Analysis of the Seasonal and Solar Effect on the Vertical Magnetic Transfer Function at Eskdalemuir Observatory

Wang, Guanren ORCID: https://orcid.org/0000-0001-9563-8864; Huebert, Juliane ORCID: https://orcid.org/0000-0003-0526-5609; Whaler, Kathy ORCID: https://orcid.org/0000-0002-7386-223X. 2024 Analysis of the Seasonal and Solar Effect on the Vertical Magnetic Transfer Function at Eskdalemuir Observatory. [Poster] In: Magnetosphere, Ionosphere and Solar-Terrestrial, Birmingham, UK, 29 Nov 2024. (Unpublished)

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Abstract/Summary

In deep electromagnetic sounding, the vertical magnetic transfer function, or “tipper’, relate the variations in the induced vertical magnetic field to the horizontal field components. They are sensitive to lateral contrasts in the subsurface electrical conductivity. The source of these fields are large-scale current systems in the ionosphere assumed to cause uniform magnetic field variations at mid-latitude. However, non-uniform source effects, e.g. related to increased geomagnetic activity due to strong solar winds, challenge this assumption and can bias tipper estimates. What do we do if this assumption breaks down? Taking advantage of the availability of high-quality geomagnetic observations at Eskdalemuir observatory in the Scottish borders, we attempt to investigate. We analysed 1 s and 1 min magnetic field data from 2001-2019 and observed seasonal differences at Eskdalemuir for signal periods between 1000 s and 10000 s. In order to quantify the variations, we determined that the tipper estimate from 2016 winter data (during a period of minimal solar activity) forms a suitable baseline. To quantify daily tipper variability relative to this baseline we applied a simple empirical model dependent on either daily F10.7 cm solar flux or daily geomagnetic index, Ap. Neither model fits to expected error, but the model parameterised by Ap produced a better fit to data. We observed dominant peaks in tipper deviations between summer and winter observations, indicating that long-period magnetotelluric (LMT) surveys collected over many months may be affected by seasonal field variations. We propose a correction based on our model using the daily Ap.

Item Type:	Publication - Conference Item (Poster)
NORA Subject Terms:	Earth Sciences Space Sciences
Date made live:	14 Jan 2025 09:46 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538723

Item Type:

Publication - Conference Item (Poster)

NORA Subject Terms:

Earth Sciences
Space Sciences

Date made live:

14 Jan 2025 09:46 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/538723