Lightning spectrum

[Bajastro]

Strong storms are rolling over Poland, causing fear and destruction, one of such storms took place on July 13, 2024 at night in the Lodz Voivodeship.
It so happened that for about 2 years, when there is a chance of a thunderstorm at night with lightning, I have been using the spectrograph Low Spec 2 with ZWO ASI533MC Pro camera to record spectra,
I put it by the window and go to sleep, hoping that something will register.
I used a color camera for slit spectroscopy. Unfortunately, the QHY163M was a bit outdated and I sold it, and I haven't bought a new monochrome camera yet.

Finally, I found a sufficiently strong flash that allowed me to obtain a reasonable spectrum with a much larger signal than generated by urban light pollution (urban LED-sodium glow).
Nothing special, the discharge leads to the ionization of air molecules and their glow, and since air is mainly nitrogen (78%) and oxygen (21%), the emission lines come from them.
Hydrogen emission lines are very interesting, as there is not much of it in the air (only 0.00005%).

The spectrum was calibrated and I was able to remove almost all the light pollution. Spectral calibration is approximate. I used the solar spectrum to calibrate the instrumental response.

Also interesting is the strong CN emission line with a maximum at 388.3 nm in the far violet, already at the edge of the visible range.
Before calibrating the device's sensitivity, it didn't seem that strong.
In one of the publications I found the following explanation:

Source: Orville, R. E.; Henderson, R. W., 1984, Absolute Spectral Irradiance Measurements of Lightning from 375 to 880 nm.
This paper available online under the link:
https://journals.ametsoc.org/view/journals/atsc/41/21/1520-0469_1984_041_3180_asimol_2_0_co_2.xml

Websites mainly publish photos of spectra obtained with low-resolution diffraction gratings, which are placed in front of the camera lens.
I identified emission lines based on scientific literature from the 1970s and 1980s, and there is not much of it either.

Edited July 16 by Bajastro