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Kozyra, J. U.

Publications and source records attributed to Kozyra, J. U..

At least 37 records · Page 2
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NASA NTRS1994

A bounce-averaged kinetic model of the ring current ion population

A bounced-averaged ring current kinetic model for arbitrary pitch angle, including losses due to charge exchange and Coulomb collisions along ion drift paths, is developed and solved numerically. Results from simplifield model runs, intended to illustrate the effects of adiabatic drifts and collisional losses on the proton population, are presented. The processes of: (1) particle acceleration under the conditions of time-independent magnetospheric electric fields; (2) a predominant loss of particles with small pitch angles due to charge exchange; and (3) a buildup of a low-energy population caused by the Coulomb drag energy degradation, are discussed.

Jordanova, V. K.↗
NASA NTRS1994

Interaction of ring current and radiation belt protons with ducted plasmaspheric hiss. 1: Diffusion coefficients and timescales

Protons that are convected into the inner magnetosphere in response to enhanced magnetic activity can resonate with ducted plasmaspheric hiss in the outer plasmasphere via an anomalous Doppler-shifted cyclotron resonance. Plasmaspheric hiss is a right-hand-polarized electromagnetic emission that is observed to fill the plasmasphere on a routine basis. When plasmaspheric hiss is confined within field-aligned ducts or guided along density gradients, wave normal angles remain largely below 45 deg. This allows resonant interactions with ions at typical ring current and radiation belt energies to take place. Such field-aligned ducts have been observed both within the plasmasphere and in regions outside of the plasmasphere. Wave intensities are estimated using statistical information from studies of detached plasma regions. Diffusion coefficients are presented for a range of L shells and proton energies for a fixed wave distribution. Harmonic resonances in the range N = +/-100 are considered in order to include interactions between hiss at 100 Hz to 2 kHz frequencies, and protons in the energy range between approximately 10 keV and 1000 keV. Diffusion timescales are estimated to be of the order of tens of days and comparable to or shorter than lifetimes for Coulomb decay and charge exchange losses over most of the energy and spatial ranges of interest.

Kozyra, J. U.↗
NASA NTRS1993

Decay of equatorial ring current ions and associated aeronomical consequences

The decay of the major ion species which constitute the ring current is studied by solving the time evolution of their distribution functions during the recovery phase of a moderate geomagnetic storm. In this work, only equatorially mirroring particles are considered. Particles are assumed to move subject to E x B and gradient drifts. They also experience loses along their drift paths. Two loss mechanisms are considered: charge exchange with neutral hydrogen atoms and Coulomb collisions with thermal plasma in the plasmasphere. Thermal plasma densities are calculated with a plasmaspheric model employing a time-dependent convection electric field model. The drift-loss model successfully reproduces a number of important and observable features in the distribution function. Charge exchange is found to be the major loss mechanism for the ring current ions; however the important effects of Coulomb collisions on both the ring current and thermal populations are also presented. The model predicts the formation of a low-energy (less than 500 eV) ion population as a result of energy degradation caused by Coulomb collision of the ring current ions with the plasmaspheric electrons; this population may be one source of the low-energy ions observed during active and quiet periods in the inner magnetosphere. The energy transferred to plasmaspheric electrons through Coulomb collisions with ring current ions is believed to be the energy source for the electron temperature enhancement and the associated 6300 A (stable auroral red (SAR) arc) emission in the subauroral region. The calculated energy deposition rate is sufficient to produce a subauroral electron temperature enhancement and SAR arc emissions that are consistent with observations of these quantities during moderate magnetic activity levels.

Fok, M.-C.↗
NASA NTRS1993

The role of ring current nose events in producing stable auroral red arc intensifications during the main phase - Observations during the September 19-24, 1984, equinox transition study

A set of observations describing ionospheric conditions, magnetospheric populations, and 6300-A emission intensities on stable auroral red (SAR) arc field lines during the solar minimum 19-24 Sept. 1984 magnetic storm period prompted a study of solar cycle and magnetic storm phase variations in SAR arc emissions and their magnetospheric energy source. It was found that medium-energy H(+) was significantly enhanced during the main phase compared to the late recovery phase of the 19-20 Sept. 1984 storm. Enhanced heating of the thermal electron plasma caused by this population resulted in more than an order of magnitude greater SAR arc emissions in the main phase compared to the recovery phase. O(+) was found to be the dominant energy source for SAR arcs in the late recovery phases of storms in the 19-24 Sept. period.

Kozyra, J. U.↗
NASA NTRS1991

Seasonal variations in the subauroral electron temperature enhancement

A statistical study of the seasonal variations of the subauroral electron temperature enhancement was undertaken using data from the Langmuir probe experiment on the DE 2 satellite throughout most of the mission (1981-1982). In the winter hemisphere the nighttime background electron temperature is the highest and the magnitude of the peak Te responds most weakly to the geomagnetic activity. This behavior can be explained by seasonal trends in the nighttime downward heat flux due to conjugate photoelectrons. Moreover, model results indicate that a factor of about three increase in heat inflow during equinox relative to solstice is required to raise the electron temperature to a given level. This is a consequence of the higher electron densities at the Te peak near equinox. The Te peak occurs on field lines which thread the outer plasmasphere in the vicinity if the plasmapause and thus can be used as a tracer of the plasmapause position.

Fok, M.-C.↗
NASA NTRS1991

Solar cycle variation in the subauroral electron temperature enhancement - Comparison of AE-C and DE 2 satellite observations

The elevation of the subauroral electron temperature is one of the phenomena showing the energy transfer from the magnetosphere and the response of the ionosphere. This study addresses solar cycle variations in the subauroral Te peak by comparing observations of the subauroral peak by the Atmosphere Explorer C (AE-C) satellite near solar minimum (1974 and 1977) with similar observations by the Dynamics Explorer 2 (DE 2) satellite near solar maximum (1981-1982). Te peaks with magnitudes sufficient to produce observable stable auroral red arc emissions occurred more frequently during solar maximum than in solar minimum, but the variation in the magnitudes and positions of these peaks with magnetic activity did not change significantly with solar cycle. These results are discussed in terms of the solar cycle changes in the ionosphere and the magnetospheric energy source.

Fok, M.-C.↗
NASA NTRS1989

Energetic (above 60 eV) atmospheric photoelectrons

Data from low altitude plasma instrument (LAPI) on Dynamics Explorer 2 document a population of high-energy (up to 800 eV) atmospheric photoelectrons that has not been reported in the published literature. The source of these photoelectrons is postulated to be the soft X-ray portion of the whole sun spectrum. This conclusion is supported by sunrise-sunset characteristics that track those of the classical (below 60 eV) EUV-produced photoelectrons, and theoretical results from two models that incorporate the soft X-ray portion of the solar spectrum. The models include K-shell ionization effects and predict peaks in the photoelectron spectrum due to Auger electrons emitted from oxygen and nitrogen. The peak for nitrogen is observed as predicted, but the peak for oxygen is barely observable. Excellent quantitative agreement is achieved between theory and experiment by using reasonable adjustments to the few published soft X-ray spectra based on solar activity. The upflowing energetic photoelectrons provide a heretofore unknown source of electrons to the magnetosphere. They occur whenever and wherever the sun is up, that is, at all invariant latitudes. Their density is low, but they are steady and ubiquitous. If scattering and trapping occur on closed field lines, then photoelectrons could contribute as a significant particle source and thus represent a new facet of magnetosphere-ionosphere coupling.

Winningham, J. D.↗
NASA NTRS1988

Modeling of the thermal plasma in the outer plasmasphere - A magnetospheric heat source

A case study has been carried out using data from the Dynamics Explorer 1 and 2 spacecraft to study the effect of Coulomb interactions between ring current and suprathermal O(+) and thermal protons on the plasmasphere. Results from a one-dimensional plasmaspheric model suggest that heating due to Coulomb collisions may be sufficient to raise the ion and electron temperatures to observed values. The resultant high temperature produced enhancements in the model O(+) and O(++) densities in agreement with observations.

Chandler, M. O.↗
NASA NTRS1987

Electron impact ionization in the vicinity of comets

The solar wind interacts very strongly with the extensive cometary coma, and the various interaction processes are initiated by the ionization of cometary neutrals. The main ionization mechanism far outside the cometary bow shock is photoionization by solar extreme ultraviolet radiation.Electron distributions measured in the vicinity of comets Halley and Giacobini-Zinner by instruments on the VEGA and ICE spacecraft, respectively, are used to calculate electron impact ionization frequencies. Ionization by electrons is of comparable importance to photoionization in the magnetosheaths of Comets Halley and Giacobini-Zinner. The ionization frequency in the inner part of the cometary plasma region of comet Halley is several times greater than the photoionization value. Tables of ionization frequencies as functions of electron temperature are presented for H2O, CO2, CO, O, N2, and H.

Cravens, T. E.↗
NASA NTRS1987

The role of ring current O(+) in the formation of stable auroral red arcs

Observations of thermal and energetic ion populations by the Dynamics Explorer 1 satellite in the magnetospheric energy source region as well as nearly simultaneous Langmuir probe measurements of enhanced electron temperatures by Dynamics Explorer 2 within the stable auroral red (SAR) arc at F region heights are used to examine the role of heavy ions in the formation of SAR arcs. It is found that sufficient energy is transferred to the electron gas at high altitudes via Coulomb collisions between the observed ring current ions and thermal electrons to support the enhanced F region electron temperatures measured on these field lines. The latitudinal variation in the electron heating rates calculated using observed ion populations is consistent with the observed variation in electron temperature across the SAR arc. In all cases, ring current O(+) is the major source of energy for the SAR arcs.

Kozyra, J. U.↗
NASA NTRS1987

A possible energy source to power stable auroral red arcs - Precipitating electrons

Results of coincident measurements by ground-based photometers and the low-altitude plasma instrument on board the Dynamics Explorer 2 satellite are presented that demonstrate the association of precipitating low-energy electrons with stable auroral red (SAR) arcs. A search of available data has yielded 23 instances of DE 2 overflights during the presence of SAR arcs being monitored by the photometers. For each case, downward fluxes of electrons are found to be enhanced along field lines penetrating the arcs in relation to regions both north and south of the features. Modeling of the atmospheric response to these influxes indicates that these electrons can represent a major source of the energy required to establish temperature profiles within the ionospheric electron gas that are sufficient to produce the recorded 6300-A emission rates. The sensitivity of these results to uncertainties of the assumed spacecraft potential and thermospheric composition has been investigated and found to be important, but does not alter the conclusion that precipitating electrons are a fundamental link in the production of SAR arcs.

Slater, D. W.↗
NASA NTRS1987

Satellite observations of new particle and field signatures associated with SAR arc field lines at magnetospheric heights

Enhancements in thermal ion densities, an oxygen dominated ring current at energies below 17 keV, and invariant latitude-limited bands of intense ELF hiss have been discovered on Stable Auroral Red (SAR) arc field lines at magnetospheric heights. These new signatures were revealed by an examination of 31 coordinated data sets taken simultaneously at magnetospheric and ionospheric heights by the De-1 and -2 satellites during SAR arc traversals within the period September 1981 through April 1982. Data sets from DE-2, for the first time, provide information on the location of a SAR arc (determined by the F region electron temperature enhancement) during the nearly simultaneous passage of these field lines by DE-1 in the magnetosphere. These new high altitude signatures are examined in the context of possible magnetospheric SAR arc energy source mechanisms.

Kozyra, J. U.↗
NASA NTRS1986

A statistical study of the subauroral electron temperature enhancement using dynamics Explorer 2 Langmuir probe observations

A statistical study of the subauroral electron temperature enhancement was undertaken using Langmuir probe observations during 488 traversals of the midlatitude plasmapause region by the DE-2 satellite. The subauroral electron temperature enhancement on the nightside is a quasi-permanent feature at all altitudes between 350 and 1000 km with an occurrence frequency that depends on altitude. The occurrence frequency of the subauroral electron temperature peak has a strong altitude dependence on the dayside. The position of the subauroral Te peak decreases with increasing magnetic activity in a manner similar to that of the equatorial plasmapause and other midlatitude plasmapause signatures.

Kozyra, J. U.↗
NASA NTRS1986

A possible SAR arc energization source - Precipitating electrons

Coincident measurements by ground-based photometers and satellite-borne electron sensors have shown the association of precipitating electrons and Stable Auroral Red Arcs at midlatitudes. Modeling of these events has suggested that, within the constraints imposed by uncertainties of the electron energy spectrum, the electron influx carries sufficient energy to establish ionospheric temperatures required to power the arcs.

Slater, D. W.↗
NASA NTRS1985

Radar and photometric measurements of an intense type A red aurora

On the evening of March 5, 1981, an intense, type A red aurora appeared over southern Alaska. Radar and photometric measurements were made of the aurora from the Chatanika radar site. The line of sight intensity of the 630.0-nm emissions exceeded 150 kR and was accompanied by enhanced emissions at 486.1 and 427.8 nm. The Chatanika radar measured electron densities of 10 to the 6th per cu cm and electron temperatures of 6000 K at an altitude of 400 km and an invariant latitude of 59 deg in association with the aurora. Comparison of optical and radar measurements indicated that the 630.0-nm emissions were produced to a large degree by thermal excitation of O(1D) in the region of high electron temperatures and densities. Model calculations indicate that the observed density and temperature enhancements and the related optical emissions were the results of a relatively short duration (5-10 min) pulse of precipitating, low-energy (about 30 eV) electrons. Whereas conventional stable auroral red arcs are associated with a gradual decrease in ring current energy density during the recovery phase of a magnetic storm, the type A red aurora may be produced by impulsive ring current energy loss during the main phase.

Robinson, R. M.↗
NASA NTRS1984

Effects of energetic heavy ions on electromagnetic ion cyclotron wave generation in the plasmapause region

An expression for electromagnetic ion cyclotron convective growth rates is derived. The derivation of the dispersion relation and convective growth rates in the presence of a multicomponent energetic and cold plasma is presented. The effects that multiple heavy ions in the ring current and cold plasma produce in the growth and propagation characteristics of ion cyclotron waves are explored. Results of growth rate calculations using parameters consistent with conditions in the plasmapause region during the early recovery phase of geomagnetic storms are presented and compared with ground-based and satellite observations of waves in this region. The geophysical implications of the results are discussed.

Kozyra, J. U.↗
NASA NTRS1982

Characteristics of a stable auroral red arc event

The present investigation is concerned with an analysis of the measurements of the stable auroral red (SAR) arc of October 23, 1981, using data from orbit 1192 of Dynamics Explorer (DE) 2, during which a magnetic coincidence occurred with the DE-1 spacecraft near the red arc field line, and for which simultaneous ground-based intensity measurements from Richland, WA were available. The altitude of the DE-2 satellite was approximately 850 km during arc passage in the Northern Hemisphere and approximately 395 km during the conjugate hemisphere passage. The DE-1 satellite was at an altitude of approximately 6000 km during the magnetic coincidence with DE-2 in the Northern Hemisphere. The described observations and calculations reconfirm a previous understanding that the actual excitation of the O(1D) state responsible for the 6300 A emission of red arcs is caused by hot ionospheric thermal electrons.

Kozyra, J. U.↗