Journal
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
Volume 120, Issue 8, Pages 6930-6940Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015JA021235
Keywords
electric field; gravity waves; equatorial spread F; prereversal vertical drift; large-scale wave structure; PRE vertical drift
Categories
Funding
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [CNPq 300883/2008-0]
Ask authors/readers for more resources
In this paper we present the results of a study on the characteristics of large-scale wave structure in the equatorial ionospheric F region that serve as precursor to postsunset development of the spread F/plasma bubble irregularities. The study is based on analysis of Digisonde data from three equatorial sites in Brazil (Fortaleza, Sao Luis, and Cachimbo) for a period of about 2months at a medium solar activity phase. Small-amplitude oscillations in the F layer heights, extracted at a number of plasma frequencies, present characteristics as them being generated from upward propagating gravity waves. They represent wave structures in polarization electric field having zonal scale of a few hundred kilometers. Their amplitudes in the afternoon hours undergo amplification toward evening, leading to postsunset development of equatorial spread F/plasma bubble irregularities, on a statistical basis. On the days of their larger amplitudes they appear to occur in phase coherence on all days, and correspondingly, the evening prereversal vertical drift velocities are larger than on days of the smaller amplitudes of the wave structure that appear at random phase on the different days. The sustenance of these precursor wave structures is supported by the relatively large ratio (approaching unity) of the F region-to-total field line-integrated Pedersen conductivities as calculated using the Sheffield University Plasmasphere-Ionosphere Model simulation of the low-latitude ionosphere. The significant amplification in the wave structure toward sunset and the phase coherent nature of their occurrences on different days are explained tentatively on the basis of the spatial resonance mechanism.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available