  The Lorentz term raises the linear matter power on small scale which leads to
interesting signatures in the 21 cm signal. Numerical simulations of the
resuting nonlinear density field, the distribution of ionized hydrogen and the
21 cm signal at different values of redshift are presented for magnetic fields
with field strength B=5 nG, and spectral indices $n_B=-2.9, -2.2$ and -1.5
together with the adiabatic mode for the best fit data of Planck13+WP.
Comparing the averaged global 21 cm signal with the projected SKA1-LOW
sensitivities of the Square Kilometre Array (SKA) it might be possible to
constrain the magnetic field parameters.
