The Earth's magnetic field is described by seven parameters.To measure the Earth's magnetism in any place, we must measure the direction and intensity of the field. The parameters describing the direction of the magnetic field are declination (D), inclination (I). D and I are measured in units of degrees. The intensity of the total field (F) is described by the horizontal component (H), vertical component (Z), and the north (X) and east (Y) components of the horizontal intensity. These components may be measured in units of Oersted (1 oersted=1gauss) but are generally reported in nanoTesla (1nT * 100,000 = 1 0ersted). The Earth's magnetic field intensity is roughly between 25,000 - 65,000 nT (.25 - .65 oersted). Magnetic declination is the angle between magnetic north and true north. D is considered positive when the angle measured is east of true north and negative when west. Magnetic inclination is the angle between the horizontal plane and the total field vector. The geomagnetic field measured at any point on the Earth's surface is a combination of several magnetic fields generated by various sources. These fields are superimposed on and interact with each other. More than 90% of the field measured is generated INTERNAL to the planet in the Earth's outer core. This portion of the geomagnetic field is often refered to as the Main Field. The Main Field varies slowly in time and can be described by Mathematical Models such as the International Geomagnetic Reference Field (IGRF) and World Magnetic Model (WMM). The Main Field creates a cavity in interplanetary space called the magnetosphere, where the Earth's magnetic field dominates in the magnetic field of the solar wind. The magnetosphere is shaped somewhat like a comet in response to the dynamic pressure of the solar wind. It is compressed on the side toward the sun to about 10 Earth radii and is extended tail-like on the side away from the sun to more than 100 Earth radii. The magnetosphere deflects the flow of most solar wind particles around the Earth, while the geomagnetic field lines guide charged particle motion within the magnetosphere. The differential flow of ions and electrons inside the magnetosphere and in the ionosphere form current systems, which cause variations in the intensity of the Earth's magnetic field. These EXTERNAL currents in the ionized upper atmosphere and magnetosphere vary on a much shorter time scale than the INTERNAL Main Field and may create magnetic fields as large as 10% of the Main Field. Other important sources are the fields arising from electrical currents flowing in the ionized upper atmosphere, and the fields induced by currents flowing within the Earth's crust. The Main field component varies slowly in time and can be grossly described as that of a bar magnet with north and south poles deep inside the Earth and magnetic field lines that extend well out into space. The Earth's magnetic field varies both in space and time. Historically, magnetic observatories were established to monitor the secular change of the Earth's magnetic field, and this remains one of their most important functions. This generally involves absolute measurements sufficient in number to monitor instrumental drift and to produce annual means. Over 70 countries operate more than 200 observatories worldwide. The magnetic observatory mean data are crucial to the studies of secular change, investigations into the Earth's interior, and to global modeling efforts

Geomagnetic Indices

Geomagnetic Indices Data Description

Geomagnetic indices constitute data series aiming at describing at a planetary scale the magnetic activity, or some of its components. The data series are homogeneous since 1932 for Kp and Ap, 1957 for Dst.

Three-Hour-Range Index K

K 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 logarithmical- ly to its corresponding disturbance amplitude. Three-hour indices discriminate conservatively between true magnetic field perturbations and the quiet-day variations produced by ionospheric currents. K indices range in 28 steps from 0 (quiet) to 9 (greatly disturbed) with fractional parts expressed in thirds of a unit. A K-value equal to 27, for example, means 2 and 2/3 or 3-; a K-value equal to 30 means 3 and 0/3 or 3 exactly; and a K-value equal to 33 means 3 and 1/3 or 3+. The arithmetic mean of the K values scaled at the 13 specific observatories gives Kp: ( Lerwick (UK), Eskdalemuir (UK), Hartland (UK), Ottawa (Canada), Fredericksburg (USA) , Meannook (Canada), Sitka (USA), Eyrewell (New Zealand), Canberra (Aus- tralia), Lovo (Sweden), Brorfelde (Denmark), Wingst (Germany), and Niemegk (Germany).) .

Equivalent Amplitudes a Index

: a 3-hourly "equivalent amplitude" index of local geomagnetic activity; "a" is related to the 3-hourly K INDEX according to the following scale:

K = 0 1 2 3 4 5 6 7 8 9
a = 0 3 7 15 27 48 80 140 240 400

: A daily index of geomagnetic activity derived as the average of the eight 3-hourly a indices.

: An averaged planetary ApIndex based on data from a set of specific Kp stations.

DST (Disturbance Storm Time)

Dst (Disturbance Storm Time) equivalent equatorial magnetic disturbance indices are derived from hourly scalings of low-latitude horizontal magnetic variation. They show the effect of the globally symmetrical westward flowing high altitude equatorial ring current, which causes the "main phase" depression worldwide in the H-component field during large magnetic storms. Unit - nT.

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).

A conversion of the 0-to-2.5 range of the Cp index to one digit between 0 and 9

AA             1868 - Present                            (3 hourly and daily)(monthly)(yearly)(Lists and 
                                                                   histograms of geomagnetic disturbance and Solar Sunspots)
KP_AP     1932 - Present                              (3 hourly and daily) (Lists and histograms of
                                                                   geomagnetic disturbance  and Solar Sunspots)
AE_HV     1957-75, 78-88                              (hourly)
AE_MIN    1978-881-6;198903;1990-94           (minute)
DST           1957 - Present                             (hourly)
PC             1975 - Present                             (15-minute)
AMANAS  1959 - Present                              (3 hourly and daily)
KMKNKS  1983 - Present                              (3 hourly)

================================================================
 OBSERVATORIES   CODE  CO      LAT.    LON.    DATA YEARS
================================================================
ALMA ATA         AAA  FSU-Kaz. 43.25   76.92  63 - 72,75-82,84-90
ARKHANGELSK      ARK  FSU-Rus. 64.60   40.50  82 - 89
ASHKHABAD        ASH  FSU-Tur. 37.95   58.11  59 - 70,72-85
BOROK            BOX  FSU-Rus. 58.03   38.97  80 - 91
CAPE CHELYUSKIN  CCS  FSU-Rus. 77.72  104.28  57 - 85
CAPE WELLEN      CWE  FSU-Rus. 66.16  190.17  57 - 87
DIXON ISLAND     DIK  FSU-Rus. 73.54   80.56  57 - 86
HEISS ISLAND     HIS  FSU-Rus. 80.62   58.05  58 - 69
IRKUTSK          IRT  FSU-Rus. 52.46  104.04  57 - 90
KARAGANDA        KGD  FSU-Kaz. 49.82   73.08  65 - 76, 80, 84-89
KAZAN            KZN  FSU-Rus. 55.83   48.85  64 - 74, 78 - 89
KIEV             KIV  FSU-Ukr. 50.72   30.30  58 - 91
LENINGRAD        LNN  FSU-Rus. 59.95   30.71  48 - 88
LVOV             LVV  FSU-Ukr. 49.90   23.75  57 - 72,78
MAGADAN          MGD  FSU-Rus. 60.12  151.02  66 - 89
MINSK            MNK  FSU-Rus. 54.50   27.88  61 - 89
MIRNY            MIR    AY    -66.55   93.02  56 - 85
MOLODEZHNAYA     MOL    AY    -67.67   45.85  65 - 77
MOSCOW           MOS  FSU-Rus. 55.48   37.31  58 - 89
MURMANSK         MMK  FSU-Rus. 68.95   33.05  59 - 80
NOVOKAZALINSK    NKK  FSU-Kaz. 45.80   62.10  80
NOVOLAZAREVSKAYA NVL    AY    -70.77   11.83  61 - 78
NOVOSIBIRSK      NVS  FSU-Rus. 55.03   82.90  67 - 91,94,95
OASIS            OAS    AY    -66.30  100.72  57 - 58
ODESSA           ODE  FSU-Ukr. 46.78   30.88  57 - 91
P. TUNGUSKA      POD  FSU-Rus. 61.60   90.00  69 - 91
PETROPAVLOVSK    PET  FSU-Rus. 52.90  158.43  69 - 90
PIONERSKAYA      PIO    AY    -69.73   95.50  57,58,71,72
SVERDLOVSK(V.DUB)SVD  FSU-Rus. 56.73   61.07  45-52,54,56-74,79,80
SVERDLOVSK(ARTI) ARS  FSU-Rus. 56.43   58.57  73 - 88
TASHKENT         TKT  FSU-Uzb. 41.33   69.62  57 - 71,80,84-91
TBILISI          TFS  FSU-Geo. 42.09   44.71  59 - 90
TIKHAYA BAY      TKH  FSU-Rus. 80.33   52,80  57
TIXIE BAY        TIK  FSU-Rus. 71.58  129.00  57 - 86
VLADIVOSTOK      VLA  FSU-Rus. 43.78  132.03  57 - 89
VOSTOK           VOS    AY    -78.45  106.87  58 - 61,63-85
YAKUTSK          YAK  FSU-Rus. 62.02  129.72  57 - 89
YUZHNO SAKHALINS YSS  FSU-Rus. 46.95  142.72  57 - 88
==========================================================

===============================================================
 1-3     A3   OBSERVATORY 3-LETTER CODE
 4-5     I2   YEAR (last 2 digits, 82=1982)
 6-7     I2   MONTH (01-12)
 8       I1   ELEMENT (D, H, F, X, Y, or Z)
 9-10    I2   DAY OF MONTH (01-31)
 11-12   I2   Blanks for hourly values. Values of hourly (00-23)
              for 2.5 minute values.
 13-15   A3   Arbitrary
 16      I1   Blank for data since 1900, 8 for data before.
 17-20   I4   Tabular base, in degrees for D  and  I,  hundreds
              of nanoTeslas (gammas) for the intensity elements.
 21-116  24I4 24 Twenty-four 4-digit Hourly Values  for  the  day.
              Values are in tenth-minutes  for  D  and  nanoTeslas
              (gammas)for the intensity  elements.  Or  twenty-four
              4-digit 2.5 minute values in the hour. A missing
              value is identified by 9999.
 117-120 I4   Daily Mean or Hourly for the 2.5 minute data.
=================================================================