Analysis of geomagnetic sudden impulses at low latitudes A06209

Abstract

We present an analysis of the SI characteristics at λ ≈ 36° examining 54 events for a 5-year interval (2000-2004). In the H component, the ground responses are typically greater than expected for changes of the magnetopause current; they are also accompanied by significant changes of the D component. Both these aspects suggest a remarkable, long-lasting contribution of the ionospheric currents on geomagnetic measurements associated with changes of the solar wind pressure. The relative response (i.e., as normalized to the change of the square root of the solar wind pressure) exhibits a local time modulation, with highest values in the afternoon hours for both components. For the H component, the average ratio between the observed and the predicted response is ≈1.5 in the central part of the day and ≈1.2 in the dark sector. Copyright 2009 by the American Geophysical Union.