Observation of Alfvn Ion Cyclotron Waves in ICME Magnetic Clouds at 1 au

Waves in plasma play an essential role in the energy transfer and plasma-heating processes. This article discusses the in situ observation of Alfv & eacute;n ion cyclotron (AIC) waves and their characteristics within interplanetary coronal mass ejection (ICME) flux ropes. We analyzed 401 ICME flux ropes, observed by WIND spacecraft from 1995 to 2021 at 1 au. We found only five ICME flux ropes that show an explicit presence of AIC waves; two have normalized magnetic helicity sigma(m) <= -0.5, and the remaining three show sigma(m) >= 0.5 polarization. The angle between velocity and magnetic field (theta(VB)) for sigma(m) <= -0.5 is <40 degrees, whereas for sigma(m) >= 0.5, theta(VB) > 140 degrees. This result supports the existence of quasi-parallel and quasi-antiparallel left-handed polarized AIC waves within ICME flux ropes. We suggest that AIC waves are possibly triggered by (i) proton temperature anisotropy Tp(perpendicular to)/Tp(parallel to) > 1 driven by cyclotron instability and (ii) low-frequency Alfv & eacute;n waves through the magnetohydrodynamic turbulent cascade. This study shows evidence of fluid and kinetic scales coupling in the ICME flux rope.