Development and Cancellation of Long‐Duration Positive Ionospheric Storms: Both Changes of the F2‐Layer Peak Height and O/N 2 Ratio Can Be Decisive

For decades, two competing hypotheses on the key drivers of mid‐latitude long‐duration positive ionospheric storms (LDPS) have been considered: (a) an increase of the F2‐layer peak height ( h m F 2 ) and (b) an increase in the atomic oxygen to molecular nitrogen density ratio (O/N 2 ). This study examined ionospheric disturbances near mid‐latitude magnetically conjugate points caused by the intense magnetic storm on 26–28 February 2023. Observation‐based simulations found that, for this storm, neither h m F 2 nor O/N 2 ratio increases can be considered an exclusive mechanism for forming an LDPS. Depending on the region of the globe and day, either driver acting alone was able to cause an LDPS, or both the drivers acting together created or enhanced an LDPS, or opposing changes in h m F 2 and O/N 2 inhibited or canceled the development of an LDPS. The results of the simulations are supported by the independent measurement of the neutral composition by the NASA TIMED Global Ultraviolet Imager (GUVI).