Responses of CIPS/AIM noctilucent clouds to the interplanetary magnetic field

Abstract

This study investigates the link between the interplanetary magnetic field (IMF) By component and the noctilucent clouds (NLCs) measured by the Cloud Imaging and Particle Size (CIPS) experiment onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite. The mean ice particle radius in NLCs is found to be positively correlated with IMF By in the Southern Hemisphere (SH) and negatively correlated with IMF By in the Northern Hemisphere (NH), respectively, on a day-to-day timescale in most of the 20 summer seasons during the 2007–2017 period with a near 0 d lag time, and the response in the SH is stronger than that in the NH. Moreover, the albedo, ice water content and frequency of occurrence of NLCs present positive correlation with IMF By in the SH but no significant correlation in the NH. The superposed epoch analysis (SEA) further indicates the rm on average changes by about 0.73 nm after IMF By reversals, which is significant at the 90 % confidence level in Monte Carlo sensitivity tests. Our results suggest an IMF By-driven pathway: the influence of the solar wind on the polar ionospheric electric potential affects the nucleation processes in NLCs and consequently the ice particle radius and NLC brightness.