Long-term variation of ionospheric slab thickness from WACCM-X simulations (1965–2008)

The slab thickness, defined as the ratio of total electron content (TEC) to the F2-region maximum electron density (NmF2) in the ionosphere, is a key parameter for characterizing the vertical distribution of electron density above the F2 peak. This study aims to investigate the long-term trends in topside ionospheric electron density and the associated evolution of slab thickness using the Whole Atmosphere Community Climate Model with thermosphere–ionosphere extension (WACCM-X).Four long-term WACCM-X simulations, each with distinct numerical configurations, were conducted for the period 1965–2008, spanning four solar cycles. These experiments are designed to examine the relative contributions of increasing greenhouse gas concentrations and secular changes in the geomagnetic field to long-term ionospheric variability. The monthly mean plasma temperature, ion temperature, slab thickness, and exponential decay factor of electron density for June from 1965 to 2008, based on four experiments, are provided in the following NetCDF files:TP_casex.nc – Monthly mean plasma temperature (June, 1965–2008)TI_casex.nc – Monthly mean ion temperature (June, 1965–2008)SlabThickness_casex.nc – Monthly mean slab thickness (June, 1965–2008)k_folding_casex.nc – Monthly mean exponential decay factor of electron density (June, 1965–2008)Here, x (1–4) denotes the experiment index. Detailed descriptions of the experimental configurations can be found in Hsu et al. (2026), “How do changes in the geomagnetic field and greenhouse gas concentrations affect the upper ionosphere in the long term?”