Cosmic-Ray Negatron and Positron Spectra Between 12 and 220 MeV

The interplanetary negatron and positron spectra from 12 to 220 MeV have been determined with a balloon-borne magnetic spectrometer. The observed charge ratio $\frac{e^{+}}{(e^{+}+e^{-})}\approx 0.3$ indicates that the flux most likely consists of a mixture of "primary" negatrons and interstellar "secondary" negatrons and positrons. We deduce an absolute solar modulation of the interstellar positron flux which decreases with decreasing magnetic rigidity below about 80 MV.