nanoteslas

Nanotesla (symbol nT) is a unit of magnetic flux density in the International System of Units (SI). It equals one billionth of a tesla: 1 nT = 1 × 10^-9 T. The nanotesla is commonly used in geophysics and space physics to express relatively weak magnetic fields such as those encountered in the Earth’s magnetosphere and the solar wind.

Because 1 tesla is a large magnetic field, most natural terrestrial fields are measured in microteslas or nanoteslas. The Earth’s average magnetic field at the surface ranges from about 25 to 65 μT, which is 25,000 to 65,000 nT. Interplanetary magnetic-field strengths are typically a few nanoteslas, with variations tied to solar activity. The unit also facilitates reporting local field variations, such as diurnal changes or anomalies, on a convenient scale.

Measurement and instrumentation: Magnetic-field data are obtained with magnetometers that report in nanoteslas or fractions thereof. Fluxgate magnetometers commonly measure in the nT range, while optically pumped magnetometers can achieve high precision; more sensitive devices such as SQUIDs can reach pico- or femto-tesla levels, but are specialized.

Conversions: 1 μT = 1,000 nT, and 1 nT = 10^-5 gauss. The nanotesla is therefore a convenient scale for describing small magnetic fields in natural environments and in laboratory experiments.