The direct measurements of electrons and positrons over the last 30 years , corrected for the solar effect in the force-field approximation , are considered .
The resulting overall electron spectrum may be fitted with a single power law above few GeV with spectral index ( \gamma _ { - } = 3.41 \pm 0.02 ) , consistent with the spectral index of the positron spectrum ( \gamma _ { + } = 3.40 \pm 0.06 ) , therefore suggesting a common acceleration process for both species .
We propose that the engine was a shock wave originating from the last supernova explosion among those that formed the local bubble .
In addition , at low energy , the electron spectrum measured during the last A + solar phase is damped , whereas the positron spectrum is well represented by a single power law down to the lowest inferred local interstellar energy ( 0.8 GeV ) .
We suggest that this difference arises from a time- and charge-dependent effect of the solar modulation that is not taken into account by the force-field approximation . OBSOLETE : please refer to ApJ 612 ( 2004 ) 262-267 , that is the final version of this work .