Yes...around May 8, 1998 there were a series of large, solar disturbances which caused a new van Allen belt to form in the so-called 'slot region' between the inner and outer van Allen belts. The new belt eventually dissappeared once the solar activity subsided. For more details you can read the NASA Press Release about it. There were also a number of satellite upsets around this same time involving the Galaxy IV satellite, Iridium satellites and others. This is not the first time that a temporary, new belt has been observed to form in the same region, but it takes a prolonged period of solar storm activity to populate this region with particles.