Ions of the O-18(+) oxygen isotope: Mass-spectrometer data of the Interkosmos-24 satellite

The altitude and latitude behavior of the oxygen O-18(+) isotope and the ra tios of ion densities (O-18(+)/O-16(+)) at altitudes of 500-1800 km, as wel l as the dependence of this ratio on geophysical conditions, were investiga ted by data obtained aboard the Interkosmos-24 satellite. This ratio is fou nd to increase at high latitudes with a maximum observed near the auroral o val region. Sometimes, the maximum in latitude distribution of this ratio i s observed at middle latitudes. During the effects of the equatorial anomal y at low latitudes, the ratio of the ion densities of oxygen isotopes decre ases in the region of "humps" of the equatorial anomaly in comparison with the middle latitudes. An altitude dependence of the ratio of ion densities of oxygen isotopes is obtained for the middle latitudes; these data and the data published previously cover altitudes from 200 to 1800 km. Values of t he ratio vary from 1.5 x 10(-3) to 0.35 x 10(-3) for different altitudes wi th scattering up to approximate to 30%. The altitude dependence of the rati o obtained for high latitudes differs from the dependence for middle latitu des by higher values and their larger scattering. During periods of high ge omagnetic activity, the ratio of ion densities of oxygen isotopes is higher than under quiet conditions. It is suggested that the value of the ratio o f ion densities of oxygen isotopes is determined by ion and neutral tempera tures alike, and also by dynamical processes leading to ion lifting from lo wer altitudes.