TY - JOUR

T1 - The Influence of Localized Dynamics on Dusk-Dawn Convection in the Earth’s Magnetotail

AU - Lane, James

AU - Grocott, Adrian

AU - Case, Nathan

PY - 2022/5/31

Y1 - 2022/5/31

N2 - 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.

AB - 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.

KW - magnetotail

KW - dusk-dawn

KW - transient

KW - dynamics

KW - localized

KW - convection

U2 - 10.1029/2021ja030057

DO - 10.1029/2021ja030057

M3 - Journal article

VL - 127

JO - Journal of Geophysical Research: Space Physics

JF - Journal of Geophysical Research: Space Physics

SN - 2169-9402

IS - 5

M1 - e2021JA030057

ER -