Revealing Flare Energetics and Dynamics with SDO EVE Solar Extreme Ultraviolet Spectral Irradiance Observations

Abstract NASA’s Solar Dynamics Observatory (SDO) Extreme-ultraviolet Variability Experiment (EVE) has been making solar full-disk extreme ultraviolet (EUV) spectral measurements since 2010 over the spectral range of 6 nm to 106 nm with 0.1 nm spectral resolution and with 10 – 60 sec cadence. A primary motivation for EVE’s solar EUV irradiance observations is to provide the important energy input for various studies of Earth’s upper atmosphere. For example, the solar EUV radiation creates the ionosphere, heats the thermosphere, and drives photochemistry in Earth’s upper atmosphere. In addition, EVE’s observations have been a treasure trove for solar EUV flare spectra. While EVE measures the full-disk spectra, the flare spectrum is easily determined as the EVE spectrum minus the pre-flare spectrum, as long as only one flare event is happening at a time. These EVE flare observations provide EUV variability with 0.1 nm spectral resolution and have been used to study flare phases (including the discovery of the EUV Late Phase flare class), flare energetics (plasma temperature variations), corona heating (plasma abundance changes that support nano-flare heating mechanism), flare dynamics (downwelling and upwelling plasma flows during flares from Doppler-related wavelength shifts), and coronal mass ejections (CME) energetics (CME mass and velocity derived from coronal dimming in some EUV lines). A brief review of each of these flare research topics using EVE data are presented. With over 10,000 flares detected in the EVE observations, there is still much to study and to learn about solar flare physics using EVE solar EUV spectra.