Global observations of E region plasma density morphology and variability

Abstract

[1] The global morphology and variability of the ionospheric E region plasma density are estimated from satellite-based radio occultation total electron content (ROTEC) measurements. Vertical profiles of E region electron density are estimated using the inversion technique recently proposed by Nicolls et al. (2009). In this technique, the F-region contribution to each ROTEC measurement is removed using an assimilative model of the ionosphere in order to mitigate the effects of F-region gradients in the estimation of E region profiles. The technique is applied to occultation observations made by GPS receivers onboard COSMIC satellites aided by F-region electron density specification provided by the Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm. Global estimates of h m E, N m E, and E region total electron content (TEC) are presented for two different months: April 2007 and January 2008. Results of our analysis show that ROTEC measurements such as those provided by the COSMIC constellation can produce reasonable and valuable estimates of E region parameters on a global scale when properly treated for the effect of F-region density gradients. The agreement between the a-Chapman theory of ionization and recombination and estimated profiles is demonstrated. Reasonable estimates of E region variability can also be specified by the global measurements. The dependence of the E region variability on latitude is quantified and presented.

Ionospheric model‐observation comparisons: E layer at Arecibo Incorporation of SDO‐EVE solar irradiances

“…Above the valley region is the F 1 layer while below 95 km is the D region. The electron densities approximately track the expected local time morphology with a noon maximum [ Chu et al ., ; Moore et al ., ; Nicolls et al ., ; Pavlov and Pavlova , ; Titheridge , ]. Two different techniques were used to obtain the electron density profiles shown in Figure and for all 22 profiles of this study.…”

“…[], Nicolls et al . [], and the earlier work of Titheridge [, ]. However, as will be seen in the following subsections there is significant work still to be undertaken in order to model the E region processes accurately.…”

Effect of small‐scale ionospheric variability on GNSS radio occultation data quality

“…Nighttime and daytime ionospheric conditions in the ionospheric E layer are different from each other. Nicolls et al [2012] analyzed global morphology of E layer plasma density variability. They showed that electron density variability is much larger at night.…”

Long-term monthly statistics of the mid-latitude ionospheric E-layer peak electron density in the Northern geographic hemisphere during geomagnetically quiet and steadily low solar activity conditions

“…Noontime day-to-day ionosonde and incoherent scatter radar measurements of the E layer parameters were used by Moore et al [2006] to calculate the standard relative deviations of NmE from noontime NmE mean values in the range of 5-7% at middle latitudes for 9-27 March 1999 and 4 October -4 November 2002. Slightly larger values of NmE variability were estimated by Nicolls et al [2012] using the inversion technique from satellite-based radio occultation total electron content measurements. However, little attention has been given in these and other published morphological studies to NmE data sorting due to apparent variability of solar and geomagnetic activity.…”