First Detection of Prominence Material Embedded within a 2 × 10⁶ K CME Front Streaming away at 100-1500 km s^-1 in the Solar Corona

Abstract

Coronal mass ejections (CMEs) are the largest and most dynamic explosions detected in the million degree solar corona, with speeds reaching up to 3000 km s^-1 at Earth’s orbit. Triggered by the eruption of prominences, in most cases, one of the outstanding questions pertaining to the dynamic CME-prominence system is the fate of the cool {10}⁴{--}{10}⁵ {{K}} ejected filaments. We present spectroscopic observations acquired during the 2015 March 20 total solar eclipse, which captured a plethora of redshifted plasmoids from Fe xiv emission at 2× {10}⁶ {{K}}. Approximately 10% of these plasmoids enshrouded the same neutral and singly ionized plasma below 2× {10}⁵ {{K}}, observed in prominences anchored at the Sun at that time. This discovery was enabled by the novel design of a dual-channel spectrometer and the exceptionally clear sky conditions on the island of Svalbard during totality. The Doppler redshifts corresponded to speeds ranging from under 100 to over 1500 km s^-1. These are the first comprehensive spectroscopic observations to unambiguously detect a 2× {10}⁶ {{K}} filamentary CME front with inclusions of cool prominence material. The CME front covered a projected area of 2.5× 1.5 {R}_{{s}}² starting from the solar surface. These observations imply that cool prominence inclusions within a CME front maintain their ionic composition during expansion away from the Sun.