Previously, we presented a picture showing that the magnetometer readings experienced a sudden drop in early 2019. Some may have interpreted that as a “collapse of the magnetic field.” However, we have determined the actual cause.
We found a strong correlation between satellite altitude and the magnetometer reading, so we used some simple AI to remove the effect of the changes in altitude, which explained all of the “apparent drop.” The blue line shows the altitude of the satellite. The red line is a smoothed reading of the raw magnetometer field strength data (block dots are raw.) As the satellites get further from the earth, the magnitude drops. The black line represents a corrected magnitude after subtracting the influence of the spacecraft’s height, which yields a relatively stable magnetic field through the period.