1) One billionth of a tesla 
(from the article `geomagnetic field`) ...terms of the rate of change of potential, volts per metre (V/m). Magnetic fields are measured in units of tesla (T). The tesla is a large unit for ...
nanotesla One billionth (10-9) of a tesla. The tesla (symbol T) is the SI derived unit of magnetic flux density (or magnetic induction). It is a unit that defines the intensity (density) of a magnetic field.
The international unit for measuring magnetic flux density.
one billionth of a tesla.