The response of field-aligned and horizontal ionospheric currents to HSS/SIR driven storms and comparison to ICME driven storms

The time delay from an interplanetary driver arriving at the magnetopause to the response in the ionospheric and field-aligned currents (FAC) has never been quantified separately for different types of storm drivers. The development and evolution of the total FAC during storms driven by high speed streams and associated stream interaction regions (HSS/SIR) are different compared to these driven by the sheath and magnetic clouds of interplanetary coronal mass ejections (ICME), as shown in Pedersen et al. (2021, 2022). The main differences are that the FACs in HSS/SIR storms maximize earlier in the storm main phase and are less intense than during ICME storms. Likewise, differences in response times is possible. The delay time for HSS/SIR driven storms is investigated using cross correlation analysis between the total FAC and SME index and the Newell coupling function (NCF), and is compared to sheath and MC driven storms. It is found that the total FAC and SME index lag the NCF by 40 ± 10 min during storms driven by HSS/SIR and sheaths, and by 60 ± 10 min for MCs. Additionally, the total FAC best correlate with the NCF when using solar wind data averaged over the preceding 60 min for sheath, 100 min for HSS/SIR and 120 min for MC driven storms.