Solar-generated disturbances in the heliosphere
It has long been known that disturbances can propagate from Sun to Earth with periods of a few days following large solar flares. Other disturbances re-occur with the solar rotation rate implying that they are more or less stably generated by a specific region on the solar surface. At the Sun some of these disturbances are readily observed in coronagraphs and against the solar disk. Several techniques have been used to remotely detect and follow different disturbances in the interplanetary medium as they propagate outward from the Sun. These techniques include interplanetary scintillation, kilometric radio and Helios photometer observations. In situ, spacecraft can mark the passage of disturbances by direct measurement along the column convected past the observation point. As probes of the heliospheric magnetic field and disturbances in themselves, particles above the energy of the thermal plasma traverse the heliosphere and indicate the extent of its structures. Both the basic physics, as well as the spatial and temporal evolution of disturbances, can be confused as they propagate through the interplanetary medium largely because of the data coverage limitations. However, as their basic physics becomes better known through more complete observations and theory, the extent and accuracy of these disturbances can be better described.