LOWER LIMIT ON PULSAR BIRTHRATE SET BY COSMIC-RAY POSITRON MEASUREMENTS

A recent measurement of the e(+)/(e(+) + e(-)) ratio in cosmic rays be tween 5 and 50 GeV (HEAT experiment), is consistent with positron prod uction theories via primary cosmic radiation interactions in the inter stellar medium. This paper will show that atmospheric corrections resu lt in a 50% level of uncertainty in the e(+)/(e(+) + e(-)) ratio measu rements carried out with balloon-borne experiments. In light of the cu rrent theories on electron-positron production in neutron stars and by using different calculations for atmospheric corrections, a lower lim it on Milky Way pulsar birthrate of 30-60 years can be set on the basi s of recent observations of the positron fraction in cosmic rays.