The 2014 geomagnetic jerk as observed by southern African magnetic observatories

P B Kotzé

doi:10.1186/s40623-017-0605-7

P B Kotzé

Open Access

https://doi.org/10.1186/s40623-017-0605-7

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Abstract

Rapid secular variation pulses in the Earth’s geomagnetic field have been identified during the last decade. In particular, the 2014 jerk is the latest in a series of localised rapid secular variation events observed at the Earth’s surface which are thought to be the result of rapid oscillations at the core surface approximately at a depth of 3000 km. In Southern Africa, the 2014 jerk has been analysed using data from four observatories located at Hermanus, Hartebeesthoek, Keetmanshoop and Tsumeb and found that this event occurred with varying strengths in the different components at a particular observatory, while different observatories in the region showed strong individual characteristics. The changes in the secular variation patterns at individual magnetic observatories in this study took place in an area characterised by rapid changes in the geomagnetic field with time. Of particular interest is that global field models like CHAOS-6 and POMME 10 derived from various combinations of ground and satellite data do not always indicate similar short-period patterns in X, Y and Z as revealed by observatory measurements. This has been confirmed by comparing the secular variation pattern at the Kourou magnetic observatory located in French Guiana, a station close to the current centre of the South Atlantic Anomaly.

Highlights

Since the identification of the first geomagnetic jerk in 1969 by Courtillot et al (1978) and Malin et al (1983), several events related to rapid changes in the secular variation (SV) pattern of the Earth’s magnetic field have been identified
Both CHAOS-6 and POMME 10 models were compared to measurements made at the Kourou (KOU) magnetic observatory located in French Guiana well inside the South Atlantic region and confirmed, like in Southern Africa, that SV observations are not always reproduced by model predictions, around the 2014 geomagnetic jerk interval
Secular variation behaviour around 2014 In order to characterise the times of the rapid secular variation changes and compare how well the CHAOS-6 and POMME 10 models describe the secular variation in Southern Africa, the different X, Y- and Z-component time series were investigated at the four individual observatory locations at HER, HBK, KMH and TSU

Summary

Introduction

Since the identification of the first geomagnetic jerk in 1969 by Courtillot et al (1978) and Malin et al (1983), several events related to rapid changes in the secular variation (SV) pattern of the Earth’s magnetic field have been identified (see e.g. Mandea et al 2010; Pinheiro et al 2011; Brown et al 2013). Both CHAOS-6 and POMME 10 (http:// www.geomag.org/models/pomme10.html) models were compared to measurements made at the Kourou (KOU) magnetic observatory located in French Guiana (latitude = 5.21°, longitude = 307.3°, elevation = 10 m) well inside the South Atlantic region and confirmed, like in Southern Africa, that SV observations are not always reproduced by model predictions, around the 2014 geomagnetic jerk interval.

Results

Conclusion