Search for Magnetic Monopoles in Polar Volcanic Rocks

For a broad range of values of magnetic monopole mass and charge, the abundance of monopoles trapped inside Earth would be expected to be enhanced in the mantle beneath the geomagnetic poles. A search for magnetic monopoles was conducted using the signature of an induced persistent current following the passage of igneous rock samples through a SQUID-based magnetometer. A total of 24.6 kg of rocks from various selected sites, among which 23.4 kg are mantle-derived rocks from the Arctic and Antarctic areas, was analyzed. No monopoles were found, and a 90% confidence level upper limit of $9.8\times {10}^{-5}/\mathrm{g}$ is set on the monopole density in the search samples.

Figure 1

Top: Persistent current after the first passage through the magnetometer for all samples. Bottom: Results of repeated measurements of candidate samples with absolute measured values in excess of $0.25g_D$.