases with magnetic activity but is found to be somewhat less sensitive to Kp than is the equatorial plasmapause.

Brace, L. H.↗
NASA NTRS1973

Predawn enhancement of 6300-A emission observed near the plasmapause from the Isis-2 spacecraft.

Data from several Isis-2 spacecraft passes are described in which the 6300-A atomic oxygen red line photometer mapped intensity steps resembling the predawn enhancement. Comparison with the electron density measured at the spacecraft indicates a plasmapause influence on the 6300-A emission rate, in that the intensity varies roughly inversely with the electron density at 1400 km. A simple calculation demonstrates the idea that field line opacity differences for photoelectrons are significant across the plasmapause. The measured electron temperatures are inadequate to account for the 6300-A excitation, thus confirming that it must arise from another mechanism.

Shepherd, G. G.↗
NASA NTRS1973

An observation of polar auroral and airglow from the ISIS-II spacecraft.

This is a preliminary but comprehensive report on coordinated data obtained with the ISIS-II spacecraft, fourth in the ISIS series, launched 1 April 1971, into a near circular 1400 km orbit. The capabilities of the ISIS-I spacecraft have been extended in a number of ways, including the global mapping of the 3914, 5577 and 6300 A emissions. Data obtained during a 30-min pass over the south pole depict the nightside oval and polar cap, as well as mid-latitude airglow effects; these data are described and discussed.

Shepherd, G. G.↗
NASA NTRS1973

The behavior of the plasmapause at mid-latitudes: ISIS-1 Langmuir probe measurements

Observations of the electron concentration, N sub e, and temperature, T sub e, from the electrostatic probes on the ISIS-1 satellite were used to examine the location and behavior of the plasmapause at about 3000 kilometers altitude in the vicinity of L = 4. At these altitudes, the N sub e measurements are equivalent to measurements of H(+) since the satellite is well into the protonosphere. The plasmapause as is evident as a sharp drop in N sub e by a factor of 10 to 100 as the satellite passes into the polar cap, and a corresponding increase is observed as it enters the plasmasphere on the opposite side of the Earth. An enhancement of T sub e is also observed at the plasmapause, an effect that is most visible at night when the temperatures at latitudes above and below the plasmapause are usually very low. The position of the plasmapause decreases with magnetic activity but is found to be somewhat less sensitive to K sub p than is the equatorial plasmapause. Also unlike its equatorial behavior, the mid-latitude plasmapause exhibits no detectable late afternoon bulge. These differences imply rather complex coupling of the thermal plasma along the field lines that link these two regions of the plasmasphere. An additional factor may be the recently observed axial asymmetry in the geomagnetic field at high altitudes.

Brace, L. H.↗
NASA NTRS1973

The Atmosphere Explorer spacecraft system.

Brief description of the design goals, spacecraft, data system, and data analysis concept for the Atmosphere Explorer (AE) mission. The AE mission is shown to have been conceived and to be implemented for making possible a variety of studies of the lower thermosphere. The spacecraft support system, including an onboard propulsion system, will enable investigations to be carried out deep in the thermosphere and at all points of aeronomic significance about the earth.

Spencer, N. W.↗
NASA NTRS1973

The cylindrical electrostatic probes for Atmosphere Explorer -C, -D, and -E.

This paper briefly describes the cylindrical electrostatic probes to be used on the new Atmosphere Explorer-C, -D, and -E, and outlines the methods to be employed to analyze the experimental data in terms of electron temperature and ion and electron concentration. Two independent cylindrical sensors and partially redundant electronic systems permit greater reliability in measurements. Measurements are made at 1-sec and 2-sec intervals along the orbit. The sensors themselves have been modified from previous applications to cope with the lower electron temperature expected in these low-altitude orbits and to counter possible surface contamination caused by the hydrazine engines used for orbit adjustments.

Brace, L. H.↗
NASA NTRS1973

Comparison of Te and Ti from Ogo 6 and from various incoherent scatter radars.

Langmuir probe and retarding potential analyzer (RPA) data on the electron and ion temperatures Te and Ti obtained from Ogo 6 are compared with Te and Ti values obtained from the incoherent scatter network. The satellite to radar temperature ratio TeS/TeR is 1.15 on the average for these comparisons. This discrepancy is larger than the uncertainties usually placed on the probe and radar Te values. The ion temperature ratio TiS/TiR approximately 1.0, independent of the particular radar examined. This comparison serves as an intercalibration of the incoherent scatter network.

Mcclure, J. P.↗
NASA NTRS1972

Isis 1 observations of the high-latitude ionosphere during a geomagnetic storm.

The Isis 1 satellite has made measurements of several ionospheric and related parameters, and the results of the various measurements have been compared in detail for two north transpolar passes during the geomagnetic storm of February 3, 1969. Simultaneous measurements were made of local electron and ion densities and temperatures, electron density between the satellite and the peak of the F layer, radio noise, and particle fluxes over a wide energy range extending down to 10 eV. Several features of the ionosphere (in particular, enhancements of radio noise, scale height, and plasma temperatures) appear to be due to soft-particle (100 eV to 1 keV) precipitation, which is related to magnetospheric structure as delineated by the observation of more energetic particles. The magnetosheath particles precipitating on the dayside of the polar cap are particularly effective.

Whitteker, J. H.↗
NASA NTRS1972

Neutral-particle wake method for measuring the atmospheric temperature from a satellite.

Description of a method that would permit a satellite-borne neutral mass spectrometer to measure the atmospheric temperature. The spectrometer examines the partial pressure variations that occur as the wake of a small rectangular baffle is swept across the entrance orifice of the spectrometer. For a given baffle size and for a mounting distance from the orifice, the depth of the resulting pressure minimum depends only on the thermal velocity or temperature of the observed species. The validity of the method can be checked by measuring the wake characteristics of more than one species and/or by employing each of several baffle sizes. The theory includes the effect of a finite orifice size, finite baffle length, and the backscattering of particles from the baffle into the orifice. It is found that a suitable baffle arrangement can be achieved that will permit the temperature to be measured over at least the range normally encountered in the thermosphere (200 to 2000 K) and, depending on the sensitivity and background pressure of the spectrometer, over an altitude range of about 140 to 600 km.

Brace, L. H.↗
NASA NTRS1972

The electron heating rate and ion chemistry in the thermosphere above Wallops Island during the solar eclipse of 7 March 1970.

Measurement of the N2 concentration and temperature, the ion composition and concentrations, and the electron temperature up to 290 km about 30 and 5 min before totality during the Mar. 7, 1970, eclipse. The rockets traveled similar trajectories, thus permitting the purely temporal changes between flights to be resolved. The neutral temperature and N2 concentration changed little, but the electron temperature decreased by as much as 20% in the lower F region. The ion concentration decreased by about 30% in the F region and about 50% in the E region, with little change in relative ion composition. The electron cooling rates decreased by a factor of 6 in the lower F region, approximately in proportion to the change in the visible solar disk. A smaller than expected decrease in the cooling rate below 150 km between the two flights indicates a hardening of the solar spectrum and suggests a significant heat contribution from the solar corona near totality. The ion composition measurements were consistent with solutions of the ion continuity equations. A proper fit required a factor-of-three enhancement of the flux below 200 A, an amount also consistent with the electron heat balance analysis. Reactions involving the minor ions N(+) and N2(+) were found to be important for the ion chemistry of the major ions O2(+) and NO(+), especially at the time of eclipse.-

Brace, L. H.↗
NASA NTRS1971

A neutral particle wake method for measuring the atmospheric temperature from a satellite

A method is described that permits a satellite-borne neutral mass spectrometer to perform measurements of the atmospheric temperature. The method employs the spectrometer to examine the partial pressure variations that occur as the wake of a small rectangular baffle is swept across the entrance orifice of the spectrometer. For a given baffle size and mounting distance from the orifice the depth of the resulting pressure minimum depends only upon the thermal velocity, or temperature, of the observed species. A check upon the validity of the method is obtained by measuring the wake characteristics of more than one species and/or by employing each of several baffle sizes.

Brace, L. H.↗