2016/01/18 by Yan Xu, Wenda Cao, Mingde Ding +10 · 1 citation
Physics and Astronomy · #Brightness #Coronal mass ejection #Flare #Ionosphere and magnetosphere dynamics #Nanoflares #Radiative transfer #Solar and Space Plasma Dynamics #Solar flare #Solar telescope #Stellar, planetary, and galactic studies #Telescope #astro-ph.SR
paper · pdf · doi:10.3847/0004-637x/819/2/89
arxiv created 2016/01/18 · openalex publication_date 2016/03/02 · arxiv updated 2016/03/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
ABSTRACT Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6 m New Solar Telescope at Big Bear Solar Observatory, we show a striking “negative” flare with a narrow but unambiguous “dark” moving front observed in He i 10830 Å, which is as narrow as 340 km and is associated with distinct spectral characteristics in H α and Mg ii lines. Theoretically, such negative contrast in He i 10830 Å can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in astronomical objects.