We present particle observations by two polar-orbiting satellities, supplemented by observations of cosmic noise absorption and magnetic activity on ground during the maximum magnetic activity of an intense substorm on November 11, 1969. The first satellite to cross the evening auroral zone observes a narrow 40-keV electron spike at ~69¿ only 1/2¿ poleward of the trapping boundary for 100-keV electrons; 3 min later the second satellite encounters intense fluxes of 40-keV electrons and also of relativistic electrons and energetic protons poleward of the previously observed trapping boundary. The most intense fluxes occur in the vicinity of the Harang discontinuity. It appears that the two satellites provide snapshots of a poleward expansion of substorm activity, as this is also indicated by the ground-based observations. Our observations are consistent with a stochastic acceleration mechanism for both electrons and protons.