Forecasting Extreme Space Weather Events

Abstract:

A key goal for space weather studies is to define extreme conditions that might plausibly afflict human technology. On 23 July 2012, a solar active region gave rise to a powerful coronal mass ejection (CME) with an initial speed that was determined to be over 2500 km/s. The eruption was directed away from Earth toward the NASA STEREO-A spacecraft. The satellite sensors detected the CME arrival less than 19 hours later and made in situ measurements of the solar wind and interplanetary magnetic field. In earlier work, we addressed the question of what would have happened if this powerful interplanetary event had been Earthward-directed. We found that the 23–24 July event would certainly have produced a geomagnetic storm that was comparable to the largest events of the twentieth century (Dst~−500 nT). Using plausible assumptions, the most extreme modeled value of storm-time disturbance would have been Dst~−1200 nT. This is larger than estimates for the famous Carrington storm of 1859. This finding has significant implications because it demonstrates that extreme space weather conditions more powerful than those during March of 1989 or September of 1859 can happen even during a modest solar activity cycle such as at present. Based on this July 2012 extreme event we have thought at some length about what needs to be done by the space weather community to forecast and prepare for such extreme space weather effects with suitable observations and forecasting tools, huge impacts on technological systems such as the electric power grid and other modern human technology systems could be greatly diminished. We discuss future NASA, NOAA, and other agency missions that could permit efficient and effective forecasting of extreme events in the future.