High-precision Calibration of the Fluxgate Magnetometer Offset Vector in the Terrestrial Magnetosheath

Abstract

High-precision magnetic field measurements are of great significance for the in-depth study of the physical processes in the astrophysical plasma environment. To obtain accurate natural magnetic fields, in-flight calibration is one key step to obtaining zero offset of the spaceborne fluxgate magnetometer (FGM). Mirror mode structures, widely existing in the solar wind and planetary magnetosheaths and magnetospheres, can be used to calculate the zero offset. However, it is difficult to obtain an accurate zero offset by the current methods using mirror mode structures in the planetary magnetosheath. Here, we develop a new method to calculate the zero offset of the spaceborne FGM using magnetic dips, which are a kind of mirror mode structure. This method is based on the assumption that the magnetic field is zero in the cross section of the magnetic dip. Our method is able to calculate the zero offset using only one magnetic dip. We test this method by using the data from the Magnetospheric Multiscale Mission, and find that the calculation errors of 78.1% of the estimated zero offsets are <0.5 nT when using 25 magnetic dips in the terrestrial magnetosheath. This suggests that our method is able to achieve a high accuracy of the zero offset in the planetary magnetosheath.

A New Method of Fluxgate Magnetometer Offset Vector Determination in the Solar Wind Using Any Magnetic Field Variations

“…The offset cube is created according to the possible range of the IMF strength at a certain heliocentric distance (Wang & Pan 2021a). Wang & Pan (2021a, 2022 developed a series of methods to find the most likely value of the zero offset in the offset cube based on properties of Alfvén waves, mirror mode structures, or current sheets. Our method is also designed to find the most likely value of the zero offset in the offset cube based on the statistical properties of the IMF variation events as shown in Figure 3.…”

“…Recently, four methods have been developed to determine the zero offset without the derived formula by using Alfvén waves, mirror mode structures, and current sheets, respectively (Wang & Pan 2021a, 2022Wang 2022). The authors first created an offset cube according to the possible range of the IMF strength.…”

“…Assuming that the magnetic field strength is zero along the normal direction of current sheets, the most likely value of the zero offset is found to be in a plane, which is defined as the optimal offset plane (OOP; Wang & Pan 2022). At least two nonparallel OOLs or three nonparallel OOPs can be used to determine the zero offset (Wang & Pan 2021a, 2022. The methods developed by Wang & Pan (2021a, 2022 can simultaneously use Alfvén waves, mirror mode structures, and current sheets to determine the zero offset.…”

“…At least two nonparallel OOLs or three nonparallel OOPs can be used to determine the zero offset (Wang & Pan 2021a, 2022. The methods developed by Wang & Pan (2021a, 2022 can simultaneously use Alfvén waves, mirror mode structures, and current sheets to determine the zero offset.…”

“…So far, all the methods of calculating the zero offset have been based on properties of Alfvén waves, mirror mode structures, or current sheets (Davis & Smith 1968;Belcher 1973;Hedgecock 1975;Plaschke & Narita 2016;Plaschke et al 2017;Wang & Pan 2021a, 2022Cheng et al 2022). If not enough Alfvén waves, mirror mode structures, or current sheets are detected in the solar wind in a certain interval, all these methods will fail to determine the zero offset.…”