Observations of nighttime equatorial-upper-E-valley region irregular structures from Sao Luis radar and their occurrence statistics: A manifestation of vertical coupling between E and F regions

Author(s)

Kherani, E. Alam ; de Paula, E. R. ; Cueva, R. Y. C. ; Camargo, L. A. P.

• Document type: Journal article
• Source: JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS; v. 75, p. 7-pg., 2012-02-01.

Abstract

Radar observations of nighttime irregular structures in the equatorial upper-E-valley region are presented. These structures are observed strictly during occurrences of an ascending irregular bottomtype or bottomside F layer, during or prior to the appearance of a high-rising F region plume and a momentarily intensification of E-region irregularities. The slope and the altitude coverage of these structures are proportional to the ascending rate of the irregular bottomtype/bottomside F layer and the altitude coverage of the plume respectively. These structures are found to consist of substructures separated in times suggesting the presence of quasi-periodic striations within these irregular structures. On the basis of occurrence statistics during October 2001-December 2008, the occurrence rate of these structures is found to be 3.5%, indicating the nature of rare occurrence of these structures over Soa Luis. Moreover, their occurrence remains confined to the maximum solar-flux period (2001-2003) and to the summer months (October-January). The presence of these structures is a manifestation of the vertical coupling of E and F regions owing to the ambient electric fields of the ionosphere and the fringe-field associated with the F region plume. (C) 2011 Elsevier Ltd. All rights reserved. (AU)