1. Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, Colorado 80305, USA; National Solar Observatory, University of Colorado Boulder, Boulder, Colorado 80303, USA; and Department of Astronomy, University of Texas at Austin, Austin, Texas 78712, USA
2. Faculty of Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
3. Department of Astronomy, University of Texas at Austin, Austin, Texas 78712, USA and Computational Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA