  We use the multi-spacecraft capabilities of the Cluster and THEMIS missions
to show that two types of foreshock may be detected in spacecraft data. One is
the global foreshock that appears upstream of the Earth's quasi-parallel
bow-shock under steady or variable interplanetary magnetic field. Another type
is a traveling foreshock that is bounded by two rotational discontinuities in
the interplanetary magnetic field and propagates along the bow-shock. Foreshock
compressional boundaries are found at the edges of both types of foreshock. We
show that isolated foreshock cavities are a subset of the traveling foreshock
that form when two bounding rotational discontinuities are so close that the
ultra-low frequency waves do not develop in the region between them. We also
report observations of a spontaneous hot flow anomaly inside a traveling
foreshock. This means that other phenomena, such as foreshock cavitons, may
also exist inside this type of foreshock. In the second part of this work we
present statistical properties of phenomena related to the foreshock, namely
foreshock cavities, cavitons, spontaneous hot flow anomalies and foreshock
compressional boundaries. We show that spontaneous hot flow anomalies are the
most depleted transient structures in terms of the B-field and plasma density
inside them and that the foreshock compressional boundaries and foreshock
cavities are closely related structures.
