Observation of ULF Geomagnetic Anomalies at Tlamacas Station, Volcano Popocatepetl, in 2005

First results of ULF geomagnetic anomalies observed at the Tlamacas station (98deg 37\´ 41" W, 19deg 04\´ 01" N) located at 4 km near the volcano Popocatepetl (active volcano, 98.62 W, 19.02 N) for the period March-July, 2005 and their analysis are presented. The geomagnetic data were collected by a 3-axial fluxgate magnetometer designed at UCLA, (1 Hz sampling rate frequency, GPS). Our analysis reveals some anomalies, which are suspected to be generated by the local volcanic origin: the EM background in the vicinity of the volcano is significantly noisier than in other reference stations; the sporadic strong noise-like geomagnetic activity observed in the H-component; some geomagnetic pulsations (without preferred polarization) observed only at the Tlamacas station. Also the dynamics of the geomagnetic fractal index for the Tlamacas station in a comparison with the reference station points out to the some changes in critical processes, which may occur in the vicinity of the volcano.