Polar Cap May Have A Geoelectric Field Available to Purchase

During the period of high solar and geomagnetic activity in late May 1967 the Air Force satellite OV1‐9 detected energetic proton fluxes coming up the magnetic field lines from the earth at high magnetic latitudes $(λ⩾65–70 deg).$ Ludwig Katz and Paul L. Rothwell of Air Force Cambridge Research Laboratories suggest that, because the flux is highly collimated along magnetic‐field lines, there may be a radial polar electric field of about 0.14 volts/meter (Phys. Rev. Letters 21, 1764, 1968). Electric fields had been suggested earlier as a possible explanation for aurora or other polar‐cap particle precipitation.