A method of estimating horizontal vectors of ionospheric electric field deduced from HF Doppler data

Abstract

A formulation providing time variations of the horizontal electric field in the ionosphere from HF Doppler data is presented. The relationship between the electric field and frequency deviations of ionospherically reflected HF radio waves has been extended from the theory given by Jacobs and Watanabe in 1966. In the present formula, the effect of electron decay due to attachment and/or recombination processes is taken into account for long‐lasting variations in the electric field. The developed formula can provide time variations of the horizontal field vector even from data observed at only one station. The formula has been applied to an isolated substorm event. In examining the validity of the deduced results, equivalent ionospheric current systems have been used. These have been deduced from worldwide magnetometer data. With these current systems, we can roughly estimate the horizontal electric field in the ionosphere under some assumptions. The time variation of the electric field deduced from the HF Doppler data agrees with that deduced from current systems and high latitude electrojet activity. The results indicate that the HF Doppler method is a sensitive and useful tool for estimating the electric field in the ionosphere.

Response of the incompressible ionosphere to the compression of the magnetosphere during the geomagnetic sudden commencements

“…In particular, the production/loss of the ionization is critical to the Doppler frequency for long‐period disturbances [ Tsutsui et al , ]. Nevertheless, the HF Doppler sounder has been proved powerful to detect the long‐period disturbances such as the DP2 and substorms [ Abdu et al , ; Tsutsui et al , ] as well as the short‐period SC, PC, and Pi2.…”

“…The HFD is proportional to the frequency of the radio wave when it is caused by the changes in the reflection height, while inversely proportional when the HFD is caused by changes in the refractive index below the reflection height [ Davies et al , ]. Quite a few papers have shown that the HFD is proportional to the radio frequency for the SC events [ Davies et al , ; Huang et al , ; Kikuchi et al , ; Kikuchi , ], geomagnetic pulsations [ Chan et al , ], and substorms [ Tsutsui et al , ].…”

“…As shown above, the reflection height is moved by the electric field transmitted from the polar ionosphere with the ionospheric currents, leading to that the capability greatly depends on the reflection condition in the F region ionosphere. In particular, the production/loss of the ionization is critical to the Doppler frequency for long-period disturbances [Tsutsui et al, 1988]. Nevertheless, the HF Doppler sounder Journal of Geophysical Research: Space Physics 10.1002/2015JA022166 has been proved powerful to detect the long-period disturbances such as the DP2 and substorms [Abdu et al, 1998;Tsutsui et al, 1988] as well as the short-period SC, PC, and Pi2.…”

Substorm Overshielding Electric Field at Low Latitude on the Nightside as Observed by the HF Doppler Sounder and Magnetometers

“…The HF Doppler sounders have been widely used to detect the motion of the reflection height of the HF radio signal, providing the ionospheric electric fields of the geomagnetic sudden commencements (SCs), geomagnetic pulsations (Pc5, Pi2), quasiperiodic DP 2 fluctuations, and substorms (Abdu et al, ; Davies et al, ; Huang et al, ; Jayachandran et al, ; Kikuchi, ; Kikuchi et al, , ; Sastri & Subrahmanyam, ; Tsutsui et al, ).…”

Radio Techniques for Probing the Terrestrial Ionosphere

“…Simpler corrections to the foregoing equations can be obtained by assuming various layer shapes, i.e., for a layer for which the electron density is zero below some reference height and increases linearly with height above the reference height, it can be shown that HF Doppler data have also been used to estimate time variations of the horizontal vectors of the ionospheric electric field at mid-Iatitude by Jacobs and Watanabe (1966) and by Tsutsui et al (1988). Since different frequencies are reflected from different levels in the ionosphere, this can only be accounted for rigorously by ionospheric ray tracing.…”