We noticed, first in VIM spectrograms, that the infamous low frequency magnetic glitches seen by all magnetometers site-wide suddenly disappeared during last week-end.
Searching information we found out that railway traffic was suspended during those two days between Pisa and Empoli stations because of works along the line (also in the attached pdf):
Few observations:
We altready knew that these glitches are related to trains but...
- This finally proves that they are generated within the Pisa - Empoli railway section
- These glitches disappeared completely from CEB and NEB magnetometers, instead some are still seen in WEB magnetometers (Figure 4). This probably tell us that the WEB sees also glitches from a different railway line, the freight line that runs approx. North-South: see the map in Figure 5.
Spectrograms in Figures 6 to 9 show an insight of the time of the disappearing/reappearing:
- Figure 6, 7 and 8 show the NEB magnetometer (the closest to the Pisa-Empoli railway): the interpretation (Federico) is that first the train transit stops, than approx one hour later (/ one hour before) the electric line is de-electrified (/ re-electrified). A large glitch can be seen at these times: in Figures 7 and 8, respectively.
- Figure 9 is the WEB magnetometer, on the same color scale and time window as Figure 6: note that in this case the glitch density reduces just a bit.
