Measurements of atmospheric corona currents have been made for over 100 years to indicate the atmospheric electric field. Corona currents vary substantially, in polarity and in magnitude. The instrument described here uses a sharp point sensor connected to a temperature compensated bi-polar logarithmic current amplifier. Calibrations over a range of currents from textpm10 fA to textpm3 muA and across textpm20 textopenbulletC show it has an excellent logarithmic response over six orders of magnitude from 1 pA to 1 muA in both polarities for the range of atmospheric temperatures likely to be encountered in the southern UK. Comparison with atmospheric electric field measurements during disturbed weather confirms that bipolar electric fields induce corona currents of corresponding sign, with magnitudes $0.5 muA.
- atmospheric electricity, electric current measurement, electric field measurement