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.

Effect of the seasonal variations in the lower atmosphere on the altitude of the ionospheric main peak at Mars

Abstract: [1] The heights of the Martian ionospheric main electron density peak observed by the Mars Global Surveyor Radio Science experiment in the northern and southern high-latitude regions (60°–90°) are investigated. The data sets for both hemispheres were obtained in the same narrow solar longitude interval (∼134°–146°). The subsolar height of the main peak derived from the southern hemisphere data is 7.7 ± 4.3 km lower than that derived from the northern hemisphere data. The southern and northern hemispheres are in opposite seasons. The seasonal variations of the neutral atmospheric density and its scale height in the lower atmosphere are found to be the dominant reasons for the reported difference. Further analysis shows that the neutral atmosphere density at the altitude 20 km had the strongest effect.

Equatorial and low‐latitude ionosphere‐thermosphere system response to the space weather event of August 2005

Abstract: [1] The response of the equatorial and low-latitude ionosphere-thermosphere system to the geomagnetic storm during 23–26 August 2005 is investigated. The study is carried out using the vertical total electron content (VTEC) measured by GPS receivers along the 77–78°E longitude and the O/N2 ratio obtained from the Global Ultraviolet Imager instrument on board the TIMED satellite. The equatorial ionization anomaly (EIA) shows a poleward latitudinal expansion on 24 August, probably associated with an eastward prompt-penetration electric field. The equatorial and low latitudes show an increase in VTEC during the main phase of the storm on 24 August. The prompt-penetration eastward electric field, along with an increase in the O/N2 ratio, could be responsible for this observed positive phase. The VTEC variations on 24 August also reveal the signature of a large-scale acoustic gravity wave/traveling atmospheric disturbance propagating with a horizontal velocity of ∼750 m/s. Suppression of the EIA is observed during the storm recovery phase on 25 August, which probably is associated with the westward disturbance dynamo electric field and the equatorward expansion of the neutral composition changes (O/N2 depletion).

A 3-D mesoscale map of primary production at the Antarctic Polar Front: results of a diagnostic model

Abstract: A diagnostic model is established to estimate synoptically the mesoscale distribution of primary production at the Antarctic Polar Front (APF). The model domain is a 3-D box, centred at roughly 50 S and 10 E, of about 1 degree latitude and 2 degree longitude horizontal extent, and of 300 m depth. The box was surveyed in high resolution during austral summer 1995/1996 with a towed undulating vehicle and by complementary ship-based measurements. Measurements of global solar radiation, of the underwater light field, and of the chlorophyll concentration from the survey are used as input variables for the model. The model is based on photosynthesis-light relationships, with parameters taken from in vitro incubations performed during the survey. The model results show mesoscale patches of elevated primary production along a meander of the APF, and lowest production in a cold cyclonic eddy south of the front. Production is confined to a shallower depth range in the front than outside, due to self-shading effects from generally higher mixed-layer chlorophyll concentrations. Self-shading effects account for variations of the percent light depths, and of the saturation light depth, by a factor of 2 within the survey area. Primary production at the surface varies horizontally between 7 and 56 mg C m^-3 d^-1, with a mean of 26 mg C m^-3 d^-1, and vertically integrated production ranges from 295 to 975 mg C m^-2 d^-1, with an areal mean of 585 mg C m^-2 d^-1. Changes by a factor of 2 in integrated production occur on horizontal scales as small as 10 km. Production rates also differ significantly between days as a result of changes in global solar radiation.

Daily variation of the geomagnetic field near the focus of Sq-current system in Indian longitude

Abstract: The paper presents the first results on the behaviour of solar quiet-day variations of the geomagnetic field components at Gulmarg. Combining the data from Russian stations in the same longitude belt, the annual average daily variations are calculated which show, in the horizontal component (H), a reversal of phase between Gulmarg and Tashkent. Studying the Sq-variations at Gulmarg separately for the three seasons, the daily variation of H duringd-months is predominantly diurnal in character with the maximum before noon. Duringe-months, and more so inj-months, daily variation of the H field is predominantly semidiurnal in character with minimum around 08–09 hr LT and maximum around 14 hr LT consistently during 1978, 1979 and 1980. These features of the Sq at Gulmarg are suggested to be due to the deformations of the current loops caused by the changing latitude of focus during the course of the day.