ULF wave modulation of the ionospheric parameters: Radar and magnetometer observations

• ULF waves may cause significant (up to 60%) modulation of the ionospheric density and conductance.
• ULF waves provide periodic ion heating in F-layer.
• ULF wave–ionosphere interaction results in a non-linear distortion of the wave form.

The global Pc5 pulsations at the recovery phase of strong magnetic storm on October 31, 2003 are examined using the IMAGE magnetometer and EISCAT radar data from the tri-static Tromsø–Kiruna–Sodankylä system. This radar facility gives possibility to determine the vertical profile of basic ionospheric parameters and their variations with time cadence 30 s. The comparison of magnetometer data from Tromsø with the ionospheric parameters shows a significant (up to ~60%~60%) modulation by Pc5 pulsations of the electron density in the E-layer, height-integrated ionospheric conductances, and ion temperature in the F-layer. This modulation has been observed in the absence of quasi-periodic electron precipitation as evidenced by riometer data. The mechanisms underlying the modulation effects, probably, comprise the Joule ion heating by ULF wave electric field, and feeding/depleting the ionospheric electron content by the wave field-aligned current. The impact of ULF waves on the ionosphere results in a non-linear distortion of ULF wave form, as revealed by the phase portrait method.