It immediately went offline (though fixed, finally, in August 2012). The malfunction was due to a high-energy, ionizing radiation cloud, identified in 1958 by James Van Allen, when Sputnik I's instruments were also affected. He believed the cause to be anomalous radiation, which led to his discovery of the Van Allen radiation belts. The innermost belt dips closest to Earth above an area 300 km east of Brazil, at 200 km altitude, because the Earth's magnetic field is weakest there. On 8 Mar 2012, the Earth's upper atmosphere experienced the disruptive effects of solar flares. 2013 is the apex of that 11-year solar cycle, Once it has past, we'll only have the more predictable though not well-understood effects of the South Atlantic Anomaly to contend with.