24
2 Environment Analysis of Lunar Soft Landing Exploration
value macula over months in the solar proton event during the No. 19~23 solar
activity week. It is shown that the larger solar proton events (with higher proton flux)
often occur at the time of more intense solar activity (with more macula). Significant
correlation exists between the intensity/numbers of solar proton event and the solar
activity period. Around the peak year of solar activity, the number of solar proton
events may be as many as 10 times, while in the valley year of solar activity the
number of solar proton events may reduce to three or four times, or even less [6].
2.2.3 Plasma Environment in Lunar Orbit
While the Moon is orbiting the Earth in different phases, it is either inside or outside
the magnetic tail of Earth. The relationship between the orbit of the Moon and the
magnetic tail of the Earth is shown in Fig. 2.2. When the Moon is outside the magnetic
tail, it is exposed to the solar wind. The energy and component of particles are very
different under the plasma environment of the solar wind and the magnetic tail.
Orbit of Moon
Solar wind
Direction of Sun
Earth
Magnetic tail of Earth
Bow shock
Fig. 2.2 Relationship between the orbit of the Moon and the magnetic tail of the Earth
2 Environment Analysis of Lunar Soft Landing Exploration
value macula over months in the solar proton event during the No. 19~23 solar
activity week. It is shown that the larger solar proton events (with higher proton flux)
often occur at the time of more intense solar activity (with more macula). Significant
correlation exists between the intensity/numbers of solar proton event and the solar
activity period. Around the peak year of solar activity, the number of solar proton
events may be as many as 10 times, while in the valley year of solar activity the
number of solar proton events may reduce to three or four times, or even less [6].
2.2.3 Plasma Environment in Lunar Orbit
While the Moon is orbiting the Earth in different phases, it is either inside or outside
the magnetic tail of Earth. The relationship between the orbit of the Moon and the
magnetic tail of the Earth is shown in Fig. 2.2. When the Moon is outside the magnetic
tail, it is exposed to the solar wind. The energy and component of particles are very
different under the plasma environment of the solar wind and the magnetic tail.
Orbit of Moon
Solar wind
Direction of Sun
Earth
Magnetic tail of Earth
Bow shock
Fig. 2.2 Relationship between the orbit of the Moon and the magnetic tail of the Earth