This study investigates subauroral phenomena during the main phase of the 10 May 2024 geomagnetic storm using a combination of ground-based observations from the WD IZMIRAN observatory (magnetometer, ionosonde, and all-sky imager) and Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) simulations. During 18:00–20:00 UT, we identified the simultaneous occurrence of ionospheric signatures of Polarization Jets (PJ)/Sub-Auroral Ion Drifts (SAID) and Strong Thermal Emission Velocity Enhancement (STEVE) over Kaliningrad, consistent with previously reported PJ/SAID identification from DMSP drift velocity measurements. This identification is supported by: (1) characteristic purple emissions (clearly visible in all three channels) moving rapidly westward; (2) U-shaped structures in ionogram sequences; (3) the reproduction of supersonic westward plasma drifts within a narrow latitudinal band by the first-principles model; and (4) observed and simulated significant Ne depletion. The estimated ion drift velocity from all-sky imaging (assuming an emission altitude of 200 km) is consistent with GSM TIP simulations, which predicted PJ/SAID velocities of ~750 m/s driven by a latitudinally narrow (~3°) but longitudinally extended (>50°) poleward electric field (40 mV/m). Simulations reveal that this PJ/SAID phenomenon causes a reversal of the zonal thermospheric wind at 250 km and induces Ne disturbances across the 200–700 km altitude range. The electron temperature enhancement (up to 1500 K) exhibits a “falling drop” shape, peaking at 350 km, while ion heating exceeds 150 K. The neutral temperature shows a dual response: frictional heating at 120–160 km and localized cooling at 175–250 km due to drop in electron density. Additionally, an increase in atomic oxygen concentration was predicted within the 90–200 km range across the PJ/SAID longitudinal sector.

Enhanced radiation during flares increases ionisation in the Earth's ionosphere, yet different ionospheric layers absorb different emissions because they differ in composition and plasma characteristics. To investigate the relative timings of the responses at different altitudes, we analyse 66 X-class flares from 2024–2025 using EUV and X-ray irradiance with simultaneous GNSS vertical total electron content (VTEC), very-low-frequency (VLF) phase measurements and magnetometer observations of the horizontal geomagnetic perturbation (\(\Delta B_{\mathrm{h}}\)). Response lags were measured by cross-correlating time derivatives and feature matching. Against the same EUV drivers, \(\Delta B_{\mathrm{h}}\) response lags by \(\approx\)13 s and VTEC by \(\approx\)33 s, consistent with slower electron loss in the F region than the E region. \(\Delta B_{\mathrm{h}}\) responses reproduce unique EUV and X-ray features, indicating the influence of both wavelength ranges on E-region ionisation. In the D region, VLF phase lags the X-ray rise by +51, +30 and +12 s relative to progressively softer channels, and phase maxima precede softer X-ray peaks, indicating that recombination begins to prevail over ionisation before flux reaches its maximum. These results, for the first time, empirically demonstrate the altitude difference in recombination rates of the ionosphere and the noticeable contribution of both EUV and X-ray emission to E-region dynamics during flares.