1. A complete solar cycle (2006–2016) studies of scale heights derived using COSMIC radio occultation retrieved electron density profiles.
- Author
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Uma, G., Brahmanandam, P.S., Tulasi Ram, S., Wu, K.-H., and Chu, Y.H.
- Subjects
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SOLAR cycle , *ELECTRON density , *IONOSPHERE , *SOLAR activity - Abstract
Abstract Various ionospheric vertical scale heights (VSH) including, the Chapman (H m), VSH at upper ionosphere (VSH UP) and 500 km (VSH 500) derived using COSMIC radio occultation (RO) retrieved electron density profiles during a complete solar cycle (2006–2016) are presented in this research. VSH show distinct latitudinal variations and solar-activity dependencies. VSH follow the geomagnetic equator with a longitudinal structure irrespective of the season and year, although mid and high latitudes show higher values and irregular variations in low (2006–2010) and moderate-to-high (2011–2016) sunspot years during the daytime hours (1300 LT-1500 LT). The longitudinal structure of VSH 500 appears only in moderate-to-high sunspot years, which is an important observation reported for the first time in this communication. Diurnal variations of Hm at equatorial latitudes show higher values starting from ∼0400 LT to ∼2300 LT with a post-sunset peak. However, an absence of the post-sunset peak is seen in VSH UP and VSH 500 which is probably due to the altitudinal gradients of vertical drifts that increase (decrease) below (above) the F-layer peak during evening pre-reversal enhancements. The reduced drifts above the F-layer peak thereby, suppresses the post-sunset peak in VSH. Concurrent and large-scale structures in VSH 500 and VSH UP at mid and high latitudes in summer hemispheres during June and December solstice seasons are reported for the first time, which occurred possibly due to the long-duration exposure to the Sun's strong radiation during summer seasons. A one-to-one correlation exists between the Chapman scale heights and peak height of the F 2 layer (hmF 2) at equatorial latitudes in different seasons, while moderate correlation is seen between them away from the equatorial latitudes. These presented scale heights at a global scale are very significant, particularly, for future empirical modeling studies and the long-term availability of COSMIC RO retrieved electron density profiles allowed us to present these scale heights. Highlights • Vertical scale heights during one complete solar cycle (2006–2016) are presented. • A substantial longitudinal structure is evident in the equatorial regions. Absence of a post-sunset peak in VSH UP and VSH 500 is an interesting observational finding. • Concurrent and large-scale structures found in VSH 500 and VSH UP in summer hemispheres during June and December solstice. • A significant (moderate) correlation is found between hmF 2 and H m at (away from) equatorial latitudes. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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