This paper will report on the effects of an extreme space weather event. On January 20^th, 2005, a balloon-borne experiment intended to measure relativistic electron precipitation and its effects was aloft over Antarctica (~32 km; near 70º S, 345º W geographic) throughout the duration of the solar energetic particle (SEP) event. The balloon carried an x-ray scintillation counter, dc electric field, and scalar electrical conductivity sensors. Intense energetic proton precipitation and large increases in the energetic proton population of the outer radiation belts were observed by a global array of observatories and spacecraft. The stratospheric conductivity increased by nearly a factor of 20 above ambient at the time of the SEP event onset and returned to within a factor of two above normal levels within 17 hours. The electric field decreased to near zero following the increase in particle flux at SEP onset. Combined with an atmospheric electric field mapping model, these data are consistent with a shorting out of the global electric circuit and point toward substantial ionospheric convection modifications. It is shown that the conductivity profile predicted by the Sodankylä Ion and Neutral Chemistry (SIC) model does not shield the balloon payload at 32 km from the ionospheric horizontal field. Thus, the data really do indicate a very low level of ionospheric convection over the balloon during the 6 hours following the SEP event. We have used global magnetometer and satellite data to interpret the changes in the vertical field as indicators of large scale convection changes.