1. GeoForschungsZentrum Potsdam; Telegrafenberg,; D-14473; Potsdam; Germany
2. Sektion Geophysik, LMU München; Theresienstrasse 41/IV,; D-80333; Munich; Germany
3. Physics Department; Gadjah-Mada University; Yogyakarta; Indonesia
4. Meteorological and Geophysical Agency (BMG); JI. Angkasa I No. 2, Kemayoran,; Jakarta; 10720; Indonesia