Sudden commencements in the X and Y fields at equatorial stations in the African sector
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2007
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.