Professor Chao Xiong from our school was selected as a new member of the International Reference Ionosphere Working Group

Recently, the 34th General Assembly and Scientific Symposium (GASS) of the International Union of Radio Science (URSI) was held in Rome, the capital of Italy. In this meeting, Professor Chao Xiong from the Department of Space Physics of our school was selected as a new member of the International Reference Ionosphere (IRI) working group. His recent work about the topside ionosphere correction of IRI model was summarized as a research highlight in the final meeting report.
The IRI model is based on a large number of ground-based observations and accumulated ionospheric results over several decades. It is currently the most widely used ionospheric empirical model in the world, which provides monthly average values ​​of the ionospheric parameters, such as electron density, electron temperature, ion density, and ion compositions ranging from 60 to 2000 km altitudes. The model predicts can well reflect the average state of the ionosphere under geomagnetic quiet conditions. However, since the IRI model does not include observations of the top ionosphere under extreme solar activity levels, the predicted electron density during the solar minimum years (2008-2010) of 23/24th solar cycle was quite large than the in situ measurements of low Earth orbit (LEO) satellites, with a relative error close to 100%.
By visiting and changing ideas with Professor Dieter Bilitza, the principle investigator of the IRI model, Professor Xiong Chao has analyzed the relationship between top ionospheric electron density and solar radiation flux in detail, and nearly 20-year continues observations from multiple LEO satellites (e.g., the Alouette/ISIS, CAHMP GRACE, Swarm) have been utilized to correct this relationship. The corrected model greatly improves the model prediction of topside ionosphere electron density under extreme solar activity levels. The corrected model has also been included in the latest version of the IRI model (www.irimodel.org).

Figure 1. (top) the variation of solar activity index, P10.7 from 2000-2020; (bottom) the relative error between the IRI model predicted topside ionospheric electron density and satellite measurements, separately plotted before (dotted lines) and after (solid lines) the IRI model correction corrected.

During the past 10 years, professor Chao Xiong mainly works on the topics related to Earth’s ionosphere, e.g., the ionospheric physics, magnetosphere-ionosphere-thermosphere coupling, space weather effects, and space-borne measurements calibration, etc. His outstanding work has been widely recognized by the national and international colleagues. He was supported by the Alexander von Humboldt foundation through 2-year postdoctoral funding, and was awarded as the COSPAR "Outstanding Young Scientist Paper Award (2012)" as well as the EGU "Outstanding Young Scientist Award (2019). Now, he is one of the members of the Chinese Space Physics Professional Committee, IRI working group, and the Sino-European CSES (China Electromagnetic Satellite)-Swarm (European Swarm Satellite) joint expert group.