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Low‐latitude E s capable of controlling the onset of equatorial spread F
Author(s) -
Joshi L. M.,
Patra A. K.,
Rao S. V. B.
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/jgra.50189
Subject(s) - sunset , latitude , ionosonde , low latitude , blanketing , f region , sporadic e propagation , ionosphere , geology , atmospheric sciences , physics , geodesy , geophysics , astrophysics , plasma , optics , electron density , stars , quantum mechanics
To investigate their role on the occurrence of equatorial spread F (ESF), the low‐latitude E region in the evening hours has been characterized in terms of sporadic E ( E s ) activity based on ionosonde observations from Sriharikota, a low‐latitude station in India. While prior to the sunset, either Chapman type E layer, or E s , or a combination of the two was observed, after sunset, when observed, the E layer was exclusively E s . E s , however, could be either blanketing or nonblanketing type. Observations revealed that while the occurrence of ESF had a broad relationship with the type of E s , a detailed investigation suggested that (1) ESF occurred (did not occur) irrespective of E s type if the virtual height of the F layer base (h' F ) was greater than ~360 km (less than ~290 km), and (2) ESF occurrence depended strongly on the type of E s if 290 km < h' F < 360 km. Model computation shows that low‐latitude E s can significantly influence the growth of the Rayleigh‐Taylor instability for the cases corresponding to category 2 by increasing the total field‐line integrated Pedersen conductivity, consistent with the observations. The results presented in this paper highlight under what circumstances the low‐latitude E s would play a critical role in the occurrence of ESF, which can be used to understand the day‐to‐day variability of ESF.