Utforskning av bogchocksprocesser på Merkurius dagsida med BepiColombo

Mercury is the innermost of the terrestrial planets, and has, in contrast to Venus and Mars, an intrinsic magnetic field.

However, the much weaker planetary magnetic dipole moment compared to Earth, and the higher solar wind density at Mercury’s orbit results in a much smaller, and more dynamic system than Earth’s magnetosphere.

Similar to Earth, Mercury’s interaction with the solar wind results in a bow shock, where the solar wind brakes, and is compressed and heated, forming the magnetosheath region, which further interacts with the planetary magnetic field, forming the magnetosphere.

Many aspects of the Mercury bow shock and associated phenomena are still poorly understood, due to a lack of investigations with a complete plasma physics instrumentation.The general goal of this study is to investigate how processes at the dayside bow shock of Mercury contribute to forming the space environment around the innermost planet of the solar system.

In order to do this we will use data from the BepiColombo mission, which is the first mission to orbit Mercury with a comprehensive plasma physics payload.

We will investigate and answer the following science questions (SQ):SQ 1: What are the properties of the Mercury foreshock, and how does it compare to other planetary foreshocks?Part of the solar wind population is reflected at planetary bow shocks and can travel far upstream, especially at the quasi-parallel part of the shock.

This triggers to ultra-low frequency (ULF) waves and short large-amplitude magnetic structure (SLAMS), which may further interact with the bow shock.

The properties of these phenomena and their role in the low Mach number environment of Mercury are not well known.SQ 2: Does the Mercury bow shock generate energized ion populations?To what energies are ions accelerated at the Mercury bow shock? Does this depend on the angle between the interplanetary magnetic field to the bow shock normal?

What is the role of SLAMS?

The answer to these questions will give clues on what mechanism is mainly responsible for the energization.SQ 3: What are downstream consequences of Mercury bow shock processes?The Mercury magnetic field and magnetosphere does not interact directly with the solar wind, but with the shocked magnetosheath plasma.

Recently it has been realized that at Earth this may include interaction with coherent structures in the magnetosheath, such as magnetosheath jets, and transmitted ULF waves and SLAMS.

These structures are likely created at the bow shock and represents a new type of bow shock mediated solar wind interaction. It is unclear if similar effects are important at Mercury.

An open question is also if the high-energy ions created at the bow shock propagate downstream.SQ 4: What is the role of the electric field in bow shock related processes at Mercury?The electric field plays a fundamental role in plasma physical processes, it is e.g. the ultimate agent responsible for particle energization, and carries much information of the properties of plasma waves.

With the first ever electric field measurements at Mercury, we will be in a unique position to investigate the role of the electric field in the processes involved in the other Science Questions.Answering these questions will give new information about the dayside space environment around Mercury, as well as insight into the processes available for their creation.

Investigations in a different paramer regime than at Earth, will also help testing our understanding of similar phenomena at our home planet.This project will be implemented as a PhD project, where a PhD student will be hired for a period of four years.

The Science Questions will be addressed in four Work Packages, with two additional Work Packages devoted to preparation for the science phase, and writing the introduction to the PhD thesis. A time plan, as well as other details on the PhD position, is presented.