  We use broadband sensitive LOFAR observations in the 25-80 MHz frequency
range to study the single-pulse emission properties of the mode-switching
pulsar B0943+10. We review the derivation of magnetospheric geometry,
originally based on low-frequency radio data, and show that the geometry is
less constrained than previously thought. This may be used to help explain the
large fractional amplitudes of the observed thermal X-ray pulsations from the
polar cap, which contradict the almost aligned rotator model of PSR B0943+10.
We analyse the properties of drifting subpulses in the Bright mode and report
on the minutes-long variations of the drift period. We searched for the
periodic amplitude modulation of drifting subpulses, which is a vital argument
for constraining several important system parameters: the degree of aliasing,
the orientation of the line-of-sight vector with respect to magnetic and spin
axes, the angular velocity of the carousel, and thus, the gradient of the
accelerating potential in the polar gap. The periodic amplitude modulation was
not detected, indicating that it may be a rare or narrow-band phenomenon. Based
on our non-detection and review of available literature, we chose to leave the
aliasing order unconstrained and derived the number of sparks under different
assumptions about the aliasing order and geometry angles. Contrary to the
previous findings, we did not find a large (of the order of 10%) gradual
variation of the separation between subpulses throughout Bright mode. We
speculate that this large variation may be due to the incorrect accounting for
the curvature of the line of sight within the on-pulse window. Finally, we
report on the frequency-dependent drift phase delay, which is similar to the
delay reported previously for PSR B0809+74. We provide a quantitative
explanation of the observed frequency-dependent drift phase delay within the
carousel model.
