Space weather forecasting might not have a dedicated segment on the evening news, but the disruptive power looming above the Earth’s atmosphere cannot be underestimated. One form of space weather in particular, the coronal mass ejection (CME), has the potential to take down satellites and power grids on a national and even international scale.
A coronal mass ejection occurs when eruptions of plasma from inside the sun’s corona are released into the solar wind. In the cases where these winds reach the Earth’s magnetosphere, the resulting geomagnetic storm can disrupt radio communications and damage electrical systems. Human and animal life can also be harmed by the intense cosmic radiation. Predicting such events is a crucial step on the way toward developing accurate space weather forecasting.
One of the largest and most troublesome CME events of the last two decades occurred in late-October 2003. Multiple CMEs sent magnetic shockwaves hurtling toward earth, wrecking havoc with communications systems. So far events like these can be tracked, but due to heavy compute and data demands, predictive capabilities that would enable a defense to be marshaled are still emerging. Advancing toward that goal, a team of researchers at Japan’s Nagoya University have developed a new simulation code for CME events, based on a realistic model of the mechanisms behind CME generation and how the phenomena move through space. The method was successfully validated using observational data from the 2003 events.
In the February 2016 issue of Space Weather, the team describes how their newly developed magnetohydrodynamic (MHD) simulation of the solar wind was able to predict the time profile of the southward interplanetary magnetic field at the Earth, in relation to the passage of a magnetic cloud within a CME. “We find that the observed complex time profile of the solar wind parameters at the Earth could be reasonably well understood by the interaction of a few specific CMEs,” they affirm.
Lead author Daikou Shiota of the Nagoya University Institute of Space and Earth Environmental Research explains further:
“Our model is able to simulate complex ‘flux ropes’, taking into account the mechanisms behind CME generation derived from real-time solar observations. With this model, we can simulate multiple CMEs propagating through space. A part of the magnetic flux of the original flux rope inside the CME directed southward was found to reach the Earth, and that can cause a magnetic storm. The inclusion of the flux rope mechanism helps us predict the amplitude of the magnetic field within a CME that reaches the Earth’s position, and accurately predicts its arrival time.”
Achieving the speed required for predictive capability meant slimming down the parameter profile.
“Because our model does not simulate the solar coronal region, its computational speed is fast enough to operate under real-time forecasting conditions,” observes Shiota. “This has various applications in ensemble space weather forecasting, radiation belt forecasting, and for further study of the effects of CME-generated solar winds on the larger magnetic structure of our solar system.”