I. Michaloliakos, A. Matas, S. Banagiri, J. Ni
In an attempt to identify the source of peaks in the magnetic coupling function of H1, we have investigated the behavior of OSEM channels during weekly magnetic injections at H1 from 10 to 100Hz. The peaks in the magnetic coupling function can be seen in this summary plot from PEM:
We compared the spectra of 287 OSEM channels during magnetic injections to their spectra immediately before and after. We identified the following CS channels that display peaks consistent with those of the magnetic coupling function:
- H1:SUS-BS_M2_OSEMINF_UL_OUT_DQ - Displays prominent peaks at 100.5Hz and 40.9Hz only during magnetic injections. The position of the peak which first appears at 100.5 Hz in the CS magnetic injection of 2020-01-14 evolves this time to 85.4Hz from January to late March (see plots below). The same behavior is observed by the peak on the magnetic coupling function which first appears on 2020-01-14 at 100.4Hz (https://ldas-jobs.ligo-wa.caltech.edu/~philippe.nguyen/weekly-magnetic-injections/output/2020-03-24/summary-peaks.png). These peaks do not appear during EX or EY magnetic injections. We also include a combined plot of the spectra during the last few CS injections.
- H1:SUS-PR2_M3_OSEMINF_LR_OUT_DQ - Starting at the injection on 2020-01-14, a new peak appears just above 100Hz, exactly like BS_M2_OSEMINF_UL and evolves also in the same way ending up at 85Hz. It does not display a peak at 41Hz during CS injections. See the normalized spectrogram below. The vertical dashed lines in the spectrogram correspond to the start and end times of a CS magnetic injection on 2020-03-24.
- H1:SUS-PRM_M3_OSEMINF_UL_OUT_DQ - Similar behavior as SUS-BS_M2_OSEMINF_UL, but less prominent.
- We have identified also a number of CS OSEM channels that consistently display an overall increase from 10Hz to 100Hz during magnetic injections. The ASD of H1:SUS-BS_M1_OSEMINF_F2_OUT_DQ is attached as an example, We do not have a complete list of these channels.
The repository we used to do the data analysis can be found at (https://git.ligo.org/stochastic/magnetic_coupling_resonances), which includes a short wiki that expands on our methodolody.
