On the Influence of the Data Sampling Interval on Computer-Derived K-Indices

TL;DR

This study examines how the sampling interval of geomagnetic data affects the accuracy of computer-derived K indices, crucial for monitoring geomagnetic activity, by comparing different sampling rates at a specific observatory.

Contribution

It provides an analysis of the influence of data sampling intervals on the computation of K indices using a specific algorithm, informing best practices for digital geomagnetic monitoring.

Findings

Sampling interval impacts K index accuracy during geomagnetic activity.

Differences observed between 1-second and 1-minute sampling rates.

Results guide optimal data sampling for reliable K index computation.

Abstract

The K index was devised by Bartels et al. (1939) to provide an objective monitoring of irregular geomagnetic activity. The K index was then routinely used to monitor the magnetic activity at permanent magnetic observatories as well as at temporary stations. The increasing number of digital and sometimes unmanned observatories and the creation of INTERMAGNET put the question of computer production of K at the centre of the debate. Four algorithms were selected during the Vienna meeting (1991) and endorsed by IAGA for the computer production of K indices. We used one of them (FMI algorithm) to investigate the impact of the geomagnetic data sampling interval on computer produced K values through the comparison of the computer derived K values for the period 2009, January 1st to 2010, May 31st at the Port-aux-Francais magnetic observatory using magnetic data series with different sampling rates (the smaller: 1 second; the larger: 1 minute). The impact is investigated on both 3-hour range values and K indices data series, as a function of the activity level for low and moderate geomagnetic activity.