Format Documentation of kpyymm.wdc Files
The most recent kpyymm.wdc (yymm stands for year and month, each
expressed with two digits) files are distributed per e-mail
Dr. H.-J. Linthe,
Both recent and past tables (since 1932) are supplied as an archive
on the FTP servers
Note: FTP sites sometimes refuse connections due to excessive traffic.
- Germany: ftp://ftp.gfz-potsdam.de/pub/home/obs/kp-ap/
- WWW access: http://www.gfz-potsdam.de/~kp_index/kp-ap/
Your mileage may vary with a different FTP program or the WWW access
Background information on geomagnetic indices and the classification
of days is supplied at the WWW startpage
For the intermediate data transfer between the calculation and plot programs
the Institut fuer Geophysik (Goettingen) has decided to use the standard
format as published by the National
Geophysical Data Center (NGDC) in Boulder, Colorado.
The following scientific and format documentation is adapted from
- the columns for the solar radio flux (columns 66-71) are not
maintained or used by our programs
- the list of most quiet and most disturbed days is not contained
in this format; if you need those, please refer to the other
- we do not guarantee the correctness of the international sunspot
number R; these values are published separately (Brussels, Belgium)
Selected Geomagnetic and Solar Activity Indices
The subscript p means planetary and designates a global
magnetic activity index. The following 13 observatories, which lie
between 46 and 63 degrees north and south geomagnetic latitude, now
contribute to the planetary indices: Lerwick (UK), Eskdalemuir (UK),
Hartland (UK), Ottawa (Canada), Fredericksburg (USA), Meanook (Canada),
Sitka (USA), Eyrewell (New Zealand), Canberra (Australia), Lovo
(Sweden), Brorfelde (Denmark), Wingst and Niemegk (Germany).
Three-hour-range Index Kp
Ks indices isolate solar particle effects on the earth's
magnetic field; over a 3-hour period, they classify into disturbance
levels the range of variation of the more unsettled horizontal field
component. Each activity level relates almost logarithmically to its
corresponding disturbance amplitude. Three-hour indices discriminate
conservatively between true magnetic field perturbations and the
quiet-day variations produced by ionospheric currents.
Ks indices range in 28 steps from 0 (quiet) to 9 (greatly
disturbed) with fractional parts expressed in thirds of a unit.
A Ks-value equal to 27, for example, means 2 and 2/3 or 3-;
a Ks-value equal to 30 means 3 and 0/3 or 3 exactly;
and a Ks-value equal to 33 means 3 and 1/3 or 3+.
The arithmetic mean of the Ks values scaled at the
13 observatories listed above gives Kp.
Equivalent Amplitude ap
The ap-index ranges from 0 to 400 and represents a
Kp-value converted to a linear scale in nT (nanoTesla)
- a scale that measures equivalent disturbance amplitude of a station
at which K=9 has a lower limit of 400 nT.
Column Format Description
====== ====== ===========
1- 2 i2 yy, last two digits of year
3- 4 i2 mm, month (1-12)
5- 6 i2 dd, day of month (1-31)
7-10 i4 Bartels solar rotation number - a sequence of 27-day
intervals counted continuously from February 8, 1832
11-12 i2 Number of day within the Bartels 27-day cycle
13-28 8i2 3-hourly Kp indices (0-3, 3-6, 6-9, 9-12, 12-15,
15-18, 18-21, 21-24 UT)
29-31 i3 Daily Kp sum, expressed to the nearest third of a unit
(supplied only for tradition, use Ap scientific purposes!)
32-55 8i3 3-hourly ap indices (0-3, 3-6, 6-9, 9-12, 12-15,
15-18, 18-21, 21-24 UT)
56-58 i3 Ap equivalent daily amplitude - the arithmetic mean
of the day's eight ap values
59-61 f3.1 Cp or Planetary Daily Character Figure - a qualitative estimate
of overall level of magnetic activity for the day determined
from the sum of the eight ap amplitudes. Cp ranges, in steps
of one-tenth, from 0 (quiet) to 2.5 (highly disturbed)
62-62 i1 C9 - a conversion of the 0 to 2.5 range of the Cp index to one
digit between 0 and 9
63-65 i3 International Sunspot Number. Records contain
* Zurich number through December 31, 1980
* International Brussels number thereafter
66-70 f5.1 Ottawa 10.7 cm Solar Radio Flux adjusted to 1 AU - measured
at 1700 UT daily and expressed in units of 10^-22 W/m^2/Hz.
Observations began on February 14, 1947. From that date
through December 31, 1973, the fluxes given here do not
reflect the revisions Ottawa made in 1966.
71-71 i1 Flux Qualifier
0: indicates flux required no adjustment;
1: indicates flux required adjustment for burst
in progress at time of measurement;
2: indicates a flux approximated by either
interpolation or extrapolation;
3: indicates no observation.
For questions concerning specific data or the contents of this page,
Dr. H.-J. Linthe,
Last modified: Jul 5 2000