1. Department of Earth and Space Sciences; University of California; Los Angeles California USA
2. Institute of Geophysics and Planetary Physics; University of California; Los Angeles California USA
3. School of Earth and Space Sciences; Peking University; Beijing China
4. Geophysical Observatory; Athabasca University; Athabasca Alberta Canada
5. Goddard Space Flight Center; NASA; College Park Maryland USA
6. Institute of Geology and Geophysics; Chinese Academy of Sciences; Beijing China
7. Arctic Research; Finnish Meteorological Institute; Helsinki Finland