Predictive Capabilities and Limitations of Stream Interaction Region Observations at Different Solar Longitudes

Abstract

Advanced warning of a stream interaction region (SIR) or corotating interaction region (CIR) impinging upon the magnetosphere of Earth is important for space weather forecasting, due to the ability of SIRs/CIRs to trigger geomagnetic storms and affect ionospheric composition and winds. However, a focused investigation of the likelihood that either an L5 monitor or Earth-trailing “string-of-pearl” constellation of satellites would be able to serve as an effective warning buoy for SIRs/CIRs that will affect the near-Earth space environment has yet to be extensively performed. Through comparing 10 years of SIRs/CIRs observed at L1 and at STEREO, we have investigated the probability of sequentially detecting SIRs/CIRs at two locations as a function of the difference in heliospheric longitude and latitudinal separation between the two spacecraft. By examining the probability of repeat detection of SIRs/CIRs using variable separation distances between two observing points, we explore the utility of an Earth-trailing monitor for SIR/CIR predictability (i.e., 74.6% of SIRs observed at L5 reach L1 within ±3 days of rigid corotation). While the probability of predicting the occurrence of SIRs/CIRs at another spacecraft decreases with longitudinal separation, there is no significant dependence on latitude. The primary source of error in reliably predicting the arrival time of an SIR/CIR is uncertainty in the rotational speed of the structure. While an L5 monitor would be an advancement in our operational warning ability, an Earth-trailing “string-of-pearls” constellation utilizing multiple point of measurements would engender much more certainty in predicting the arrival time of SIRs/CIRs.