scispace - formally typeset
Search or ask a question
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
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors report image measurements of plasma depletions in the equatorial F region ionosphere over Christmas Island (2.1°N, 157.4°W; dip latitude 2.8°N) in the central Pacific Ocean.
Abstract: [1] We report image measurements of plasma depletions in the equatorial F region ionosphere over Christmas Island (2.1°N, 157.4°W; dip latitude 2.8°N) in the central Pacific Ocean. The observations were made during the equinox period, September-October 1995, using a Utah State University CCD imaging system filtered to observe thermospheric O I (630.0 nm) airglow emissions centered at ∼280 km altitude. Well-defined magnetic field-aligned depletions were observed on 18 nights during the campaign, including strong postmidnight fossilized structures, enabling detailed measurements of their morphology and dynamics. The number of depletions was influenced by their initial onset times and their persistence. The separations between adjacent depletions ranged from ∼150 to ∼250 km in good agreement with prior observations from other sites. However, measurements of their eastward zonal drift speeds indicated normal behavior peaking around 90–100 m/s prior to local midnight, with exceptionally high velocities, ∼80 m/s during the postmidnight period that persisted until dawn. These results differ markedly from optical measurements at similar equatorial latitudes but at different longitude sectors, suggesting that the zonal drift velocities can have a significant longitudinal dependence. Model drift velocities calculated using a simple electric field model with winds defined by the horizontal wind model (HWM-07) produced an eastward drift throughout the night, but their postmidnight magnitudes were much smaller than observed. Using a modified HWM-07 wind field, a basic nighttime trend similar to the Christmas Island trend was successfully obtained.

28 citations

Journal ArticleDOI
01 Aug 1989-Icarus
TL;DR: A mapping of the rate of occurrence of impulsive VLF noise bursts in Venus' dark low altitude ionosphere, which increases rapidly with decreasing altitude, as a function of latitude and longitude indicates enhanced occurrence rates over Atla as discussed by the authors.

28 citations

Journal ArticleDOI
TL;DR: In this article, the first 10° of longitude in the Mopra CO survey of the southern Galactic plane was observed at 35-arcsec spatial resolution and 0.1 km s?1 spectral resolution.
Abstract: We present observations of the first 10° of longitude in the Mopra CO survey of the southern Galactic plane, covering Galactic longitude l = 320–330° and latitude b = ±0.5°, and l = 327–330°, b = +0.5–1.0°. These data have been taken at 35-arcsec spatial resolution and 0.1 km s?1 spectral resolution, providing an unprecedented view of the molecular clouds and gas of the southern Galactic plane in the 109–115 GHz J = 1–0 transitions of 12CO, 13CO, C18O, and C17O. Together with information about the noise statistics from the Mopra telescope, these data can be retrieved from the Mopra CO website and the CSIRO-ATNF data archive.

28 citations

Journal ArticleDOI
TL;DR: In this article, a composite of anomalously warm (and dry) surface conditions with spatial coherence over a given longitude band is constructed from satellite data covering a single wet season.
Abstract: Cloud-free brightness temperatures from satellite are used to interpret changes in the state of the land surface energy balance from day to day across the tropical semi-arid region of North Africa. The method provides an assessment of the spatial and temporal patterns in the surface characteristics. The variability in brightness temperature is closely linked to precipitation, as inferred from available rain-gauge data and satellite cold-cloud imagery. Temperatures drop sharply after rainfall, and increase gradually in subsequent days consistent with surface drying. The analysis shows that surface temperatures (and therefore fluxes) are well-organized at the synoptic scale, and can be linked to the westward propagation of mesoscale convective systems and African easterly waves (AEWs). The modulation of rainfall and cloud cover by weather systems is a key element in producing variability in surface fluxes of heat and moisture. To examine the relationships between surface variability and the atmosphere, a composite of anomalously warm (and dry) surface conditions with spatial coherence over a given longitude band is constructed from satellite data covering a single wet season. Operational analyses are used to examine atmospheric anomalies associated with these composited ‘hotspots’. Surface moisture variations on the scale of several hundred km and larger can generate anomalous heat-lows during the day and, according to the operational analyses, generate cyclonic vorticity overnight. These vortices appear to be responsible for the observed modulation of cold cloud in the vicinity of the hotspot, and may influence the characteristics of AEWs in the Northern Sahel. Furthermore, theoretical ideas suggest that surface hotspots are likely to trigger a westward-propagating Rossby-wave response; this process is demonstrated here in a simple numerical model. Copyright © 2005 Royal Meteorological Society

28 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a four-channel receiver tracking coded signals from the NAVSTAR Global Positioning System satellites to estimate the mean variation and correlation coefficient for the approximately 1200-km or 1-hour local time radius ionospheric region within view of a mid-latitude station.
Abstract: The integrated line-of-sight electron density within the ionosphere, known as the total electron content (TEC), is commonly used to quantify ionospheric propagation effects. In order to extrapolate single-point measurements of TEC to other locations and times, some characterization of the TEC spatiotemporal variation must be available. Using a four-channel receiver tracking coded signals from the NAVSTAR Global Positioning System satellites, estimates of both the mean variation and correlation coefficient have been made for the approximately 1200-km or 1-hour local time radius ionospheric region within view of a mid-latitude station. Results were obtained for morning and midday over a 4-week period near the autumnal equinox in 1989. The derived mean variation was found to be well characterized by linear functions of the local time and latitude separation between the ground site and the ionospheric penetration point of the signal. The correlation coefficient during midday was found to decrease linearly with latitude, longitude, and time separation, with values of about 0.91 for a 1000-km separation and 0.98 for a 1-hour separation. During morning hours the longitude and time coefficients were similar to the midday values, but the latitude coefficient was found to have a nonlinear dependence, with values as small as 0.70. The combined results suggest that the decorrelation is due primarily to longer term TEC fluctuations, such as day-to-day variation in the TEC spatial dependence, rather than to transient effects such as traveling ionospheric disturbances. The analysis provides a spatiotemporal characterization of TEC that can be used to extrapolate TEC values from single-point measurements.

28 citations


Network Information
Related Topics (5)
Solar wind
26.1K papers, 780.2K citations
88% related
Planet
27K papers, 980.6K citations
82% related
Sea surface temperature
21.2K papers, 874.7K citations
80% related
Climate model
22.2K papers, 1.1M citations
79% related
Sea ice
24.3K papers, 876.6K citations
78% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023240
2022432
202142
202042
201960
201851