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

Abstract

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.

Dominant role of charged meteoric smoke particles in the polar mesospheric clouds

“…The CMN scheme provides a new pathway for the solar activity to affect PMCs via the charging process of MSPs. Zhang et al (2022) report a positive response of the ice particle radius r, IWC and albedo to the IMF By in the SH with a lag time of about zero days, and an opposite but weak response in the NH. These results are difficult to understand in the GS scheme, however, they are readily explicable in the CMN scheme: the increase in IMF By induces an increase in the electric potential of the ionosphere in the SH, which reduces the concentration of electrons and the negatively charged-MSPs, ultimately leading to an increase in the ice particle radius.…”

“…In contrast, the response in the Northern Hemisphere (NH) is opposite (Lam and Tinsley, 2016;Tinsley and Heelis, 1993). Zhang et al (2022) have demonstrated a positive/negative correlation between the IMF By and the ice particle radius of PMCs in the SH/NH with a lag time of about zero days, providing evidence in favor of the charged-MSPs acting as ice nuclei.…”

“…What's more, satellite observations indicate a negative correlation between ice particle radius and albedo in the PMC regions affected by gravity waves (Gao et al, 2018;Rusch et al, 2017). Furthermore, the response of the ice particle radius in PMCs to the IMF By, as reported by Zhang et al (2022), is also challenging to comprehend, given that the effects of the solar wind magnetic field are not incorporated into the GS scheme.…”