The UNIGRAZ ESA H-ESC tool “STEREO+CH” – upgrade and preparation for cycle 25

We present the ESA service STEREO+CH which forecasts the solar wind speed for Earth, based on persistence modeling from STEREO in situ measurements combined with multi-viewpoint EUV observational data. By comparing the fractional areas of coronal holes (CHs) extracted from EUV data of STEREO and SoHO/ SDO, we add an uncertainty level derived from changes in the CH areas, and apply those changes to the predicted solar wind speed profile at Earth (see Temmer, Hinterreiter, and Reiss, 2018). In principle, the service was developed to work with in situ and EUV data from the location behind Earth (e.g., future Vigil mission) providing a lead time of solar wind speed forecast for a couple of days. As STEREO-A will switch its location to ahead of Earth, we perform additional statistical studies and upgrade the service by adding co-latitude information of the CHs and dynamic thresholding for CH extraction to keep the performance level up. With that we make the ESA service ready for solar cycle 25.