Engineering topics

Strickland, Douglas J.

Publications and source records attributed to Strickland, Douglas J..

4 records

NASA NTRS2004

Next Generation Transport Phenomenology Model

This report describes the progress made in Quarter 3 of Contract Year 3 on the development of Aeronomy Phenomenology Modeling Tool (APMT), an open-source, component-based, client-server architecture for distributed modeling, analysis, and simulation activities focused on electron and photon transport for general atmospheres. In the past quarter, column emission rate computations were implemented in Java, preexisting Fortran programs for computing synthetic spectra were embedded into APMT through Java wrappers, and work began on a web-based user interface for setting input parameters and running the photoelectron and auroral electron transport models.

Strickland, Douglas J.↗

NASA NTRS1996

Thermospheric O/N2 Based on DE-1 FUV Dayglow Imaging Data

Work performed during the second half of Year 1 of the contract is summarized. The primary objective of the work is to derive global dayside thermospheric oxygen concentrations from DE-1 far ultraviolet imaging data which we are considering under both magnetically quiet and disturbed times. Work to date has been more qualitative in producing maps showing intensity variations beyond those that can be explained by changes in solar zenith angle (SZA) and look angle across an image (Craven et al., 1995; Meier et al., 1994; Gladstone, 1994). In meeting our primary objective, four tasks have been addressed during the reporting period: (1) Investigating the uniqueness of the relationship between the dayglow emission seen using DE-1's 123 filter (dominated by OI 130.4 nm emission) and the column abundance of O relative to N2 referenced to an N2 depth of 10(exp 17) cm(exp 2); (2) Completion of the algorithm for rapid conversion of DE-1 disk dayglow measurements to O/N2 values; (3) Applying the algorithm to a simulation in which a model DE image was constructed using TIGCM atmospheres. The retrieved image of O/N2 was compared to TIGCM O/N2 obtained by integrations of the TIGCM densities; and (4) Applying the algorithm to selected DE-1 data.

Strickland, Douglas J.↗

NASA NTRS1991

Nitrogen airglow sources - Comparison of Triton, Titan, and earth

The individual contributions of direct solar excitation, photoelectron excitation, and magnetospheric electron excitation of Triton and Titan airglow observed by the Voyager Ultraviolet Spectrometer (UVS) are quantified. The principal spectral features of Triton's airglow are shown to be consistent with precipitation of magnetospheric electrons with power dissipation about 500 million W. Solar excitation rates of the dominant N2 and N(+) emission features are factors of 2-7 weaker than magnetospheric electron excitation. On Titan, the calculated disk center and bright limb N(+) 1085 A intensities due to solar excitation agree with observed values, while the 970 A feature is mostly N21 c5 band emission. The calculated LBH intensity by photoelectrons suggests that magnetospheric electrons play a minor role in Titan's UV airglow. On earth, solar/photoelectron excitation explains the observed N(+) 1085 A and LBH intensites and accounts for only 40 percent of the N(+) 916 A intensity.

Strobel, Darrell F.↗

NASA NTRS1990

Magnetospheric interaction with Triton's ionosphere

The large electron densities measured by the Voyager radio occultation experiment are attributed to the precipitation of magnetospheric electrons with energy above 10 keV. Because the ionospheric electric Pedersen conductivity of Triton is about 10,000-20,000 mho and the Alfven conductance is about 3.5 mho, direct convective flow of plasma into the essentially infinitely conducting ionosphere is negligible. Magnetospheric electrons are transported to Triton's ionopause by curvature drift as a result of weak magnetic field line draping in a sub-Alfvenic plasma interaction with Triton. At the ionopause energetic electrons have a high probability of elastic and inelastic scattering and precipitate into the upper atmosphere. The average power dissipation is estimated to be about (2 - 3) x 10 to the 8th W.

Strobel, Darrell F.↗