Near infrared and ultraviolet spectra of TLEs

Abstract

[1] We have found that sprites, beads and halos have similar optical spectra, but measurable differences in the near IR and near UV spectra. In particular, near infrared (NIR) and ultraviolet (UV) spectra of sprites, halos and beads corresponding to the first (1PG) and second positive (2PG) bands of N 2 have been calculated for different observation altitudes from mountains (3.25 km) to airplanes (14 km), balloons (35 km) and space (nadir) platforms. The calculated non-equilibrium vibrational distribution functions (VDF) of the N 2 (B 3 P g ) states in halos and beads show that the calculated NIR emissions produced through strong N 2 -1PG (B 3 P g → A 3 S u + ) transitions differ from the calculated sprite spectral emission patterns at $888 nm but particularly pronounced differences are found in the NIR spectral region at $1046 nm and $1231 nm corresponding to the N 2 -1PG (0,0) and (0,1) transitions, respectively. The blue -near UV spectra from N 2 -2PG (C 3 P u → B 3 P g ) transitions in halos and beads also exhibits slightly different spectral features when compared to the blue -near UV spectrum of sprites for bands originating from higher v-levels (v > 0) although they might not be above electronic noise level to be distinguished.

Spectroscopic diagnostics of laboratory air plasmas as a benchmark for spectral rotational (gas) temperature determination in TLEs

“…We have represented in Figure the VDF of N 2 ( B 3 Π g ) experimentally derived from the N 2 1PG 53 km sprite emission spectra [ Bucsela et al , ; Kanmae et al , ], and 74 km emission spectra [ Kanmae et al , ], from model calculations for halos and sprites [ Gordillo‐Vázquez , ; Luque and Gordillo‐Vázquez , ; Gordillo‐Vázquez et al , ; Gordillo‐Vázquez et al ] and from the present hollow cathode discharges in air. Figure a shows the VDF of N 2 ( B 3 Π g ) obtained from N 2 1PG sprite emission spectra recorded at low altitude (53 km) or relatively high pressure (≃ 1 mbar).…”

“…The intensity of the (1,0) band is almost a factor of two higher than the (2,1) band intensity in the 53 km sprite spectrum (dashed line), while it is 40 % lower in the lab HC spectrum (solid line). In Figure b we see a comparison between the VDF of N 2 ( B 3 Π g ) recorded from sprite instrument corrected N 2 1PG emission spectra at 74 km using Δ λ =3 nm [ Kanmae et al , ], from a kinetic model (assuming T R =220 K) to predict the VDF of N 2 ( B 3 Π g ) in sprites and halos at, respectively, 74 and 80 km [ Luque and Gordillo‐Vázquez , ; Gordillo‐Vázquez et al , ; Gordillo‐Vázquez et al , ] and from the N 2 ( B 3 Π g ) 1PG spectrum of a hollow cathode air discharge generated at 0.11 mbar (≃ 70 km) recorded with Δ λ =2 nm. The agreement between the experimentally recorded VDF of sprites at 74 km [ Kanmae et al , ] and the model predicted VDF of sprites and halos is now more evident, while at 0.11 mbar, the discrepancy with the VDF ( v ′ =1) obtained from emission spectra recorded in hollow cathode discharges persists.…”

“…(a) A comparison of the VDF of N 2 ( B 3 Π g ) derived from the N 2 1PG instrument corrected sprite emission spectrum at 53 km (≃ 1 mbar) using Δ λ =7 nm [ Bucsela et al , ] and Δ λ =3 nm [ Kanmae et al , ], from the N 2 1PG spectrum of a hollow cathode air discharge generated at 1 mbar (≃53 km) recorded with Δ λ =2 nm and from a kinetic model to predict the VDF of N 2 ( B 3 Π g ) in sprites at 74 km [ Luque and Gordillo‐Vázquez , ; Gordillo‐Vázquez et al , ; Gordillo‐Vázquez et al , ]. (b) A comparison between the VDF of N 2 ( B 3 Π g ) recorded from the instrument corrected N 2 1PG sprite emission spectra at 74 km using Δ λ =3 nm [ Kanmae et al , ], from a kinetic model to predict the VDF of N 2 ( B 3 Π g ) in sprites and halos at, respectively, 74 and 80 km [ Luque and Gordillo‐Vázquez , ; Gordillo‐Vázquez et al , ; Gordillo‐Vázquez et al , ] and from the N 2 1PG spectrum of a hollow cathode air discharge generated at 0.11 mbar (≃70 km) recorded with Δ λ =2 nm. The VDF is normalized to the sum of the populations from v ′ =2 to v ′ =6.…”

“…(a) A comparison of the instrument corrected N 2 1PG spectra recorded from sprites at 53 km using Δ λ =3 nm (circles) [ Kanmae et al , ] and Δ λ =7 nm (blue dashed line) [ Bucsela et al , ], from a laboratory hollow cathode air discharge (green solid line) generated at 1 mbar (≃53 km) recorded with Δ λ =2 nm and a transmission corrected synthetic sprite spectrum (dotted line) for a sprite at 74 km calculated with a kinetic model of sprites and halos assuming Δ λ =3 nm [ Gordillo‐Vázquez et al , ]. (b) The spectral fit (blue dashed line), using T gas =385 K, to the N 2 1PG spectrum recorded in a hollow cathode air discharge generated at 0.11 mbar (≃70 km) recorded with Δ λ =2 nm.…”

“…The resulting VDFs were compared with those recorded for sprites by, respectively, Bucsela et al [] at 53 km and Kanmae et al [] at 53 and 74 km. In addition, we will compare present VDF laboratory results with available sprite and halo VDF model predictions [ Gordillo‐Vázquez , ; Luque and Gordillo‐Vázquez , ; Gordillo‐Vázquez et al , ; Gordillo‐Vázquez et al , ] where a gas temperature of 220 K is assumed.…”