The effect of background conditions on the ionospheric response to solar flares

The ionospheric response to two X5 solar flares that occurred in different seasons was investigated using the global ionosphere-thermosphere model. Two questions were investigated: (a) how do different solar flares with similar X-ray peak intensities disturb the ionosphere during the same background and driving conditions? and (b) how do the geomagnetic field and season affect the ionospheric response to solar flares? These questions were investigated by exchanging the two X5 flares for each other so that there were two pairs of flares with (1) the same background conditions but different irradiances and (2) different background conditions but the same irradiance. The simulations showed that the different solar flares into the same background caused ionospheric disturbances of similar profiles but different magnitudes due to differences in the incident energies, while the same flare spectra caused perturbations of similar magnitudes but different profiles in different backgrounds. On the dayside, the response is primarily controlled by the total integrated energy of the flare, independent of the background. For the northern and southern polar regions, the response is strongly controlled by the solar zenith angle and the incident energy, while the background plays a secondary role. On the nightside, the background conditions, including the magnetic field and season, play a primary role, with the neutral winds and electrodynamics driving the ionospheric response.