Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

Total electron content over the Pan‐American longitudes: March‐April 1994

Abstract: An experimental campaign to measure diurnal changes in total electron content (TEC) over the wide latitude range from approximately 50°N to 40°S was carried out from March 28 through April 11, 1994, by monitoring the differential carrier phase from the U.S. Navy Navigation Satellite System using a chain of ground stations aligned along the approximate 70°W longitude meridian. This Pan-American campaign was conducted primarily to study the day-to-day variability of the equatorial anomaly region. The experimental plan included using the received values of TEC from the chain of stations to construct profiles of electron density versus latitude using tomographic reconstruction techniques and, then, to compare these reconstructions against a theoretical model of the low-latitude ionosphere. The diurnal changes in TEC along this latitude chain of stations showed a high degree of variability from day to day, especially during a magnetic storm which occurred near the beginning of the campaign. The equatorial anomaly in TEC showed large changes in character in the two hemispheres, as well as differences in magnitude from day to day. The latitudinal gradients of TEC, especially in the lower midlatitudes, also showed large differences between magnetic storm and quiet conditions. Comparisons of the TEC data with the theoretical model illustrate the sensitivity of the model calculations to changes in magnetic E×B drift and serves to validate the strong influence that these drifts have on the formation and the strength of the equatorial anomaly regions.

Mid-winter intensities of the night airglow O2 (0–1) atmospheric band emission at high latitudes

Abstract: Absolute intensities of the O2 (0–1) atmospheric band night airglow emission have been observed from near Longyearbyen on West Spitsbergen (78.4°N latitude, 15°E longitude, geographic) during a 2-month period around winter solstice (1982–1983). Intensities ranging from 110 R to 1590 R with a mean of 570 R ± 60 R are observed. There is no clear maximum or minimum around solstice. A semidiurnal tide component giving rise to a 25–30% intensity variation of the O2 (0–1) atmospheric emission is present in the data. The maximum and minimum are found to occur at about 0400 and 1000 local time, respectively. No diurnal tide component larger than ±3–4% is present in the data. The day-to-day and short time variations both show a quasi-regular wave pattern which may be associated with gravity waves.

Geochronology and Continental Drift-The North Atlantic

Abstract: A geometrical fit of the land masses of northern Europe, Canada and Greenland has been constructed by Dr A. G. Smith using the method devised by Sir Edward Bullard and M r J. E. Everett. The method involves taking points of latitude and longitude on the 500 fm. line at intervals of about 30 miles along the two coasts to be fitted. Young features such as oceanic islands are ignored. By a method of successive approximation, the computer ‘homes in ’ on to the centre of rotation which gives the minimum root mean square misfit between the rotated coastlines j the misfit being measured as the discrepancy of longitude relative to the centre of rotation. In this manner the 500 fm. line along the east coast of Greenland has been fitted to that of northwestern Europe to form one unit. This unit, that is, the 500 fm. line of the west coast of Greenland and the Channel approaches have been fitted on to the 500 fm. line of Canada. Maps of this fit drawn as a conical projection with two standard parallels of latitude will be presented and will show the geochronological patterns across the reconstructed land masses.

Longitude structure of the ionosphere F region from TOPEX/Poseidon and ground-based data during January 20-30, 1993, including the quasi 2-day oscillation

Abstract: The global structure of the F region ionosphere during January 20-30, 1993, is examined with emphasis on longitudinal variations. The database consists of total electron content (TEC) measurements from the TOPEX/Poseidon dual-frequency altimeter experiment from -66° to +66° geographic latitude for prenoon and premidnight conditions, and hourly f o F 2 and hmF 2 values from eight ionosonde stations between -42° and +26° geographic latitude in the Pacific sector. The 10-day averaged daytime TEC data reveal latitude versus longitude structures whose salient features are captured (within ∼10 TEC units) by the 1990 International Reference Ionosphere (IRI-90), and which can be explained by dynamically induced neutral composition changes due to a combination of solar and magnetically driven circulation systems. The premidnight TEC data at low latitudes reveal the double-banded structure of the equatorial ionization anomaly with, however, pronounced variations in amplitude and position as a function of geomagnetic longitude. None of these features, which probably reflect some combination of electric field and neutral wind effects, are captured by IRI-90. Time series analyses of the f 0 F 2 and hmF 2 data, and space-time Fourier spectra of the TEC data, reveal the presence of a quasi 2-day (QTD) oscillation in the ionosphere which is associated with QTD wind and temperature oscillations in the mesosphere and lower thermosphere previously documented for this time period. The satellite-based QTD results are subject to significant caveats described herein. Nevertheless, the TOPEX/Poseidon TEC data set clearly represents an important resource for global studies of ionospheric structure and plasmaneutral interactions.

Pressure-Wind Relationships in the Equatorial Surface Westerlies

Abstract: Seasonally persistent westerly winds at the surface in the vicinity of the equator from 40E to 170E longitude are shown to be the generally predictable result of a geostrophically appropriate pressure gradient at latitudes higher than about 5° north or south, and a negative value of the second derivative of the pressure with latitude within about five degrees latitude of the equator. Existing empirical equatorial wind-pressure relationships are shown to be specific cases of these general relationships. The initiating mechanism for equatorial westerlies seems to be a movement of the equatorial trough more than five degrees of latitude from the equator.