The Lunar Tide in ƒbEs


  • J. D. Tarpley,

  • S. Matsushita


Hourly measurements of the blanketing frequency of sporadic EbEs) made during the years 1958 through 1965 have been analyzed for lunar daily variations. The data, which came from ten stations, were analyzed by the Chapman-Miller method. Both seasonal and yearly average lunar variations were obtained. The lunar semidiurnal oscillations in ƒbEs ranged from 0.01 to 0.04 MHz, with maximums occurring from 7 to 9 hours lunar time. The amplitude of the lunar tide in ƒbEs is an order of magnitude less than the lunar variations of ƒ0Es. Since ƒbEs is close to the plasma frequency of Es, the oscillation in ƒbEs represents a lunar variation in the electron density of Es layers, whereas the significance of the lunar variation of ƒ0Es is not clear. The phases of the lunar tides in ƒbEs, ƒ0Es, and hEs are found to be nearly the same. Two sources of lunar influence on Es electron density are considered (1) wind shears in the lunar tide acting to augment or decrease the wind shears responsible for E8, and (2) interaction of E8 with electrostatic fields associated with the lunar current system.