Comets: coma and beyond

  • Károly Szegö


There is no clear definition of what the coma of a comet is. Most frequently it means the faint visible halo around comets, and in other context it denotes material that reflects or emits electromagnetic radiation (including light) back to observers. In this chapter we shall use the word ‘coma’ to describe all materials around the cometary nucleus, solids and volatiles, neutral and charged, irrespective how effectively a certain component is able to scatter or emit radiation. The origin of the coma is the nucleus itself, and we shall discuss the processes that eject or emit materials from the surface to the cometary atmosphere and beyond.We consider only physical processes; coma chemistry is not the topic of this chapter. It is unavoidable to take into account in this context the structure and the physics of the cometary surface layer as well, because this is the source of the coma. Comets are believed to contain pristine materials from the period when the Solar System was born; the cometary surface, however, has been exposed to many perturbations (cosmic rays, solar wind, heat cycles, etc.) and it definitely cannot be considered as pristine. How deep we have to dig to find unprocessed material is an open question. There is only limited experimental evidence on surface evolution obtained in simulations, and we have to rely mostly on guesses.


Solar Wind Dust Particle Cometary Nucleus Solar Wind Flow Lower Hybrid Wave 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Kluwer Academic Publishers 2001

Authors and Affiliations

  • Károly Szegö
    • 1
  1. 1.Research Institute for Particle and Nuclear PhysicsBudapestHungary

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