LAUSR

In this paper, recent comparison tests are performed on smartphone magnetometer “apps” with a view toward their suitability for detecting and measuring magnetic storm events. Although the iPhone and Samsung smartphone magnetometer sensors in this study have a nominal sensitivity of ±150 nT, this “digitization” noise level is not a Gaussian process and cannot be further reduced by co-adding more measurements to obtain $\surd \text{N}$ improvements. Moreover, there are a variety of systematic effects including apparently uncontrollable glitches and “dc” baseline changes that have amplitudes of ±2000 nT during long-term measurement operations. These systematic variations appear to mask the detection of all but the strongest geomagnetic storms with K > 8. It is possible that other existing smartphones outside this study have improved magnetic sensors, and that future improvements in sensor design may change these conclusions, so a continued study of this issue is warranted.