%0 Journal Article
%T Ring current space-time inhomogeneities in intense geomagnetic storms
%A Alicia L. Cl¨²a de Gonzalez
%A Aracy Mendes da Costa
%A Walter D. Gonzalez
%J Geof¨ªsica internacional
%D 2004
%I Universidad Nacional Aut¨®noma de M¨¦xico
%X Partial ring currents during the main phase of a geomagnetic storm cause a longitudinal asymmetry in the magnetic field at the earth¡¯s surface at low and mid latitudes. The horizontal component of the magnetic field obtained by ground magnetometers (H), for the magnetic storms on May 14-15, 1997, September 24-25, 1998 and October 18-19, 1998, was studied by means of UT LT diagrams at six magnetic observatories, with approximately uniform longitudinal distribution. Following the same steps used to generate lyemori¡¯s symmetric index (Dst), local time minute by minute profiles of the H-component were obtained for each magnetic storm. An asymmetric disturbance associated with the presence of a partial ring current is identified in the UT-LT maps as contours of depleted magnitude in the H-component, centered around dusk. Increased H-magnitude around midnight is attributed to the substorm expansion current. The UT-LT maps are compared to geomagnetic indices, solar wind parameters and interplanetary magnetic fields.
%K Ring current
%K geomagnetic storm
%K UT-UL diagrams
%U http://www.geofisica.unam.mx/unid_apoyo/editorial/publicaciones/investigacion/geofisica_internacional/anteriores/2004/02/Clua.pdf