GB/T 46138-2025Grade of geomagnetic activity (English PDF)

3.1

The magnetic flux density vector of the Earth's magnetic field.

3.2

The projection of the geomagnetic field vector (3.1) onto the horizontal plane in the local rectangular coordinate system.

3.3

The variation of a certain element of the geomagnetic field (usually the horizontal component of the geomagnetic field) relative to the background field during a quiet period.

Note. The varying amplitude of magnetic disturbances can be used to describe the strength of geomagnetic activity.

3.4 geomagnetic index

A parameter describing the degree of magnetic disturbance in the mainland over a certain period of time.

3.5 K-index

Geomagnetic activity description parameters for a single station with a time interval of 3 hours.

Note 1.Data is collected in Greenwich Mean Time, starting from midnight, with each 3-hour period representing a total of 8 data points per day. Records of the three geomagnetic parameters from each geomagnetic station.

Based on the component with the largest amplitude after eliminating regular daily variations within each time period, geomagnetic activity is divided into 10 levels, from level 0 to level 9, according to its strength.

Note 2.The magnitude of the K exponent has an approximately logarithmic relationship with the amplitude of the magnetic disturbance over the 3-hour period. Since the amplitude of the magnetic disturbance increases with latitude, to ensure that the amplitude of the disturbance varies across different geomagnetic observatories globally...

The determined K-index values are approximately equal, but the magnetic disturbance amplitudes corresponding to the K-index values of geomagnetic observatories at different latitudes are also different. The K-index value is related to the 3-hour geomagnetic water...

The corresponding relationship of the amplitude range of the average component disturbance is shown in Appendix A.

[Source. GB/T 31160-2014, 2.8, with modifications]

3.6 Kp index

Description of global geomagnetic activity at 3-hour intervals (divided into time intervals of 0.00-3.00 and 3.00-6.00 GMT). parameter.

Note 1.The Kp index is calculated by averaging the K-indexes of 13 geomagnetic stations located between geomagnetic latitudes of 47° and 63°. These 13 geomagnetic stations are commonly used internationally.