Box plots of the annual distribution of daily geomagnetic USAF estimated Ap index from 1986 through 2006. Stars indicate the minimum and maximum values observed in the year, the small square indicates the mean observed value, and the horizontal line within the box indicates the median. The box contains the observed values from the lower quartile (25%) to the upper quartile (75%) of the distribution and includes 50% of the observed values. The box “whiskers” encompass 98% of the observed values (1% to 99% of the distribution).

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