Online IMAGE magnetometer data - instructions

Available times

We provide final IMAGE data from October 1982. More information can be found in the data availability charts. See also the rules of the road and the description of the data quality.

Selection of events

For practical reasons, we have limited the maximum length of a single event to be 48 hours.
Exception: Monthly files containing all stations are available in the IAGA format using the original sampling interval (10 or 20 s).

Station sets

Five different sets of stations are available. You can also define your own list by typing in the text box 3-letter codes, e.g. NUR HAN SOD (capital letters, separated by blankos). Codes are given in the table of the IMAGE stations.

Predefined sets:

  • Fennoscandia = all available stations in the continental part of IMAGE.
  • Svalbard = BJN, HOP, HOR, LYR, NAL (since October 1993).
  • TAR-SOR = meridional chain TAR-HAN-OUJ-PEL-MUO-MAS-SOR (TAR since September 2001).
  • To get the EISCAT magnetometer sites (until summer 1991), select all.

    Data file formats

    The magnetic field components are the geographical ones: X (north), Y (east), and Z (downwards). The time definition is as given in the IAGA format description.

    1. IAGA - standard format for IMAGE. Unit 0.1 nT
    2. Column. Very simple (view by an editor). Unit 1 nT. Note that there are two options: column and column_old.
    3. WDC. World Data Center format. One-minute averages only. Unit 1 nT.
    4. GADF. General Archival Data Format (binary).
    5. PostScript: for high-quality magnetogram plots. Width of the time axis is 165 mm as agreed within the Cluster ground-based community.
    6. JPG: for quick-look purposes.

    NOTE: If you only need magnetogram plots (jpg, PostScript) you can also use jpg/jpg_form.html.

    Sampling interval

    The original sampling interval was 20 s until November 1992 and thereafter 10 s. You can also request one-minute averaged data. One-minute values are simply arithmetical averages of 10 s or 20 s data.

    WDC format is only for one-minute values. So, even if you request a shorter sampling interval you will get one-minute data.

    With one-minute GADF files you may get some unnecessary missing values. This is due to the fact that we use a block definition of 180 data points. For example, one-minute values of a 1-hour event will produce a three hour event with the hours 2 and 3 with missing values.


    Compression by gzip is recommended if you request a long event of many stations. A 10 s IAGA file of one day and one site is about 207 Kbytes. The column file is about as large, but the WDC file is only about 29 Kbytes (because it is one-minute data). Sizes of PostScript files vary, but they are about the same as IAGA files. JPG plots are not compressed.

    File string

    Files are named by default as follows: imageYYYYMMDDHH.#, where YYYYMMDDHH is the starting time of the event and # is a suffix describing the file format (e.g. "iaga"). You can edit the file string or leave it empty.

    Personal information

    You must give your name, institute and email address to get data. This information is just for log purposes.

    Message field

    If you like you can describe briefly the purpose of using data (send long stories separately to Ari Viljanen). If you need immediate assistance then use email.

    Saving files

    How to transfer data files conveniently depends on your computer and browser. If you simply click on a link the file may appear to your browser window. There may be some keyboard tricks with which you can avoid this. If you are unsure try first with a short event and a small station set!

    Because requested data files are not saved permanently on our hard disk you should transfer them immediately.

    Additional software

    Some C language software by Lasse Häkkinen for data file manipulation is available ("as is" principle to be accepted by the users).

    Main data page
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    Updated: 10.2.2010 - AV