PC is an index for magnetic activity in the (P)olar (C)ap. It is based on data from a single nearpole station, and aimed to monitor the polar cap magnetic activity generated by such solar wind parameters as the southward component of the interplanetary magnetic field (IMF), the azimuthal component of the IMF (By), and the solar wind velocity v. The station Thule, located in the village Qaanaaq in Greenland at 86.5 degrees geomagnetic invariant latitude, fulfills the requirement of being close to the magnetic pole in the northern hemisphere.

A full description of the indices Kn, Ks, Km is given in a monography,"Indices Kn, Ks et Km, 1964-1967", edited in 1968 by the Centre National de la Recherche Scientifique, 15 quai Anatole, France, 75007 Paris, which contains these indices for 2964-1967 while the International Association of Geomagnetism and Aeronony (IAGA) Bulletin NO. 39 contains those for 1959-1963. Yearly computations of these data are published in the series of IAGA Bulletin No.32. All

ERA-40 project was to produce and promote the use of a comprehensive set of global analysis describing the state of the atmosphere and land and ocean-wave conditions from during the 45 years from September 1957 to August 2002. The atmospheric model used for ERA-40 is known as IFS CY23r4.

Ionograms are recorded tracings of reflected high frequency radio pulses generated by an ionosonde. Unique relationships exist between the sounding frequency and the ionization densities which can reflect it. As the sounder sweeps from lower to higher frequencies, the signal rises above the noise of commercial radio sources and records the return signal reflected from the different layers of the ionosphere.

Ionograms are recorded tracings of reflected high frequency radio pulses generated by an ionosonde. Unique relationships exist between the sounding frequency and the ionization densities which can reflect it. As the sounder sweeps from lower to higher frequencies, the signal rises above the noise of commercial radio sources and records the return signal reflected from the different layers of the ionosphere.

Ionospheric Parameters such as FoF2, FoF1, FoE derrived from hand scaling of analog Ionograms

All the data contributed come from 1957 through 1990. They have been digitized, reformatted, converted to universal time (the software also can display the data in local meridian time), and passed through quality control filters.

The ionosphere is that part of the Earth's atmosphere that results mainly from the ionizing effect of Solar electromagnetic radiation. For poleware latitudes, the ionizing effect of incident energetic particles is also significant. Traditionally, the following ionospheric regions and their approximate height ranges have been designated: D region (60-90 km); E region (90-150 km); F1 region (150-250 km); and F2 region (above 250 km). Ionosondes utilize the radio wave-reflecting properties of the ionosphere.

The Electron Density Profile, N(h), data set contains both individual profiles and composite months. The data consist of virtual height/frequency pairs from a profile or profiles (composite months) of ionograms. Data includes the station, year, month and hour (or composite month) for each record. Data are available on 9-track magnetic tape. Electron density profiles are also available in Dataset_ID: G10145. The stations included are Argentia, Bermuda,
College, Dyess, Goose Bay, Narssarssuaq, Puerto Rico, Sondestrom, Thule, and Wallops Island.

The standard (analog) ionosonde produces photographic records known as ionograms, which show the variations of the virtual height of reflection as a function of the radio frequency. The frequency band normally used is from about 1 MHz to about 20 MHz though some ionosondes operate down to about 0.20 MHz and up to 30 MHz. The ionograms actually show the time of travel of the pulse signal from the transmitter to the ionosphere and back to the receiver. A given station typically generates a sweep-frequency ionogram in about two minutes.