The Effects of Temperature and Thermal Gradients on Fluxgate Stability and Core Performance

Fluxgate magnetometers are an important tool for measuring space plasmas. Fluxgate instruments aboard recent magnetospheric missions have observed instrumental instabilities that have been attributed to changes in the fluxgate core's temperature as well as thermal shocks and gradients across the core and sensor. However, the underlying mechanisms of these instabilities are not clear, as several factors influence the on-orbit in-situ quality of fluxgate measurements. Here we present results of a laboratory experimental investigation of how thermal variations across a fluxgate core affect its measurement characteristics. Five simplified fluxgate sensors were constructed using racetrack geometry cores of varying permalloy material. These were tested using a purpose-built laboratory apparatus that allowed us to vary the sensor temperature and impose thermal gradients across each fluxgate sensor. We observe strong correlations between changes in temperature across the core and changes in gain, offsets, and instrumental noise. We find that stability over temperature varies with the permalloy material of the fluxgate core and suggest possible underlying mechanisms that cause these variations.