FIGURE 5.3 Example of an x-ray event alert. SOURCE: NOAA Space Weather Prediction Center, available at http://www.swpc.noaa.gov/alerts/archive/archive_01Jan2005.html.

FIGURE 5.4 A 1989 geomagnetic storm caused a blackout in the Quebec region and damaged a high-voltage transformer. SOURCE: Rodney Viereck, NOAA Space Environment Center, “Space Weather: What Is It? How Will It Affect You?,” available at lasp.colorado.edu/~reu/summer-2007/presentations/SW_Intro_Viereck.ppt.

which corresponds to K = 7, whereas the SWPC warned of K = 6 at 02:09, 38 minutes later. The SWPC uses ground magnetometer stations located in Boulder, Colorado, and Fredericksburg, Virginia, which are at geomagnetic mid-latitudes. A 4-hour delay in collecting and averaging ground magnetometer sampling (Boulder and Fredericksburg), with a consequent 4-hour lag in issuing K index alerts, requires system operators to rely on their own instrumentation, which may not be as accurate. Further, the northeastern U.S. power grids and particularly the Canadian power