Format Documentation of kpyymm.wdc Files ---------------------------------------------------------------------------- Important Note: Filename Ambiguity in 2020 Since January 2020, the conventional filenames for the Kp index in the WDC format would have become ambiguous, as Kp2001.wdc could mean a monthly file for January 2020 or a yearly file for the year 2001. From January 2020, all yearly files are moved to a subdirectory called 'yearly'. Please find the updated format description below that takes into account this change. Despite the fact that each line in these WDC files has its own, correct time stamp, we noticed that some of our users, depending on how they reformat the downloaded data files, have produced corrupted files on their side as a consequence of the filename ambiguity and our mitigation step. We recommend our users to check their reformatted files when downloading our WDC files, especially for the early 2000s and the early months of 2020 and especially if they are not sure how their downloading and reformatting algorithm deals with the filename ambiguity. Our other file formats (e.g. *.tab) are not affected. Availability The most recent kpyymm.wdc (yymm stands for year and month, each expressed by two digits) files are distributed half-monthly by the email: kp_index@gfz-potsdam.de Both recent and past files since 0101 are distributed from the FTP server: ftp://ftp.gfz-potsdam.de/pub/home/obs/kp-ap/wdc/ FROM 2020 ONWARDS: The yearly files kpyyyy.wdc (yyyy stands for year expressed by four digits) since 1932 are distributed from the FTP server: ftp://ftp.gfz-potsdam.de/pub/home/obs/kp-ap/wdc/yearly/ A description of the FTP server, nowcast indices and background information on geomagnetic indices and the classification of days can be found on the webpage: http://www.gfz-potsdam.de/en/kp-index/ Preliminaries We use the standard format as published by the National Geophysical Data Center (NGDC) in Boulder, Colorado. Caution: * the columns for the solar radio flux (columns 66-71) are not reported from 2007 onwards * the list of most quiet and most disturbed days is not contained in this format; if you need those, please refer to the other tables (kpyymm.tab) * we do not guarantee the correctness of the international sunspot number R; these values are published separately (Brussels, Belgium) * note that the sunspot number calculation has been changed by WDC-SILSO, Royal Observatory of Belgium, on July 2015, affecting sunspot numbers from January 2015. * sunspot numbers are not reported from 2015 onwards The following scientific and format documentation is adapted from: ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/KP_AP/kp_ap.fmt Selected Geomagnetic and Solar Activity Indices Worldwide Indices The subscript p means planetary and designates a global magnetic activity index. The following 13 observatories 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), Uppsala (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. Format Description 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 NOT ANY MORE REPORTED FROM 2015 ONWARDS 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. NOT ANY MORE REPORTED FROM 2007 ONWARDS 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. NOT ANY MORE REPORTED FROM 2007 ONWARDS ---------------------------------------------------------------------------- For questions concerning specific data or the contents of this page, please contact: Dr. J. Matzka, contact details on http://www.gfz-potsdam.de/en/kp-index/ Last modified: April 15, 2020 Previous modifications: October 8, 2015