How Does the Definition of a Geomagnetic Storm Affect the Contents of the Resulting Storm List?

Patrick, Atlas M. and Coxon, John C. and Bentley, Sarah N. and Walach, Maria‐Theresia and Murphy, Kyle R. and Rae, I. Jonathan and Lockley, Isobel S. (2026) How Does the Definition of a Geomagnetic Storm Affect the Contents of the Resulting Storm List? Space Weather, 24 (5): e2025SW004. ISSN 1542-7390

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Abstract

Plain Language Summary: A geomagnetic storm is a period of time when the Earth's magnetic field changes significantly from its usual behavior. This change is caused by particles from the Sun entering the Earth's magnetic field, increasing the amount of charged particles that are orbiting the Earth, and this results in a change in the strength of the ring current. The change creates a magnetic field, which affects magnetic field measurements that are made on Earth. There isn't yet a specific definition of what exactly a geomagnetic storm is, as the criteria can vary between sources. This means that when a large number of storms are found and a list of the times that they occurred is created, the contents of the list are highly dependent on how geomagnetic storms were defined. The differences in the definitions may cause the physical properties of the storms in the resulting lists to be different, and this could affect the science that is done using the storm lists.