Intermittent non-axial dipolar-field dominance of twin Laschamp excursions

• Published in: Communications earth & environment Vol. 3; no. 1; pp. 1 - 10
• Main Authors: Hyodo, Masayuki, Nakagawa, Takeshi, Matsushita, Hayato, Kitaba, Ikuko, Yamada, Keitaro, Tanabe, Shota, Bradák, Balázs, Miki, Masako, McLean, Danielle, Staff, Richard A., Smith, Victoria C., Albert, Paul G., Bronk Ramsey, Christopher, Yamasaki, Akiteru, Kitagawa, Junko, Schlolaut, Gordon, Gotanda, Katsuya, Tsumura, Kosuke, Inagawa, Kaito, Kumazawa, Koyo, Abe, Haruka, Sugo, Saki, Takahashi, Koki, Kitamura, Atsumi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 04.04.2022; Nature Portfolio
• Subjects: Dominance; Dynamo theory; Geomagnetism; High resolution; Lake sediments; Lakes; Paleomagnetism; Poles; Sediments; Lake Suigetsu; Japan
• ISSN: 2662-4435; 2662-4435
• DOI: 10.1038/s43247-022-00401-0

Abstract Geomagnetic excursions represent the dynamic nature of the geodynamo. Accumulated palaeomagnetic records indicate that such excursions are dominated by dipolar-fields, but exhibit different structures. Here we report a palaeomagnetic record from the varved sediments of Lake Suigetsu, central Japan, which reveals fine structures in the Laschamp Excursion and a new post-Laschamp excursion that coincides with the Δ 14 C maxima. The record’s high-resolution chronology provides IntCal20 mid-ages and varve-counted durations. Both excursions comprise multiple subcentennial directional-swings. Simulations of filtering effects on sediment-magnetisations demonstrate that this high-resolution record replicates most of the features in existing, lower-resolution Laschamp excursion records, including the apparent clockwise open-loop of the virtual geomagnetic pole pass. The virtual geomagnetic poles during the ‘swing’ phases make four clusters centred in hemispherically-symmetric regions, three of which encompass the virtual geomagnetic poles associated with the Laschamp Excursion recorded in lavas at various locations. The stationary dipolar-field sources under each cluster should have intermittently dominated one after another during the excursions.