Reply to “Comment on ‘‘Unraveling the Role of IMF Bx in Driving Geomagnetic Activity’’” by Lauri Holappa et al

We thank Lauri Holappa, Jone Peter Reistad and Anders Ohma for their interest in our research and for having published their comments, referred hereafter as HEA2023. Here we present our counterarguments to the points presented in HEA2023. We explain the observed excess of AL values for different polarities of IMF By over different IMF Bx polarities by an additional negative IMF Bz, which exist due to the 7.25‐degree tilt of the solar equatorial plane to the ecliptic plane. We emphasize again that the AL index strongly depends on the dipole tilt, so that under the same driving conditions is more than twice larger during non‐tilted dipole periods than at solstices. The IMF Bx component, depending on its polarity, moves the magnetotail plasma sheet away from or toward the equatorial plane, and thus changes the effective dipole tilt angle. That change may be a cause of the asymmetric response of the AL‐index to positive or negative values of the IMF Bx. Key Points AL index is strongly modulated by the dipole tilt angle under the same coupling function IMF Bx component affects the effective dipole tilt and, hence, may affect the AL‐index The contention that AL index is strongly modulated by the IMF By during large dipole tilt periods is not that evident