Eruption-Related Ultraviolet Irradiance Enhancements Associated with Flares.

Area of Science:

• Solar physics
• Astrophysics
• Space weather

Background:

• Large solar flares (M-class or higher) are linked to material eruptions.
• The role of erupted material in flare irradiance enhancements and dynamics like chromospheric evaporation has been historically neglected.

Purpose of the Study:

• To quantify the contribution of erupted material to irradiance enhancements during eruptive solar flares.
• To analyze the relative importance of erupted material versus flare ribbons in energy output.

Main Methods:

• Analysis of nine eruptive M- and X-class solar flares from 2024-2025.
• Utilized Atmospheric Imaging Assembly (AIA) images from four channels (131Å, 171Å, 304Å, 1600Å).
• Employed a semi-automated masking method to separate ribbon and eruption irradiance contributions.

Main Results:

• Erupted material contributed sample-averaged percentages of excess radiated energy: 10% (131Å), 24% (171Å), 21% (304Å), and 13% (1600Å).
• Hard X-ray imaging showed minimal nonthermal heating signatures within eruptions for three detailed events.
• Results indicate significant UV irradiance enhancements from erupted material during flares.

Conclusions:

• Erupted material is a significant contributor to UV irradiance enhancements during solar flares.
• Potential heating mechanisms include nonthermal particle heating, Ohmic heating, or MHD wave dissipation.
• Further research is needed to clarify heating mechanisms and the impact on spectral variability, especially for Sun-as-a-star and stellar flare observations.