Magnetic-field effects on strongly localized electrons

The magnetic-field response of strongly localized electrons is probed by examining the quantum interference of forward scattering paths. With no disorder, there is a rich structure in the tunneling rate, which is sensitively dependent upon commensurability of the flux per plaquette with the flux quantum. With nonmagnetic impurities, there is a positive magnetoconductance, and the localization length appears to increase as ${\mathit{B}}^{1/2}$. With impurities breaking time-reversal symmetry, the distribution of tunneling rates is not changed by the magnetic field.