Do cities have a unique magnetic pulse?

TL;DR

This study compares magnetic field patterns in Berkeley and Brooklyn, revealing distinct urban magnetic signatures and demonstrating methods to analyze and utilize urban magnetometry data for city characterization.

Contribution

It introduces a comparative analysis of urban magnetic fields using advanced magnetometry techniques and discusses potential applications of magnetometer networks for city magnetic field characterization.

Findings

Berkeley exhibits near-zero magnetic activity at night.

Brooklyn maintains magnetic activity during nighttime.

Cross-correlation and frequency analysis effectively extract urban magnetic signals.

Abstract

We present a comparative analysis of urban magnetic fields between two American cities: Berkeley (California) and Brooklyn Borough of New York City (New York). Our analysis uses data taken over a four-week period during which magnetic field data were continuously recorded using a fluxgate magnetometer of 70 pT/$\sqrt{\mathrm{Hz}}$ sensitivity. We identified significant differences in the magnetic signatures. In particular, we noticed that Berkeley reaches a near-zero magnetic field activity at night whereas magnetic activity in Brooklyn continues during nighttime. We also present auxiliary measurements acquired using magnetoresistive vector magnetometers (VMR), with sensitivity of 300 pT/$\sqrt{\mathrm{Hz}}$, and demonstrate how cross-correlation, and frequency-domain analysis, combined with data filtering can be used to extract urban magnetometry signals and study local anthropogenic activities. Finally, we discuss the potential of using magnetometer networks to characterize the global magnetic field of cities and give directions for future development.