A homogeneous aa index: 2. Hemispheric asymmetries and the equinoctial variation - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Space Weather and Space Climate Année : 2018

A homogeneous aa index: 2. Hemispheric asymmetries and the equinoctial variation

Mike Lockwood
  • Fonction : Auteur
Ivan D Finch
  • Fonction : Auteur
Mathew J Owens
  • Fonction : Auteur
Ellen Clarke
  • Fonction : Auteur

Résumé

Paper 1 (Lockwood et al., 2018) generated annual means of a new version of the aa geomagnetic activity index which includes corrections for secular drift in the geographic coordinates of the auroral oval, thereby resolving the difference between the centennial-scale change in the northern and southern hemisphere indices, aaN and aaS. However, other hemispheric asymmetries in the aa index remain: in particular, the distributions of 3-hourly aaN and aaS values are different and the correlation between them is not high on this timescale (r = 0.66). In the present paper, a location-dependant station sensitivity model is developed using the am index (derived from a much more extensive network of stations in both hemispheres) and used to reduce the difference between the hemispheric aa indices and improve their correlation (to r = 0.79) by generating corrected 3-hourly hemispheric indices, aaHN and aaHS, which also include the secular drift corrections detailed in Paper 1. These are combined into a new, “homogeneous” aa index, aaH. It is shown that aaH, unlike aa, reveals the “equinoctial”-like time-of-day/time-of-year pattern that is found for the am index.
Fichier principal
Vignette du fichier
Lockwood et al. - 2018 - A homogeneous aa index 2. Hemispheric asymmetries.pdf (3.12 Mo) Télécharger le fichier
Origine Fichiers éditeurs autorisés sur une archive ouverte
Loading...

Dates et versions

hal-02369584 , version 1 (19-11-2019)

Identifiants

Citer

Mike Lockwood, Ivan D Finch, Aude Chambodut, Luke Barnard, Mathew J Owens, et al.. A homogeneous aa index: 2. Hemispheric asymmetries and the equinoctial variation. Journal of Space Weather and Space Climate, 2018, 8, pp.A58. ⟨10.1051/swsc/2018044⟩. ⟨hal-02369584⟩
23 Consultations
27 Téléchargements

Altmetric

Partager

Gmail Mastodon Facebook X LinkedIn More