The Solar Orbiter Magnetometer Instrument: In-flight Performance

Abstract:

The magnetometer (MAG) instrument on Solar Orbiter is providing essential information about the largest scale structures in space around the Sun, as well as the smallest scale kinetic processes in the plasma. The magnetic field plays a central role in plasma dynamics since charged particles generally travel along the magnetic field, making it the route from the Sun into space. The accurate measurement of the local magnetic field is therefore central to the scientific success of Solar Orbiter. Magnetometer data are expected to lead to significant advances in our understanding of how the Sun’s magnetic field links into space and evolves over the solar cycle; how particles are accelerated and propagate around the solar system, including to the Earth; and how the corona and solar wind are heated and accelerated, among many others.

In order to achieve these objectives, the magnetometer is operating continuously to quantify fluid-scale phenomena throughout the mission and, for around 3 hours each day in burst mode, to study ion kinetic phenomena. MAG is a conventional dual fluxgate instrument which measures the magnetic field in the vicinity of the spacecraft. Both sensors are mounted on the instrument boom in shadow, removed from the spacecraft body so as to reduce the effects of artificially-induced magnetic fields: however with 9 other instruments, and the relatively compact size of the spacecraft, artificial signals are generated.

MAG was commissioned on 24 February 2020 and has largely been running continuously ever since. From the 24 February, to the end of spacecraft commissioning on June 14 2020, MAG was producing science data continuously in burst mode at 128Hz cadence from both the outboard and inboard sensors: this data set has been invaluable for characterising the spacecraft magnetic signature, but also provides a wealth of science phenomena from CMEs to shocks and whistler waves. Since the start of the cruise phase, MAG has operated continuously with 8Hz data from both sensors. We present the data set provided so far, comparing the performance of the instrument in flight to the performance measured on ground and summarising the main findings with respect to the magnetic signature of the spacecraft and ongoing work into magnetic contamination removal algorithms used to prepare the data for full scientific exploitation.