Open AccessSudden commencement event of 17 April 2002: Aspects of the geomagnetic response at low latitudes
Author(s) -
Villante U.,
Piersanti M.,
Di Giuseppe P.,
Vellante M.,
Zhang T. L.,
Magnes W.
Publication year - 2005
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004ja010978
Subject(s) - earth's magnetic field , latitude , morning , local time , amplitude , atmospheric sciences , middle latitudes , variation (astronomy) , low latitude , ionosphere , geomagnetic secular variation , geology , physics , climatology , astrophysics , geodesy , geophysics , geomagnetic storm , astronomy , mathematics , magnetic field , statistics , quantum mechanics
An analysis of a sudden commencement (SC) manifestation reveals a significant contribution of the polar current system which influences the long‐term behavior of the H component at low‐latitude ground stations located in the subsolar sector. A transition between “morning” and “afternoon” characteristics of the geomagnetic response occurs at ≈1300 MLT. “Morning” events are characterized by a positive then negative variation (P/N) preceding the longer‐term variation and show a gentle latitudinal decrease of the asymptotic response; conversely, “afternoon” events, which are characterized by a N/P structure, show a steep latitudinal gradient. PPI and PRI structures are observed on opposite sides of the ≈1300 MLT boundary. The PPI consists of three dominant fluctuations at well‐defined frequencies and the small differences in the signal manifestation at nearby stations can be imputed to the occurrence of local resonance phenomena. Large‐amplitude pulsations appear soon after the SC occurrence at subauroral latitudes.