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 geomagnetic nature of the F2‐layer longitude‐effect

Abstract: Attention has been drawn to the extensive research on radio wave-propagation and the ionosphere done by the Japanese during the recent war [see 1 of “References” at end of paper] The Japanese, owing to the large number of ionospheric stations they operated, were able to delineate very well the essential characteristics of the ionosphere over eastern Asia and the western Pacific As a result of their observations, together with the generally available observations made in other parts of the world before the war, the Japanese made the first known study of the longitude-effect in the F2-layer characteristics They attributed the effect to geomagnetic influences

Meridional Flows from Ring Diagram Analysis

Abstract: In order to search for meridional circulation in the solar envelope, we have applied ring diagram analysis to a set of small regions over the surface. The helioseismic data consist of Solar Oscillation Investigation/Michelson Doppler Imager Dopplergrams taken over a time span of about 50 hr (~3000 images) on 1998 June 20-22. The regions studied cover 115° in latitude centered on the equator and 30° in longitude. We find poleward flows between r/ R=0.97 and the surface. There is no evidence in this depth range for the return path of these meridional flows. The temporal stability of these flows will be discussed after the analysis of a synoptic map obtained using the same technique.

Characterizing the 10 November 2004 storm‐time middle‐latitude plasma bubble event in Southeast Asia using multi‐instrument observations

Abstract: [1] The development and dynamics of ionospheric plasma bubble (PB) irregularity during the super storm of 7–11 November 2004 are investigated using the data from a multi-instrument network operated in Southeast Asia. Analysis of fluctuations in Global Positioning System total electron content (GPS TEC), ionosonde, GPS scintillation, and in situ satellite density data indicates a series of intense PB-associated irregularities at equatorial, low, and middle latitudes in the Japanese longitude on 10 November. However, in the Chinese sector, the scintillations and PB irregularities are confined within the range of 20–50°N in geographic latitude and 110–125°E in geographic longitude. The absence of equatorial PB irregularities in this sector shows a major difference from that in the close-by longitude Japanese sector. In the Southern Hemisphere Australian sector, the irregularities occurrence is present as a symmetrical distribution at conjugate latitudes. Combined analysis of the data from Osan and Wuhan ionosondes illustrates that the middle-latitude spread F irregularities initially develop at the lower part of the F region and then distribute in the whole F region. This initiation of spread F at lower altitudes indicates that the middle-latitude PB-associated irregularities are locally generated. These results together with the irregularities occurrence sequence from higher to lower latitudes, and the onset time delay of several hours implies that the presence of PB-associated irregularities within a latitude range of 20–50°N in the Chinese sector cannot be attributed to the effects of prompt penetration electric fields (PPEFs), although the equatorial PBs in the close-by longitude are seen to be associated with PPEFs. The possible mechanism is the F region plasma instabilities triggered by wave structures, which act as an external driving force and seed active plasma dynamics and instability growth at middle latitude.

Altitude‐extended equatorial spread F observed near sunrise terminator over Indonesia

Abstract: [1] Spatial structure of a post-sunrise backscatter plume associated with a plasma bubble has been observed for the first time with the 47–MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20°S, 100.32°E; dip latitude 10.36°N). This plume is likely associated with a geomagnetic storm. It extended from what appears to be the base of the F layer into the topside ionosphere and differed from all plumes previously observed. It was also extended in longitude (i.e., in the east-west direction), and appeared to involve two spatially separated regions. The plume was first observed around sunrise, close to 200–250 km altitude, but at a time when the E region was not yet sunlit. Spatial maps of the line-of-sight Doppler velocity show that there was upward development and westward drift of backscatter regions, indicative of daytime drift conditions. The observations remain puzzling because the plume continued for approximately two hours after E region sunrise.