Ionospheric Response to the Severe Geomagnetic Storm of 19-21 January 2026 over Almaty (Kazakhstan) According to the Digisonde and GPS Data.

We present observations of the ionospheric response to the severe geomagnetic storm of 19-21 January 2026, obtained using a Digisonde DPS-4D and GPS-based vertical Total Electron Content (TEC) measurements over Almaty, Kazakhstan. Solar wind parameters, geomagnetic indices (AE and SYM-H), and Interplanetary Magnetic Field (IMF) components were analyzed to characterize the storm drivers. The ionospheric response to the geomagnetic storm of 12-13 November 2025 was additionally analyzed to provide an overall picture of the ionospheric effects within the specified latitude-longitude region. The evolution of the ionospheric disturbances revealed highly complex processes. The critical frequency and total electron content during the severe geomagnetic storms exhibited morphological similarities, reflecting a general response to geomagnetic storms, as well as notable differences in their storm-time responses and in the observed percentage deviations of foF2 and TEC relative to reference-day baselines. A combined observational approach provides a more complete picture of the ionospheric response during extreme space weather events.