Null Results, Real Learning: Geomagnetic Response to an X1.8 Solar Flare with Research-Grade and Smartphone Magnetometers in a Citizen-Science Classroom Activity

TL;DR

This study evaluates the use of smartphone magnetometers in citizen science for monitoring geomagnetic responses during a solar flare, finding they are useful for education but lack the precision for scientific analysis.

Contribution

It demonstrates the potential of smartphones as accessible tools for space weather education and integrates them into a tiered scientific instrumentation framework.

Findings

Smartphone magnetometers show a bias of about 630 nT compared to research-grade sensors.

They lack the precision for detecting nanotesla-scale flare signatures.

Smartphones are valuable for pedagogical engagement and inquiry-based learning.

Abstract

Introductory college Earth and space science courses offer rich opportunities for citizen science projects. One especially compelling context is Earth's geomagnetic field: a self-excited dynamo in the liquid outer core generates a global field that couples Earth's interior to solar forcing, providing a natural laboratory for space weather education. We tested the viability of smartphone magnetometers for quantitative monitoring during the 4 November 2025 X1.8 solar flare, linking planetary magnetism, space weather, and authentic undergraduate research. Co-located observations were obtained with a Geometrics G-857 proton-precession magnetometer and tri-axial smartphone sensors logging via Physics Toolbox in a course-based undergraduate research experience (CURE) emphasizing the Nature of Science (NOS). Fourteen one-minute paired averages spanning 17:27-17:40 UT revealed a systematic smartphone bias of about 630 nT (95% confidence interval 550-710 nT) relative to the G-857 and a weak negative correlation (r ~ -0.4). Smartphone magnetometers thus lack the precision and calibration stability needed for nanotesla-scale flare signatures but remain valuable as pedagogical and engagement tools. We frame smartphones within a tiered instrumentation ladder linking research-grade observatories, intermediate-cost community magnetometers (for example, HamSCI Personal Space Weather Stations), and smartphones as high-engagement entry points to geomagnetic and space weather studies. This hierarchy aligns citizen science with open data protocols and NOS pedagogy, transforming low-cost sensing into epistemically grounded inquiry suitable for introductory college laboratories.