Ionic mobility, mean mass, and conductivity in the middle atmosphere from near ground level to 70 km

Mean ionic mass and conductivity, the product of mobility and ion concentration, are important in calculations of low‐frequency propagation. Progress made mostly over the last decade concerning these parameters is reviewed. The mean positive ion mass has a range of about 90±35 amu with lighter masses more prevalent at the higher altitudes. The mean negative ion mass is generally greater and reaches a peak value of 300 amu near 35 km. Reduced mobilities μ 0 for both positive and negative ions appear to lie within 1.6±0.6 cm 2 (V s) −1 . Somewhat finer resolution of μ 0 with altitude is tabulated in the text. It is argued that ion concentrations and hence total conductivities are easily and well defined where galactic cosmic rays are the dominant ionization source and electron concentrations are negligible.