Tuesday 1 March 2022
A team of Russian scientists has developed a mathematical model that explains the height of charged dust particles above the sunlit surface of the moon at almost any latitude.
For the first time, the model takes into account Earth’s magnetic tail, a region formed by the pressure that the solar wind creates on the planet’s magnetosphere.
In the research paper published in Physics of Plasmas, scientists from the National Research University Graduate School of Economics (HSE) point out that the research data is important for planning the Luna-25 and Luna-27 space missions.
In space, the Moon is surrounded by plasma (ionized gas), which contains dust particles of solid matter. On the moon, dust particles affected by solar wind photons, electrons and ions acquire a positive charge.
Its interaction with the surface of the moon with a positive charge causes it to bounce, move, and form dusty (dusty) plasma.
Given these factors, scientists may assume that dusty lunar plasma develops only over part of the lunar surface (around latitudes above 76 degrees).
But dusty plasma is expected to be observed over the entire sunlit part of the Moon.
The study authors developed a physical-mathematical model of dust plasma motion in which the influence of the Earth’s magnetic tail plays an important role.
The Earth’s magnetosphere develops due to the interaction of the planet’s magnetic field with charged particles from space. For example, solar wind particles deviate from their initial path and form a region around the planet affected by the magnetic field.
It is noteworthy that the magnetic field is asymmetric: on the day side, it reaches 8-14 the size of the radius of the Earth, and on the night side, it expands and forms a magnetic tail several hundred radii long.
During regarding a quarter of its orbit, the Moon is in the Earth’s magnetic tail, which affects the movement of particles along the meridian: they are affected by the magnetic field, and begin to move from the polar region to the equator.
The particles are also affected by gravity and electrostatic forces, so that the first attracts the grain of dust to the surface, while the other side repels it. This results in a vertical oscillation of the particles.
Then, the particles move to a hovering state. Scientists explain this effect by the long days of the sun on the moon: approximately 15 Earth days.
During this time period, the particle oscillation process fades away, and they have enough time to transition into levitation.
According to the team, opposite phenomena were also observed. For example, on the moons of Mars, Phobos and Deimos, dust grains have a longer demise time than daylight, which is why there is not enough time to transition to a hover state.
“The Luna-25 and Luna-27 missions are in preparation today, and they will study the properties of dust and dusty plasma near the lunar surface. To make it successful, preliminary research is necessary,” explains Sergey Poppel, Head of the Laboratory for Dusty Plasma Operations in Space Objects, RAS Space Research Institute. Today we have used a simplified approach to explain the transmission of dust over the lunar surface taking into account the magnetic fields in the Earth’s magnetic tail.In future studies, it will be necessary to take into account the axial tilt and the inclination of the orbit to the ecliptic plane of the Earth and the Moon, as well as to consider more accurate parameters of the tail plasma. Magnetic”.
