1. Big Bear Solar ObservatoryNew Jersey Institute of Technology Newark New Jersey USA
2. Also at W. K. Kellogs Radiation Laboratory, California Institute of Technology, Pasadena, California, USA.
3. Department of PhysicsThe Chinese University of Hong Kong Hong Kong China
4. Department für Physik und AstronomieUniversität Basel Basel Switzerland
5. W. K. Kellogs Radiation LaboratoryCalifornia Institute of Technology Pasadena California USA