The K-index is an excellent indicator of disturbances in the Earth's magnetic field. The
principal users affected by geomagnetic storms are the electrical power grid, spacecraft
operations, users of radio signals that reflect off of or pass through the ionosphere, and
observers of the aurora.
Data is obtained in intervals of 3 hours from the Space weather prediction center of the NOAA.
More information in: https://www.swpc.noaa.gov/products/planetary-k-index