Whistler observations of the interchange of ionization between the ionosphere and the protonosphere

TLDR: In this article, the electron content in magnetospheric tubes of force in the range 3.5 to 5.5 was measured at Eights, Antarctica, in June 1965, and the observed rate of increase in daytime tube content gives an upward flux of ∼3×108 electrons/cm² sec across the 1000-km level, which is larger than the downward flux necessary to maintain the nocturnal ionosphere.

Abstract: Whistlers recorded at Eights, Antarctica, in June 1965 were used to measure the electron content in magnetospheric tubes of force in the range 3.5<L<5. Under quiet geomagnetic conditions, the observed rate of increase in daytime tube content gives an upward flux of ∼3×108 electrons/cm² sec across the 1000-km level, which is larger than the downward flux necessary to maintain the nocturnal ionosphere. The observed upward flux is primarily due to diffusion of protons through the diffusive barrier, rather than to an increase in the height of the barrier. The downward flux at night under quiet conditions is ∼1.5×108 electrons/cm² sec, an amount that is considered sufficient to maintain the nocturnal ionosphere. The protonosphere is depleted in less than a day during a magnetic storm or polar substorm activities, and subsequent recovery of tube content takes place at a rate of 3-5×1012 electrons/cm² per day. At this rate, an ‘empty’ tube requires about 5 days to reach the monthly median value, and even after 8 days of quiet conditions it continues to fill. The average spacing of geomagnetic disturbances is such that we expect that the protonosphere almost never reaches the saturation level it would attain if it were in equilibrium with the ionosphere.