Empirical models of Total Electron Content based on functional fitting over Taiwan during geomagnetic quiet condition

Abstract

Abstract. Empirical models of Total Electron Content (TEC) based on functional fitting over Taiwan (120 • E, 24 • N) have been constructed using data of the Global Positioning System (GPS) from 1998 to 2007 during geomagnetically quiet condition (D st >−30 nT). The models provide TEC as functions of local time (LT), day of year (DOY) and the solar activity (F), which are represented by 1-162 days mean of F10.7 and EUV. Other models based on median values have been also constructed and compared with the models based on the functional fitting. Under same values of F parameter, the models based on the functional fitting show better accuracy than those based on the median values in all cases. The functional fitting model using daily EUV is the most accurate with 9.2 TECu of root mean square error (RMS) than the 15-days running median with 10.4 TECu RMS and the model of International Reference Ionosphere 2007 (IRI2007) with 14.7 TECu RMS. IRI2007 overestimates TEC when the solar activity is low, and underestimates TEC when the solar activity is high. Though average of 81 days centered running mean of F10.7 and daily F10.7 is often used as indicator of EUV, our result suggests that average of F10.7 mean from 1 to 54 day prior and current day is better than the average of 81 days centered running mean for reproduction of TEC. This paper is for the first time comparing the median based model with the functional fitting model. Results indicate the functional fitting model yielding a better performance than the median based one. Meanwhile we find that the EUV radiation is essential to derive an optimal TEC.

A comparison of a model using the FORMOSAT-3/COSMIC data with the IRI model

“…The accuracy of the IRI model improves with an increase of EUV. This tendency of the IRI model to solar flux is similar to that of TEC over Taiwan (Kakinami et al, 2009). The altitude profile of N e derived by the F3/C and the IRI models above Inamori Hall, Kagoshima University (42.5…”

“…The F3/C model reproduces N e as functions of the solar EUV flux, day of year (DOY), local time (LT), altitude and location. A similar methodology has been applied to empirical models of transition height (Marinov et al, 2004;Kutiev and Marinov, 2007), vertical scale height in the top-side ionosphere (Kutiev et al, 2006) and TEC over Taiwan (Kakinami et al, 2009). Daily EUV (0.1-50 nm) measured by the Solar Heliospheric Observatory (SOHO) (Judge et al, 1998) and posted on the web site of the Space Science Center of the University of Southern California (http://www.usc.edu/dept/space science/), is used to construct the model.…”

Ionospheric assimilation of radio occultation and ground-based GPS data using non-stationary background model error covariance

“…However, most stations do not provide the differential code bias (DCB) of GPS receivers. Kakinami et al (2009) used the Global Ionospheric Map (GIM) developed by the Jet Propulsion Laboratory (Mannucci et al, 1998) as a reference to eliminate the instrumental biases. The differential instrumental biases of GPS receivers are estimated by the GIM minimum TEC value during 04:00 and 06:00 local time at GPS receivers, while the DCB of GPS satellite is calibrated by using the Center for Orbit Determination in Europe (CODE) values (Schaer, 1999).…”

Seismo-Tsunamigenic Ionospheric Hole Triggered by M 9.0 2011 off the Pacific Coast of Tohoku Earthquake

“…Since there are several factors such as the satellite and receiver instrumental biases, we used the Global Ionospheric Map (GIM) developed by the Jet Propulsion Laboratory (Mannucci et al 1998) as a reference to define the biases. Values of instrumental biases are estimated by comparing minimum values of GIM TEC at the receiver location with those of observed TEC approximately from 400 to 600 (local time: LT) (Kakinami et al 2009). The point that the ray path from a GPS satellite to a ground-based receiver intercepts the ionospheric surface is named as a ionospheric point.…”