A complete solar cycle (2006–2016) studies of scale heights derived using COSMIC radio occultation retrieved electron density profiles. (January 2019)

• Record Type: Journal Article
• Authors: Uma, G.; Brahmanandam, P.S.; Tulasi Ram, S.; Wu, K.-H.; Chu, Y.H.
• Is Part Of: Journal of atmospheric and solar-terrestrial physics. Volume 182(2019)
• Page Start: 101
• Page End: 118
• Publication Date: 2019-01
• Subjects: Vertical scale heights -- COSMIC RO technique -- Electron density profiles -- Middle and high latitudes; Geophysics -- Periodicals; Atmospheric physics -- Periodicals; Géophysique -- Périodiques; Météorologie physique -- Périodiques; Electronic journals; 551.51
• DOI: 10.1016/j.jastp.2018.11.010
• Languages: English
• ISSNs: 1364-6826

Abstract

Abstract: Various ionospheric vertical scale heights (VSH) including, the Chapman (Hm ), VSH at upper ionosphere (VSHUP ) and 500 km (VSH500 ) 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 VSH500 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 VSHUP and VSH500 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 VSH500 and VSHUP 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 F2 layer (hmF2 ) 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 VSHUP and VSH500 is an interesting observational finding. Concurrent and large-scale structures found in VSH500 and VSHUP in summer hemispheres during June and December solstice. A significant (moderate) correlation is found between hmF2 and Hm at (away from) equatorial latitudes.