Last Updated: 12/08/2023

KASI Geomagnetic Storm Forecast Model

Version: 1.0

KASI Geomagnetic Storm Forecast Model is an empirical model to forecast not only the geomagnetic storm strength in Dst index, but also its possibility based on initially observed parameters of coronal mass ejection. During the running process of the model, it is possible to forecast when a geomagnetic storm will occur by using a shock arrival model together. Since this model can be operated just after CME eruption, it allows us to make an earlier warning of geomagnetic storms 2-3 days in advance.


In the solar source region of CME, Magnetic Field Orientation (MFO) angle is calculated as the median orientation angle of extrapolated field lines relative to the flaring neutral line. The southward event has MFO angle smaller than 90 deg. Otherwise, the event has northward MFO.

The Earth’s response is very different for southward (S) and northward (N) MFOs, however, it is hard to find any good correlation between minimum Dst index and using whole events including southward and northward events together. Instead, by considering two groups of CMEs according to their MFOs (S or N), we can get better correlations. To reflect this fact, we adopt two different formulars for each of them, depending on their MFOs . As the input parameters for those formular, we use normalized values of the Longitude (L) , propagating Speed (V) and Direction (D) . We normalized speed V by dividing 2500 km/s, which is expected the maximum speed in this solar cycle. So, V can be larger than 1, if the propagating speed of CME is faster than 2500 km/s. Earthward direction parameter (D) is directly measured using GUI.

In the coronagraph running difference image, we make points along the CME’s leading edge and draw an ellipse connecting these points. Then the ratio (b/a) of the shorter (b) to longer (a) distance of the CME front from the solar center is automatically obtained as the D (Kim et al., 2008). Those input parameters have no unit since they are normalized. For the forecast of storm time, we use the equation from Gopalswamy et al., 2001.


KASI Geomagnetic Storm Forecast Model gives the Storm Time and expected Minimum Dst index as the storm strength from the forecast result. It also provides the geo-effective Probability for the CME empirically.


  • Solar
  • Heliosphere / Inner Heliosphere
  • Geospace



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