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Full-Text Articles in Physics

Mst Radar Data-Base Management, Vincent B. Wickwar Dec 1983

Mst Radar Data-Base Management, Vincent B. Wickwar

All Physics Faculty Publications

No abstract provided.


Equatorial Disturbance Dynamo Electric Fields, Bela G. Fejer, M. F. Larsen, D. T. Farley Jul 1983

Equatorial Disturbance Dynamo Electric Fields, Bela G. Fejer, M. F. Larsen, D. T. Farley

Bela G. Fejer

F-region vertical drift data from Jicamarca, Peru show that equatorial east-west electric fields are sometimes perturbed 16-24 hours after the onset of geomagnetic storms. These disturbance dynamo electric fields, which must be caused primarily by the action of neutral winds at low and middle latitudes, decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime. The long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed. The data also show that after some storms there are no such delayed disturbances, a fact which may be due ...


Studies Of Self-Focusing Instability At Arecibo, D. T. Farley, C. Lahoz, Bela G. Fejer Mar 1983

Studies Of Self-Focusing Instability At Arecibo, D. T. Farley, C. Lahoz, Bela G. Fejer

Bela G. Fejer

Precisely simultaneous radar and satellite measurements at the altitude of reflection of a strong HF heating wave above the Arecibo Observatory were made on June 7, 1977. Parametric instabilities produce strong enhancements in the plasma line and ion line incoherent scatter radar echoes. These echoes also exhibit periodic deep fading that is attributed to a self-focusing instability. This explanation was confirmed by the in situ observation of electron density fluctuations with peak-to-peak amplitudes reaching at least 3% and a spatial dependence that corresponded closely to the radar fading pattern, at least for irregularity wavelengths ranging from a few hundred meters ...


First Vhf Auroral Radarinterferometer Observations, J. Providakes, W. E. Swartz, D. T. Farley, Bela G. Fejer Jan 1983

First Vhf Auroral Radarinterferometer Observations, J. Providakes, W. E. Swartz, D. T. Farley, Bela G. Fejer

Bela G. Fejer

The radar interferometer technique first used at the magnetic equator in Peru is also a very powerful means for studying auroral plasma instabilities. We present here the first results, obtained with a 49.92 MHz, 20-25 KW peak power pulsed radar located in Ithaca, NY (42.5° N, 76.4° W). Strong auroral echoes were obtained during several highly active periods. Phase differences between the signals received on the two antennas accurately determine the E-W position, within the scattering volume, of localized scattering centers, and changes in this phase determine the corresponding velocity. The signal Doppler shift describes radial (essentially ...


Large-Scale Counterstreaming Of H+ And He+ Along Plasmaspheric Flux Tubes, P. G. Richards, Robert W. Schunk, Jan Josef Sojka Jan 1983

Large-Scale Counterstreaming Of H+ And He+ Along Plasmaspheric Flux Tubes, P. G. Richards, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

An interhemispheric plasma transport model has been used to study the flow characteristics of H+, He+, and O+ along closed geomagnetic field lines for solstice conditions at noon local time. The calculations were carried out for the flux tube that passes through Millstone Hill. Both symmetric and asymmetric neutral winds in the conjugate ionospheres were considered. Initially, the flux tube content was partially depleted, and the subsequent refilling was studied until a steady state flow was established between the winter and summer hemispheres. The main conclusion to be drawn from this study is that H+-He+ counterstreaming can be expected ...


Preferential Perpendicular Acceleration Of Heavy Ionospheric Ions By Interactions With Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka Jan 1983

Preferential Perpendicular Acceleration Of Heavy Ionospheric Ions By Interactions With Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

The energization of heavy ionospheric ions by electrostatic hydrogen cyclotron (EHC) waves is examined. In particular, the problem of preferential perpendicular acceleration of heavy ions above 5000 km along auroral field lines is examined critically. Observations have indicated that above this altitude the occurrences of ion beams and EHC waves are highly correlated and that the occurrence rates are high. The EHC waves are found to be coherent. The energization process is examined in the light of interactions of a single coherent wave with the ions. The interactions can be stochastic or nonstochastic, depending on the parameters of the wave ...


A Theoretical Study Of The High Latitude F Region’S Response To Magnetospheric Storm Inputs, Jan Josef Sojka, Robert W. Schunk Jan 1983

A Theoretical Study Of The High Latitude F Region’S Response To Magnetospheric Storm Inputs, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

The response of the polar ionosphere to magnetospheric storm inputs was modeled. During the storm the two major processes that couple the F region to the magnetosphere, namely the electric field distribution and the particle precipitation from the magnetosphere, undergo drastic modification on relatively short F region time scales. These time-dependent changes are not simply related to the F region storm time dependent changes. The lower F region responds on a time scale of only minutes to the storm associated changes in the auroral precipitating electron flux, owing to the dominance of chemistry production-loss mechanisms over transport processes. At higher ...


Comparison Of Model High-Latitude Electron Densities With Millstone Hill Observations, Jan Josef Sojka, Robert W. Schunk, J. V. Evans, J. M. Holt, R. H. Wand Jan 1983

Comparison Of Model High-Latitude Electron Densities With Millstone Hill Observations, Jan Josef Sojka, Robert W. Schunk, J. V. Evans, J. M. Holt, R. H. Wand

All Physics Faculty Publications

Model predictions of the diurnal variations of plasma convection velocities and electron densities in the high-latitude ionosphere were compared with Millstone Hill incoherent scatter radar observations for an equinox day on which there was moderate magnetic activity. On the observation day, three major morphological features were evident at 500 km, including a dayside high density region, a nightside mid-latitude trough, and a region of slightly enhanced densities in the auroral zone. Although the dayside high density region was due to solar EUV radiation, it was not symmetrical about local noon (1000-1900 LT sector) owing to the effect of horizontal transport ...


Characteristics Of Thermal And Suprathermal Ions Associated With The Dayside Plasma Trough As Measured By The Dynamics Explorer Retarding Ion Mass Spectrometer, Jan Josef Sojka, Robert W. Schunk, J.F. E. Johnson, J. H. Waite, C. R. Chappell Jan 1983

Characteristics Of Thermal And Suprathermal Ions Associated With The Dayside Plasma Trough As Measured By The Dynamics Explorer Retarding Ion Mass Spectrometer, Jan Josef Sojka, Robert W. Schunk, J.F. E. Johnson, J. H. Waite, C. R. Chappell

All Physics Faculty Publications

The retarding ion mass spectrometer (RIMS) instrument on Dynamics Explorer 1 has carried out high-altitude measurements of the polar wind. During an outbound pass through the outer plasmasphere and plasma trough at 0900 LT the RIMS instrument measured the detailed characteristics of the thermal and suprathermal ions. Three distinct populations were observed: (1) thermal ions (H+ and He+) with densities ranging from > 500 ions/cm3 to < 1 ion/cm3, temperatures around 2 eV (20,000° K), and H+/He+ density ratios of 2 to 4, (2) warm anisotropic plasma with densities ranging from 2 to 12 ions/cm3, temperatures between ...


Fluorescence Quenching At High Quencher Concentrations, David Peak, T C. Werner, R M. Dennin Jr., J K. Baird Jan 1983

Fluorescence Quenching At High Quencher Concentrations, David Peak, T C. Werner, R M. Dennin Jr., J K. Baird

All Physics Faculty Publications

Chemical reactions occurring in dense media at high reactant concentrations can be described by rate ‘‘constants’’ which are actually functions of concentration. We present a theoretical model in which this so‐called rate constant ‘‘renormalization’’ occurs for the specific case of fluorescence quenching in solution. We show that both the quenching and the excitation rate constants can become concentration dependent. We fit our theory to several sets of experimental data—our own and some from the literature—and show that excellent agreement is obtained by varying a single free parameter, namely, the efficiency with which a fluorophore‐quencher collision leads ...


Incoherent Scatter Measurements Of Ion-Neutral Collision Frequencies And Temperatures In The Lower Thermosphere Of The Auroral Region, C. Lathuillere, Vincent B. Wickwar, W. Kofman Jan 1983

Incoherent Scatter Measurements Of Ion-Neutral Collision Frequencies And Temperatures In The Lower Thermosphere Of The Auroral Region, C. Lathuillere, Vincent B. Wickwar, W. Kofman

All Physics Faculty Publications

Incoherent scatter observations performed in March and November 1978 at Chatanika have been used for studying the lower thermosphere in the auroral region. Neutral temperatures and densities have been found during periods without Joule heating. We present mean profiles of temperatures and collision frequencies (approximately proportional to neutral densities) for each month and profiles obtained during four specific nights. Between 93 km and 110 km the mean profiles of temperature are in good agreement with the Jacchia (1971) model, and the profiles of collision frequency are similar to those deduced from the model. Consistency checks between these collision frequencies and ...


Experimental Evidence For The Acceleration Of Thermal Electrons By Ion Cyclotron Waves In The Magnetosphere, A. J. Norris, J.F. E. Johnson, Jan Josef Sojka, G. L. Wrenn, N. Cornilleau-Wehrlin, S. Perraut, A. Roux Jan 1983

Experimental Evidence For The Acceleration Of Thermal Electrons By Ion Cyclotron Waves In The Magnetosphere, A. J. Norris, J.F. E. Johnson, Jan Josef Sojka, G. L. Wrenn, N. Cornilleau-Wehrlin, S. Perraut, A. Roux

All Physics Faculty Publications

Ion cyclotron waves (ICWs) at frequencies just above f He+ , the helium gyrofrequency, are often observed by the ESA satellites GEOS 1 and GEOS 2. Young et al. (1981) have shown the close connection between these ICWs and the presence of thermal He+ ions in the outer magnetosphere. The purpose of this paper is to provide experimental evidence for the acceleration of thermal electrons by the large amplitude ICWs. The wave power in the ultra low frequency (ULF) range near f He+ is compared with the distribution function of low energy electrons, measured by instruments aboard the GEOS satellites. It ...