1. Departamento de Física, Instituto Tecnológico de Aeronáutica (ITA), 12228-900 São José dos Campos, SP, Brazil
2. Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main, Germany
3. Department of Physics, San Diego State University (SDSU), 5500 Campanile Drive, 92182 San Diego, California, USA
4. Center for Astrophysics and Space Sciences, University of California at San Diego, 92093 La Jolla, California, USA