Palm trees and islands – Current filaments in the edge of JET

Abstract

It is now well known that edge localized modes (ELMs) lead to the ejection of a number of filamentary structures into the scrape-off layer (SOL). ELMs thus generate structures with excess energy and density. Recent results show that ELM filaments also carry current. Furthermore it can be conjectured that ELM filaments leave corresponding holes behind. If such a hole is able to reach a resonant magnetic surface it may close on itself and thus increase its lifetime significantly, thereby becoming detectable. We presume that the Palm Tree Mode (PTM) is a signature of such an event. Understanding PTMs therefore enhances our knowledge of ELMs and edge physics and contributes to the verification of ELM models.