Plasma transport and acceleration in Mercury’s magnetosphere

This project is devoted to significantly increase the understanding of the plasma environment of one of the solar system’s least known objects: Mercury.

Mercury’s plasma environment is controlled mainly by the interaction between the solar wind, a stream of charged particles continuously emitted from the Sun, and Mercury’s internal dipole magnetic field.

This interaction creates a magnetosphere, similar to the magnetosphere of Earth but much smaller due to the weaker dipole magnetic field strength and the more extreme solar wind at its shorter distance to the Sun.

The smaller size results in a much more dynamic magnetosphere than that of Earth, where charged particles, plasma, is rapidly transported inside the system.

The transport can lead to either precipitation of matter onto the planetary surface, as Mercury lacks an atmosphere, or to the escape of matter from the system.Despite two previous missions to Mercury, MESSENGER and Mariner 10, we have not yet fully understood which acceleration processes that dominates the control the rapid transportation of plasma inside the different regions of the magnetosphere of Mercury.

In this project we will use the exciting new opportunity created by the European Space Agency’s and Japan Aerospace Exploration Agency’s BepiColombo mission, currently on its way to Mercury, to make a more detailed investigation of these acceleration and transport processes inside the dynamic magnetosphere of Mercury.BepiColombo has so far made two out of its six planned flybys of Mercury and will enter an orbit around Mercury in the end of 2026.

The mission is composed of two spacecraft, which both have extensive plasma instrumentation onboard that will make unprecedented measurements of the Hermean plasma environment.

In this project we will use the plasma particle and the plasma wave packages, which will provide the first ever in situ measurements of the direct DC electric fields.

The combination of these instruments will be invaluable as they are capable of directly measuring the properties that control the acceleration of charged particles, such as, e.g., electromagnetic convection, electric field structures, and waves of various types.

This will allow us to directly investigate what processes that dominate the control of the plasma transport within different regions of the magnetosphere, as well as if, and how, that shifts for different solar wind and solar radiation conditions present in the vicinity of Mercury.

We will combine these unprecedented measurements by BepiColombo, from its six flybys and its first year in orbit around Mercury, with the previous measurements by NASA’s MESSENGER mission. This will provide a fundamental insight into how the still quite unknown magnetosphere of Mercury works.