The International Quiet and Disturbed Days are determined from the Kp values of the respective
month based on a combination of criteria like the sum of the Kp values for a day, the sum of their
squares, and the maximum Kp. The 10 quiet days are selected and ordered, with the quietest day 
being labelled Q1 and the least quiet day of these 10 days being labelled Q10. Any of these days 
can be assigned the letter A if Ap exceeds 6 for this day or the letter K if Ap is smaller or equal 
6, but one Kp value exceeds 3, or two Kp values exceed 2+. The 5 disturbed days are selected and 
ordered from D1 (the most disturbed day) to D5. An asterisk (*) is assigned to a disturbed day if 
Ap is smaller 20. The Kp index was introduced by Bartels (1949) and is produced by Geomagnetic
Observatory Niemegk, GFZ German Research Centre for Geosciences.


DOI, license and references are given here:
# DOI: https://doi.org/10.5880/Kp.0001
# LICENSE: CC BY 4.0, please cite:
# Matzka, J., Bronkalla, O., Tornow, K., Elger, K. and Stolle, C., 2021.
# Geomagnetic Kp index. V. 1.0. GFZ Data Services,
# https://doi.org/10.5880/Kp.0001
# Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O. and Morschhauser, A.,
# 2021. The geomagnetic Kp index and derived indices of geomagnetic activity.
# Space Weather, https://doi.org/10.1029/2020SW002641

The strucutre of the dowmloaded data is:

  International           Quietest Days                 Most Disturbed Days
  Month
            Q1  Q2  Q3  Q4  Q5    Q6  Q7  Q8  Q9  Q10   D1  D2  D3  D4  D5

with the first two columns giving month and year,
the next 10 columns giving the 10 quietest days of the month Q1 to Q10,
with Q1 being the most quiet day, Q2 being the second-most quiet days etc.,
and the last 5 columns giving the 5 most disturbed days D1 to D5,
with D1 being the most disturbed day, D2 being the escond-most disturbed day etc.