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A severe geomagnetic storm, and the largest in solar cycle 24, occurred on 17-18 March 2015 without significant precursor X-or M-type solar flares.Figure 1 shows (first to fourth panels) solar wind variables, auroral electrojets indices, and the Disturbance Storm Time (Dst) index associated with the event, which was classified as a G4 (severe) level storm (http://www.swpc.noaa.gov/noaa-scales-explanation).Red auroras were seen even from the northern part of Japan for first time during the present cycle, attracting considerable interest by the media and general public.Some of the headlines in Japan are as follows: Auroras came to northern Japan after 11 years (Asahi newspaper) and space weather prediction came off and low-latitude auroras appeared (Yomiuri newspaper).Unfortunately, space weather agencies worldwide, including the ones in the United States, Japan, and Europe failed to predict that a severe geomagnetic storm would arrive at the near-Earth environment.Does this example show that our present ability of predicting the occurrence of geomagnetic storms is still primitive or that some unusual conditions existed that are not included in current predictive models?Improving predictive models of geomagnetic disturbances is essential for the ultimate practical utility of these models to avert the disruption of the operations of technical systems susceptible to such disturbances.In view of the importance and urgency of the problem, an emergency workshop was called in Japan by Professor K. Kusano of the Solar-Terrestrial Environment Laboratory, Nagoya University, to evaluate what may be wrong with the presently available prediction algorithms of solar-terrestrial processes.Professor Kusano is the Principal Investigator of a proposed 5 year research project on space weather where observations and physics-based numerical simulations are most effectively combined.It is facing the final selection procedure with the Japanese government.Naturally, most of the meeting attendees tended to look for something unusual on the Sun as the source of this severe storm at Earth.