The Influence of Localized Dynamics on Dusk‐Dawn Convection in the Earth's Magnetotail. Issue 5 (24th May 2022)

• Record Type: Journal Article
• Authors: Lane, J. H.; Grocott, A.; Case, N. A.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-24
• Subjects: magnetotail -- dusk‐dawn -- transient -- dynamics -- localized -- convection; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA030057
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Previous work has shown that earthward convective flow bursts in the magnetotail have a dusk‐dawn ( v ⊥ y ${v}_{\perp y}$ ) component that is controlled by the historical state of the Interplanetary Magnetic Field (IMF) B y component. Here, we analyze 27 years of Cluster, THEMIS and Geotail plasma and magnetic field data and identify 1, 639 magnetotail fast flow "detections" that demonstrate a dusk‐dawn asymmetry. We find that ∼70% has a dusk‐dawn direction consistent with that expected from the penetration of IMF B y . Superposed epoch analysis suggests that the inconsistency of the remaining ∼30% is not due to a lack of the expected IMF B y penetration. Instead, we find that on average, the expected sense of IMF B y penetration is associated with flows irrespective of whether those flows agree or disagree with the expected dusk‐dawn asymmetry. IMF B y, and the penetrated B y do, however, tend to be stronger for "agree" flows. Detections which agree (disagree) tend to be accompanied by a localized perturbation to the B y component of the magnetotail magnetic field in the same sign as (opposite to) the prevailing IMF B y conditions, which temporarily enhances (overrides) the penetrated field. Agree (disagree) flows also appear to be observed further away from (closer to) the neutral sheet ( B x = 0) and are associated with weaker (stronger) magnetic field dipolarization. Finally, we find that the slower "background" convective flow has an average direction which is consistent with penetration of the expected IMF B y, regardless of whether the fast flow itself agrees or disagrees. Key Points: Magnetotail fast flows with a dusk‐dawn direction inconsistent with IMF B y can occur irrespective of the sense of IMF B y penetration These inconsistent flows occur within a slower "background" convection that is consistent with the expected IMF B y sense Localized, transient dynamics can override or prevent IMF B y control of the flow, notably when IMF B y is weaker