Probing the Penrose Process: Images of Split Hotspots and Their Observational Signatures

TL;DR

This paper explores the observational signatures of the Penrose process in rotating black holes, focusing on how magnetic reconnection-induced plasmoid fragmentation produces distinct flares that could serve as evidence for energy extraction.

Contribution

It introduces a new method to identify the Penrose process through the analysis of hotspot light curves and flare signatures resulting from plasmoid fragmentation.

Findings

Fragmentation causes observable flares with distinct features.

Negative-energy fragments produce different signatures than positive-energy ones.

Results suggest potential observational markers for the Penrose process.

Abstract

While theoretically established for decades, the Penrose process - energy extraction from rotating black holes - still lacks clear observational evidence. A promising theoretical framework posits magnetic reconnection in the ergosphere as a trigger, causing a plasmoid to separate into an escaping positive-energy fragment and an infalling negative-energy one. In this work, we investigate the observational imprints of this scenario. We treat the energized plasmoid as a hotspot and calculate its light curves for a realistic plasma magnetization. In particular, we further compare with the scenario in which the plasmoid, after fragmentation, falls into the black hole with positive energy, while all other conditions remain unchanged. Our results reveal that the process of fragmentation generates distinct flares, whose characteristics depend heavily on whether the infalling fragment carries negative or positive energy. We propose that these differences serve as identifiable signatures of the Penrose process.