Gradually about all
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What color ball lightning has?
But whether is correct to ask the question on color of object which has only luminescent radiation, complex, almost casual chemical composition and relaxing energy release? For search of the answer let's turn to spectra of radiation of the fireballs being created by the electric discharge from a power main 380 V 50 Hz through a resonant series-tuner circuit. Spectra of discharges and afterglow plasma when using of electrodes of copper and aluminium (electrical wire), technical carbon and steel (a basis of a bass string) and also a spectrum of flash of aluminium powder (used for entering into a paint) are given below.
Spectral resolution is small - in middle of an optical band about angstroem unit, falls to UV and with reduction of brightness, it is connected to properties of camcoder DCR TRV-11E, its objective, the filter. For a line spectrum, excepting exact identification of lines, resolution is almost enough. Molecular rotational spectra are not resolved but whereas plasma is overcooled, i.e. has almost room temperature, features of vibrational-rotational bands are distinctly visible.
Time of recording of each spectrum is 20 ms, that allows to watch spectrum dynamics being divided into five - six stages at transitions between which the spectrum can transforms qualitatively :
At spectra the reference lines of helium-mercuric lamp are presented, lengths of waves of some of them are specified in nanometers. Slot of our spectrograph represented a gap about 1mm between two big metal thick sheets of the rectangular form and was removed from the graiting with a camcoder to 2-3 m, and discharges were carried out directly behind the slot. Therefore distribution of intensity of a spectrum line down a vertical reflects the corresponding distribution in the fireballs. It is useful considering spectra to play by brightness of the monitor .
It is thought that looking on these spectra the interested researcher intrigued in the Ball Lightning Mystery can compose own opinion on the second question or even on the first.
Copper electrodes
stage 2
stage 2
stage 3
stage 5
Fig. 1. Spectrum of the discharge and afterglow in an orange range. Reference lines: from the right - HeI 587,6 nm, more to the left - HgII 615 nm.
stage 5
Fig. 2. Spectrum of afterglow in orange and yellow ranges. Reference lines: - green HgI 546 nm, right yellow HgI 577nm, left yellow HgI 579,0 nm and 579,1 nm, orange-yellow HeI 587,6 nm.
stage 2
stage 3
stage 4
stage 4
stage 5
stage 6
stage 6
Fig. 3. Spectrum in a green and blue range. Reference lines from right to left: - HeII 468,6 nm, HeI и HgI 492 nm, HeI 501,6 nm, HgI 546 nm.
stage 1
stage 2
stage 3
stage 4
stage 5
Fig. 3. Spectrum in the nearest ultraviolet, violet and blue ranges. Reference lines from right to left: UV - HeI 389 nm, violet - HgI 404,7 nm, first blue - HgI 436 nm, second blue - HeI 447 nm, third blue - HeII 468,6 nm.
Spectra of discharges with aluminium
electrodes and afterglow (0,3 MB).