The Hermean magnetosphere and its ionosphere-magnetosphere coupling

A short review is given of major features of the magnetosphere of planet Mercury. Beside its weak surface magnetic field, its slow rotation rate, and close proximity to the Sun, Mercury differs from other planets due to its rather tenuous atmosphere. This causes interesting possible effects coneerning ionosphere-magnetosphere coupling and substorm development. Based on a first simplified model it is hypothesized that this development is hampered by unfavourable ionosphere/surface conditions leading to a quasi-periodic intermittent behaviour.