Analysis of Ionospheric Correlation Time Variations Based on Long‐Term GIMs Data

Abstract Ionospheric correlation time measures the temporal correlation of the ionosphere and is an important parameter for characterizing the temporal connection of ionospheric variability. Ionospheric correlation times are obtained from high resolution global ionospheric TEC maps spanning 2005 to 2020. Their spatiotemporal variations and causal relationships with external drivers are then analyzed quantitatively. Ionospheric correlation times exhibit obvious seasonal variations, characterized by much larger values in March, as well as noticeable latitudinal asymmetries with higher values in the equatorial and low‐latitude regions. Solar activity, geomagnetic activity, and lower atmosphere forcing have marked one‐way causality with ionospheric correlation times. The time delays between solar (geomagnetic) index and ionospheric correlation times are generally less than one day, while the time delays between lower atmosphere forcing and ionospheric correlation times vary considerably ranging from less than one day to more than 27 days. From the view of information flows, lower atmosphere forcing has the largest information contributions to ionospheric correlation times, followed by solar activity and geomagnetic activity, while interplanetary parameters have relatively small information contributions.