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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The polar wind

The classical polar wind is considered to be an ambipolar outflow of thermal plasma from the terrestrial ionosphere at high latitudes. The paper reviews the characteristic features of this flow, with emphasis placed on recent theoretical predictions. Consideration is given to H(+) and He(+) outflow characteristics both with and without convection electric field effects, the collisionless polar wind characteristics (including the formation of temperature anisotropies), and the time-dependent polar wind behavior in response to localized density perturbations and localized heat sources.

Schunk, R. W.↗
NASA NTRS1981

Investigation from Japanese MAGSAT team

The acquisition of tapes which contain vector and scalar data decimated at an interval of 0.5 sec, together with time and position data, is reported. Progress in the study of magnetic anomalies in the vicinity of Japan and in electric currents in the ionosphere and magnetosphere is also reported. MAGSAT data was used in obtaining a map of total force anomaly for the area of latitude 10-70 deg N and longitude 110-170 deg E. One of the outstanding features in the map of the magnetic anomaly is a negative magnetic anomaly in the Okhotsk Sea, which is of geophysical interest because of its possible connection with high heat flow values in that area.

Fukushima, N.↗
NASA NTRS1972

The ionosphere during a subauroral red arc

The enhancements of the red 6300A line in the midlatitudes during maximum solar activity are discussed. From Explorer 31 and OGO-4 satellite data, electron and ion temperatures were obtained at altitudes of 880km and 2500km. It was found that there is an increased plasma temperature in the region of the optical emissions, a difference of 1000k between the plasma temperature at 880km and that at 2100km, and the ion temperatures are less than the electron temperatures. It is concluded that red arcs are observed only when there is heat flow from above, combined with decreased density caused by composition changes at the lower boundary.

Maier, E.↗
NASA NTRS1989

Monte-Carlo modeling of polar wind photoelectron distributions with anomalous heat flux

In situ measurements above the polar cap by the DE satellites show asymmetric field-aligned electron velocity distributions in the photoelectron energy range 5-60 eV. The formation of these anisotropic distributions is described by a collisional kinetic equation that includes the effects of Coulomb collisions (via a Fokker-Planck operator), those of a parallel electric field, and the magnetic mirror effects of the geomagnetic field. This equation is solved using a Monte Carlo simulation method. The simulation illustrates the formation of the portion of the observed electron distributions originating in the ionosphere and makes it possible to evaluate the significance of the suprathermal electrons at higher altitude. Both observations and calculations indicate that these electrons possess an energy flux which, by its effect on the polar-wind electric field, may influence the dynamics of the polar-wind outflow.

Yasseen, F.↗
NASA NTRS1978

Helium ion outflow from the terrestrial ionosphere

For situations where ion outflow occurs from the topside ionosphere, steady-state solutions for the He(+) continuity, momentum, and energy equations have been obtained self-consistently, yielding density, velocity, and temperature profiles of He(+) from 200 to 2000 km altitude. The study indicates that the outflowing He(+) has density profiles of similar shape to those of H(+), for basically different reasons; the effect of the perpendicular electric field differs considerably for H(+) and He(+); the fractional heating of He(+) due to the He(+)-O(+) relative flow is not as effective in heating He(+) as the flow is in heating H(+); during magnetospheric disturbances the He(+) peak density decreases only by approximately a factor of 2; and the He(+) escape flux over the winter pole is approximately a factor of 20 greater than the He(+) escape flux over the summer pole. The possibility of interhemispheric He(+) flux from winter to summer on high-latitude closed field lines is considered.

Raitt, W. J.↗
NASA NTRS1974

Temperature and density structure of thermal proton flows

Thermal proton flows along magnetic field lines are an important feature of magnetosphere-ionosphere coupling. In this paper we report the results of a theoretical study of the thermal structure of such flows. The adopted steady state model is based upon O+, H+, and electrons with self-consistent solutions for the separate O+, H+, and electron temperatures, the O+ and H+ densities and the H+ drift velocity. Through investigation of a number of parameters affecting the model, it is shown that Joule heating arising from the flow of H+ through O+ preferentially heats H+, so that the H+ temperature is substantially greater than the O+ temperature. Low O+ densities characteristic of the trough region appear to give high H+/O+ temperature ratios. Typical O+ densities characteristic of polar wind flow regions give moderate H+/O3 temperature ratios. The Mach number of H+ outflow is substantially reduced in the present models in comparison with the older fixed temperature calculations.

Banks, P. M.↗
NASA NTRS1981

Energization of ionospheric ions by electrostatic hydrogen cyclotron waves

Interactions between ionospheric ions and electrostatic hydrogen cyclotron waves are studied numerically in an investigation of a possible mechanism for the energization of the low-energy ionospheric ions flowing along geomagnetic field lines to high altitudes. Ion equations of motion are solved numerically for a given number of O(+), He(+) and He(2+) ions initially in a Maxwellian distribution. All the ions considered are found capable of undergoing stochastic acceleration by a coherent electrostatic hydrogen cyclotron wave with parameters typical of the auroral plasma above 1 earth radius. The fraction of the initial ion population undergoing heating depends strongly on the mass, charge and initial temperature of the ion species, with O(+) ions only heated when their initial temperature is approximately greater than the hydrogen temperature and the lighter ions able to be heated even when cold, due to cyclotron resonant stochastic heating.

Singh, N.↗
NASA NTRS1984

Direct evidence for two-stage (bimodal) acceleration of ionospheric ions

Energetic ion composition spectrometer data gathered on hybrid conical ion distributions by the Dynamics Explorer 1 in the topside ionosphere are reported. The observed ion distributions were field-aligned and upward flowing, with energies up to 5 keV. Increases in ion energy were accompanied by a departure from field-alignment and a cone patterned upward flow, with the apex in the auroral field lines and the cone angle widening upward as the energy increased. Both transverse and parallel accelerations were imparted to the ions, with the transverse heating occurring in a 5000 km extent region centered at 18,000 km altitude. A bi-Maxwellian distribution, a temperature of 1.2 keV and a 260 eV parallel temperature were found at the top of the region.

Klumpar, D. M.↗
NASA NTRS2002

Kinetics of Fast Atoms in the Terrestrial Atmosphere

This report summarizes our investigations performed under NASA Grant NAG5-8058. The three-year research supported by the Geospace Sciences SR&T program (Ionospheric, Thermospheric, and Mesospheric Physics) has been designed to investigate fluxes of energetic oxygen and nitrogen atoms in the terrestrial thermosphere. Fast atoms are produced due to absorption of the solar radiation and due to coupling between the ionosphere and the neutral thermospheric gas. We have investigated the impact of hot oxygen and nitrogen atoms on the thermal balance, chemistry and radiation properties of the terrestrial thermosphere. Our calculations have been focused on the accurate quantitative description of the thermalization of O and N energetic atoms in collisions with atom and molecules of the ambient neutral gas. Upward fluxes of oxygen and nitrogen atoms, the rate of atmospheric heating by hot oxygen atoms, and the energy input into translational and rotational-vibrational degrees of atmospheric molecules have been evaluated. Altitude profiles of hot oxygen and nitrogen atoms have been analyzed and compared with available observational data. Energetic oxygen atoms in the terrestrial atmosphere have been investigated for decades, but insufficient information on the kinetics of fast atmospheric atoms has been a main obstacle for the interpretation of observational data and modeling of the hot geocorona. The recent development of accurate computational methods of the collisional kinetics is seen as an important step in the quantitative description of hot atoms in the thermosphere. Modeling of relaxation processes in the terrestrial atmosphere has incorporated data of recent observations, and theoretical predictions have been tested by new laboratory measurements.

Kharchenko, Vasili A.↗
NASA NTRS1993

Comparison of hydrodynamic and semi-kinetic treatments for plasma flow along closed field lines

Hydrodynamic and semi-kinetic treatments of plasma flow along closed geomagnetic field lines are compared. The hydrodynamic treatment is based on a simplified 16-moment set of transport equations as the equations for the heat flows are not solved; the heat flows are treated heuristically. The semi-kinetic treatment is based on a particle code. The comparison deals with the distributions of the plasma density, flow velocity, and parallel and perpendicular temperatures as obtained from the two treatments during the various stages of the flow. In the kinetic treatment, the appropriate boundary condition is the prescription of the velocity distribution functions for the particles entering the flux tubes at the ionospheric boundaries; those particles leaving the system are determined by the processes occurring in the flux tube. The prescribed distributions are half-Maxwellian with temperature T(sub 0) and density n(sub 0). In the hydrodynamic model, the prescribed boundary conditions are on density (n(sub 0)), flow velocity (V(sub 0)) and temperature (T(sub 0). It was found that results from the hydrodynamic treatment critically depend on V(sub 0); for early stages of the flow this treatment yields results in good agreement with those from the kinetic treatment, when V(sub 0) = square root of (kT(sub 0)/2 (pi)m), which is the average velocity of particles moving in a given direction for a Maxwellian distribution. During this early stage, the flows developing form the conjugate ionospheres show some distinct transitions. For the first hour or so, the flows are highly supersonic and penetrate deep into the opposite hemispheres, and both hydrodynamics and kinetic treatments yield almost similar features. It is found that during this period heatflow effects are negligibly small. When a flow penetrates deep into the opposite hemisphere, the kinetic treatment predicts reflection and setting up of counterstreaming. In contrast, the hydrodynamic treatment yields a shock in the flow. The reasons for this difference in the two treatments is discussed, showing that in view of the relatively warm ions, the coupling of ion beams and the consequent shock formation in the offequatorial region are not likely due to the enhancements in the beam temperatures. The counterstreaming in the kinetic treatment and the shock in the hydrodynamic treatment first advance upward to the equator and then downward to the ionospheric boundary from where the flow originated. The transit time for this advancement is found to be about 1 hour for the respective models. After 2 hours or so, both models predict that the flows from the ionospheric boundaries are generally subsonic with respect to the local ion-sound speed. At late stages of the flow, when a substantial fraction of ions entering the flux tube begin to return back in the kinetic treatment, the hydrodynamic treatment with the boundary condition V(sub 0) = square root of (kT(sub 0)/2(pi)m) yields an over-refilling, and the choice of V(sub 0) becomes uncertain.

Singh, Nagendra↗
NASA NTRS1980

Solar zenith angle dependence of ionospheric ion and electron temperatures and density on Venus

The measurements taken during the first year of the Pioneer Venus orbiter retarding potential analyzer indicate the changes of ion and electron temperatures with solar zenith angles. The ion density decreases by an order of magnitude from dayside to nightside; median ion temperatures above 300 km are constant with the solar zenith angle below 150 deg and reach 2300 K at the ionopause. The ion temperatures below 300 km are almost constant with solar zenith angles during the dayside, but increase with the angles on the nightside. The electron temperatures suggest a constant heat flux into the electron gas at the ionopause which may be supplied by dissipation of energy by the whistler mode plasma waves at the ionopause and/or conduction of heat from the ionosheath through the mantle.

Miller, K. L.↗
NASA NTRS1980

Suprathermal electron energy distribution within the dayside Venus ionosphere

The suprathermal electron energy distribution for the dayside ionosphere has been derived from data returned by the Pioneer-Venus orbiter retarding potential analyzer. The shape and magnitude of the spectrum are consistent with the assumption that solar EUV radiation is the only significant source. The magnitude of the spectrum and its variation with altitude suggest that significant vertical transport occurs, with the electrons being lost through the ionopause. In turn, significant vertical transport suggests that the effective vertical electron heat conductivity may be comparable to the field-free value. The heat input to the thermal electron gas from the measured suprathermal electron flux is too small by a factor of at least five to maintain the observed electron temperature profile if the electron thermal conductivity is assumed to be close to the field-free value. It is thus inferred that most of the heat is supplied by the solar wind.

Knudsen, W. C.↗
NASA NTRS1994

The microphysics of particle acceleration in the auroral ionosphere: Why sounding rocket measurements are essential

Through the combination of attitude controlled, high altitude rockets (altitudes greater than 600 km), high telemetry rates (several megabits/sec), pitch angle imaging particle sensors and interferometric wave measurements giving wavelength in addition to frequency data, the series of TOPAZ flights have uncovered a low altitude acceleration mechanism by which ionospheric ions receive their initial energy transverse to B in order to leave the ionosphere and populate the trapped radiation. The transverse acceleration of oxygen and hydrogen ionospheric ions is the result of Landau resonance of these ions with intense (up to 400 mv/m) lower hybrid waves on the resonance cone within caviton structures. Future work is directed toward trying to measure the size of the solitary wave structures. From a statistical argument, they appear to be the order of 100 m across B and much longer in dimension along B. Important questions remain: are there other low altitude heating mechanisms acting as well; is the dayside ion outflow driven differently. To answer these questions, it is intended to make sounding rocket measurements in the cusp/cleft region. The proposed Norwegian rocket launch facility at Svalbard could play a very important role by providing easy access to the cusp/cleft region.

Arnoldy, Roger L.↗
NASA NTRS2000

Interhemispheric Plasma Flows in the Equatorial Topside Ionosphere

Latitudinal, longitudinal, and seasonal variations in the field-aligned and perpendicular flows measured at an altitude near 830 km, by the Defense Meteorological Satellite Program F10 satellite are examined. These profiles are studied during the nighttime (2100 magnetic local time) for solstice periods in 1991 when the solar activity is high. Latitude and longitude variations show the influence of F region winds in modulating the observed field-aligned flows. At night, large downward field-aligned flows of the order 400-600/ ms are observed in the winter hemisphere and coincide in longitude with the location of previously identified adiabatic heating effects studied by Venkatraman and Heelis. Interhemispheric flows at 2100 hours local time are seen to extend up to apex heights of approx. 1000 km during times of high solar activity. Perpendicular drifts, however are relatively invariant with latitude as expected.

Venkatraman, Sarita↗
NASA NTRS1990

Solar cycle variations in F-region Te in the vicinity of the midlatitude trough based on AE-C measurements at solar minimum and DE-2 measurements at solar maximum

Magnetospheric energy deposited in the plasmasphere produces large enhancements in the electron temperature in the nightside ionosphere at the foot of the geomagnetic L shell that traverses the plasmapause. This temperature peak, which is associated with the midlatitude trough in electron density, often has a great enough amplitude to produce 630 nm emission known as a Sar-arc. The Atmosphere Explorer-C measurements made at solar minimum and the Dynamics Explorer-2 measurements made at solar maximum are used to illustrate how this signature of F-region electron heating changes with solar activity. Global empirical models of the electron temperature and density have not been able to resolve these features thus far because of their large movements with geomagnetic activity and because of the large bin sizes used in the models. It is not yet clear how this major feature of the F-region temperature structure could be included easily in the IRI model.

Brace, Larry H.↗
NASA NTRS1985

A time-dependent theoretical model of the polar wind Preliminary results

The coupled, time-dependent continuity, momentum, and energy equations of a two-ion O(+) and H(+) quasi-neutral plasma were solved in order to extend understanding of polar wind behavior. This numerical code allows studies of the time dependent behavior of polar wind-type flows into and out of the ionosphere. Initial studies indicate that the typical time constants for electron and ion temperature changes are of the order of minutes and tens of minutes, respectively. The response time of the minor high altitude ion O(+) is less than an hour, whereas that of the major ion, H(+), is many hours. The initial test runs also demonstrate the fact that temporary supersonic flows of both O(+) and H(+) are possible, especially in the presence of significant ion heating.

Gombosi, T. I.↗
NASA NTRS1993

The role of ring current nose events in producing stable auroral red arc intensifications during the main phase - Observations during the September 19-24, 1984, equinox transition study

A set of observations describing ionospheric conditions, magnetospheric populations, and 6300-A emission intensities on stable auroral red (SAR) arc field lines during the solar minimum 19-24 Sept. 1984 magnetic storm period prompted a study of solar cycle and magnetic storm phase variations in SAR arc emissions and their magnetospheric energy source. It was found that medium-energy H(+) was significantly enhanced during the main phase compared to the late recovery phase of the 19-20 Sept. 1984 storm. Enhanced heating of the thermal electron plasma caused by this population resulted in more than an order of magnitude greater SAR arc emissions in the main phase compared to the recovery phase. O(+) was found to be the dominant energy source for SAR arcs in the late recovery phases of storms in the 19-24 Sept. period.

Kozyra, J. U.↗
NASA NTRS1985

Observations of E region irregularities generated at auroral latitudes by a high-power radio wave

The initial results of a series of observations made with the high-power HF heating facility near Tromso, Norway are reported. During these experiments, attention was focused on the production of artificial geomagnetic field-aligned irregularities (AFAIs) in the auroral E region by HF waves. A mobile 46.9-MHz radar was used to diagnose the formation of AFAIs having spatial scales of 3.2 across geomagnetic field lines. The dynamic characteristics of the AFAIs are discussed within the context of current theoretical work dealing with the natural production of AFAIs in the ionosphere.

Djuth, F. T.↗