  Stepwise changes of the photospheric magnetic field, which often becomes more
horizontal, have been observed during many flares. Previous interpretations
include coronal loops that contract and it has been speculated that such jerks
could be responsible for sunquakes. Here we report the detection of stepwise
chromospheric line-of-sight magnetic field (B$_{\rm LOS}$) changes obtained
through spectropolarimetry of Ca II 8542 \AA\ with DST/IBIS during the X1-flare
SOL20140329T17:48. They are stronger ($<$640 Mx cm$^{-2}$) and appear in larger
areas than their photospheric counterparts ($<$320 Mx cm$^{-2}$). The absolute
value of B$_{\rm LOS}$ more often decreases than increases. Photospheric
changes are predominantly located near a polarity inversion line, chromospheric
changes near footpoints of loops. The locations of changes are near, but not
exactly co-spatial to hard X-ray (HXR) emission and neither to enhanced
continuum emission, nor a small sunquake. Enhanced chromospheric and coronal
emission is observed in nearly all locations that exhibit changes of B$_{\rm
LOS}$, but the emission also occurs in many locations without any B$_{\rm LOS}$
changes. Photospheric and chromospheric changes of B$_{\rm LOS}$ show
differences in timing, sign, and size and seem independent of each other. A
simple model of contracting loops yields changes of opposite sign to those
observed. An explanation for this discrepancy could be increasing loop sizes or
loops that untwist in a certain direction during the flare. It is yet unclear
which processes are responsible for the observed changes, their timing, size
and locations, especially considering the incoherence between photosphere and
chromosphere.
