Engineering topics

Hanson, W. B.

Publications and source records attributed to Hanson, W. B..

At least 91 records · Page 5

NASA NTRS1980

The morphology of metallic ions in the upper atmosphere

Analysis of metallic ion data from a day-night pair of rockets, OGO 6, and the elliptic phases of AE-C and AE-D shows the presence of Fe(+) ions at altitudes above 400 km only at low magnetic latitudes. The detection probability of this ion decreases with altitude, with a maximum over the Atlantic and a minimum over India; the rocket data indicate ions in the E region during the day and on the bottom of the F layer at night. Mg(+) and Fe(+) are the dominant ions below 250 km at all latitudes, but Al(+), Na(+), Si(+), and Ca(+) are also detectable; a correlation was found between solar activity and metallic ion detection probability at low latitudes and high altitudes at night

Kumar, S.↗

NASA NTRS1980

Magnetospheric multiprobes: Investigations and instrumentation

The multiprobe scientific objectives are to: (1) determine the spatial structure of plasma phenomena such as the aurora, convection reversals, and ion troughs; (2) separate spatial and temporal variations in these phenomena; (3) determine field aligned current densities; (4) perform multiple point analysis of particle beams, wave fields, and plasma clouds that are injected into the ionosphere and magnetosphere by Spacelab active experiment facilities. Trade studies described include: instrument accommodations, power, attitude determination, electric field antennas, storage and ejection, thermal control, tracking communications, command and data management, payload and mission specialist support, functional objectives, and orbital analysis.

Burch, J. L.↗

NASA NTRS1980

Coordinated study of equatorial scintillation and in situ and radar observations of nighttime F region irregularities

A coordinated set of Atmospheric Explorer E (AE-E) satellite in situ, VHF radar backscatter, and scintillation measurements performed during 1977 over a common ionospheric volume is used to study the relationship between the plasma depletions or bubbles, the extended 3-m irregularity structures known as plumes, and bursts of scintillation activity or patches in the nighttime equatorial F region. The implications of the observed spatial structures and the level of ambient concentration on the generation of 3-m irregularities and scintillation modeling are discussed.

Basu, S.↗

NASA NTRS1980

The relationships between high-latitude convection reversals and the energetic particle morphology observed by Atmosphere Explorer

A statistical investigation and a case study of simultaneous particle and ion convection velocity measurements from Atmosphere Explorer are presented. They show that at all local times between 1800 and 0600 hours the gross convection reversal boundary lies equatorward of the boundary between the discrete, highly structured boundary plasma sheet precipitation and the polar rain. This study indicates the existence of shear and rotational convection reversals on closed field lines; the observed morphology is consistent with a partially closed magnetosphere in which some portion of convection electric field is generated in the low-latitude boundary layer.

Heelis, R. A.↗

NASA NTRS1980

Interhemispheric transport induced by neutral zonal winds in the F region

Reliable measurements of the interhemispheric ion transport velocity have shown a large longitudinal variability at equinox. The roles of zonal and meridional F region neutral winds have been evaluated in a simple way to account for the observed longitude dependence. The magnetic declination and relative displacement of the geographic and geomagnetic equators are both important considerations. It is shown that the zonal wind makes a strong contribution to the observed interhemispheric transport velocities near equinox.

Heelis, R. A.↗

NASA NTRS1980

High-latitude ion convection in the nighttime F region

A large data base of Atmosphere Explorer C measurements of the bulk ion velocity vector in the high-latitude F region has been examined. The concept of shear and rotational flow reversals is expanded upon to determine the extent to which the boundary between antisunward and sunward convection (i.e., a polar cap boundary) is an electrostatic equipotential. A most important factor in characterizing the nature of the large-scale geometrical configuration of the nighttime F region convection is the location and extent of quasi-equipotential regions of the convection reversal boundary.

Heelis, R. A.↗

NASA NTRS1980

The relationships between high latitude convection reversals and the energetic particle morphology observed by the Atmosphere Explorer

Simultaneous measurements of the auroral zone particle precipitation and the ion convection velocity by Atmosphere Explorer show a consistent difference between the location of the poleward boundary of the auroral particle precipitation and the ion convection reversal. The difference of about 1.5 degrees of invariant latitude is such that some part of the antisunward convection lies wholly within the auroral particle precipitation region. The nature of the convection reversals within the precipitation region suggests that in this region the convection electric field is generated on closed field lines that connect in the magnetosphere to the low latitude boundary layer.

Heelis, R. A.↗

NASA NTRS1980

Simultaneous observations of field-aligned currents and plasma drift velocities by Atmosphere Explorer C

The three-axis flux gate magnetometer on board the Atmosphere Explorer C (AE-C) has provided an additional magnetic field data set to the already broad spectrum of AE-C measurement. The results of an investigation into the feasibility of using the magnetometer for scientific purposes are described. It is shown that within the limitations inherent in the device and in the data reduction technique used, meaningful results can be obtained when the spacecraft is in the spinning mode. From a comparison between the field-aligned current signatures and the simultaneously observed ion convection velocity, it proved possible to locate regions of ionospheric conductivity gradients.

Bythrow, P. F.↗

NASA NTRS1979

Direct in situ measurements of thermospheric temperature

The open source neutral mass spectrometer on the Atmosphere Explorer satellites used for direct in situ measurements of the neutral gas temperature by means of the 'fly-through' mode of operation is evaluated. The derived neutral temperature (Tn) is compared with ion temperatures (T1) obtained simultaneously from the on-board retarding potential analyzer for altitudes and conditions where the two temperatures should be equal. A statistical analysis showed consistency between concurrently observed values of Tn and T1, also shown through profiles depicting their altitude distributions between 150 and 225 km. The overall magnitude of temperatures calculated from the Jacchia (1971) model results in a better representation of the observations than the higher temperatures predicted for this region by the MSIS model (Hedin, 1977), and agreement is also found between observed temperatures and neutral temperatures derived from altitude distributions of N2 particle densities.

Kayser, D. C.↗

NASA NTRS1979

Rapid subauroral ion drifts observed by Atmosphere Explorer C

Results are presented for an investigation of rapid subauroral ion drift features using data obtained over a nearly five-year period from the ion RPA/drift meter on Atmosphere Explorer-C. These latitudinally narrow features are found to be confined predominantly to the local time sector between 18:00 and 02:00 hr. They occur either singly or as multiple events, one of which almost always straddles the equatorward edge of the auroral zone. Their occurrence probability suggests a dependence of magnetic substorm activity.

Spiro, R. W.↗

NASA NTRS1979

Determination of the sources and sinks of N/+/ ions in the thermosphere

Measurements of atmospheric parameters made by the Atmosphere Explorer-C satellite used to identify mechanisms for the production and loss of N(+) ions in the ionosphere are presented. Photo-dissociative ionization of N2 is the main source below 250 km. Above 250 km the reaction O(+)(4S) + N(2D) yields N(+)(3P) + O(3P) is dominant, and a possible minor source of N(+) is the reaction O(+)(2P) + N2 yields N(+) + NO. Photoionization of N(4S) and dissociative charge exchange of He(+) with N2 constitute detectable sources above 350 km. Charge exchange of N(+) with O is a significant sink above 300 km, and the rate coefficients for these reactions are derived.

Torr, D. G.↗

NASA NTRS1979

A new concept for the daytime magnetosphere of Venus

A different type of interaction between the solar wind and the ionosphere of a non-magnetized planet suggested by the Pioneer Venus magnetic field measurements is presented. They found that the magnetic field of the shocked solar wind does not penetrate the ionosphere, and it appears that the latter acts approximately as a superconductor, excluding any substantial penetration of interplanetary magnetic field. Just beyond the ionopause is a magnetized region with little plasma whose magnetic pressure is approximately equal to the impact pressure of the solar wind. This suggests an interaction where the current system associated with the enhanced magnetic field region flows along the ionopause and is closed by currents in the shocked solar wind plasma, where the J times B forces slow down the plasma approaching the stagnation region and accelerate the plasma flowing away from it. Thus, the lack of magnetic constraint in the ionosphere would allow ionospheric plasma to flow freely from the day to the night side, and this flow could probably maintain the nighttime ionosphere.

Johnson, F. S.↗

NASA NTRS1979

An experimental and theoretical study of the mean diurnal variation of O/+/, NO/+/, O2/+/, and N2/+/ ions in the mid-latitude F1 layer of the ionosphere

A theoretical model of the diurnal variations in the compositions of the ions O(+), NO(+), O2(+) and N2(+) in the midlatitude F1 layer is presented and compared with measurements made by AE-C. The theoretical model includes the rate coefficients and branching ratios for the dissociative recombination of NO(+), O2(+) and N2(+) with electrons and the ion-atom interchanges of O(+) with N2 and N2(+) with O. Input parameters to the model comprise measurements of ion and electron temperatures, neutral atmosphere composition, the solar EUV flux and the photoelectron spectrum. In general, model calculations are found to agree with satellite measurements, confirming the major ion sources and sinks of the photochemical model, which has an accuracy of + or - 60%.

Torr, D. G.↗

NASA NTRS1979

Photoelectron fluxes in the Martian ionosphere

Calculations are presented of the steady-state photoelectron distribution in the upper atmosphere of Mars, consistent with the neutral upper atmosphere and ionosphere particle concentrations and temperatures measured by Viking 1. Uncertainties in the calculations affect the thermal electron gas heating rate. Major conclusions are that (1) over most of the altitude range of the Martian ionosphere, the steady-state photoelectron flux amplitude is larger than that in the earth's, so that photoelectron-impact-excited airglow on Mars is generally more significant than it is on earth; (2) the steady-state photoelectron energy distribution in the Martian ionosphere is softer and more structured than that in the terrestrial ionosphere; (3) photoelectron impact ionization contributes about 30% to the total ionization rate in the Martian ionosphere; and (4) photoelectron impact excitation contributes 20-30% of the CO2(+) and CO zenith airglow emissions on Mars.

Mantas, G. P.↗

NASA NTRS1979

Charge exchange of metastable 2D oxygen ions with molecular oxygen - A new source of thermospheric O2/+/ ions

Reactions involving metastable ions are difficult to study in the laboratory. Much new information on these reactions has been derived from satellite measurements of aeronomic parameters. In this paper, Atmosphere Explorer D data are used to study charge exchange of metastable O(+)(2D) ions with O2. Using direct measurements of the O2 at 200 km to compute O2 densities at 300 km and supporting ionic concentrations and temperature observations, we find the rate coefficient for this reaction to be 1 + or - 0.6 times 10 to the minus 9th cu cm/sec. The process constitutes a significant source of O2(+) ions in the F2 layer at times when the N2 and O2 densities are enhanced. This finding leads to the conclusion that charge exchange with O2 must be a major sink for O(+)(2D) and an important source of O2(+) ions in the E region, because of the increase in the O2 concentration/N2 concentration ratio with decreasing altitude. The results imply that 80% of all O(+) ions formed in the E region are converted to O2(+) and that only about 20% of the metastable O(+) ions are converted into N2(+) through charge exchange with N2.

Torr, D. G.↗

NASA NTRS1978

Ion convection and the formation of the mid-latitude F region ionization trough

Total ion concentration and ion drift velocity data from Atmospheric Explorer C are used to examine the convective flow of plasma in the vicinity of the midlatitude F region ionization trough. It is found that the low-latitude portion of the premidnight trough is a region of slow eastward plasma drift while the poleward portion is characterized by generally westward flow. The reversal from eastward to westward flow is described. It is proposed that the plasma flux tubes within the premidnight trough have corotated eastward into the evening local time sector from dusk before stagnating and flowing westward at higher latitudes in the nighttime sector. The role of F region recombination in trough formation is considered.

Spiro, R. W.↗

NASA NTRS1978

Ion temperature troughs and interhemispheric transport observed in the equatorial ionosphere

Ion temperature and ion drift velocity data from Atmosphere Explorer D have verified the existence of interhemispheric plasma transport and ion temperature troughs in the topside equatorial ionosphere. The data were taken during solar minimum conditions at night where the exospheric temperature was typically 700 K and the O(+)-H(+) transition height was 520 km. Large field-aligned ion velocities were observed above about 700 km, where the H(+)/O(+) number density ratio was about 3. Model calculations have shown that the ion temperature decrease is produced by quasi-adiabatic expansion of the plasma, but the expansion cooling mechanism is less efficient at solar minimum than at solar maximum owing to the lower O(+)-H(+) transition height. Ion temperature troughs greater than 400 K were not observed even when the field-aligned ion velocity was greater than 700 m/s. Most of the expansion occurs below the transition height, and during sunspot minimum, thermal coupling to the neutral atmosphere is much more effective in quenching the cooling which the field-aligned transport tends to produce.

Heelis, R. A.↗

NASA NTRS1977

Determination of the N2 recombination rate coefficient in the ionosphere

Measurements of aeronomic parameters made by the Atmosphere Explorer-C satellite are used to determine the recombination rate coefficient of N2(+) in the ionosphere. The rate is found to increase significantly with decreasing electron density. Values obtained range from approximately 1.4 x 10 to the -7th to 3.8 x 10 to the -7th cu cm/sec. This variation is explained in a preliminary way in terms of an increase in the rate coefficient with vibrational excitation. Thus, high electron densities depopulate high vibrational levels reducing the effective recombination rate, whereas, low electron densities result in an enhancement in the population of high vibrational levels, thus, increasing the effective recombination rate.

Orsini, N.↗