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Quiet Q and Disturbed D International Days
Determination of quiet Q (quietest) and disturbed D (most disturbed) days of each month
is carried out according to the values Kp index of the geomagnetic activity based on three criteria:
the sum of eight values of Kp per day;
the sum of squares of eight values Кp;
maximum of eight valuesКp.
According to each of these criteria, the corresponding sequence number is assigned to each day of the month.
For the three received sequence numbers, an average sequence number is calculated for each day.
Ten days with the smallest and five days with the largest ordinal numbers are considered as ten/five
international quiet and disturbed days respectively.
It should be noted that these selection criteria give only a relative indication of the nature of the selected days
in relation to other days of the same month. Since the general level of disturbance can be very different
for different years, as well as for different months of one year, the selected quietest days of the month
can sometimes be rather disturbed or vice versa.
To indicate such a situation, individual days that do not meet certain absolute criteria are designated as follows:
* The chosen quiet day is considered not quiet and marked by the letter A, if Ap is more than 6,
or marked with the letter K, if Ap is less than or equal to 6, and either one Kp value is greater than 3
or two Kp values greater than 2+.
* The selected perturbed day is considered to be non-disturbed and marked with an asterisk (*) if Ap is less than 20.
Q and D are defined and published
World Data Center for Geomagnetism, Kyoto.
Continuous series of values
Q and D days from 1932.
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