Improved Modeling of Global Ionospheric Total Electron Content Using Prior Information

Abstract

Abstract:The Ionosphere Working Group of the International GNSS Service (IGS) has been a reliable source of global ionospheric maps (GIMs) since 1998. Modeling of the global ionospheric total electron content (TEC) is performed daily by several Ionosphere Associate Analysis Centers (IAACs). Four IAACs (CODE, ESA, CAS and WHU) use the spherical harmonic (SH) expansion as their primary method for modeling GIMs. The IAACs generally solve a normal equation to obtain the SH coefficients and Differential Code Biases (DCBs) of satellites and receivers by traditional least-squares estimation (LSE) without any prior knowledge. In this contribution, an improved method is proposed and developed for global ionospheric modeling based on utilizing prior knowledge. Prior values of SH coefficients and DCBs of satellites and receivers, as well as the variance factor and covariance matrix, could be obtained from the ionospheric modeling on the previous day. The parameters can subsequently be updated through GNSS measurements to achieve higher accuracy. Comparisons are carried out between WHU products based either on priori information or original LSE and IGS final products, other IAAC products, and JASON data for the year 2014. The results indicate that there is improved consistency between WHU GIMs and IGS final GIMs, other IAAC products, and JASON data, particularly in comparison with ESA and UPC products, with the probabilities of achieving better consistency with these products exceeding 95%. Moreover, WHU-produced DCBs of satellites also have slightly improved consistency with IGS final GIMs and IAAC products.

Global Ionospheric Model Accuracy Analysis Using Shipborne Kinematic GPS Data in the Arctic Circle

“…To acquire highly accurate information about the absolute TEC of the ionosphere, this study adopted the carrier-phase smoothed pseudo-range method and extracted the ionospheric TEC information from the dual-frequency GPS data. The function expression is given as follows [17]:…”

“…The International GNSS Service (IGS) has been using the continuously operating GNSS reference stations around the world to develop a global ionospheric model, which has become one of the most important tools for ionosphere research and applications [17]. Therefore, analyzing and evaluating the accuracy and reliability of the IGS ionospheric product is essential for its proper use.…”

“…For many years, the IGS has been acquiring ionosphere information from the continuously operating GNSS reference stations around the world. In 1998, it approved and started implementing the TEC Ionosphere Exchange Format (IONEX) [17], which has become an important component of the IGS products and has provided abundant fundamental data for ionospheric studies around the world.…”

An Ionospheric Climate Index Based on GNSS

“…In this contribution we perform the global ionospheric TEC modeling with spherical harmonics (SH) function by using several hundreds of IGS stations and generate the daily global ionospheric maps (GIMs) from 1998 to 2018 (Wang, Shi et al 2016;Cheng, Shi et al 2018). An ionospheric climate index (ICI) is derived from a daily GIMs, which is helpful to describe the general state of the ionosphere.…”

Near-real-time VTEC maps: New contribution for Latin America Space Weather

“…These products are required both in scientific applications and in practical services. Among others, for the monitoring of space weather events such as solar flares, solar energetic particles events and coronal mass ejections (Meza et al, 2009;VanZele and Meza, 2011;Monte-Moreno and Hernández-Pajares, 2014;Wang et al, 2018), also for reliable high frequency (HF) communications along short-, medium-and long-range paths, and for satellite communication, navigation, and positioning systems (Gao et al, 2006;Le et al, 2009). Therefore, continuous monitoring of the spatial and temporal variations of ionized plasma parameters, such as the F 2 layer peak electron density, N m F 2 , and TEC, are of particular interest.…”