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Title: Contrasting features of the F3 layer during high and low solar activity conditions observed from Indian low latitude
Authors: Chaitanya, P Pavan
Patra, A K
Rao, S V B
Keywords: F3 layer occurrence
F3 layer critical plasma frequency
Low solar activity
High solar activity
Issue Date: Apr-2012
Publisher: NISCAIR-CSIR, India
PACS No.: 94.20.dj; 96.60.Q-
Abstract: Observations of the F3 layer made during the extremely low solar activity (LSA) condition during 2008-2009 and high solar activity (HSA) condition during 2002-2003 from 6.5oN magnetic latitude in the Indian sector are presented. Structure of the ionogram, displaying the F3 layer, is found to be very distinct and clear in the LSA as compared to that in the HSA. The occurrence rate and the duration of occurrence of the F3 layer is maximum during the summer solstice, moderate during the equinox, and minimum during the winter solstice. While there is no significant difference in the occurrence of the F3 layer in the equinox and the summer solstice during the HSA and LSA periods; in the winter solstice, it is extremely low in the LSA when compared to those observed in the HSA. Mean foF3 is as high as 13 MHz in the HSA and 7 MHz in the LSA. In general, mean foF3 is found to be 4-6 MHz higher in the HSA than that of the LSA. Notably, foF3 values observed during 2008-2009 are found to be 2-3 MHz lower than those reported for the previous LSA periods. While in the summer and winter solstices, mean hmF3 is higher in the HSA than in the LSA; in the equinox, it is higher in the LSA than in the HSA. Also there exists large variability of hmF3 irrespective of local time, season and solar activity levels, indicating the roles of E×B drift and meridional neutral wind on the height of the F3 layer. In an overall sense, while the observations agree well with the model prediction, they are found to agree on some counts and differ on some other counts with those reported earlier. The similarity and dissimilarity of the observations from different low-latitude locations are discussed in the light of current understanding on the F3 layer.
Page(s): 121-129
CC License:  CC Attribution-Noncommercial-No Derivative Works 2.5 India
ISSN: 0975-105X (Online); 0367-8393 (Print)
Source:IJRSP Vol.41(2) [April 2012]

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