We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Excursions, Reversals, and Secular Variation: Different Expressions of a Common Mechanism?
- Authors
Buffett, B. A.
- Abstract
Fluctuations in the geomagnetic field occur over a broad range of timescales. Short‐period fluctuations are called secular variation, whereas excursions and reversals are viewed as anomalous transient events. An open question is whether distinct mechanisms are required to account for these different forms of variability. Clues are sought in trends b of the axial dipole moment from six time‐dependent geomagnetic field models. Variability in b has a well‐defined dependence on the time interval (or window) for the trend. The variance of b reveals a simple relationship to trends during excursions and reversals. This connection hints at a link between reversals, excursions and secular variation. Stochastic models exhibit a similar behavior in response to random fluctuations in dipole generation. We find that excursions, reversals and secular variation can be distinguished on the basis of trend durations rather than differences in the underlying physical process. While this analysis does not rule out distinct physical mechanisms, the paleomagnetic observations suggest that such distinctions are not required. Plain Language Summary: Geomagnetic field models capture details of excursions and reversals over the past 2 Myr. A comparison of these transient events with field behavior during times of stable polarity offers insights into the underlying physical mechanisms. The focus of comparison is the trend of the axial dipole moment over a prescribed duration. Six geomagnetic field models reveal consistent and predictable changes in the variance of dipole trends as a function of duration. Trends into reversals and excursions can also be recovered from the geomagnetic field models. A simple relationship between transient events and the trends during stable polarity hints at a common underlying mechanism. This connection is supported by a stochastic model for dipole fluctuations, which is capable of reproducing the observed changes in the trend variance with duration. The same model quantitatively reproduces the relationship between transient events and secular variation. Given that trends in the stochastic model are driven entirely by fluctuations in dipole generation, a similar interpretation may account for excursions, reversals and secular variation without requiring different physical mechanisms. Key Points: Statistics of dipole trends are computed for six paleomagnetic field modelsTrends during excursions and reversals are linked to variability during stable polarityA relationship between excursions, reversals and secular variation suggests a common underlying mechanism
- Subjects
GEOMAGNETISM; DIPOLE moments; STOCHASTIC models; GEOMAGNETIC reversals; TRENDS; OPEN-ended questions
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2024, Vol 25, Issue 6, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2024GC011604