Forecasting solar wind high-speed streams (STEREO+CH)

   STEREO+CH is based on a persistence method, using STEREO-A in-situ measurements shifted forward by a variable time span (2017: ~9-10 days) according to the angle of the STEREO spacecraft with Earth (see Figure to the left). As additional input, we apply the information on the evolution of coronal holes (CHs), by comparing CH areas extracted in EUV data from STEREO and Earth perspective. By tracking the CH evolution as observed from multiple satellites we perform an uncertainty assessment and apply the derived changes in the CH area (given as ratio between STEREO and SDO) to the predicted solar wind speed profile arriving at 1AU. The statistical evaluation covers the time range 2008-2012 from which we derive that the STEREO+CH persistence model performs better than an ACE persistence model (increase of 12% for correctly predicted high-speed streams, decrease of misses by 25% and false alarms by 20%). Temmer, Hinterreiter, Reiss (2017, SWSC under review).

SWAMI L5 solar wind forecasting algorithm: STEREO+CH solar wind speed forecast (gray curve for 9 days in advance) compared to DSCOVR/ACE
measurements (black curve). The uncertainties in the speed forecast, due to observed changes in the CH areas (expansion/decay) leading to an
under-/overestimation of persistence result (see bottom panel) are marked in grey (top and middle panel). From that we derive the uncertainty in the
forecast (red curve for 4 days in advance). 


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