Three-hourly Indices of Ionospheric Activity.

A system of local and global 3-hourly indices of ionospheric activity is introduced representing the weighted average of the positive ionospheric disturbance W-indices, negative disturbance W-indices, and the range of disturbances. The analysis of global 3-hourly indices of positive ionospheric disturbances WU, negative WL, and their range WE = WU – WL is performed using JPL global maps of total electron content, GIM-TEC, from 1994 to 2020. A high correlation (r2 ≅ 0.85) between ionospheric and solar activity is obtained while a weak correlation (r2 ≅ 0.47) is identified for the geomagnetic kp index with solar and ionospheric activity. A retrospective study of 3-h indices of local ionospheric disturbance DU, DL and DE is carried out using critical frequency foF2 (the peak electron density NmF2) at Moscow, Slough-Chilton, Canberra and Port Stanley stations from 1945 to 2020. We find an asymmetry in the trends of ionospheric activity in the Northern and Southern Hemisphere: a decrease of 3-h indices at Moscow and Slough-Chilton and an increase of ionospheric disturbance at Canberra and Port Stanley. The decrease of geomagnetic activity (kp-index) during the recent solar cycles is possibly due to a restricted set of stations located primarily in the Northern hemisphere providing data to calculate the planetary kp-index. [ABSTRACT FROM AUTHOR]