Estimates of the Size of the Ionosphere of Comet 67P/Churyumov–Gerasimenko During Its Perihelion Passage in 2014/2015 - Planetary Exploration and Science: Recent Results and Advances - page 265

Chapter 10
Estimates of the Size of the Ionosphere of Comet
67P/Churyumov-Gerasimenko During Its
Perihelion Passage in 2014/2015

Wing-Huen Ip

Abstract The Rosetta mission will begin its comet rendezvous and lander mission
in mid 2014. The plasma instruments onboard Rosetta will provide detailed
measurements of the plasma environment of comet 67P/Churyumov-Gerasimenko
and its responses to solar wind interaction. In this chapter the basic scale lengths
connected to the dimension of the radial-expanding magnetic field-free ionosphere
and to the boundary separating photoelectrons cooled by collisional interaction
with water molecules, respectively, are explained. Their variations at different
heliocentric distances along the orbit of comet 67P are described. It is found that
the radii of the diamagnetic ionospheric cavity ( 35 km at perihelion) and that
of the cold photoelectron zone ( 350 km at perihelion) are all much smaller than
those of comet Halley. These theoretical estimates will be tested by the upcoming
in situ plasma measurements and remote-sensing observations onboard the Rosetta
spacecraft.

Keywords Rosetta mission ￿ Comet 67P ￿ Solar wind interaction

10.1 Introduction

The Rosetta mission for comet rendezvous and nucleus landing measurements of
comet 67P/Churyumov-Gerasimenko provides a unique opportunity to study the
structure, composition, and dynamics of the neutral gas, dust, and plasma emitted
from the nucleus surface. The Rosetta spacecraft will start to approach the target
comet after being successfully reactivated from deep-space hibernation on January
20, 2014. It will arrive at the flight-formation orbit around comet 67P in May in
preparation of the Philae lander deployment in November. After accomplishment of