This is an attempt to solve the energetic problem of the primary detection of weak parallel static (DC) and alternating (AC) extremely low frequency (ELF) magnetic fields. We studied the equations of motion for an ion situated inside a macromolecule under the influence of these fields. The main concern is with the magnetic field influence on thermal motion of the ion in the macromolecule. The resonance effects are revealed at discrete frequencies of the ion thermal oscillations determined by the DC field magnitude and the AC field frequency. These phenomena result from the Larmor precession of the ion thermal motion. When the DC field or, to a greater extent, the combined DC and AC fields with the specific frequencies are turned on or cut off, changes occur in the energy of the ion thermal motion. If, inside the macromolecule, the ion is sufficiently protected against immediate impacts of particles of the medium surrounding the macromolecule, these changes may be enough to trigger alteration in the quantum state of the macromolecule.