CONICET | Buscador de Institutos y Recursos Humanos

Given the crucial consequences for Earth and its near-space activity, space weather forecasting has been given great importance in the past decades. This materializes nowadays in the rich and detailed data sets provided by multiple experiments, both ground-based and space-borne, specifically devoted to study the Sun-Earth connection. In this respect, coronal mass ejections (CMEs) constitute a key phenomenon, because their arrival to Earth and their magneto hydrodynamic (MHD) associated shock are capable of triggering geomagnetic storms. Since it is difficult to predict the occurrence of an Earth-directed CME, it is of vital importance to ascertain its associated shock arrival time (SAT) at Earth with the best accuracy possible. The present study addresses this problem by combining type II radio emission in the km domain (kmTII) detected by Wind/WAVES, near-Sun kinematic profiles deduced from white light coronagraph images and in-situ SAT measurements. In a first stage, the SAT forecasting linear method previously introduced by the authors and based only on kmTII emissions was revised and improved by both an automatic mean local plasma frequency estimation and an enhanced kmTII detection methodology. The technique, tested on 96 events, reduces considerably the mean SAT forecasting error to a value of 5 h, as opposite to the original method which averaged 8 h. Subsequently, the kinematics of SOHO/LASCO C2 CMEs temporally associated with the studied kmTII events were also considered. Due to important projection effects present in the identified CMEs, several models were employed to account for this effect. The height-time diagrams resulting from the combination of white-light corona, kmTII radio, and in-situ data lead to characteristic height-time profiles that represent them best. At the same time, the performance of the various models used to remove projections effects could be assessed, in order to recognize the models that work best under the different circumstances. This synergistic study appears promising towards achieving better-educated SAT forecasts solely based on spacecraft located in the Sun-Earth line.

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