With Fscans generating daily data on a limited channel list over the last month, I was able to get a better look at the lines situation. This study uses H1_DMT-GRD_ISC_LOCK_NOMINAL data due to availability in the time frame of interest; in the future we should use the new undisturbed bit for similar studies.

There are a number of comb-like features which fluctuate with time. I will not attempt to catalog them all here. This is a list of the most troublesome and notable entries.

Figure 1 is a snapshot of a daily spectrum from 11/25, which shows most of the persistent features clearly.

Most wanted: 1.661124 Hz comb, apparently new in November

This comb is clearly visible in all available November weekly spectra. It has a notable peaked structure around 280 Hz, and at lower frequencies every 3rd harmonic is visible. It's strong, consistent, and contaminating a lot of frequencies. Figure 2 is a zoomed version of figure 2 showing the region where the comb is strongest.

This alog post about 280 Hz DARM lines in late November points out that that bruco shows coherence with ASC-OMC_B_PIT_OUT_DQ around 280 Hz. Following up on that, I generated a higher-resolution coherence spectrum with Fscans and found the comb very clearly present in that channel (Figure 3). I will continue looking for other witness channels; so far the limited list of magnetometers being tracked by Fscans do not see this comb.

Narrow comb-like structure around 200 Hz, also new, probably related to above

First visible in weekly averaged spectra starting the week of 11/23-11/30. Centered on a strong line at 200.1 Hz (Figure 4, again a zoomed version of Figure 1) Also clearly visible in coherence spectrum with ASC-OMC_B_PIT_OUT_DQ, hence the statement that may be related.

Resurfaced from O3: 2.0 Hz comb with 1.0283 Hz offset

When I looked at early September data, I didn't see this comb, but it's visible in November. I'm not sure yet whether it was actually absent in September, or just too weak to be seen with the available data.

Still around: 11.395 (and similar) combs, 3.98735 Hz comb

Also noted in September, the near-11 Hz comb(s) seem to be less persistent and may shift in frequency, or turn up with only odd harmonics. This aligns with previous observed behavior, but makes it hard to track the comb.

The 3.98735 Hz comb was spotted in September and is still around, visible in weekly spectra especially in the latter part of November.