Missing ACE solar wind data for severe space weather events.

The ACE SWEPAM instrument usually measures the solar wind velocity and density in SWI mode, and provides good 64-second resolution data when the solar wind speed is not too high [Skoug et al., 2004]. But this mode of measurements breaks down at times of passage of strong CMEs (or at times of high solar wind speed and density), . To avoid the possibility of losing the data, ACE also collects the 64-second data in a second mode (STI mode) but in 32 minutes rsolution over nearly the full energy range of the instrument.