Topic
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.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this article, the authors investigate which coordinate representation is most appropriate when analyzing ground magnetometer data in terms of ionospheric currents, in particular the westward electrojet, and derive a new SML index, based on apex coordinates.
Abstract: In this paper we investigate which coordinate representation is most appropriate when analyzing ground magnetometer data in terms of ionospheric currents, in particular the westward electrojet. The AL and the recently introduced SML index are frequently used as monitors of the westward electrojet. Both indices are based on ground magnetometers at auroral latitudes. From these magnetometers, the largest perturbation in the southward direction is selected as the AL/SML index at 1 min cadence. The southward component is defined as antiparallel to the orientation of the horizontal part of the Earths' main field, B0,H. The implicit assumption when using these indices as a monitor of the westward electrojet is that the electrojet flows perpendicular to B0,H. However, B0,H is, in general, not perpendicular to the westward direction in coordinate systems that take nondipole terms of the Earth's magnetic field into account, such as apex and the Altitude Adjusted Corrected Geomagnetic coordinate systems. In this paper we derive a new SML index, based on apex coordinates. We find that the new index has less variation with longitude and universal time (UT), compared to the traditionally defined SML. We argue that when analyzing ionospheric currents using magnetometers, it is appropriate to convert the components to a corrected geomagnetic system. This is most important when considering longitudinal or UT variations, or when data from a limited region are used.
29 citations
••
TL;DR: In this article, Latitude and longitude variations show the influence of F region winds in modulating the observed field-aligned flows, while perpendicular drifts are relatively invariant with latitude as expected.
Abstract: Latitudinal, longitudinal, and seasonal variations in the field-aligned and perpendicular flows measured at an altitude near 830 km, by the Defense Meteorological Satellite Program F10 satellite are examined. These profiles are studied during the nighttime (2100 magnetic local time) for solstice periods in 1991 when the solar activity is high. Latitude and longitude variations show the influence of F region winds in modulating the observed field-aligned flows. At night, large downward field-aligned flows of the order 400-600/ ms are observed in the winter hemisphere and coincide in longitude with the location of previously identified adiabatic heating effects studied by Venkatraman and Heelis. Interhemispheric flows at 2100 hours local time are seen to extend up to apex heights of approx. 1000 km during times of high solar activity. Perpendicular drifts, however are relatively invariant with latitude as expected.
29 citations
••
TL;DR: In this paper, the global structure of the lunar tide in the ionosphere is studied based on observations of the global positioning system (GPS) total electron content (TEC).
Abstract: [1] The global structure of the lunar tide in the ionosphere is studied based on observations of the global positioning system (GPS) total electron content (TEC). The unprecedented spatial and temporal resolution afforded by the GPS TEC observations enables illustration of the latitude, longitude, solar local time, and seasonal variability of the lunar tide in the ionosphere. Based on analysis of the multi-year mean from 1999–2008, the dominant component is generally the semidiurnal lunar tide. However, a significant diurnal variation is also observed in some instances. The semidiurnal component achieves a maximum amplitude of ∼6% in the equatorial ionization anomaly crest regions and a slight hemispheric asymmetry is present with larger amplitudes in the Northern Hemisphere. Furthermore, the maximum amplitudes in the semidiurnal lunar tide are found to occur during Northern Hemisphere winter and during 9–15 solar local time. During certain years, a secondary maxima in solar local time is also observed demonstrating the influence of the lunar tide on the prereversal enhancement. Lastly, the observations reveal significant longitudinal variability in the semidiurnal lunar tide that is most prominent between November and February. The presence of a longitudinal variation reveals the existence of nonmigrating components in addition to the dominant migrating semidiurnal lunar tide.
29 citations
••
University of the Basque Country1, Delft University of Technology2, University of California, Berkeley3, Goddard Space Flight Center4, University of Hawaii5, Netherlands Institute for Space Research6, Columbia University7, Jet Propulsion Laboratory8, Association of Universities for Research in Astronomy9, University of Wisconsin-Madison10, Hampton University11, Lawrence Livermore National Laboratory12, University of North Carolina at Chapel Hill13, California Institute of Technology14
TL;DR: In this paper, the authors observed a cloud system on the south side of the planet Neptune, which was first observed in January 2015 and nearly continuously from July to December 2015 in observations with telescopes in the 2-10m class and in images from amateur astronomers.
29 citations
••
TL;DR: In this paper, the impact of micrometeorites recorded by the artificial satellite Explorer I in February 1958 were examined statistically to determine their distribution with latitude, altitude, and longitude relative to the satellite-earth-sun angle (satellite local time).
Abstract: Impacts of micrometeorites recorded by the artificial satellite Explorer I in February 1958 have been examined statistically to determine their distribution with latitude, altitude, and longitude relative to the satellite-earth-sun angle (satellite local time). The latitude distribution shows an interesting peak near the equator, which is, however, not statistically significant. The distribution in longitude relative to the satellite-earth-sun angle corresponds to an altitude distribution and apparently contains no information that is not better shown in this latter distribution. With suitable analysis, the altitude distribution yields information on the velocity of the particles relative to the center of the earth. The conclusion is that the average particle measured by Explorer I was in a closed orbit around the earth rather than on an impact trajectory from a great distance to the surface of the earth.
29 citations