Subauroral red arcs as a conjugate phenomenon: comparison of OV1-10 satellite data with numerical calculations

Abstract

Abstract. This study compares the OV1-10 satellite measurements of the integral airglow intensities at 630 nm in the SAR arc regions observed in the northern and southern hemisphere as a conjugate phenomenon, with the model results obtained using the time-dependent one-dimensional mathematical model of the Earth ionosphere and plasmasphere (the IZMIRAN model) during the geomagnetic storm of the period 15±17 February 1967. The major enhancements to the IZ-MIRAN model developed in this study are the inclusion of He ions (three major ions: O , H , and He , and three ion temperatures), the updated photochemistry and energy balance equations for ions and electrons, the di usion of NO and O 2 ions and O 1 D and the revised electron cooling rates arising from their collisions with unexcited N 2 Y O 2 molecules and N 2 molecules at the ®rst vibrational level. The updated model includes the option to use the models of the Boltzmann or nonBoltzmann distributions of vibrationally excited molecular nitrogen. Deviations from the Boltzmann distribution for the ®rst ®ve vibrational levels of N 2 were calculated. The calculated distribution is highly nonBoltzmann at vibrational levels v b 2 and leads to a decrease in the calculated electron density and integral intensity at 630 nm in the northern and southern hemispheres in comparison with the electron density and integral intensity calculated using the Boltzmann vibrational distribution of N 2 . It is found that the intensity at 630 nm is very sensitive to the oxygen number densities. Good agreement between the modeled and measured intensities is obtained provided that at all altitudes of the southern hemisphere a reduction of about factor 1.35 in MSIS-86 atomic oxygen densities is included in the IZMIRAN model with the non-Boltzmann vibrational distribution of N 2 . The e ect of using of the O 1 D di usion results in the decrease of 4±6% in the calculated integral intensity of the northern hemisphere and 7±13% in the calculated integral intensity of the southern hemisphere. It is found that the modeled intensities of the southern hemisphere are more sensitive to the assumed values of the rate coe cients of O 4 S ions with the vibrationally excited nitrogen molecules and quenching of O 2 D by atomic oxygen than the modeled intensities of the northern hemisphere.

The role of vibrationally excited oxygen and nitrogen in the ionosphere during the undisturbed and geomagnetic storm period of 6-12 April 1990

“…The model used is an enhanced and updated version of the IZMIRAN model that we have steadily developed over the years (Pavlov, 1994a(Pavlov, , 1997Pavlov and Buonsanto, 1997). The chemistry, physics, and solution procedure have been described in detail by Pavlov (1994aPavlov ( , 1997 and hence only a brief description will be given here.…”

“…The chemistry, physics, and solution procedure have been described in detail by Pavlov (1994aPavlov ( , 1997 and hence only a brief description will be given here.…”

New electron energy transfer rates for vibrational excitation of N<sub>2</sub>

“…To simplify the problem, Stubbe (1971) and Stubbe and Varnum (1972) (Pavlov and Namgaladze, 1988;Pavlov, 1994aPavlov, , 1996Pavlov, , 1997Pavlov and Buonsanto, 1997). As a result, the collisions of thermal electrons with vibrationally unexcited N 2 yield the main contribution for the rate of electron energy loss associated with rotational transitions within N 2 v 0 and N 2 v b 0 , and the possible error or Eq.…”

“…(2) can be important for the calculation of v N 2 * and [in comparison with Eq. (1)] only for very high vib , which may be in the subauroral red arcs (Newton et al, 1974;Pavlov, 1989Pavlov, , 1997. If the number of vibrational level increases then 0v decreases for most values of e .…”

“…The number densities N 2 v 0 ) N 2 v b 0 during the undisturbed and geomagnetic storm periods at middle and subauroral latitudes (Pavlov and Namgaladze, 1988;Pavlov 1994aPavlov , 1996Pavlov , 1997Pavlov and Buonsanto, 1997). As a result, the collisions of thermal electrons with unexcited N 2 yield the main contribution to the electron cooling rate and the production frequency of the N 2 vibrational quanta arising from the collisions of thermal electrons with unexcited and vibrationally excited N 2 molecules (Pavlov, 1997). Therefore, in the present paper we restrict our discussion to the transitions from the ground v 0 and ®rst v 1 vibrational states of N 2 :…”