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Open Access

Sudden commencements in the X and Y fields at equatorial stations in the African sector

Earth, Planets and Space200759:BF03352700

Received: 26 December 2005

Accepted: 7 July 2006

Published: 8 June 2007


This paper describes the mean direction of the H vector due to Sq (solar quiet) and SC (sudden commencement) at equatorial stations Addis-Ababa (geographical longitude: 39°E) and at M’Bour (17°W). The Sq (H) vector aligns fairly well with the direction of the dip declination (D), and the SC (H) vector aligns along the dipole declination (Ψ) minus the dip declination D. At M’Bour, which is situated in the Atlantic Anomaly region, both the Sq (H) and the SC (H) vectors were along 32°W of N, while the dip as well as the dipole declinations were 9°W. Thus, the normal and the disturbance current in the Atlantic region is modulated by some additional meridian currents, resulting in a large increase in the westward Y, the source of which cannot be currently estimated from only one station, M’Bour. This problem requires further investigation.

Key words

Equatorial sudden commencementsmeridional electrojet current