  Flares and coronal mass ejections (CMEs) are important for the evolution of
the atmospheres of planets and their potential habitability, particularly for
planets orbiting M stars at a distance < 0.4 AU. Detections of CMEs on these
stars have been sparse, and previous studies have therefore modelled their
occurrence frequency by scaling up solar relations. However, because the
topology and strength of the magnetic fields on M stars is different from that
of the Sun, it is not obvious that this approach works well. We used a large
number of high-resolution spectra to study flares, CMEs, and their dynamics of
the active M dwarf star AD Leo. The results can then be used as reference for
other M dwarfs. We obtained more than 2000 high-resolution spectra (R~35000) of
the highly active M dwarf AD Leo, which is viewed nearly pole on. Using these
data, we studied the behaviour of the spectral lines Halpha , Hbeta , and He I
5876 in detail and investigated asymmetric features that might be Doppler
signatures of CMEs. We detected numerous flares. The largest flare emitted 8.32
x 10 31 erg in Hbeta and 2.12 x 10 32 erg in Halpha . Although the spectral
lines in this and other events showed a significant blue asymmetry, the
velocities associated with it are far below the escape velocity. Although AD
Leo shows a high level of flare activity, the number of CMEs is relatively low.
It is thus not appropriate to use the same flare-to-CME relation for M dwarfs
as for the Sun.

Solar and Stellar Astrophysics;Earth and Planetary Astrophysics