  LOFAR (the Low Frequency Array) is the largest radio telescope in the world
for observing low frequency radio emission from 10 to 240 MHz. In addition to
its use as an interferometric array, LOFAR is now routinely used to detect
cosmic ray induced air showers by their radio emission. The LOFAR core in the
Netherlands has a higher density of antennas than any dedicated cosmic ray
experiment in radio. On an area of $12 \mathrm{km}^2$ more than 2300 antennas
are installed. They measure the radio emission from air showers with
unprecedented precision and, therefore, give the perfect opportunity to
disentangle the physical processes which cause the radio emission in air
showers. In parallel to ongoing astronomical observations LOFAR is triggered by
an array of particle detectors to record time-series containing cosmic-ray
pulses. Cosmic rays have been measured with LOFAR since June 2011. We present
the results of the first year of data.
