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Full-Text Articles in Physics
Theoretical Study Of The High-Latitude Ionosphere’S Response To Multicell Convection Patterns, Jan Josef Sojka, Robert W. Schunk
Theoretical Study Of The High-Latitude Ionosphere’S Response To Multicell Convection Patterns, Jan Josef Sojka, Robert W. Schunk
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It is well known that convection electric fields have an important effect on the ionosphere at high latitudes and that a quantitative understanding of their effect requires a knowledge of the plasma convection pattern. When the interplanetary magnetic field (IMF) is southward, plasma convection at F region altitudes displays a two-cell pattern with antisunward flow over the polar cap and return flow at lower latitudes. However, when the IMF is northward, multiple convection cells can exist, with both sunward flow and auroral precipitation (theta aurora) in the polar cap. The characteristic ionospheric signatures associated with multicell convection patterns were studied …
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
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
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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. …
Predicted Diurnal Variations Of Electron Density For Three High-Latitude Incoherent Scatter Radars, Jan Josef Sojka, Robert W. Schunk
Predicted Diurnal Variations Of Electron Density For Three High-Latitude Incoherent Scatter Radars, Jan Josef Sojka, Robert W. Schunk
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We have used a high‐latitude ionospheric model to predict the diurnal variations of electron density that should be observed by the EISCAT, Chatanika and Millstone Hill incoherent scatter facilities. Our calculations were for a strong convection model without substorms. Our results provide an indication of the quantitative differences in measured electron density that are expected when the three radars probe the high‐latitude ionosphere simultaneously. The differences are significant and vary with altitude, latitude, local time, and season, and are associated with the UT dependence of the high‐latitude ionosphere which results from the displacement between the geomagnetic and geographic poles.
Ion Temperature Variations In The Daytime High-Latitude F Region, Robert W. Schunk, Jan Josef Sojka
Ion Temperature Variations In The Daytime High-Latitude F Region, Robert W. Schunk, Jan Josef Sojka
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We improved our high-latitude ionospheric model by including thermal conduction and diffusion-thermal heat flow terms in the ion energy equation so that we could study the ion temperature variations in the daytime high-latitude F layer in a region poleward of the auroral oval for steady state conditions at local noon. From our study we found that (1) The variation of Ti with solar cycle, season, and geomagnetic activity closely follows the Tn variation. The general trend is for higher temperatures in summer than in winter, at solar maximum than at solar minimum, and for active magnetic conditions than for quiet …
Seasonal Variations Of The High-Latitude F Region For Strong Convection, Jan Josef Sojka, Robert W. Schunk, W. John Raitt
Seasonal Variations Of The High-Latitude F Region For Strong Convection, Jan Josef Sojka, Robert W. Schunk, W. John Raitt
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We combined a plasma convection model with an ionospheric-atmospheric composition model in order to study the seasonal variations of the high-latitude F region for strong convection. 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 high-latitude ionosphere exhibits a significant UT variation both during winter and summer. (2) In general, the …
Observations Of The Diurnal Dependence Of The High-Latitude F Region Ion Density By Dmsp Satellites, Jan Josef Sojka, W. John Raitt, Robert W. Schunk, F. J. Rich, R. C. Sagalyn
Observations Of The Diurnal Dependence Of The High-Latitude F Region Ion Density By Dmsp Satellites, Jan Josef Sojka, W. John Raitt, Robert W. Schunk, F. J. Rich, R. C. Sagalyn
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Data from the DMSP F2 and F4 satellites for the period December 5-10, 1979, have been used to study the diurnal dependence of the high-latitude ion density at 800-km altitude. A 24-hour periodicity in the minimum orbital density (MOD) during a crossing of the high-latitude region is observed in both the winter and summer hemispheres. The phase of the variation in MOD is such that it has a minimum during the 24-hour period between 0700 and 0900 UT. Both the long term variation of the high-latitude ion density on a time scale of days, and the orbit by orbit variations …
Radar Measurements Of High-Latitude Ion Composition Between 140 And 300 Km Altitude, J. D. Kelly, Vincent B. Wickwar
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 …
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
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 …
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
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. …
Plasma Density Features Associated With Strong Convection In The Winter High-Latitude F Region, Jan Josef Sojka, W. John Raitt, Robert W. Schunk
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 …
High Latitude Plasma Convection: Predictions For Eiscat And Sondre Stromfjord, Jan Josef Sojka, W. John Raitt, Robert W. Schunk
High Latitude Plasma Convection: Predictions For Eiscat And Sondre Stromfjord, Jan Josef Sojka, W. John Raitt, Robert W. Schunk
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We have used a plasma convection model to predict diurnal patterns of horizontal drift velocities in the vicinity of the EISCAT incoherent scatter facility at Tromso, Norway and for Sondre Stromfjord, Greenland, a proposed new incoherent scatter facility site. The convection model includes the offset of 11.4° between the geographic and geomagnetic poles (northern hemisphere), the tendency of plasma to corotate about the geographic pole, and a magnetospheric electric field mapped to a circle about a center offset by 5° in the antisunward direction from the magnetic pole. Four different magnetospheric electric field configurations were considered, including a constant cross‐ …
Effect Of Displaced Geomagnetic And Geographic Poles On High-Latitude Plasma Convection And Ionospheric Depletions, Jan Josef Sojka, W. J. Raitt, Robert W. Schunk
Effect Of Displaced Geomagnetic And Geographic Poles On High-Latitude Plasma Convection And Ionospheric Depletions, Jan Josef Sojka, W. J. Raitt, Robert W. Schunk
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We assumed that the ionospheric plasma at high latitudes has a tendency to corotate about the geographic pole and that magnetospheric convection is relative to the geomagnetic pole. With this assumption we calculated plasma drift patterns over the polar cap for a range of constant magnetospheric electric fields as well as for asymmetric electric fields with enhanced plasma flow on either the dawnside or the duskside of the polar cap. We calculated the drift patterns in both the geographic inertial and the geomagnetic inertial frame taking into account the displacement between the geographic and geomagnetic poles. We found that this …