Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “wind interaction”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Magnetic field observations near Mercury - Preliminary results from Mariner 10

Results are presented from a preliminary analysis of data obtained near Mercury on Mar. 29, 1974 by the NASA-GSFC magnetic field experiment on Mariner 10. Rather unexpectedly, a very well-developed, detached bow shock wave, which develops as the super-Alfvenic solar wind interacts with the planet, has been observed. In addition, a magnetosphere-like region, with maximum field strength of 98 gammas at closest approach (704 kilometers altitude), has been observed, contained within boundaries similar to the terrestrial magnetopause. The obstacle deflecting the solar wind flow is global in size, but the origin of the enhanced magnetic field has not yet been uniquely established. The field may be intrinsic to the planet and distorted by interaction with the solar wind.

Ness, N. F.↗
NASA NTRS1990

Magnetic asymmetries of unmagnetized planets

This letter discusses the results produced by three-dimensional hybrid particle code simulations of the solar wind interaction with unmagnetized planets such as Venus and Mars. The solar wind velocity is perpendicular to the IMF in the cases studied. It is found that there are asymmetries in both the magnetic structure and shock location for spherical obstacles ranging in radius from 1000 km to 6000 km. The asymmetries found are due to differences in the electron and ion current paths (diamagnetic behavior). Mass loading of 0(+) was not included in these simulations.

Brecht, Stephen H.↗
NASA NTRS2008

Radiation Transport of Heliospheric Lyman-alpha from Combined Cassini and Voyager Data Sets

Heliospheric neutral hydrogen scatters solar Lyman-alpha radiation from the Sun with '27-day' intensity modulations observed near Earth due to the Sun's rotation combined with Earth's orbital motion. These modulations are increasingly damped in amplitude at larger distances from the Sun due to multiple scattering in the heliosphere, providing a diagnostic of the interplanetary neutral hydrogen density independent of instrument calibration. This paper presents Cassini data from 2003-2004 obtained downwind near Saturn at approximately 10 AU that at times show undamped '27-day' waves in good agreement with the single-scattering models of Pryor et al., 1992. Simultaneous Voyager 1 data from 2003- 2004 obtained upwind at a distance of 88.8-92.6 AU from the Sun show waves damped by a factor of -0.21. The observed degree of damping is interpreted in terms of Monte Carlo multiple-scattering calculations (e.g., Keller et al., 1981) applied to two heliospheric hydrogen two-shock density distributions (discussed in Gangopadhyay et al., 2006) calculated in the frame of the Baranov-Malama model of the solar wind interaction with the two-component (neutral hydrogen and plasma) interstellar wind (Baranov and Malama 1993, Izmodenov et al., 2001, Baranov and Izmodenov, 2006). We conclude that multiple scattering is definitely occurring in the outer heliosphere. Both models compare favorably to the data, using heliospheric neutral H densities at the termination shock of 0.085 cm(exp -3) and 0.095 cm(exp -3). This work generally agrees with earlier discussions of Voyager data in Quemerais et al., 1996 showing the importance of multiple scattering but is based on Voyager data obtained at larger distances from the Sun (with larger damping) simultaneously with Cassini data obtained closer to the Sun.

Pryor, W.↗
NASA NTRS2011

Eta Carinae - A Demanding Mistress

Over the past 15 years, a number of observers and modelers have increasingly focused on this massive system that is approaching its end stage, a supernova? a hypernova? When? The discovery by Augusto Damineli that Eta Carinae had a 5.5-year period proved timely as the newly-installed STIS was primed to observe its properties in the visible and ultraviolet. Initial observations occurred on January 1998, and through multiple programs, including the multi-cycle Hubble Treasury program, have sampled changes across two cycles. Now a multi-cycle program, focused on mapping variations in the extended wind-wind collision zones through early 2015, will test 3-D models of the interacting winds. In parallel, studies have been accomplished in X-rays with RXTE and CHANDRA, now in the far infrared with Herschel and from the ground with VLT. Each new observation is helping to peel back the veil of mystery on this massive binary system, but also opening up more questions to be answered. Timely inclusion of laboratory studies and models have greatly enhanced the observational results. We will summarize the latest results including submitted papers and very recent results with Herschel.

Gull, Theodore R.↗
NASA NTRS1987

Asymmetry of the heliosphere

The outflowing solar wind interacts with the local interstellar medium to form the heliospheric cavity within which the solar wind is supersonic. Because the interstellar medium is moving with respect to the sun, and because the solar wind has a latitude dependence, the heliosphere is asymmetric. The flow of the interstellar medium past the heliosphere produces an asymmetry because of the Bernoulli effect, which draws the heliosphere out in a direction orthogonal to the upstream-downstream axis, and because of a viscous interaction, which draws out the heliosphere downstream. A variety of cases are considered and the effects are found to be significant with, typically, the upstream direction having a heliospheric dimension that is 2/3 the downstream dimension. Suggestions have been put forth to the effect that a spacecraft penetration of the heliospheric shock wave may be imminent. Because one of the most distant spacecraft is moving roughly in the upstream direction relative to the interstellar flow, and the other is moving in the downstream direction, the distance to their encounters with the heliospheric shock may differ by as much as 40 AU.

Suess, S. T.↗
NASA NTRS1984

A comparative review of bow shocks and magnetopauses

Bow shock and magnetopauses formation is discussed. Plasma and magnetic field environments of all the planets from Mercury to Saturn were measured. It was found that all the planets have bow shocks and almost all have a magnetopause. Venus is the only planet with no measurable intrinsic magnetic field and the solar wind interacts directly with Venus' ionosphere. The bow shock characteristics depend on the changing solar wind conditions. The shape of a magnetopause or any obstacle to flow depends on the three dimensional pressure profile that it presents to the solar wind. Jupiter is unusual because of the considerable amount of plasma which is contained in its magnetosphere. Magnetopause boundaries in ecliptic plane projection are modelled by segments of ellipses, matched to straight lines for the magnetotool boundaries or parabolas. Specific properties of known planetary bow shocks and magnetopauses are reviewed.

Lepping, R. P.↗
NASA NTRS1982

The cometary atmosphere and its interaction with the solar wind

The present state of knowledge of cometary atmospheres and their interaction with the solar winds is assessed. Current models of the magnetospheres and ionospheres of comets are based on either an atmospheric chemistry approach, minimizing the effects of atmospheric dynamics and thermodynamics, while the other method takes the exact opposite viewpoint and roles and significance are reversed. A major difficulty in completing the models is a lack of data on the chemical composition of the cometary nucleus, although UV observations have revealed the H, C, O, and S elemental abundance ratios. It is suggested that further studies of collisional ionization by energetic electrons be performed to characterize processes in the cometary atmosphere. Hydronium may be the dominat molecule in the inner coma, if the assumption that the ionosphere is a magnetic field-free cavity separated from the solar wind by an unyielding tangential discontinuity surface is accurate. Particular observations and theoretical attention are recommended for the solar wind interaction in the intermediate range, i.e., 2.5-5 AU, when the cometary atmosphere develops.

Mendis, D. A.↗
NASA NTRS1994

One-dimensional multispecies magnetohydrodynamic models of the ramside ionosphere of Titan

The interaction of the Saturnian magnetosphere with the ionosphere of Titan has much in common with the solar wind interaction with nonmagnetic bodies in general. A one-dimensional magnetohydrodynamic model was developed, for radial distances of 1.3 to 2 Titan radii (R(sub T)), to study the dynamics of H2CN(+), C(sub n) H(sub m) (+) (n, m greater than z), C2H5(+), and CH5(+), in the ramside ionosphere of Titan. For the case of a dayside ramside ionosphere (solar zenith angle of 60 degs) we found that the external magnetospheric plasma interacting with Titan's ionosphere produced a very broad region of ionospheric magnetic field whose peak field strength was approximately 26 nT. The ionosphere was magnetized well below the ionospheric peak, allowing ionizing Saturnian magnetospheric electrons access to this region. The sources of ionization and the electron temperature profiles incorporated into the model depend on the relative locations of Titan, Saturn, and the Sun. The calculated electron and ion density profiles as well as the magnetic field profile also depend on the relative positions of Titan, Saturn, and the Sun.

Keller, C. N.↗
NASA NTRS2003

Reduction and Analysis of Data from the IMP 8 Spacecraft

The IMP 8 spacecraft was launched in 1973 and the MIT solar wind Faraday Cup experiment continues to produce excellent data except for a slightly increased noise level. Those data have been important for determining the solar wind interaction with Earth's magnetic field; studies of interplanetary shocks; studies of the correlation lengths of solar wind features through comparisons with other spacecraft; and more recently, especially important for determination of the regions in which the Wind spacecraft was taking data as it passed through Earth's magnetotail and for understanding the propagation of solar wind features from near 1 AU to the two Voyager spacecraft.

Source record↗
NASA NTRS1978

The interaction between a magnetized plasma flow and a magnetized celestial body - A review of magnetospheric studies

Previous studies of solar-system magnetospheres are reviewed. Attention is given to the internal structure of the magnetospheres of earth and Mercury, the open structure of the terrestrial magnetosphere, aurorae, functions of the terrestrial magnetosphere, the disklike outer structure of Jupiter's magnetosphere, and the plasma processes involved in the development of a magnetospheric potential drop and electric field. The interaction between a turbulent magnetized plasma flow and a magnetosphere is discussed on the basis of studies of the solar-wind interaction with the terrestrial magnetosphere. A 'gathered' or folded magnetic equatorial plane is suggested for the sun, coronal holes are identified as the source region for fast solar-wind streams, and magnetic energy conversion processes of relevance to earth and the sun are considered. Two models of a magnetospheric substorm are examined, and difficulties encountered in understanding substorm processes are summarized.

Akasofu, S.-I.↗
NASA NTRS1980

Solar wind absorption by Venus

The portion of solar wind interacting with the dayside ionosphere and atmosphere of Venus was determined based on magnetic field fluctuations in the ionosheath and the interaction with the upper neutral atmosphere above the ionopause. Fluctuations with the ratio of the number of particles intersecting the daytide ionopause to the total number of particles of 0.3 suggest that about 0.3% of solar wind may be absorbed. Most of fast H atoms resulting from the charge exchange interactions with the atmosphere escape; some of the energy deposition processes produce observable signatures (such as a narrow Lyman alpha emission region), but penetrating solar wind particles do not control the physical and/or chemical structure of the daytime Venus ionosphere.

Gombosi, T. I.↗
DOE OSTI2024

Thermal Bekenstein-Hawking entropy from the worldsheet

We define and compute the leading sphere diagram contribution to the entropy of the BTZ black hole supported by Kalb-Ramond flux in bosonic string theory. In a winding condensate description, integrating exactly over the constant mode for the radial direction of AdS 3 reduces the problem to one of the correlation functions of winding operators in the free theory. The volume of the residual PSL(2,ℂ) gauge group of the sphere is canceled by the action of conformal transformations on the winding interaction insertions. We formulate a precise version of the replica trick in terms of (infinitesimally) non-integer winding condensates to produce the entropy of the BTZ black hole. The resulting entropy can be calculated from the one-point function of a non-local operator on the worldsheet.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1979

Mars in the solar wind

Recent spacecraft observations and model calculations of the solar wind interaction (SWI) at Mars have shown that the particle pressure is not large enough to stand off the solar wind unless the electron temperature is 4 times the ion temperature in the ionosphere, but the additional pressure is presumably magnetic, provided by a planetary magnetic field. In addition, a planetary field corresponding to a surface field of about 20 gammas, and a dipole moment of about 8 x 10 to the 21st gauss per cu cm are implied. Calculations indicate that 60-70% of the pressure is supplied by the magnetic field, and 30-40% by the ionosphere. Thus, the SWI at Mars is unique, being an interaction both with the atmosphere and with the planetary magnetic field.

Intriligator, D. S.↗