Abstract
From black hole quasinormal frequencies (QNFs), we can extract characterising information about their perturbed source. For the Reissner-Nordström de Sitter (RNdS) black hole, the damping of the QNF spectrum relays information about whether these fields evolve past the Cauchy horizon, in violation of Strong Cosmic Censorship. Here, we examine the QNF spectrum corresponding to a massive scalar test field carrying an electric charge, oscillating in the outer region of a RNdS black hole. Our analysis provides insight into QNF behaviour, particularly in regions approaching the extremal conditions of the black hole. Our semi-classical analysis suggests that Strong Cosmic Censorship may be violated for black holes that are in close proximity to extremality.