Modeling the ionospheric parameters influence on the geomagnetic pulsationpolarization: ULF magnetic field

The influence of the ionospheric parameters on the polarization characteris tics of magnetosonic or ULF compressional wave disturbances is modeled. The parameters that have a significant impact on the polarization signature of the ULF compressional disturbances are the maximum height (h,e) and maximu m concentration (N-mE) Of the E-region. The polarization rotation angle lie s in the interval 0-90 degrees for every critical frequency f(0E) (in MHz). but its magnitude is controlled by the maximum height h(mE). For low maxim um heights (h(m) approximate to 100km) and higher critical frequencies (f(0 E)) determined by the maximum concentration N-mE (f(oE) > 2), the rotation angle is nearly 90 degrees. For high maximum heights (h(mE) approximate to 130km) and a lower critical frequency (f(0E) < 2), the rotation angle reduc es to zero. The second effect, the ellipticity of the ULF wave disturbance, also varies in a wide interval, from a linear (the ellipticity effect is z ero) to circular (the ellipticity is 1), depending on the E-region's maximu m height (h(mE)). It is shown that the ellipticity effect has a maximum val ue for only a certain combination of foe and hmE The F-region ionization do es not contribute essentially to the ionospheric effects on the ULF disturb ance penetrations. (C) 2001 Published by Elsevier Science Ltd.