Flux Variations in Lines of Solar EUV Radiation Beyond Flares in Cycle 24

TL;DR

This study analyzes the variations in solar EUV radiation beyond flares during cycle 24, comparing fluxes in specific EUV lines with radio and X-ray fluxes to understand their interrelations and implications for Earth's ionosphere.

Contribution

It provides a detailed comparison of EUV background fluxes with radio and X-ray fluxes during solar cycle 24, highlighting their close interrelation.

Findings

EUV fluxes are closely related to F10.7 radio flux.

EUV background fluxes correlate with X-ray flux F0.1-0.8.

Variations in EUV lines reflect solar activity levels.

Abstract

Studies in the extreme ultraviolet (EUV) and X-ray ranges of the solar spectrum are important due to the active role of radiation of these ranges in the formation of the Earth's ionosphere. Photons of the EUV range are completely absorbed in the upper layers of the Earth's atmosphere and induce the excitation, dissociation, and ionization of its different components and, finally, the atmospheric heating. From the archive data of the EUV Variability Experiment of the Solar Dynamics Observatory (SDO/EVE), we formed series of diurnal values of the background fluxes radiated beyond flares in the EUV lines HeII (30.4 nm), HeI (58.4 nm), CIII (97.7 nm), and FeXVIII (9.4 nm) in cycle 24 (from 2010 to 2017). These fluxes are compared to the corresponding values of the radio flux F10.7 at a wavelength of 10.7 cm and the background radiation flux F0.1-0.8 in the X-ray range between 0.1 and 0.8 nm measured onboard the GOES-15 satellite of the Geostationary Operational Environmental Satellite system. Comparative analysis has shown that the solar radiation in individual lines of the EUV range and the fluxes F10.7 and F0.1-0.8 are closely interrelated.