Overview

• Ion temperatures in flares could exceed 60 million degrees, according to an analysis by a University of St Andrews team published September 3 in The Astrophysical Journal Letters.
• Recalculations with modern observations indicate ion–electron temperature differences can persist for tens of minutes in key flare regions.
• Evidence supporting a roughly 6.5-to-1 ion-to-electron heating ratio comes from near-Earth space measurements, the solar wind and computer simulations.
• The findings challenge the long-held assumption of equal ion and electron temperatures and imply lower turbulence amplitudes and adjusted energy budgets in flare models.
• The authors outline tests using high-throughput spectroscopy and new loop-evolution models, highlighting NASA’s MUSE and the EUVST mission as priority platforms.