Magnetic Moments ofHe3andH3

The electromagnetic structure of a nucleon in a nucleus is different from that of a free nucleon. This difference is examined for the two-pion part of the form factor by considering interactions with other nucleons in the course of pion emission and absorption, but without exchanging charge. For ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$, the isovector part of the magnetic moment increases by an amount which is comparable to the outstanding discrepancy between the experimental and theoretical values.