Almost all information about the physics of the nucleus is based on deductions from observations of the coma and tails. It is well to keep in mind the hierarchy of events on which these deductions are based:
1. The material properties of the constituents of the nucleus and the detailed physical and chemical structure of the nucleus form the basis for the behavior of coma and tails.
2. Interaction of solar radiation with the surface of the nucleus determines the overall temporal development of the coma.
3. The subsequent interaction of solar radiation and solar wind with the coma determine the gross features of the tails.
4. Short term fluctuations primarily in the solar wind (and associated magnetic, field) cause disturbances of comparable duration observable mostly in the tail but also in the coma.