On the utility of the ionosonde Doppler‐derived EXB drift during the daytime

Abstract

Vertical EXB drift measured using the ionosonde Doppler sounding during the daytime suffers from an underestimation of the actual EXB drift because the reflection height of the ionosonde signals is also affected by the photochemistry of the ionosphere. Systematic investigations have indicated a fair/good correlation to exist between the C/NOFS and ionosonde Doppler‐measured vertical EXB drift during the daytime over magnetic equator. A detailed analysis, however, indicated that the linear relation between the ionosonde Doppler drift and C/NOFS EXB drift varied with seasons. Thus, solar, seasonal, and also geomagnetic variables were included in the Doppler drift correction, using the artificial neural network‐based approach. The RMS error in the neural network was found to be smaller than that in the linear regression analysis. Daytime EXB drift was derived using the neural network which was also used to model the ionospheric redistribution in the SAMI2 model. SAMI2 model reproduced strong (weak) equatorial ionization anomaly (EIA) for cases when neural network corrected daytime vertical EXB drift was high (low). Similar features were also observed in GIM TEC maps. Thus, the results indicate that the neural network can be utilized to derive the vertical EXB drift from its proxies, like the ionosonde Doppler drift. These results indicate that the daytime ionosonde measured vertical EXB drift can be relied upon, provided that adequate corrections are applied to it.

Characteristics of the equatorial plasma drifts as obtained by using Canadian Doppler ionosonde over southern tip of India

“…So our motive in this paper is not to discuss about daytime vertical drifts. While we present here daytime vertical drifts as well for brevity, however, a detailed study on daytime vertical drifts and their possible corrections are investigated in a separate paper by Joshi and Sripathi []. We present here drifts during evening hours when photoionization is minimum.…”

“…They showed that their PRE drift variations are in good agreement with solar flux variations. More recently Joshi and Sripathi [] have studied the daytime vertical drifts by using ionosonde, and a correction factor is being identified and is applied based on neural network technique. These drifts were also compared with C/NOFS ion drifts and EEJ strength.…”

“…Since then, we have been monitoring movement of various ionospheric layers and its dynamics by using these ionosondes. Already, some investigations have been made by using these systems and results have appeared in referred journals [ Nayak et al ., ; Narayanan et al ., ; Tiwari et al ., ; Joshi and Sripathi , ]. However, we have not investigated the drifts using CADI system using larger data.…”

“…However, we have not investigated the drifts using CADI system using larger data. Recently, we made some attempt to investigate the drifts and its dynamics over Tirunelveli during daytime and its correction for its utility [ Joshi and Sripathi , ]. In this paper, we present variability of both vertical and zonal drifts during different seasons and their comparison with available drift model such as Scherliess and Fejer [].…”

A novel flexible model to calibrate single-layer height for ionospheric modelling using neural network model

“…In other words, the IED varying with time passing by is partly ascribed to the solar orbit changes. Solar azimuth (AZI) and elevation (ELE) are calculated according to the observer local time and position (Wang et al 2013;Joshi and Sripathi 2016), and as the input parameters, they are expressed similarly as the UT variable:…”