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.

Sq field characteristics at Phu Thuy, Vietnam, during solar cycle 23: comparisons with Sq field in other longitude sectors

Abstract: . Quiet days variations in the Earth's magnetic field (the Sq current system) are compared and contrasted for the Asian, African and American sectors using a new dataset from Vietnam. This is the first presentation of the variation of the Earth's magnetic field (Sq), during the solar cycle 23, at Phu Thuy, Vietnam (geographic latitudes 21.03° N and longitude: 105.95° E). Phu Thuy observatory is located below the crest of the equatorial fountain in the Asian longitude sector of the Northern Hemisphere. The morphology of the Sq daily variation is presented as a function of solar cycle and seasons. The diurnal variation of Phu Thuy is compared to those obtained in different magnetic observatories over the world to highlight the characteristics of the Phu Thuy observations. In other longitude sectors we find different patterns. At Phu Thuy the solar cycle variation of the amplitude of the daily variation of the X component is correlated to the F.10.7 cm solar radiation (~0.74). This correlation factor is greater than the correlation factor obtained in two observatories located at the same magnetic latitudes in other longitude sectors: at Tamanrasset in the African sector (~0.42, geographic latitude ~22.79) and San Juan in the American sector (~0.03, geographic latitude ~18.38). At Phu Thuy, the Sq field exhibits an equinoctial and a diurnal asymmetry: – The seasonal variation of the monthly mean of X component exhibits the well known semiannual pattern with 2 equinox maxima, but the X component is larger in spring than in autumn. Depending of the phase of the sunspot cycle, the maximum amplitude of the X component varies in spring from 30 nT to 75 nT and in autumn from 20 nT to 60 nT. The maximum amplitude of the X component exhibits roughly the same variation in both solstices, varying from about ~20 nT to 50 nT, depending on the position into the solar cycle. – In all seasons, the mean equinoctial diurnal Y component has a morning maximum Larger than the afternoon minimum i.e. the equivalent current flow over a day is more southward than northward. During winter, the asymmetry is maximum, it erases the afternoon minimum. At the Gnangara observatory, in Asian Southern Hemisphere, the diurnal Y pattern is opposite and the current flow is more northward. It seems that in the Asian sector, the northern and southern Sq current cells both contribute strongly to the equatorial electrojet. The pattern is different in the African and American sectors where the northern Sq current cell contribution to the equatorial electrojet is smaller than the southern one. These observations can explain the unexpected maximum of amplitude of the equatorial electrojet observed in the Asian sector where the internal field is very large. During winter the Y component flow presents an anomaly, it is always southward during the whole day and there is no afternoon northward circulation.

A precision world survey of sea-level cosmic-ray intensities

Abstract: With sensitive, vibration-free, self-recording electroscopes sent to many parts of the globe on twelve different voyages a precision survey has now been completed of the variation of cosmic-ray intensities both with latitude and longitude, so that the earth as a whole can now be covered with sea-level, equal intensity, cosmic-ray lines. In going along the longitude line 75° W., which runs from the far north through Washington, D. C., and along the west coast of South America, there is no appreciable change until the magnetic latitude of about 41° is reached. The equatorial dip then begins to set in and shows a maximum decline of 8 percent off Peru and returns again to its normal value off Cape Horn. In going along longitude line 80° E. through southern India the maximum dip is 12 percent. In going south from Alaska in longitude 165° W. to New Zealand the maximum dip is 10 percent. In going south from Liverpool through the Atlantic Ocean—longitude 30° W.—and around Cape Horn the maximum dip is 8.5 percent. In the region most accurately studied—the west coast of the United States—the intensity remains exceedingly constant until the latitude of Pasadena—41° magnetic—is reached, and then drops remarkably suddenly. In the Atlantic Ocean the drop sets in at about the same magnetic latitude with equal suddenness. It appears also to take place quite suddently at about magnetic latitude 41° in the southern hemisphere. Nevertheless, the existence of a longitude effect shows that in strictness there is no such thing as magnetic latitude. In other words, the earth's magnetic field, even at the remote distances of thousands of miles at which these deflections occur, is strikingly dissymmetrical with respect to any line passing through the earth's center. This method of study opens up the possibility of determining these dissymmetries at large distances from the earth. The observed magnetic effects are to be expected quite independently of whether cosmic rays are in their origin photonic or corpuscular.

Some new data on modern tectonic deformation and active faulting in azerbaijan (according to global positioning system measurements)

Abstract: Global Positioning System (GPS) observations in Azerbaijan and surrounding areas of the Caucasus region are providing quantitative constraints of the geometry of active fault systems, and rates of present-day deformation. West of 48° E longitude, the Main Caucasus Trust Fault (MCT) follows the sharp change in slope along the south side of the Greater Caucasus as is well known from prior seismic, geophysical, and geologic studies. However, east of this longitude the MCT turns sharply to the south, crossing the Kura Depression and extending along the western side of the Caspian Sea (here called the West Caspian Fault; WCF). While the MCT is predominantly a thrust fault west of 48°E longitude, the WCF is a pure rightlateral, strike slip fault with a slip rate of 11 ± 1 mm/yr south of the Absheron Peninsula. We also document shortening of 4 ± 1 mm/yr along the northern side of the Greater Caucasus in Dagestan on a roughly E-W striking fault that turns to the south inland of the north Caspian shoreline. This fault configuration implies that the Baku area is at the junction of four fault systems, the MCT, the West Caspian Fault, the North Caspian Fault, and the Central Caspian Seismic Zone. The rate of convergence on the MCT decreases from east to west from 10 ± 1 mm/yr at 48° E longitude to 4 ± 1 mm/yr in northwestern Azerbaijan (~46°E longitude). In eastern Azerbaijan, there is no evidence of active shortening in the Lesser Caucasus or Kura Depression, indicating that any deformation in this area is below present velocity uncertainties (± 0.5 mm/yr). The present-day pattern of horizontal motions in aggregate suggests that the Lesser Caucasus and Kura Depression are rotating coherently (i.e., little or no internal deformation) in a counterclockwise sense about a pole located near the NE corner of the Black Sea, resulting in the observed W to E increase in the rate of convergence along the MCT. These new, quantitative constraints on fault activity provide an improved physical basis for estimating earthquake hazards in Azerbaijan.

Formation and variability of the south Pacific sea surface salinity maximum in recent decades

Abstract: [1] This study investigates causes for the formation and variability of the Sea Surface Salinity maximum (SSS > 36) centered near 18 � S–124 � W in the South Pacific Ocean over the 1990–2011 period at the seasonal time scale and above. We use two monthly gridded products of SSS based on in situ measurements, high-resolution along-track Voluntary Observing Ships thermo-salinograph data, new SMOS satellite data, and a validated ocean general circulation model with no direct SSS relaxation. All products reveal a seasonal cycle of the location of the 36-isohaline barycenter of about 6400 km in longitude in response to changes in the South Pacific Convergence Zone location and Easterly winds intensity. They also show a low frequency westward shift of the barycenter of 1400 km from the mid 1990s to the early 2010s that could not be linked to the El Nino Southern Oscillation phenomena. In the model, the processes maintaining the 22 year equilibrium of the high salinity in the mixed layer are the surface forcing (�þ 0.73 pss/yr), the horizontal salinity advection (�� 0.37 pss/yr), and processes occurring at the mixed layer base (�� 0.35 pss/yr).

Study of the effect of 17-18 March 2015 geomagnetic storm on the Indian longitudes using GPS and C/NOFS

Abstract: The largest geomagnetic storm in solar cycle 24 occurred during March 17-18, 2015 where the main phase of the storm commenced from 07:00 UT of March 17, 2015 and reached the Dst negative minimum at 22:00 UT. The present paper reports observations of TEC, amplitude and phase scintillations from different GPS stations of India during the storm of March 17 and highlights its effects on GPS. It also presents the global ESF occurrence during the storm using total ion density drift measurements from C/NOFS satellite. TEC enhancements were noted from stations along 77oE meridian around 10:00 UT on March 17 compared to March 16 and 18 indicating positive storm effects arising out of equatorward neutral wind in the local morning-noon sector of the main phase. Intense scintillation observations from Calcutta were most extensive during 15:00-16:00 UT, March 17 and the receiver recorded a longitude deviation of 5.2 m during this time. Cycle slips of the order of 8 s could be observed during periods of intense phase scintillations on the same night. Intense scintillation observation from Palampur is an exceptional phenomenon attributed to the dramatic enhancement of the electric field due to PPEF leading to a very high upward ion velocity over the magnetic equator as recorded by C/NOFS. The total ion density measured globally by C/NOFS reveals two distinct longitude regions of ESF occurrence during the storm: i) East Pacific sector and ii) Indian longitude during the storm. The time and longitude of ESF occurrence could be predicted using the time of southward turning of IMF Bz.