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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Ion heating by broadband low-frequency waves in the cusp/cleft

Ion heating via a cyclotron resonance process involving waves near the ion gyrofrequency is studied using data from two cusp/cleft crossings of the polar-orbiting DE 1 satellite. Observed cool O(+) distributions and wave intensities from one orbit are used as input to a Monte Carlo simulation. The results show that cyclotron resonance heating by broadband low-frequency waves can cause a major part of the ion heating observed in the cusp/cleft.

Andre, Mats↗
NASA NTRS1984

The time development of a blast wave with shock-heated electrons

Accurate approximations are presented for the time development of both edge conditions and internal structures of a blast wave with shock heated electrons, and equal ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform ambient density case) and have negligible external pressure. Account is taken of possible saturation of the thermal conduction flux. The structures evolve smoothly to the adiabatic structures.

Edgar, R. J.↗
NASA NTRS1992

Heating of solar and stellar chromospheres and coronae by MHD waves

The two general classes of models that deal with the required heating of stellar chromospheres and coronae assume that outer stellar atmospheres are heated by hydrodynamic or by magnetohydrodynamic (MHD) waves and that these waves are generated by turbulent motions in the stellar convection zones. This paper considers the types of MHD waves and the source of these waves in stars like sun, the efficiency of the generation of MHD waves, and the manner of propagation and energy dissipation of MHD waves. It is shown that the basic criteria for the validity of any theory of MHD wave heating must account for the mean level of heating observed in stellar chromospheres and coronae, and for the range of radiative losses observed for a given spectral type. It is also required that the MHD wave heating theory accounts for the existence of inhomogeneities in stellar atmospheres. The results obtained indicate that magnetic tube waves might supply enough energy for the chromospheric and coronal heating and might also account for the observed range of variations of stellar radiative losses for a given spectral type.

Musielak, Z. E.↗
NASA NTRS1974

The meridional variation of the eddy heat fluxes by baroclinic waves and their parameterization

The meridional and vertical eddy fluxes of sensible heat produced by small-amplitude growing baroclinic waves are calculated using solutions to the two-level model with horizontal shear in the mean flow. The results show that the fluxes are primarily dependent on the local baroclinicity, i.e., the local value of the isentropic slopes in the mean state. Where the slope exceeds the critical value, the transports are poleward and upward; where the slope is less than the critical value, the transports are equatorward and downward. These results are used to improve an earlier parameterization of the tropospheric eddy fluxes of sensible heat based on Eady's model. Comparisons with observations show that the improved parameterization reproduces the observed magnitude and sign of the eddy fluxes and their vertical variations and seasonal changes, but the maximum in the poleward flux is too near the equator.

Stone, P. H.↗
NASA NTRS1979

A perturbative treatment of aerosol scattering of infrared radiation

Calculations of long-wave atmospheric heating and cooling rates using the rate equations of Rodgers and Walshaw (1966) with the Malkmus (1967) random band model are presented. A perturbation scheme is developed for the inclusion of aerosol scattering effects in the numerical calculation. Unlike the flux differencing method for calculating long-wave heating and cooling rates, this scheme allows aerosol effects to be included in a simple manner with only a small additional use of computer time. The calculations indicate good agreement with those of previous investigators and demonstrate the expected equivalence of the flux-differencing method and the flux-divergence equation of Rodgers and Walshaw (1966), even at stratospheric altitudes. It is found that aerosols lead to a net heating in the lower troposphere due to infrared scattering and absorption.

Yueh, W. R.↗
NASA NTRS1980

Eddy heat fluxes and stability of planetary waves. I, II

The stability of baroclinic Rossby waves in a zonal shear flow was analyzed by a linear, quasigeostrophic, two-level, adiabatic, and frictionless midlatitude beta-plane model. The ratio of the basic wave scale and the radius of deformation together with two nondimensional parameters which describe the amplitudes of the barotropic and baroclinic components of the basic wave constitute the three parameters of the stability problem. The parameter space is partitioned according to the dominant energy source for instability; the Lorenz and Kim conditions are characterized by significant horizontal and vertical shears of the basic wave, while the Phillips regime has a strong zonal flow. The stability analysis is then applied to the atmosphere, with the primary motivation being to examine the midlatitude planetary scale (zonal wavenumbers 1, 2, 3) transient waves that transport heat. It is found that the most unstable mode consists of a spectrum of waves, with a maximum amplitude at wavenumber 3; the response is thus maximum at a zonal scale intermediate between the basic wave scale and the radius of deformation.

Lin, C. A.↗
NASA NTRS1983

The role of latent heat release in baroclinic waves - Without beta-effect

An attempt is made to understand the role of latent heat release in the development of baroclinic waves by developing the analytical theory of two-level, quasi-geostrophic baroclinic waves proposed by Phillips (1954) without beta effect, for the case of an atmosphere initially saturated with water vapor and subject to pseudo-adiabatic lifting and dry adiabatic subsistence. The saturated atmosphere condition precludes consideration of conditional convective instability. A consideration of disturbances at each level which depends only on the zonal coordinates and time results in a set of differential equations which is linear in all respects except for the latent heating term in the thermodynamic energy equation. A fundamental nonlinearity is present in this model which is due to heating via the release of latent heat when vertical motion is upward.

Tang, C.-M.↗
NASA NTRS1981

Global weather research

Modeling, prediction, and analysis of global meteorological phenomena influencing the large scale behavior of the atmosphere are summarized. Prediction of global weather phenomena based on satellite data is discussed and models of global phenomena developed. The atmospheric general circulation model (AGCE) is reviewed, axisymmetric flow calculated, and axisymmetric states in cylindrical, spherical, three dimensional, and spin up numerical models for AGCE described. The role of latent heat release in baroclinic waves, latent heat and cyclonic systems, and a theoretical study of baroclinic flow related to the AGCE and the flow regime were studied with a simplified general circulation model. AGCE and the geophysical fluid flow cell (GFFC) instrumentation are discussed. Investigation of solar and planetary convection for GFFC is described. The utilization of satellite cloud observations to diagnose the energy state and transformations in extratropical cyclones is reviewed.

Source record↗
NASA NTRS2004

FUSE Cycle 3 Program CO22: Chromospheric Activity in Population II Giants

One of the mysteries of Population II giants is that they still show chromospheric emission despite their great age. The global dynamo which was active during their main-sequence lifetimes is expected to become extremely weak through magnetic rotational braking. The nature of the observed emission is not understood; although acoustic shock waves might provide the heating, acoustic waves are not predicted to drive the observed mass loss - which in turn requires the dissipation of magneto-hydrodynamic waves. This program was designed to search for the faint stellar H Ly(beta) emission wings and the fluorescent Fe II and H2 emission from one of the brightest, metal poor, Population II stars. These FUSE diagnostics, when combined with existing UV and optical spectra, help determine the major radiative cooling channels for the chromosphere. This observation was to complement that previously planned for the mildly metal deficient giant alpha Boo (K2 III). However, a Boo has yet to be observed with FUSE.

Harper, Graham M.↗
NASA NTRS2004

Chromospheric Activity in Population II Giants

One of the mysteries of Population II giants is that they still show chromospheric emission despite their great age. The global dynamo which was active during their main-sequence lifetimes is expected to become extremely weak through magnetic rotational braking. The nature of the observed emission is not understood; although acoustic shock waves might provide the heating, acoustic waves are not predicted to drive the observed mass loss - which in turn requires the dissipation of magneto-hydrodynamic waves. This program was designed to search for the faint stellar H Ly beta emission wings and the fluorescent Fe II and H2 emission from one of the brightest, metal poor, Population II stars. These FUSE diagnostics, when combined with existing UV and optical spectra, help determine the major radiative cooling channels for the chromosphere. This observation was to complement that previously planned for the mildly metal deficient giant alpha Boo (K2 III). However, alpha Boo has yet to be observed with FUSE.

Harper, Graham M.↗
NASA NTRS2008

On Alfvenic Waves and Stochastic Ion Heating with 1Re Observations of Strong Field-aligned Currents, Electric Fields, and O+ ions

The role that the cleft/cusp has in ionosphere/magnetosphere coupling makes it a very dynamic region having similar fundamental processes to those within the auroral regions. With Polar passing through the cusp at 1 Re in the Spring of 1996, we observe a strong correlation between ion heating and broadband ELF (BBELF) emissions. This commonly observed relationship led to the study of the coupling of large field-aligned currents, burst electric fields, and the thermal O+ ions. We demonstrate the role of these measurements to Alfvenic waves and stochastic ion heating. Finally we will show the properties of the resulting density cavities.

Coffey, Victoria↗
NASA NTRS1991

Convection of ion cyclotron waves to ion-heating regions

Results are presented on calculations of the convection, to lower altitudes, of low-frequency ion cyclotron waves generated in the central plasma sheet. In the calculations, ion cyclotron waves generated in the equatorial plane by a proton temperature anisotropy are considered, and the computed growth rates are used to create a model wave distribution. Spectral densities are then mapped along the magnetic field lines, using phase space methods of Ronnmark and Larsson (1988). It was found that, even in the absence of growth associated with a plasma instability, the electric fields of ion cyclotron emissions from the equatorial region will increase substantially as the waves propagate to higher latitudes. It is shown that ion cyclotron waves propagating down the field lines may contribute to the waves observed together with ion conics.

Ronnmark, Kjell↗
NASA NTRS1990

The heating of the quiet solar chromosphere

The quiet solar chromosphere shows three distinct regions. Ordered according to the strength of the emission from the low and middle chromosphere they are (1) the magnetic elements on the boundary of supergranulation cells, (2) the bright points in the cell interior, and (3) the truly quiet chromosphere, also in the cell interior. The magnetic elements on the cell boundary are associated with intense magnetic fields and are heated by waves with very long periods, ranging from six to twelve minutes; the bright points are associated with magnetic elements of low field strength and are heated by (long-period) waves with periods near the acoustic cutoff period of three minutes; and the quiet cell interior, which is free of magnetic field, may be heated by short-period acoustic waves, with periods below one minute. This paper reviews mainly the heating of the bright points and concludes that the large-amplitude, long-period waves heating the bright points dissipate enough energy to account for their chromospheric temperature structure.

Kalkofen, Wolfgang↗
NASA NTRS1971

The solar envelope

Processes which occur within the region between approximately 2 solar radii and 25 solar radii, which is called the solar envelope and the effect on the solar wind as seen at 1 AU are discussed. In the envelope the wind speed becomes supersonic and super-Alfvenic, the magnetic energy density is larger than the flow energy density, and the magnetic energy density is much larger than the thermal energy density. Large azimuthal gradients in the bulk speed are expected in the envelope, but the stream interactions near the outer edge of the envelope are probably relatively small. Cosmic ray observations suggest the presence of hydromagnetic waves in the envelope. The collisionless damping of such waves could heat protons out to approximately 25 solar radii and thereby cause an increase in V and T sub p consistent with the observed T sub p -V relation. A mechanism which couples protons and electrons would also heat and accelerate the wind. Alfven waves can accelerate the wind in the envelope without necessarily causing heating of protons; the Lorentz force might have a similar effect.

Burlaga, L. F.↗
NASA NTRS1991

Alfven wave trapping, network microflaring, and heating in solar coronal holes

Fresh evidence that much of the heating in coronal holes is provided by Alfven waves is presented. This evidence comes from examining the reflection of Alfven waves in an isothermal hydrostatic model coronal hole with an open magnetic field. Reflection occurs if the wavelength is as long as the order of the scale height of the Alfven velocity. For Alfven waves with periods of about 5 min, and for realistic density, magnetic field strength, and magnetic field spreading in the model, the waves are reflected back down within the model hole if the coronal temperature is only slightly less than 1.0 x 10 to the 6th K, but are not reflected and escape out the top of the model if the coronal temperature is only slightly greater than 1.0 x 10 to the 6th K. Because the spectrum of Alfven waves in real coronal holes is expected to peak around 5 min and the temperature is observed to be close to 1.0 x 10 to the 6th K, the sensitive temperature dependence of the trapping suggests that the temperature in coronal holes is regulated by heating by the trapped Alfven waves.

Moore, R. L.↗