Abstract
Geomagnetic jerks are sudden changes in the geomagnetic field secular variation related to changes in outer core flow patterns. Finding geophysical phenomena related to geomagnetic jerks provides a vital contribution to better understand the geomagnetic field behavior. Here, we link the geomagnetic jerks occurrence with one of the most relevant features of the geomagnetic field nowadays, the South Atlantic Anomaly (SAA), which is due to the presence of reversed flux patches (RFPs) at the Core-Mantle Boundary (CMB). Our results show that minima of acceleration of the areal extent of SAA calculated using the CHAOS-7 model (CHAOS-7.2 release) coincide with the occurrence of geomagnetic jerks for the last 2 decades. In addition, a new pulse in the secular acceleration of the radial component of the geomagnetic field has been observed at the CMB, with a maximum in 2016.2 and a minimum in 2017.5. This fact, along with the minimum observed in 2017.8 in the acceleration of the areal extent of SAA, could point to a new geomagnetic jerk. We have also analyzed the acceleration of the areal extent of South American and African RFPs at the CMB related to the presence of the SAA at surface and have registered minima in the same periods when they are observed in the SAA at surface. This reinforces the link found and would indicate that physical processes that produce the RFPs, and in turn the SAA evolution, contribute to the core dynamics at the origin of jerks.
Highlights
The secular variation of the core geomagnetic field is generally characterized by smooth variations in time
In order to evaluate in detail the evolution of this increase, we study the rate of change of the areal extent of the South Atlantic Anomaly (SAA) by applying the first and second derivatives to the previously calculated area (S) (Figures 2B–C)
We suggest a previously unreported link between the minima of the second derivative of the areal extent of SAA at surface and the occurrence of geomagnetic jerks for the last 2 decades
Summary
The secular variation of the core geomagnetic field is generally characterized by smooth variations in time. Y, Z) registered in ground geomagnetic observatories, mainly in the East component (Y) because it is the least affected by external fields at midlatitudes (Pinheiro et al, 2011; Torta et al, 2015) Following this approach, Pinheiro et al (2011) used annual means of the geomagnetic components X, Y, and Z coming from geomagnetic observatories distributed around the world to estimate the occurrence time of the 1969, 1978, 1991, and 1999 geomagnetic jerks. Torta et al (2015) estimated the 2007, 2011, and 2014 jerks occurrence times following an analogous procedure to that described in Pinheiro et al (2011) but using only the geomagnetic component Y. They used between six and four geomagnetic observatories to estimate the occurrence times of the most recent geomagnetic jerks
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