Solar flare and geomagnetic storm effects on the thermosphere and ionosphere during 6-11 September 2017

The two largest flares, an X9.3 and an X8.2, were a disk flare and a limb flare, respectively. We conducted model simulations and data analysis to examine solar flare effects on the coupled thermosphere and ionosphere (TI) system in connection with flare location effects and to investigate the occurrences of large-scale traveling atmosphere disturbances (TADs) due to flares and storms.

Soft X-ray enhancement, which dominates E region ionization, is essentially not affected by the location of a flare on the Sun; solar extreme ultraviolet enhancement, which dominates ionization above similar to 150 km, is much weaker for a limb flare compared to a disk flare with the same magnitude. Consequently, flare responses in the lower thermosphere, and ionosphere E region are not affected by flare locations, but above similar to 150 km, the TI system responds more strongly to disk flares than to limb flares.