Speaker
Description
Magnetic monopoles arise in many beyond Standard Model scenarios. When placed in an astrophysical magnetic field, monopoles induce a magnetic analogue of plasma oscillations. In this work, we explore monopole-induced oscillations of the intergalactic magnetic field (IGMF). We show that these oscillations lead to collimation of electrically charged particle trajectories, reducing their usual deflection by the magnetic field. This collimation effect modifies the deflection angle in electromagnetic cascades from TeV blazars and decreases the angular size of secondary GeV halos. Therefore, constraints on the secondary halo angular size from combined H.E.S.S. and Fermi-LAT observations translate into bounds on the magnetic monopole abundance. The bounds on the magnetic monopole flux obtained in this work from the blazar 1ES 0229+200, depending on the IGMF strength, can be as strong as $F \lesssim 5 \times 10^{-23}\, \text{cm}^{-2} \text{s}^{-1} \text{str}^{-1}$ for low-mass monopoles $m \lesssim 10^6\, \text{GeV}$, stronger than existing laboratory and astrophysical bounds. This bound becomes subdominant to current constraints if the present-day IGMF strength is larger than $B \gtrsim 10^{-12}$ G. At the same time, in the presence of a non-zero monopole abundance, the IGMF lower bound inferred from TeV observations should itself be revised, resulting in a stronger lower bound at higher monopole number density.