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.

Observations of long‐period pulsations of electron precipitation in conjugate regions of the auroral zones

Abstract: In recent years, considerable attention has been given to the conjugate aspects of various phenomena at auroral latitudes resulting from electron precipitation on the atmosphere. By and large, most of these observations have been in connection with bay-type magnetic disturbances. Only recently [Nagata et al., 1963; Chivers and Hargreaves, 1965] has consideration been extended to other, less frequent, disturbances such as slow pulsations having periods of the order of several hundred seconds. With the aim of adding to the information about conjugate aspects of these rarer events, the present letter summarizes observations of a long-period pulsation event in ionospheric absorption of cosmic radio noise at Kotzebue, Alaska (66.87°N latitude, 162.50°W longitude), and the Australian National Antarctic Research Expeditions' station at Macquarie Island (54.50°S latitude, 158.95°E longitude). Though this record shows a striking degree of simultaneity and similarity, additional features of pulsating electron precipitation are brought forward from X-ray and riometer observations outside the immediate vicinity of the conjugate regions, indicating spatial structure on a scale of a few hundred kilometers.

The construction of an azimuthal equidistant map centered about the geomagnetic North Pole

Abstract: Before describing the construction of the accompanying map it would be appropriate to make some explanatory remarks regarding its purpose, and the particular advantages of the azimuthal equidistant projection. The map was constructed as an aid to the study of certain magnetic phenomena which take on additional significance when plotted on geomagnetic coordinates. A clear definition of this coordinate system is given by A. G. McNish:1 “Many magnetic phenomena are frequently found to have a relatively simple distribution when consideration is given to the location of the observing stations relative to the pole of the first-degree harmonics of the Earth's general magnetic field. A coordinate system having this pole as its origin is called a system of geomagnetic coordinates.” The northern geomagnetic pole, the one used as the center of projection of the map, is in latitude 78°.5 north and longitude 69°.0 west.

Lunar tides in the Mesosphere over Ascension Island (8° S, 14.4° W)

Abstract: A meteor radar has been used to measure the horizontal winds in the equatorial mesosphere and lower thermosphere over Ascension Island (8.0 S, 14.4 W). A 5-year data set covering the interval 2001-2005 over the height range 78-100 km is considered. The lunar M2 tide is clearly evident in the data and reaches amplitudes as large as 11 ms 1 in the meridional component and 6 ms 1 in the zonal component. These are the first observations of the lunar tide made over the equatorial Atlantic sector. Com- parisons of the observed seasonal behaviour with the model of Vial and Forbes (1994) reveals good agreement, but the observed amplitudes are generally larger and there is a sys- tematic phase difference of 2 h with the observed phases lagging the model. Comparisons with observations made at other equatorial sites suggest the presence of non-migrating lunar M2 tides and/or significant inter-annual variability. 14 W) are thus approximately in the centre of the 264 of longitude between these sites and thus complement these ear- lier studies. Few modelling studies of the lunar tides in the MLT region have been reported, although Vial and Forbes (1994) presented zonal-mean results in terms of horizontal winds, temperature and geopotential height.

Annual westward propagating anomalies near 26°N and eddy generation south of the Canary Islands: remote sensing (altimeter/SeaWiFS) and in situ measurement

Abstract: Seasonal changes in altimeter data are derived for the North Atlantic Ocean. Altimeter data are then used to examine annually propagating structure along 26 degree N. By averaging the altimeter data into monthly values or by Fourier analysis, a positive anomaly can be followed from 17 degree W to similar to 50 degree W along similar to 26 degree N. The methods give a westward travel speed of 1 degree of longitude a month and a half-life of one year for the average decaying structure. At similar to 50 degree W 26 degree N, the average structure is about 2.8 years old with an elevation signal of similar to 1 cm, having gravelled similar to 3300 km westward. The mean positive anomaly results from the formation of anticyclonic eddies which are generally formed annually south of the Canary Islands by late summer and which then travel westward near 26 degree N. Individual eddy structure along 26 degree N is examined and related to in situ measurements and anomalies in the annual seasonal concentration cycle of SeaWiFS chlorophyll-a.

Solar oscillation ring diagrams and large-scale flows

Abstract: A new analysis that results in the appearance of rings in the power spectrum of solar oscillations has been used to detect horizontal flows in two directions on the sun. An analysis of the rings obtained over four different solar longitude ranges suggests the presence of large-scale flows with longitudinal variations of about 20 m/s. The position of these flows are correlated with the location of an active region. 7 refs.