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.

Spatial Structure of Summertime Ionospheric Plasma Near Magnetic Noon

Abstract: Part of Special Issue "Eleventh International EISCAT Workshop" Abstract. Results are presented from a multi-instrument study of the spatial distribution of the summertime, polar ionospheric electron density under conditions of relatively stable IMF Bz<0. The EISCAT Svalbard radar revealed a region of enhanced densities near magnetic noon that, when comparing radar scans from different local times, appeared to be spatially confined in longitude. This was identified as the tongue-of-ionisation (TOI) that comprised photoionisation of sub-auroral origin that is drawn poleward into the polar cap by the anti-sunward flow of the high-latitude convection. The TOI was bounded in longitude by high-latitude troughs; the pre-noon trough on the morning side with a minimum near 78 N and the post-noon trough on the afternoon side with a minimum at 80 N. Complementary measurements by ra- dio tomography, the SuperDARN radars, and a DMSP satel- lite, together with comparisons with earlier modelling work, provided supporting evidence for the interpretation of the density structuring, and highlighted the role of plasma con- vection in the formation of summertime plasma distribution. Soft particle precipitation played only a secondary role in the modulation of the large summertime densities entering the polar cap. the magnetic noon sector under conditions of Interplane- tary Magnetic Field (IMF) Bz<0. Of particular interest is the tongue-of-ionisation (TOI), transporting photoionisation from sub-auroral latitudes into the polar cap, that separates the high-latitude density troughs in the pre- and post-noon time sector.

Observations of the cosmic-ray equator in the Pacific Ocean area

Abstract: It is the purpose of this Letter to summarize the results obtained in the course of a latitude survey of the intensity of the nucleonic component of cosmic radiation in the Pacific Ocean area. This experiment was undertaken with the aim of determining the location of the cosmic-ray equator in a longitude range that had not been investigated previously with a detector of this type. The interest in the position of the cosmic-ray equator (position of minimum cosmic-ray intensity) stems from the work of Simpson, Fenton, Katzmann, and Rose [1956] which first demonstrated that the cosmic-ray equator did not coincide with the position of the magneticdipole equator. Further studies of this problem [Katz, Meyer, and Simpson, 1958], involving an extensive series of airborne crossings of the cosmic-ray equator, have confirmed this result. The present experiment was directed toward making observations in a region not covered by these flights.

Statistical behavior of the longitudinal variations of daytime electron density in the topside ionosphere at middle latitudes

Abstract: Electron density in the topside ionosphere has significant variations with latitude, longitude, altitude, local time, season, and solar cycle. This paper focuses on the global and seasonal features of longitudinal structures of daytime topside electron density (Ne) at middle latitudes and their possible causes. We used in situ Ne measured by DEMETER and F2 layer peak height (hmF2) and peak density (NmF2) from COSMIC. The longitudinal variations of the daytime topside Ne show a wave number 2-type structure in the Northern Hemisphere, whereas those in the Southern Hemisphere are dominated by a wave number 1 structure and are much larger than those in the Northern Hemisphere. The patterns around December solstice (DS) in the Northern Hemisphere (winter) are different from other seasons, whereas the patterns in the Southern Hemisphere are similar in each season. Around March equinox (ME), June solstice (JS), and September equinox (SE) in the Northern Hemisphere and around ME, SE, and DS in the Southern Hemisphere, the longitudinal variations of topside Ne have similar patterns to hmF2. Around JS in the Southern Hemisphere (winter), the topside Ne has similar patterns to NmF2 and hmF2 does not change much with longitude. Thus, the topside variations may be explained intuitively in terms of hmF2 and NmF2. This approach works reasonably well in most of the situations except in the northern winter in the topside not too far from the F2 peak. In this sense, understanding variations in hmF2 and NmF2 becomes an important and relevant subject for this topside ionospheric study.