Spatial and Temporal Features of the Topside Ionospheric Electron Density by a New Model Based On GPS Radio Occultation Data

Abstract

A new method for probing the spatial and temporal features of the topside ionosphere is presented. The Vary‐Chap model given by linear functions was used to discover and report features of the topside scale height and its gradient. Based on the global coverage of the radio occultation data, spherical harmonic functions were applied to detect some spatial features of the estimated topside. In addition, a Fourier time‐dependent method was applied in 10 consecutive years to both estimate and predict the temporal evolution of the topside. As a result, the temporal variation of the peak height showed high correlation with the scale height. And on the other hand, the electron density peak showed a strong anticorrelation with the gradient of the scale height. This suggests that the equatorial topside was mainly controlled by the E × B equatorial vertical drift, which increases the scale height in the equatorial region, and the diffusion of the electrons along the geomagnetic field lines, which reduces the gradient of the scale height. Also, a 1 year prediction with a reasonable accuracy showed that the proposed model can be considered a practical and useful tool for predicting features of the topside ionosphere, which may have special interest for the development of climatological models.

α‐Chapman Scale Height: Longitudinal Variation and Global Modeling

“…The daytime VSH reaches a huge peak in equatorial region with two troughs at low latitudes in both hemispheres, VSH increases with latitude during morning, nighttime, and evening hours at higher latitudes. This characteristic also was reported in other studies (Prol et al, ; Wu et al, ). However, the knowledge of the behavior of the topside ionospheric scale heights remains insufficient, especially its longitudinal structure.…”

“…Topside scale heights in different definitions have been retrieved from diverse observations. Topside Ne profiles obtained from measurements including incoherent scatter radars (Lei et al, ; Liu, Le, et al, ; Liu, Wan, et al, ; Qiao et al, , ), radio occultations (Liu et al, ; Ma et al, ; Potula et al, ; Prol et al, ; Stankov & Jakowski, ; Su et al, ; S.‐C. Wang et al, ; Wu et al, ; T.‐L.…”

“…Xu et al, ). VSH and Hm at midlatitudes generally have larger values in summer than in winter hemisphere (Ma et al, , Prol et al, , T.‐L. Xu et al, , Yang et al, ).…”

“…Liu et al () also reported that Hm at southern midlatitudes in the region centered at 70° E are higher than that in other longitudes during daytime, while the situation in northern midlatitude has not been studied. Moreover, most empirical models neglect the longitudinal variation of the scale height (Kutiev et al, ; Prol et al, ; Wu et al, ) due to the sparse observations. Fortunately, Constellation Observing System for Meteorology, Ionosphere, and Climate ( COSMIC ) satellites have accumulated more than 11 years of data.…”

Tomographic Imaging of Ionospheric Plasma Bubbles Based on GNSS and Radio Occultation Measurements

“…The mathematical formulation of the tomographic reconstruction method was developed in two stages. The first stage uses the climatological model proposed by Prol et al [37] to build the background ionosphere based on global Radio-Occultation (RO) observations. The second refers to a slight modification of the Multiplicative Algebraic Reconstruction Technique (MART) for an iterative update of the background electron density field, using regional observations of TEC.…”