Frequently Asked Questions

Understanding the science behind Earth's electromagnetic resonances.

What are Schumann resonances?

Electromagnetic standing waves in the cavity formed between Earth's surface and the ionosphere at approximately 60 km altitude. Lightning strikes excite resonance modes at predictable frequencies, starting at the fundamental 7.83 Hz with harmonics at 14.3, 20.8, 27.3, and 33.8 Hz. First predicted by physicist W.O. Schumann in 1952 and experimentally confirmed in 1954.

What does a frequency shift mean?

A deviation from the ~7.83 Hz fundamental indicates changes in the ionospheric cavity geometry. Solar radiation, geomagnetic storms, and seasonal effects alter ionospheric height and conductivity, pushing the resonance frequency up or down. Rapid fluctuations often correlate with intense global lightning bursts, while sustained drifts suggest prolonged upper-atmosphere disturbances.

Why does the amplitude change throughout the day?

Amplitude reflects signal power, driven by global thunderstorm intensity. Earth hosts approximately 2,000 simultaneous thunderstorms producing around 50 flashes per second. As the planet rotates, three major tropical centers -- Africa (~15:00 UTC), South America (~20:00 UTC), and Southeast Asia (~08:00 UTC) -- cycle through peak activity, creating a clear diurnal pattern.

What does Q-factor tell us about Earth's cavity?

The quality factor measures how efficiently the cavity stores energy -- how sharply the peaks are defined. Nominal values of 4 to 8 for the fundamental indicate healthy conditions. A drop means more energy dissipation from increased ionospheric conductivity. Higher Q means cleaner, more defined resonance peaks.

How do I read the spectrograms?

Time runs along the horizontal axis (UTC). Frequency is on the vertical axis (Hz). Color intensity represents signal power -- brighter means stronger. Horizontal bands near 7.83, 14.3, and 20.8 Hz are the resonance modes. Look for consistent, well-spaced bright bands as a sign of healthy cavity conditions.

What are the five harmonic modes?

The Earth-ionosphere cavity supports multiple standing wave patterns: 1st (fundamental) at 7.83 Hz, 2nd at 14.3 Hz, 3rd at 20.8 Hz, 4th at 27.3 Hz, and 5th at 33.8 Hz. Each represents a different standing wave around Earth's circumference. Higher modes are progressively weaker and more sensitive to disturbances.

What are the practical applications of monitoring?

Schumann monitoring provides a continuous, global-scale diagnostic. Researchers use it to study climate patterns through thunderstorm activity, solar-terrestrial interactions, ELF radio propagation, and as a natural calibration reference. It also provides early indicators of large-scale ionospheric disturbances.

Where does this data come from?

Ground-based ELF sensors continuously record the 3 to 60 Hz band. The spectrograms displayed here are generated from raw sensor data and refresh every two minutes. All timestamps use Coordinated Universal Time (UTC).