  A model for N2 triplet states band emissions in the Venusian dayglow has been
developed for low and high solar activity conditions. Steady state
photoelectron fluxes and volume excitation rates for N2 triplet states have
been calculated using the Analytical Yield Spectra (AYS) technique. Model
calculated photoelectron flux is in good agreement with Pioneer Venus
Orbiter-observed electron flux. Since inter-state cascading is important for
the triplet states of N2, populations of different levels of N2 triplet states
are calculated under statistical equilibrium considering direct electron impact
excitation, and cascading and quenching effects. Densities of all vibrational
levels of each triplet state are calculated in the model. Height-integrated
overhead intensities of N2 triplet band emissions are calculated, the values
for Vegard-Kaplan (A^3Sigma_u^+ - X^1Pi_g^+), First Positive (B^3Pi_g -
A^3Sigma_u^+), Second Positive (C^3Pi_u - B^3Pi_g), and Wu-Benesch (W^3Delta_u
- B^3Pi_g) bands of N2, are 1.9 (3.2), 3 (6), 0.4 (0.8), and 0.5 (1.1) kR,
respectively, for solar minimum (maximum) conditions. The intensities of the
three strong Vegard-Kaplan bands (0, 5), (0, 6), and (0, 7) are 94 (160), 120
(204), and 114 (194) R, respectively, for solar minimum (maximum) conditions.
Limb profiles are calculated for VK (0, 4), (0, 5), (0, 6) and (0, 7) bands.
The calculated intensities on Venus are about a factor 10 higher than those on
Mars. The present study provides a motivation for a search of N2 triplet band
emissions in the dayglow of Venus.
