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.

Multi-instrument ground-based observations of a travelling convection vortices event

Abstract: A coordinated ground-based observational campaign using the IMAGE magnetometer network, EISCAT radars and optical instruments on Svalbard has made possible detailed studies of a travelling convection vortices (TCV) event on 6 January 1992. Combining the data from these facilities allows us to draw a very detailed picture of the features and dynamics of this TCV event. On the way from the noon to the drawn meridian, the vortices went through a remarkable development. The propagation velocity in the ionosphere increased from 2.5 to 7.4 km s−1, and the orientation of the major axes of the vortices rotated from being almost parallel to the magnetic meridian near noon to essentially perpendicular at dawn. By combining electric fields obtained by EISCAT and ionospheric currents deduced from magnetic field recordings, conductivities associated with the vortices could be estimated. Contrary to expectations we found higher conductivities below the downward field aligned current (FAC) filament than below the upward directed. Unexpected results also emerged from the optical observations. For most of the time there were no discrete aurora at 557.7 nm associated with the TCVs. Only once did a discrete form appear at the foot of the upward FAC. This aurora subsequently expanded eastward and westward leaving its centre at the same longitude while the TCV continued to travel westward. Also we try to identify the source regions of TCVs in the magnetosphere and discuss possible generation mechanisms.

Ionospheric responses to the October 2003 superstorm: Longitude/local time effects over equatorial low and middle latitudes

Abstract: [1] Ionospheric responses to the major magnetic storm disturbances of October 2003 are investigated using database selected in the Brazilian and Japanese-Asian longitude sectors. Data obtained from latitudinally spaced digisondes in the equatorial and low-latitude sites in Brazil and from the Asian and Japanese ionosonde network, the total electron content data from the extensive Japanese GPS receiver chain, and magnetometer data from the Pacific equatorial electrojet stations are analyzed during the period 28–31 October. Prompt penetrating (PP) dawn-dusk polar cap electric fields produce large F region plasma uplift on the dayside and eveningside, while the associated westward electric field on the nightside produces large downdraft of the F region plasma, and causes development of westward electrojet current, observed for the first time. Episodes of PP electric field effects appear to be of larger intensity over Brazil than over Asian longitudes. Equatorial anomaly, development due to undershielding as well as overshielding electric fields, was observed in the Brazilian and in the Asian sectors. Disturbance dynamo electric field causes large nighttime F layer uplifts that are modulated by strong meridional winds in both sectors. The disturbance electric field local time variation patterns are compared with the results of recent global model (MTIEGCM) simulation by Richmond et al. (2003) and validated in some cases. Transients of transequatorial winds, flipping direction from southward to northward, in the widely separated longitude sectors, were diagnosed to be present toward the final recovery phase of the storm. These results are presented and discussed in this paper.

Path of the Mean Rotational Pole From 1899 to 1994

Abstract: SUMMARY Historical sources of polar motion are analysed together with modern data in order to compile a set of coordinates of the mean pole in a reference system consistent with that of the International Earth Rotation Service. the trend and quasi-periodic motion of the pole are investigated, and we find that the rotational pole appears to be moving at the rate of 0.333 arcsec century−1 in the direction of 75.0° west longitude. Modern data also appear to be consistent with the possible existence of very low-frequency periodic motion (Markowitz wobble).

Monthly Mean Wind Fields for the South Atlantic Bight

Abstract: A total of 339 389 marine weather observations have been analyzed to Produce Monthly mean wind fields for the South Atlantic Bight. The results of plotting wind vectors on a 1/2° latitude by 1/2° longitude grid yields four traditional seasonal flow regimes (winter, spring, summer and fall) and an additional regime designated as mariners’ fall. These seasonal wind regimes are discussed and related to the monthly mean ocean circulation in the Bight.

Global Climatic Data for Surface, 800 mb, 400 mb: July.

Abstract: : The document is the second publication in the effort to gather, in one common format, the most representative global climatologies of certain seasonal meteorological variables. From selected data sources, the July global distributions of pressure, temperature, wind, and moisture are reconstructed for the three atmospheric levels. These data are supplemented by presentations of the global distributions of albedo, cloudiness, evaporation, precipitation, and selected elements of the surface heat balance. All data are interpolated at the 4-deg latitude by 5-deg longitude global grid used in the Mintz-Arakawa model. They are given in the form of both tabulated values and machine-analyzed maps.