Overview
The Schumann resonance is measured with ground-based antennas that detect magnetic or electric fields in the ELF (Extremely Low Frequency) and VLF (Very Low Frequency) ranges. The raw signal is dominated by lightning; signal processing is used to extract the resonant peaks. Results are shown as spectrograms (frequency vs. time) or amplitude time series for the fundamental and harmonics.
VLF/ELF Antennas
Antennas for Schumann resonance are designed to be sensitive in the roughly 5–50 Hz range. Common setups include:
- Magnetic loop antennas (inductive sensors) that measure the time rate of change of the magnetic field
- Electric field antennas (e.g. long wires or capacitive sensors)
Sites are chosen to minimize man-made noise (power lines, industry, radio). The signal is global, so a single station can observe the worldwide resonance.
From Raw Data to Spectrograms
The raw voltage from the antenna is digitized and processed. Typical steps include:
- Filtering to restrict to the ELF band (e.g. 3–50 Hz)
- Spectral analysis (e.g. FFT) to get power vs. frequency
- Averaging over time to bring out the stable resonant peaks against lightning noise
Spectrograms plot frequency on one axis, time on another, and intensity (e.g. color). The Schumann peaks (7.83 Hz, 14.3 Hz, 20.8 Hz, …) appear as horizontal bands that vary in strength over hours and days.
Example Stations: Cumiana and Tomsk
- Cumiana (Italy) – A well-known VLF station that publishes Schumann resonance spectrograms and data. Often cited in public discussions of "live" Schumann data.
- Tomsk (Russia) – The Tomsk Observatory and related institutes provide long-term Schumann resonance measurements and research data.
Other stations exist in Poland, Japan, and elsewhere. Cosmic Radar uses Schumann data (including from such sources) in the daily report alongside the Kp index and space weather.
What the Data Show
Spectrograms show amplitude (and sometimes frequency) of the fundamental and first few harmonics. Spikes and sustained increases in amplitude are normal and usually reflect:
- Increased global lightning activity
- Ionospheric disturbances (e.g. from geomagnetic storms or solar flares)
They do not indicate a permanent change in Earth's "base frequency." For context, compare with the Kp index and space weather in the Cosmic Radar daily report.
Sources and further reading
- Cumiana VLF Station – Schumann spectrograms and real-time data
- NOAA Space Weather Prediction Center – Kp index and space weather
- INTERMAGNET – Global magnetometer network and data