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.

The longitudinal dependence of whistler and chorus characteristics observed on the ground near L=4

Abstract: Whistler activity at L {approx equal} 4 is known to be a function of longitude, peaking in the Weddell Sea sector of Antarctica; a combination of source and propagation factors, the latter possibly partly associated with the South Atlantic geomagnetic anomaly, is believed to be responsible. There is evidence, for example from satellite surveys, that chorus and hiss activity may also be longitude dependent. To investigate this further, the authors have compared VLF data from four L {approx equal} 4 Antarctic stations from a 2-day period in June 1982. Siple, Halley, and Sanae form a closely spaced ({approximately}20 {degree}- 0{degree} geomagnetic longitude) triplet, while Kerguelen is {approximately}120{degrees} (geomagnetic) to the east, on the opposite side of the anomaly. To a large extent there was a repeatable diurnal variation in activity at all stations on the two days. Events observed at Siple tended to be similar to those observed {approximately} 9 hours earlier (the same MLT) at Kerguelen on the same day. There was a very marked drop-off in both whistler and VLF emission activity between Siple and Halley on the one hand and Sanae on the other. The reason for this is not clear; it may be either a sourcemore » effect such as the lower occurence of lightning over eastern North America compared to the adjacent Atlantic Ocean, or else a wave-particle interaction effect whereby the conditions for wave growth or amplification are more favorable, or substorm particle injections penetrate the magnetosphere more deeply, at the longitude of Siple than further east. Comparison of the spectral forms of whistler mode activity at neighboring stations suggests that wave generation occurs simultaneously over relatively wide longitude (or local time) sectors ({approx gt} 30{degrees} or 2 hours). Individual interaction regions are smaller than this, {approx lt} 5{degrees} in longitude, comparable with the previously inferred sizes of whistler ducts.« less

Investigation of the causes of the longitudinal variation of the electron density in the Weddell Sea Anomaly

Abstract: This paper investigates and quantifies the causes of the Weddell Sea Anomaly (WSA), a region near the tip of South America extending from approximately 30° to 120°W geographic longitude and 50° to 75°S geographic latitude at solar minimum between 2007 and 2010 This region is unusual because the midnight peak electron density exceeds the midday peak electron density in summer This study is far more quantitative than previous studies because, unlike other models, it assimilates selected data parameters to constrain a physical model in order to investigate other aspects of the data It is shown that the commonly accepted explanation that the WSA is related to the magnetic field declination and inclination effects on the neutral wind does not explain the longitudinal variation of the electron density Rather, longitudinal changes in the neutral winds and neutral densities are the most likely explanation for the WSA These longitudinal wind and density changes are attributed to the varying latitudinal distance from the auroral zone energy input No contributions from the plasmasphere or other sources are required Furthermore, it is shown that a widely used empirical thermosphere density model overestimates the longitudinal changes in the WSA region

Ocean mesoscale variability from repeat tracks of Geos‐3 altimeter data

Abstract: The Geos-3 satellite altimeter observed numerous sea surface profiles along nearly repeated tracks in the western North Atlantic during its 3.5-year lifetime, enabling observation of the variation of sea surface topography along these tracks. Analysis of 14 north-going and 13 south-going sets of repeated tracks has yielded the variability of the surface at a resolution of 1° from 25° to 41°N latitude and from 60° to 80°W longitude. The observed rms variation of surface topography ranges from about 8 cm in the Sargasso Sea to a maximum of 48 cm in the Gulf Stream meander region, in agreement with known mesoscale energetics of this region.

Active longitude and solar flare occurrences

Abstract: The aim of the present work is to specify the spatio-temporal characteristics of flare activity observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Geostationary Operational Environmental Satellite (GOES) satellites in connection with the behaviour of the longitudinal domain of enhanced sunspot activity known as active longitude (AL). By using our method developed for this purpose, we identified the AL in every Carrington Rotation provided by the Debrecen Photoheliographic Data (DPD). The spatial probability of flare occurrence has been estimated depending on the longitudinal distance from AL in the northern and southern hemispheres separately. We have found that more than the 60\% of the RHESSI and GOES flares is located within $\pm 36^{\circ}$ from the active longitude. Hence, the most flare-productive active regions tend to be located in or close to the active longitudinal belt. This observed feature may allow predicting the geo-effective position of the domain of enhanced flaring probability. Furthermore, we studied the temporal properties of flare occurrence near the active longitude and several significant fluctuations were found. More precisely, the results of the method are the following fluctuations: $0.8$ years, $1.3$ years and $1.8$ years. These temporal and spatial properties of the solar flare occurrence within the active longitudinal belts could provide us enhanced solar flare forecasting opportunity.