Some Connections Between the Solar Wind, Barometric Pressure, Geomagnetism, and Seismic Background Noise

All three of the original papers on seismic hum note the curious fact that some of the measured peaks in the noise spectrum do not correspond to known seismic S or T modes. We have previously noted (Thomson et al, Proc. IEEE, 2007) the presence of high--Q peaks in barometric pressure data. Similarly, (Ghosh et al, JGR 2009) peaks were noted in solar wind density at the ACE spacecraft and evidence given that solar modes can coexist with turbulence in the solar wind. Here we show that fluctuations in the solar wind density and velocity measured at ACE are coherent with those measured on the microbarograph at BFO and elsewhere. This coherence is strongest at the frequences of solar normal modes with the described peak at 404 uHz probably being P_0,2. There are many similar examples. We also examine the canonical coherence between geomagnetic and seismic data and again find that it is generally very high with peaks approaching the 100% significance level at the frequencies of low--degree solar modes. Many of these frequencies occur between those of seismic normal modes and thus explain the curious peaks noted in the original papers. Moreover, at frequencies where solar and seismic normal mode frequencies coincide, as _0S18 (2672.5 uHz) and P_3,17 (2671.0 uHz) the coupling appears to be more efficient. This coupling occurs largely on the horizontal seismic components and, because the horizontal sensors of STS-1s are insensitive to magnetic fields, must be seismic and not instrumental.