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Solar flare soft X-rays (0-7nm) and Hydrogen Lyman Alpha (121.6nm) energetics at the Sun and as drivers of the Earth’s ionosphere.

Presentation #207.03 in the session Solar X-ray and VUV Spectra: Observation, Modeling and Planetary Atmospheric Impacts I.

Published onOct 20, 2022
Solar flare soft X-rays (0-7nm) and Hydrogen Lyman Alpha (121.6nm) energetics at the Sun and as drivers of the Earth’s ionosphere.

The solar ultraviolet irradiance is the primary energy input into planetary atmospheres. Full measurement coverage, both spectrally and temporally, is necessary to most accurately quantify these energy inputs on all times scales from the solar cycle (years to decades), solar rotation (days to weeks), active region emergence (hours to days) and solar flares (seconds to hours). Due to lack of full measurement coverage, empirical models are commonly used to fill the gaps in measurements in order to cover all times scales previously mentioned at full spectral coverage from 0.1-190nm and at better than 1-minute cadence.

Proxies for solar flare variations in empirical models, such as the Flare Irradiance Spectral Model (FISM), have previously relied solely on measurements from the GOES/XRS to quantify the solar flare magnitude and duration. But, more recently with GOES-13-15 starting in 2006, and subsequently with the improved versions on GOES-16-18 (and 19 to hopefully come later) coming online in 2017, other emission lines at lower temperatures from the chromosphere and transition region are now being routinely measured to provide a more complete characterization of the radiated flare energies throughout the solar atmosphere.

This presentation will compare the timing and energetics of the radiated flare energy at the soft X-ray (SXR, 0-7nm) and Hydrogen Lyman-alpha emissions (121.6 nm) in various eruptive events using measurements from SDO/EVE and GOES/EUVS as well as the FISM2 empirical model. Additionally, a case study is performed using WACCM-X detailing the differing response of the Earth’s ionosphere to the aforementioned wavelengths during a solar flare.

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