Storm time magnetic field variations at low latitude and its association with solar wind parameters

Abstract

It is known that interplanetary plasma has significant influence on the storm time magnetic field variations observed on the surface of the earth. It has been well observed that the southward component of interplanetary magnetic field is a strong candidate in triggering and controlling the geomagnetic storm. However, apart from this, the solar wind parameters such as plasma density, velocity etc. could also have considerable contribution to the ground magnetic field variations and the present study aims to identify this association. Thus, to investigate the influence of solar wind parameters on the magnetic field variations at low latitude, we use one-minute observations of the horizontal component of the magnetic field variations at Alibag (Geomagnetic latitude = 9o N), and onboard ACE satellite measurements of plasma parameters during intense storm events. During the development and decay stage of geomagnetic storms, close correspondence of rapid changes observed at the low latitude magnetic field with solar wind parameters leads to further extended investigation using filter analysis techniques, which reveals that the bursts of solar wind density have clear marks at low latitude magnetic field measurements. Cross correlation analysis shows that the solar wind dynamic pressure has significant correlation with surface magnetic observations, which provides direct evidence of solar wind impact at low latitude magnetic field variations.