| K | Temperature in Kelvin unit |
| ES | Electric field inside the streamer channel |
| N | Molecular number density at altitude h |
| Δ | Scaling factor of the order of 7 km |
| h | Altitude above the round |
| RS | Radius of spherical streamer head |
| lρ | Thickness of space charge region |
| Emax | Maximum electric field at the head of streamer |
| n | A factor varying between 2 - 4 |
| LS | Length of streamer |
| UC | Cloud potential |
| UL | Leader tip potential |
| UO | Potential of leading front of streamer zone |
| R | Radius of spherical irregularity |
| ε0 | Permittivity of free space |