The hourly range (HR) is the most useful simple index of magnetic activity for the Canadian region. It is particularly useful for summarizing the sub-storm activity that is frequently observed during nighttime intervals. The hourly range HR (maximum value minus minimum value during the hour) is simple to obtain and yet has a direct statistical relation to the power of the geomagnetic field variations.
Another commonly used measure of activity is the mean (average) field during the hour (MHV).
For some applications, particularly those related to geomagnetic effects on technological systems, it is useful to have some indication of the rates-of- change experienced by the field during an hour, and the maximum value observed (DBMAX) is noted.
These three parameters are routinely derived from the 1-minute sample measurements of the geomagnetic field (for X north, Y east, and Z downward components) for all of the Canadian CANMOS stations. They are computed within 15 minutes of the end of each UT hour, for use in near-real-time applications. As such, the values are subject to the occasional problems inherent in near-real-time systems, and must be recognized as PROVISIONAL values only; that is user beware.
The files contain the following information: the 3-letter IAGA station code, year, day-of-year (beginning with 001), hour (01-24), HR for X, HR for Y, HR for Z, MHV for X, MHV for Y, MHV for Z, MHV for X, MHV for Y, MHV for Z. Null values are denoted by 9999 or 99999. The values for hour 01 are for the interval 00 UT to 01 UT, and so on. Values for ranges HR and means MHV are in nanotesla, values for DBMAX are in nanotesla/minute.
Hourly range files are sorted into directories based on the year of the data.
List of Canadian Magnetic Observatory IAGA codes:
For details on these observatories please see our Magnetic Observatories page