Validation of Earth atmosphere models using solar EUV observations from the CORONAS and PROBA2 satellites in occultation mode

Abstract

Aims: Knowledge of properties of the Earth's upper atmosphere is important for predicting the lifetime of low-orbit spacecraft as well as for planning operation of space instruments whose data may be distorted by atmospheric effects. The accuracy of the models commonly used for simulating the structure of the atmosphere is limited by the scarcity of the observations they are based on, so improvement of these models requires validation under different atmospheric conditions. Measurements of the absorption of the solar extreme ultraviolet (EUV) radiation in the upper atmosphere below 500 km by instruments operating on low-Earth orbits (LEO) satellites provide efficient means for such validation as well as for continuous monitoring of the upper atmosphere and for studying its response to the solar and geomagnetic activity. Method: This paper presents results of measurements of the solar EUV radiation in the 17 nm wavelength band made with the SPIRIT and TESIS telescopes on board the CORONAS satellites and the SWAP telescope on board the PROBA2 satellite in the occulted parts of the satellite orbits. The transmittance profiles of the atmosphere at altitudes between 150 and 500 km were derived from different phases of solar activity during solar cycles 23 and 24 in the quiet state of the magnetosphere and during the development of a geomagnetic storm. We developed a mathematical procedure based on the Tikhonov regularization method for solution of ill-posed problems in order to retrieve extinction coefficients from the transmittance profiles. The transmittance profiles derived from the data and the retrieved extinction coefficients are compared with simulations carried out with the NRLMSISE-00 atmosphere model maintained by Naval Research Laboratory (USA) and the DTM-2013 model developed at CNES in the framework of the FP7 project ATMOP. Results: Under quiet and slightly disturbed magnetospheric conditions during high and low solar activity the extinction coefficients calculated by both models agreed with the measurements within the data errors. The NRLMSISE-00 model was not able to predict the enhancement of extinction above 300 km observed after 14 h from the beginning of a geomagnetic storm whereas the DTM-2013 model described this variation with good accuracy.

Vertical Thermospheric Density Profiles From EUV Solar Occultations Made by PROBA2 LYRA for Solar Cycle 24

“…Prior observations of other species were made by Reid (), who used solar occultations in the 120–350 nm range made by OSO4 to estimate N 2 and O densities. Recently, Slemzin et al () used solar occultations from EUV imagers on board the CORONAS and Project for Onboard Autonomy 2 (PROBA2) satellites to measure the signal extinction between 200 and 400 km, and compared the measured extinction with that predicted by two semiempirical models without retrieving density profiles directly.…”

“…Aside from Slemzin et al (), prior thermospheric solar occultation measurements were made using full‐disk irradiance measurements, where the primary challenge for thermospheric density retrievals is accounting for the spatial extent of the solar disk, which is comparable to the retrieved density scale heights. At wavelengths shortward of 200 nm, the inhomogenous distribution of radiance over the solar disk further complicates density retrievals from UV solar occultations.…”

KORTES Mission for Solar Activity Monitoring Onboard International Space Station

“…Due to that, KORTES is mainly intended to meet goals of solar activity monitoring and space weather forecasting. Nevertheless, the KORTES facilities will also address a wide spectrum of fundamental problems in domains of solar physics and solar-terrestrial interactions (Slemzin et al, 2016(Slemzin et al, , 2019Rodkin et al, 2018;Shugay et al, 2018). KORTES will allow to study the mechanisms of solar flare generation and the formation of high-temperature plasma in active regions (ARs) and outside them, investigate statistical properties for microevents, trace the initiation and propagation of solar eruptive phenomena (prominences, coronal mass ejections) at heights up to two solar radii (Zhang et al, 2001;Byrne et al, 2014;Reva et al, 2016a,b).…”