Long Term Changes of the Ionospheric Electron Density Associated with Solar Cycle Length

NIEVES ORTIZ DE ADLER; ANA G. ELIAS

Uppsala

Congreso; 8th IAGA, Scientific Assembly of the International Association of Geomagnetism and Aeronomy; 1997

IAGA, International Association of Geomagnetism and Aeronomy

The maximum ionospheric electron density, Nmax, is considered to vary linearly with solar activity parameters such as the sunspot number, Rz, or the solar 10.7 cm radio flux, F10.7. These solar activity parameters provide a measure of the EUV radiation responsible for most of the ionospheric ionization. The solar cycle length (SCL), is considered to reflect long-term changes in solar irradiance, part of which is the EUV flux. Nmax data from Manila, Slough, Mundaring, and Tucuman ionospheric stations covering the period 1949-1995 were analyzed. The eleven-year solar cycle effect was filtered by considering the residuals of the fitted regression between Nmax and Rz, which have been called NmaxA. The time variation of NmaxA follows SCL behavior, being the correlation coefficients between both variables greater than 0.70 in all the cases. This result would indicate that statistically SCL is a good indicator of long-term changes in the EUV solar radiation which affects the ionosphere and therefore it could be an additional term in the linear relation already established between Nmax and Rz.