Search NASA⌕ Search

SEARCH · Search NASA

Results for “Plasma Solar Wind”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Search for fine scale structures in high latitude solar wind

About 25 years ago, E. Parker suggested that, as a consequence of the inhomogeneous structure of the corona, the solar wind might consist of adjacent structures with different physical conditions. Since that suggestion was made, the solar wind plasma characteristics have been measured in situ through many experiments, but little has been done to check whether the solar wind shows any evidence for fine scale structures, and, in the affirmative, how far from the Sun these structures persist. A previous work on this subject, by Thieme, Marsch and Schwenn (1990), based on Helios data, lead these authors to claim that the solar wind, between 0.3 and 1 AU, is inhomogeneous on a scale consistent with the hypothesis that the plume-interplume plasmas, at those distances, still retain their identity. In this work we present preliminary results from an investigation of the solar wind fine structure from Ulysses high latitude observations. To this end, we have analyzed data over several months, during 1994, at times well after Ulysses's last encounter with the Heliospheric Current Sheet, when the spacecraft was at latitudes above 50 degrees. These data refer to high speed wind coming from southern polar coronal holes and are best suited for plume-interplume identification. We have performed a power spectra analysis of typical plasma parameters, to test whether the wind plasma consist of two distinct plasma populations. We also examined data to check whether there is any evidence for an horizontal pressure balance over the hypothesized distinct structures. Our results are discussed and compared with previous findings.

Livi, S.↗
NASA NTRS1990

The scientific mission of Ulysses

The major aims of the Ulysses' scientific investigations of the heliosphere at all latitudes are described. Missions goals include the assessment of the global three-dimensional properties of the interplanetary magnetic field and solar wind, the study of the composition of the solar wind plasma at different heliographic latitudes, and the study of the acceleration of energetic particles in solar flares. Waves, shocks and other discontinuities in the solar wind will be investigated through sampling of various plasma conditions, and interplanetary dust and cosmic rays will be analyzed. Other important goals include the search for gamma-ray-burst sources and for low-frequency gravitational waves by using the spacecraft's radio communication link. Achievement of the Ulysses' solar pole trajectory, which will utilize both launch vehicle thrust and gravitational pull, is also described.

Wenzel, K.-P.↗
NASA NTRS2004

Radiation and Internal Charging Environments for Thin Dielectrics in Interplanetary Space

Spacecraft designs using solar sails for propulsion or thin membranes to shade instruments from the sun to achieve cryogenic operating temperatures are being considered for a number of missions in the next decades. A common feature of these designs are thin dielectric materials that will be exposed to the solar wind, solar energetic particle events, and the distant magnetotail plasma environments encountered by spacecraft in orbit about the Earth-Sun L2 point. This paper will discuss the relevant radiation and internal charging environments developed to support spacecraft design for both total dose radiation effects as well as dose rate dependent phenomenon, such as internal charging in the solar wind and distant magnetotail environments. We will describe the development of radiation and internal charging environment models based on nearly a complete solar cycle of Ulysses solar wind plasma measurements over a complete range of heliocentric latitudes and the early years of the Geotail mission where distant magnetotail plasma environments were sampled beyond X(sub GSE) = -100 Re to nearly L2 (X(sub GSE) ~-236 Re). Example applications of the environment models are shown to demonstrate the radiation and internal charging environments of thin materials exposed to the interplanetary space plasma environments.

Minow, Joseph I.↗
NASA NTRS1980

Sunward flow in Jupiter's magnetosheath

The position of Voyager crossings of Jupiter's bow shock show a dependence on solar wind pressure to the -1/3 power. This dependence is used to calculate typical bow shock speeds of 50 km/s from Voyager solar wind plasma data. Since the bow shock and magnetopause move approximately in unison in response to solar wind pressure changes, the resulting movement of the magnetosheath at a sizeable fraction of the solar wind speed leads to reversed, sunward flow in large portions of the dayside region when the boundaries are expanding. Voyager 1 plasma data show evidence of such reversed flow.

Siscoe, G. L.↗
NASA NTRS1995

Eight-moment approximation solar wind models

Heat conduction from the corona is important in the solar wind energy budget. Until now all hydrodynamic solar wind models have been using the collisionally dominated gas approximation for the heat conductive flux. Observations of the solar wind show particle distribution functions which deviate significantly from a Maxwellian, and it is clear that the solar wind plasma is far from collisionally dominated. We have developed a numerical model for the solar wind which solves the full equation for the heat conductive flux together with the conservation equations for mass, momentum, and energy. The equations are obtained by taking moments of the Boltzmann equation, using an 8-moment approximation for the distribution function. For low-density solar winds the 8-moment approximation models give results which differ significantly from the results obtained in models assuming the gas to be collisionally dominated. The two models give more or less the same results in high density solar winds.

Olsen, Espen Lyngdal↗
NASA NTRS1995

Structure of magnetic field in the solar wind

This work is concerned with empirical data on magnetic field in the solar wind in frame of a concept of dissipative solar wind, developed in papers (Solar Wind 7 Conf., Pergamon Press, 1992, 165 and 1992 STEP/5th COSPAR Coll. Pergamon Press, 1994, 117; 235; 803). Interplanetary magnetic fields should be classified with respect to their origin. It is very important for all the theoretical problems from the necessity to specify correctly boundary and initial conditions: the magnetic field must be sewed with its source. One should select the field, connected directly with the Sun (stretched out from it), and the field of moving electric currents. It occured central in discussion about the velocity of Alfven waves, probably warming up the solar wind, relative to the Sun, the magnetic field and solar wind plasma. The selection problem corresponds to an inverse problem and obviously has no single solution. The dissipative model of the solar wind introduce the slipping and leakage of plasma relative to magnetic field. There are no 'interplanetary current sheets' in it. But temporal fluctuations from the filamentation of electric currents play the key role. As a whole, the new concept requires the re-interpretation of main objects in the interplanetary magnetic field.

Chertkov, A. D.↗
NASA NTRS1974

Steady state asymmetric planetary electrical induction

An analytic solution is presented for the steady state electric and magnetic fields induced by the motional electric field of the solar wind in the atmosphere or interior of a planet that is asymmetrically surrounded by solar wind plasma. The electrically conducting ionosphere or interior must be in direct electrical contact with the solar wind over the day side of the planet. The conducting region of the planet is modeled by a sphere or a spherical shell of arbitrarily stratified electrical conductivity. A monoconducting cylindrical cavity is assumed to extend downstream on the night side of the planet. The solar wind is assumed to be highly conducting so that the induced fields are confined to the planet and cavity. Induced currents close as sheet currents at the solar wind-cavity and solar wind-planet interfaces. Numerical evaluations of the analytic formulas are carried out for a uniformly conducting spherical model.

Horning, B. L.↗
NASA NTRS1994

Ulysses at 50 deg south: Constant immersion in the high-speed solar wind

We present speed observations from the Ulysses solar wind plasma experiment through 50 deg south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km/s range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefractions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing spacecraft latitude. Trends in prevailing speed with increasing latitude support previous findings. A decrease in peak speed southward of 40 deg latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes.

Phillips, J. L.↗
NASA NTRS2012

Turbulence in a Global Magnetohydrodynamic Simulation of the Earth's Magnetosphere during Northward and Southward Interplanetary Magnetic Field

We report the results of MHD simulations of Earth's magnetosphere for idealized steady solar wind plasma and interplanetary magnetic field (IMF) conditions. The simulations feature purely northward and southward magnetic fields and were designed to study turbulence in the magnetotail plasma sheet. We found that the power spectral densities (PSDs) for both northward and southward IMF had the characteristics of turbulent flow. In both cases, the PSDs showed the three scale ranges expected from theory: the energy-containing scale, the inertial range, and the dissipative range. The results were generally consistent with in-situ observations and theoretical predictions. While the two cases studied, northward and southward IMF, had some similar characteristics, there were significant differences as well. For southward IMF, localized reconnection was the main energy source for the turbulence. For northward IMF, remnant reconnection contributed to driving the turbulence. Boundary waves may also have contributed. In both cases, the PSD slopes had spatial distributions in the dissipative range that reflected the pattern of resistive dissipation. For southward IMF there was a trend toward steeper slopes in the dissipative range with distance down the tail. For northward IMF there was a marked dusk-dawn asymmetry with steeper slopes on the dusk side of the tail. The inertial scale PSDs had a dusk-dawn symmetry during the northward IMF interval with steeper slopes on the dawn side. This asymmetry was not found in the distribution of inertial range slopes for southward IMF. The inertial range PSD slopes were clustered around values close to the theoretical expectation for both northward and southward IMF. In the dissipative range, however, the slopes were broadly distributed and the median values were significantly different, consistent with a different distribution of resistivity.

magnetohydrodynamics (MHD)↗
NASA NTRS1983

Non-planar MHD model for solar flare-generated disturbances in the heliospheric equatorial plane

An analysis, with a representative (canonical) example of solar-flare-generated equatorial disturbances, is made for the temporal and spatial changes in the solar wind plasma and magnetic field environment between the sun and 1 AU. The goal is to search for first-order global consequences rather than to make a parametric study. The analysis treats all three plasma velocity and magnetic field components in any convenient heliospheric plane of symmetry. The representative disturbance is examined for the canonical case in which the temporal and spatial changes in a homogeneous solar wind caused by a solar-flare-generated shock wave are described. All plasma and field parameters at three radial locations are examined. These are the central meridian and 33 deg W and 90 deg W of the flare's central meridian. It is found that the incorporation of a small meridional magnetic field in the ambient magnetic spiral field has negligible effect on the results. The magnetic field exhibits strong kinking within the interplanetary shocked flow, even reversed polarity that, coupled with low temperature and low density, suggests a plausible explanation for magnetic clouds' with accompanying double-streaming of electrons observed at directions approximately 90 deg to the heliocentric radius.

Wu, S. T.↗
NASA NTRS1994

Ulysses near-ecliptic observations of differential flow between protons and alphas in the solar wind

The evolution of differential streaming between protons and alpha particles in the solar wind was observed with the solar wind plasma experiment on the Ulysses spacecraft over the solar range of 1.15 to 5.40 AU between November 18, 1990, and May 5, 1992. The correlation of the difference in ion speeds, Delta V = the absolute value of V(sub alpha) - the absolute value of V(sub p), with the proton speed V(sub p) observed by other spacecraft at solar distances less than or equal to 1 AU disappeared at approximately 2 AU. At solar distances greater than or equal to 2.85 AU, the largest values of both V(sub alpha p) = the absolute value of V(sub alpha p) = the absolute value of V(sub alpha) - V(sub p) and the absolute value of Delta V were found in the interaction regions on the leading edges of high-speed streams. The differential streaming was typically enhanced just downstream of strong forward and reverse shocks, and large negative values of Delta V were frequently encountered in the interaction regions. A correlation between V(sub alpha p) and the ratio tau(sub zero)/tau(sub e) of Coulomb collision time to expansion time was observed at all distances, but it is suggested that at the larger values of tau(sub zero)/tau(sub e) observed correlation may arise from enhanced production of differential streaming by processes that also increase the entropy of the solar wind protons.

Neugebauer, M.↗
NASA NTRS1988

Preshock region acceleration of implanted cometary H(+) and O(+)

A self-consistent, three-fluid model of plasma transport and implanted ion acceleration in the unshocked solar wind is presented. The solar wind plasma is depleted by charge exchange with the expanding cometary exosphere, while implanted protons and heavy ions are produced by photoionization and charge transfer and lost by charge exchange. A generalized transport equation describing convection, adiabatic and diffusive velocity change, and the appropriate production terms is used to describe the evolution of the two cometary ion components, while the moments of the Boltzmann equation are used to calculate the solar wind density and pressure. The flow velocity is obtained self-consistently by combining the conservation equations of the three ion species. The results imply that second-order Fermi acceleration can explain the implanted spectra observed in the unshocked solar wind. Comparison of measured and calculated distribution indicates that spatial diffusion of implanted ions probably plays an important role in forming the energetic particle environment in the shock vicinity.

Gombosi, Tamas I.↗
NASA NTRS1972

Solar wind maintenance of the nighttime Venus ionosphere

An attempt is made to establish an ionization source capable of maintaining the nighttime Venus ionosphere. The corpuscular ionization and heating caused by the penetration of solar wind plasma into the nightside ionosphere was suggested as a possible source. Theoretical tests, using an interacting solar wind model, were made of the electron density and the results compared with observed electron density profiles. Results indicate the solar wind could maintain the nighttime ionosphere of Venus.

Hartle, R. E.↗
NASA NTRS1974

Suprathermal particles

Recent observations of suprathermal particles in the interplanetary medium in the energy range from solar wind (above about 1 keV) to low energy solar cosmic rays (about 1 MeV) are reviewed. A crude classification of the types of observed fluxes is given, and the sources of the suprathermal particle populations and energy contained in them are discussed. Among the possible interactions of these particles with the solar wind plasma, the particular interaction which generates type III solar radio bursts is analyzed.

Lin, R. P.↗
NASA NTRS1978

The composition of corotating energetic particle streams

The relative abundances of 1.5 to 23 MeV/nucleon ions in corotating nucleon streams were compared with ion abundances in particle events associated with solar flares and with solar and solar wind abundances. He/O and C/O ratios were found to be a factor of the order two to three times greater in corotating streams than in flare associated events. The distribution of H/He ratios in corotating streams was found to be much narrower and of lower average value than in flare associated events. H/He in corotating energetic particle streams compared favorably both in lack of variability and numerical value to H/He in high speed solar wind plasma streams. This comparison suggested that the source population for the corotating energetic particles was the solar wind.

Mcguire, R. E.↗
NASA NTRS1983

Multiple spacecraft observations of interplanetary shocks ISEE three-dimensional plasma measurements

ISEE 1 and ISEE 3 three-dimensional solar wind plasma measurements are used together with magnetic field measurements across five previously studied interplanetary shocks to test the accuracy of the mixed-mode shock-normal determination technique and to test whether the shock properties are best approximated with a ratio of specific heats of 5/3 or 2. In the shocks examined, the assumption that the velocity jump was along the normal provided an estimate of the shock normal within 15 deg of the best fit normal 50 percent of the time and within 50 deg, 90 percent of the time. The mixed-mode normals lay within 12 deg of the best fit normal 50 percent of the time and within 36 deg, 90 percent of the time. Part of this deviation may be due to differences in the orientation of the local normal from that of the average normal. Finally, the jump in plasma and field across the shock is better predicted from the Rankine-Hugoniot equations using a ratio of specific heats of 5/3 rather than 2.

Russell, C. T.↗
NASA NTRS1988

Data reduction and analysis of HELIOS plasma wave data

Reduction of data acquired from the HELIOS Solar Wind Plasma Wave Experiments on HELIOS 1 and 2 was continued. Production of 24 hour survey plots of the HELIOS 1 plasma wave data were continued and microfilm copies were submitted to the National Space Science Data Center. Much of the effort involved the shock memory from both HELIOS 1 and 2. This data had to be deconvoluted and time ordered before it could be displayed and plotted in an organized form. The UNIVAX 418-III computer was replaced by a DEC VAX 11/780 computer. In order to continue the reduction and analysis of the data set, all data reduction and analysis computer programs had to be rewritten.

Anderson, Roger R.↗