The response of high altitude ionization chambers during the 1954-1965 solar cycle

The response of an integrating ionization chamber at 10 g/cm2 depth in the atmosphere to particles of various rigidities is evaluated by using the change of ionization with latitude. This procedure yields the differential response curves at solar minimum and solar maximum and also the mean rigidity of response at any given latitude. For high latitude and Minneapolis, the mean responses are 2.5 bv and 3.2 bv, respectively, at solar minimum and 3.6 and 3.8 at solar maximum. The solar cycle effect at 10 g/cm2 is evaluated using 250 balloon flights at Minneapolis and at high latitude. Total ionization minimum lags about 18 months behind sunspot maximum. The high altitude ionization when compared with neutron monitors forms a single correlation curve over the solar cycle with significant deviations occurring only for a few months in 1957. We conclude that the relative rigidity effects between 3.6 and 15 bv are very similar during the decreasing and increasing phases of the solar cycle. Comparison of data from ionization chambers of Pioneer 5 and Mariner 2 with data from detectors on earth shows no definite gradient effects. The larger intensity changes show a correlation between earth and deep space, but real fluctuations of smaller amplitude are frequently not correlated.