nT

nT, short for nanoTesla, is a unit of magnetic flux density in the International System of Units (SI). It equals 10^-9 tesla, or one-billionth of a tesla. The tesla is the SI unit for magnetic flux density, and the nanoTesla is used for measurements that involve relatively small magnetic fields, such as those encountered in geophysics and magnetometry.

In practice, magnetic field strengths at the Earth's surface are typically expressed in nanoteslas. The field strength varies by location and time, commonly ranging from about 25,000 to 65,000 nT. Magnetometers and related instruments used in geophysics, space science, and biology often report measurements in nanoteslas to reflect these magnitudes.

Conversions and relationships: 1 nT = 1 × 10^-9 T; 1 µT (microtesla) = 1,000 nT, so 1 nT = 0.001 µT; and since 1 T = 10,000 gauss, 1 nT equals 10^-5 gauss. The nanoTesla is therefore convenient for describing small magnetic fields without resorting to many orders of magnitude in either direction.

Notes: nT is a standard SI-prefixed unit and is typically written with a lowercase n and uppercase T. It is widely used in geoscience, space physics, and related fields to express magnetic field measurements with appropriate precision.