Memoirs of the Kakioka Magnetic Observatory Vol.12 No.02， p.43, December, 1966
Notes on the Geomagnetic Disturbances for the Pre-SC stage of PCA
On Feb. 10, 1958, magnetic disturbance occurred simultaneously with the onset of PCA (Polar Cap Absorption) in the auroral zone, before SSC at 0126 Feb. 11. Hitherto, it is well known that PCA is the ionization effect of the lower ionosphere in the polar cap, caused by the solar sub-cosmic ray bombardment and has not relation with the geomagnetic disturbance. The examination of such the events as one on Feb. 10 during the IGY, results in that the magnetic disturbances may relate more closely to AA (Auroral Absorption).
An explanation of the simultaneity of the magnetic disturbance and PCA in the auroral zone is qualitatively attempted.