  We describe the detection, interpretation, and removal of the signal
resulting from interactions of high energy particles with the \Planck\ High
Frequency Instrument (HFI). There are two types of interactions: heating of the
0.1\,K bolometer plate; and glitches in each detector time stream. The
transient responses to detector glitch shapes are not simple single-pole
exponential decays and fall into three families. The glitch shape for each
family has been characterized empirically in flight data and these shapes have
been used to remove glitches from the detector time streams. The spectrum of
the count rate per unit energy is computed for each family and a correspondence
is made to the location on the detector of the particle hit. Most of the
detected glitches are from Galactic protons incident on the die frame
supporting the micro-machined bolometric detectors. In the \Planck\ orbit at
L2, the particle flux is around $5\,{\rm cm}^{-2}\,{\rm s}^{-1}$ and is
dominated by protons incident on the spacecraft with energy $>$39\,MeV, at a
rate of typically one event per second per detector. Different categories of
glitches have different signatures in the time stream. Two of the glitch types
have a low amplitude component that decays over nearly 1\,s. This component
produces excess noise if not properly removed from the time-ordered data. We
have used a glitch detection and subtraction method based on the joint fit of
population templates. The application of this novel glitch subtraction method
removes excess noise from the time streams. Using realistic simulations, we
find that this method does not introduce signal bias into the \Planck\ data.
