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1981

Physics

All Physics Faculty Publications

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Full-Text Articles in Physical Sciences and Mathematics

Radar Measurements Of High-Latitude Ion Composition Between 140 And 300 Km Altitude, J. D. Kelly, Vincent B. Wickwar Jan 1981

Radar Measurements Of High-Latitude Ion Composition Between 140 And 300 Km Altitude, J. D. Kelly, Vincent B. Wickwar

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The Chatanika radar has been used to measure the ratio of atomic (O+) ions to molecular (O2 +, NO+) ions in the high-latitude ionosphere. The radar results agreed well with simultaneous in situ rocket data, giving confidence in the radar method of deducing ion composition. Measurements made over long periods of time show seasonal variations, diurnal variations, and variations due to auroral processes. The transition altitude, where the number densities of atomic and molecular ions are equal, is a convenient parameter for describing the composition variation with altitude or ‘composition altitude profile.’ The transition …

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An Intense Wave/Particle Event In The Auroral Ionosphere, A. D. Johnstone, Jan Josef Sojka, W. Gibbons, B. K. Madahar, L.J. C. Woolliscroft Jan 1981

An Intense Wave/Particle Event In The Auroral Ionosphere, A. D. Johnstone, Jan Josef Sojka, W. Gibbons, B. K. Madahar, L.J. C. Woolliscroft

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An intense burst of VLF waves, at frequencies just above the local proton gyrofrequency, was observed shortly after each of two intense bursts of field‐aligned suprathermal electrons (E < 250eV) by instruments carried on a sounding rocket flown in diffuse aurora. If the two phenomena are associated with each other, the implication is that the electron acceleration occurred nearby, in a relatively small volume.

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Energization Of Ionospheric Ions By Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka Jan 1981

Energization Of Ionospheric Ions By Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka

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Interactions between ionospheric ions and a monochromatic electrostatic hydrogen cyclotron wave were studied numerically for conditions corresponding to the auroral plasma. Strong heating of the minority ions He+, He++, and O+ were observed. The fraction of the initial ion population which underwent heating was found to strongly depend on the mass, charge, and initial temperature of the ion species.

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A Theoretical Study Of The High-Latitude Winter F Region At Solar Minimum For Low Magnetic Activity, Jan Josef Sojka, W. J. Raitt, Robert W. Schunk Jan 1981

A Theoretical Study Of The High-Latitude Winter F Region At Solar Minimum For Low Magnetic Activity, Jan Josef Sojka, W. J. Raitt, Robert W. Schunk

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We combined a simple plasma convection model with an ionospheric-atmospheric composition model in order to study the high-latitude winter F region at solar minimum for low magnetic activity. Our numerical study produced time dependent, three-dimensional ion density distributions for the ions NO+, O2 +, N2 +, O+, N+, and He+. We covered the high-latitude ionosphere above 54°N magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day. The main result we obtained was that high-latitude ionospheric features, such as the ‘main trough,’ the ‘ionization hole,’ the ‘tongue of ionization,’ the ‘aurorally produced …

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Theoretical Predictions For Ion Composition In The High-Latitude Winter F-Region For Solar Minimum And Low Magnetic Activity, Jan Josef Sojka, W. John Raitt, Robert W. Schunk Jan 1981

Theoretical Predictions For Ion Composition In The High-Latitude Winter F-Region For Solar Minimum And Low Magnetic Activity, Jan Josef Sojka, W. John Raitt, Robert W. Schunk

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We combined a simple plasma convection model with an ionospheric-atmospheric density model in order to study the ion composition in the high-latitude winter F-region at solar minimum for low geomagnetic activity. Our numerical study produced time-dependent, 3-dimensional, ion density distributions for the ions NO+, O2 +, N2 +, O+, N+, and He+. We covered the high-latitude ionosphere above 54°N magnetic latitude and at altitudes between 160 and 800 km for a time period of 1 complete day. From our study we found the following (1) The ion composition exhibits a significant variation with latitude, local time, altitude, and universal time. …

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Plasma Density Features Associated With Strong Convection In The Winter High-Latitude F Region, Jan Josef Sojka, W. John Raitt, Robert W. Schunk Jan 1981

Plasma Density Features Associated With Strong Convection In The Winter High-Latitude F Region, Jan Josef Sojka, W. John Raitt, Robert W. Schunk

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We combined a simple plasma convection model with an ionospheric-atmospheric composition model in order to study the plasma density features associated with strong convection in the winter high-latitude F region. Our numerical study produced time-dependent, three-dimensional, ion density distributions for the ions NO+, O2 +, N2 +, O+, N+, and He+. We covered the high-latitude ionosphere above 42° N magnetic latitude and at altitudes between 160 and 800 km for a time period of one complete day. From our study, we found the following: (1) For strong convection, the electron density exhibits a significant variation with altitude, latitude, longitude, and …

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Auroral Plasma Lines: A First Comparison Of Theory And Experiment, E. S. Oran, Vincent B. Wickwar, W. Kofman, A. Newman Jan 1981

Auroral Plasma Lines: A First Comparison Of Theory And Experiment, E. S. Oran, Vincent B. Wickwar, W. Kofman, A. Newman

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In this preliminary report on low-energy (0.3 to 3 eV) secondary electrons in the auroral E layer (90 to 150 km), we compare intensities of plasma lines observed with the Chatanika radar to theoretical predictions obtained from a detailed numerical model. The model calculations are initiated with a flux of energetic auroral primary electrons which enter the atmosphere and lose energy to electrons, ions, and neutrals through a combination of elastic and inelastic collisions. This flux is chosen in order that the total calculated ionization rate matches one that is deduced from the radar measurements. From these same calculations the …

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Elevated Electron Temperatures In The Auroral E Layer Measured With The Chatanika Radar, Vincent B. Wickwar, C. Lathuillere, W. Kofman, G. Lejeune Jan 1981

Elevated Electron Temperatures In The Auroral E Layer Measured With The Chatanika Radar, Vincent B. Wickwar, C. Lathuillere, W. Kofman, G. Lejeune

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An extensive series of spectral measurements has been made in the auroral E region with the Chatanika incoherent scatter radar. Becasue of the small scale length for variations of electron density, temperatures, and ion-neutral collisions we used the operating mode with the best possible range resolution—9 km. About 5% of the time the data exhibited an unusual spectral shape that was most pronounced at 105 and 110 km. Instead of being almost Gaussian with only a small hint of two peaks, the spectra are much wider, with two well-developed peaks. After carefully considering the validity of the measurements and their …

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