- Email: [email protected]
Spectral synthesis of the O2+ 1NG bands observed in aurora
Research notes Kisabeth, J. L. and Rostoker, G. (1974). The expansive phase of magnetospheric substorms 1. Development of the amoral electrojets and auroral arc configuration during a substorm. J. geophys. Res. 79, 972. Konradi, A. (1967). Proton events in the magnetosphere associated with magnetic bays. .I. geophys. Res. 72, 3829. Lanzerotti, L. J. (1968). Comparison of the electron response in the magnetosphere at L = 5 with the solar wind during the April 17-18, 1965, magnetic storm. .I. geophys. Res. 73, 438. Lezniak, T. W. and Winckler, J. R. (1970). Experimental study of magnetospheric motions of energetic electrons during substorms. J. geophys. Res. 75,7075. Lin, R. P., Meng, C.-I. and Anderson, K. A. (1974). 30 to 100 keV protons upstream from the Earth’s bow shock. J. geophys. Res. 79, 489. Meng, C.-l. and Anderson, K. A. (1971). Energetic electrons in the plasma sheet out to 40 RE. J. geophys. Res. 76, 873. Mozer, F. S. and Manka, R. H. (1971). Magnetospheric electric field properties deduced from simultaneous balloon flights. ?. geophys. Res. 76, 1697. Muravama, T. and Simpson, J. A. (1968). Electrons within the neutral sheet of the magnetospheric tail. .I. geophys. Res. 73, 891. Ness, N. F., Behannon, K. W., Lepping, R. P., Whang, Y. C. and Schatten, K. H. (1974). Magnetic field observation near Mercury: Preliminary results from Mariner 10. Science 185, 151. Nishida, A. (1976). Outward diffusion of energetic particles from the Jovian radiation belt. J. geophys. Res. 81, 1771. Nishida, A. and Hones, E. W., Jr. (1974). Association of plasma sheet thinning with neutral line formation in the magnetotail. J. geop&ys.Res. 79, 535. Nishida. A. and Naeavama, N. (1973). Svno~tic survey for the neutral line h the magneto&l &r&g the sub: storm expansion phase. J. geophys. Res. 78, 3782. Parker, E. N. (1960). Geomagnetic fluctuations and the form of the outer wne of the Van Allen radiation belt. J. geophys. Res. 65, 3117.
Planet.
Space Sci., Vol. 24. pp.
SPECTRAL
999
to 1001.
Pergamon
SYNTHESIS
Press,
1976. Printed
OF THE
0,’
999
Parks, G. K., Amoldy, R. L., Lezniak, T. N. and Winckler. J. R. (1968). Correlated effects of energetic electrons at the 6.6 & equator and the auroral z&e during magnetospheric substorms. Radio Sci. 3, 715. Retzler, J. and Simpson, J. A. (1969). Relativistic electrons confined within the neutral sheet of the geomagnetic tail. J. geophys. Res. 74, 2149. Roederer, J. G. and Hones, E. W., Jr. (1974). Motion of magnetospheric particle clouds in a time-dependent electric field model. J. geophys. Res. 79, 1432. Sarris, E. T., Krimigis, S. M. and Armstrong, T. P. (1976). Observations of magnetospheric bursts of high energy protons and electrons at 35 RE with IMP-7. .I. geophys. Res. 81, 2341. Scarf, F. L., Frank, L. A., Ackerson, K. L. and Lepping, R. P. (1974). Plasma wave turbulence at distant crossing of the plasma sheet boundaries and at the neutral sheet. Geophys. Res. L&t. 1,189. Sentman, D. D. and Van Allen, J. A. (1975). Recirculation of energetic particles in Jupiter’s magnetosphere. Geophy; Res. ken. 2, 465. _ Simuson. J. A.. Eraker, J. H., Lamuort, J. E. and Walpole, P. H. (1974). Electrons and protons accelerated in Mercury’s magnetic field. Science 185, 160. Siscoe, G. L., Ness, N. F. and Yeates, C. M. (1975). Substorms on Mercury? J. geophys. Res. 80, 4359. Speiser, T. W. (1967). Particle trajectories in model current sheets. 2. Applications to auroras using a geomagnetic tail moddl. J. geophys. Res. 72, 3919: Stansberrv, K. G. and White. R. S. (1974). Juniter’s radiation belts. J. geophys. R&. 79, 2331. ’ L Trainor, J. H., McDonald, F. B., Teegarden, B. J., Webber, W. R. and Roelof, E. C. (1974). Energetic particles in the Jovian magnetosphere. j. geiphys. ges. 79,360O. Tsurutani. B. and Boaott. F. (1972). Onset of maanetospheric &storms. i geephy;. Rei. 77, 4677. Van Allen, J. A., Baker, D. N., Randall, B. A. and Sentman, D. D. (1974). The mannetosnhere of Jupiter as observed withPioneer 10, 1. &r&rent and p&ciDal findinas. .I. neoohvs. Res. 79. 3559. Va’syliunas, i. M.71975). Theoretical models of magnetic field line merging, 1. Reo. Geophys. Space Phys. 13, 303.
in Northern
1NG
Ireland
BANDS
OBSERVED
IN AURORA
(Received in final form 2 March 1976) Abstract-Synthetic spectral band profiles of the Os+ 1NG system are presented for use in the analysis of aurora1 observations. Observed profiles are used to check the accuracy of the simulation. In the preparation of numerical models simulating aurora1 processes many sources of data are used, one of which is the aurora1 spectrum (Valiance Jones, 1974). The successful analysis of the spectrum is based initially on the correct identification of the emission features plus careful measurements of their relative intensities. Since many of these features actually consist of blends of various atomic lines and molecular band systems it is impossible to determine accurately the relative intensities of the compo-
nents unless their spectral shapes are known. This problem may be overcome in most cases by preparing synthetic spectra of the relevant band systems (e.g. Gattinger and Valiance Jones, 1974). However, not only is the synthesis time-consuming for some systems, but also, the information required is not always readily available. Such is the case for the Ozc 1NG bands. This band system was identified in the aurora by Nicolet and Dogniaux (1950) by employing the synthetic
1000
Research notes The relative intensity of the individual rotational lines (photon units) in a vibrational band is given by I(S, J”) = Cv(J’,S?3S(.Y, .P)e-F”cJ’)
5500
5550
5600
5650
WAVELENGTH-i FIG. 1. SYNTHETIC OF THE
300K
SPECTRUM
OF THE Au=1 SEQUENCE A TEMFERATURE OF (DASHED LINE) Cow SPECTRUM (SOLID LINE-
G,+iNG BAND SYSTEM AT AND A s~rr WIDTH OF 4A
PARED
WITH
AN
OBSERVED BIRELY, 1975).
The relative band intensities in the synthetic spectrum are from Gattinger and Vallance Jones (1974). The observed spectrum was shifted 2 A to the red to match the wavelength scafe of the synthetic spectrum.
spectrum comparison technique on the 2-O band in the 5275 A region of the aurorai spectrum. However, since their 5 A synthetic O-O band profife differs somewhat from those observed for the 1-O and 2-O bands (e.g. Chamberlain, 1941), it appears likely that their method of deriving the intensities of the individual rotational lines was not sufficiently accurate. Gattinger and Vatlance Jones (1974) pursued the problem and arrived at a more satisfactory band profile which is presented here in greater detail.
-
4-2
where v(.J’, S’) is the wavenumber of the transition, S(S, J”) is the line strength factor, and the exponential term is related to the rotational population distribution in the upper state as discussed below. Although the band structure is relatively complex (4&--4Jf,) with 48 possible branches (Nevin, 1939), there is in principle no difficulty in determining the wavenumbers of all the important transitions in the system (Her&erg, 1950 and references therein). U~o~unateiy, this is not the case for the line strength factors. Formulas for Hund’s case (a) and case (b) coupiing are available (Kovacs, 1969), but they are not applicable since the coupling is intermediate between the two. Zare (1972) extended the theoretical treatment and also by private ~rnrnu~~tion provided the individual line strengths necessary for the present analysis. Since the coupling constants for the first few vibrational levels of the a‘%, state are nearly identical, the same set of line strength factors can be used for al1 bands. 6
5
g2 F z! WI a
SUM ---2 - 0 BAND . -.. 3 , S*pJD > c ‘07
j$ ,
0
BAND
5200
5250
WAVELENGTH
5300
-ii
5 lZ -
FIG. 3. SYNTHE~C SPECI-RA OF THE bu=2 SEQUENCE OF THE&+lNGBAND SYSTBMAT200K(DAsHEDLINE)AND 400K (SOLID LINE)WITH ASLITWIDTH OF 2A.
W > F: d: ii a
WAVELENGTH
- ANGSTROMS
Fro. 2.
SYNTHETIC SPECTRA OFTHE BANDS IN THE Au==2 SEQUENCE OF THE G,+lNG SYSTEM AT A ~~PE~TU~ OF 300K ANDASLI-TWIDTHOF 2ii.
The relative
band intensities are from Gattinger Valiance Jones (1974).
and
In determining the rotational population distribution in the upper state it is assumed that simultaneous ionization and excitation from the 0zX3P,- state occurs with no change in the rotational state of the molecule. Consequently, the rotational term values of the 0,X3&- VI”= 0 state, F”, have been used to calculate an assumed Boltzmann distribution in the upper state rotational levels designated by J’ (Valiance Jones, 1974, p. 158). The accuracy of the synthesis technique can be determined only if suitable observed band profiles are available for comparison. Gattinger and Valiance Jones (1974) analyzed the Au = 2 sequence but at a spectral resolution somewhat too low to make a critical assessment of the accuracy of the model. However, comparisons between
1001
Research notes laboratory observations of the Au = 1 sequence at higher resolution (Birely, 1975) and the corresponding synthetic spectrum (Fig. 1) indicate that the simulated profile is sufficiently accurate for normal analysis of the aurora1 spectrum. Since the easily observable AD = 2 sequence at 5250 8, is not as badly blended in the aurora1 spectrum as the other sequences, it is probably the most convenient feature for future observations. The synthetic spectra of the bands in the sequence (2-O 3-l and 4-2) for a triangular instrumental function of 2 x and a temperature of 300 K are given for reference in Fig. 2. The relative vibrational intensities are those determined by Gattinger and Vallance Jones (1974) for a best fit to the observed aurora1 spectrum. Synthetic band profiles of this sequence and others at various temperatures and instrumental slit widths can be readily generated with the model discussed here. As another example, an indication of the sensitivity of the profile of the Au = 2 sequence to temperature changes is contained in Fig. 3 for 200 and 400 K. Band profiles for slit widths less than about 0.5 8, cannot be accurately generated with the model since the error in the calculated wavelengths is of the order of 0.25 A; this is usually sufficiently accurate for generation of aurora1 comparison spectra. The synthetic reference spectra presented here provide much of the information required to properly calibrate photometric systems designed to measure the aurora1 brightness of the 02+ 1NG bands, and especially those in the Au = 2 sequence.
Acknowledgements-I wish to thank Dr. A. Valiance Jones for his assistance in dealing with this problem.
R. L. Gattinger Herzbern Institute of Astrophysics, National Research kouncii oj Canada, Ottawa, Canada KlA OR6
REFERENCES
Birely, J. H. (1975). Chamberlain, J. W. airglow. Academic Gattinger, R. L. and
Phys. Rev. (A) 11,79.
(1961). Physics of the aurora and Press, N.Y. Vallancc Jones, A. (1974). Can. J.
Phys. 52, 2343.
Herzberg, G. (1950). Spectra of diatomic molecues. Van Nostrand, N.Y. Kovacs, I. (1969). Rotational structure in the spectra of diatomic molecules Elsevier, N.Y. Nevin, T. E. (1939). Phil. Trans. R. Sot. Land. (A), 237, 471. Nicolet, M. and Dogniaux, R. (1950). J. geophys. Res. 55, 21. Valiance Jones, A. (1974). The Aurora. Reidel, Dordrecht, Holland. Zare, R. N. (1972). In Molecular Specrroscopy: Modem Research (Ed. K. N. Rao and C. W. Mathews), p. 207. Academic Press, N.Y.
Planet.
Space Sci., Vol. 24. pp.
SPECTRAL
999
to 1001.
Pergamon
SYNTHESIS
Press,
1976. Printed
OF THE
0,’
999
Parks, G. K., Amoldy, R. L., Lezniak, T. N. and Winckler. J. R. (1968). Correlated effects of energetic electrons at the 6.6 & equator and the auroral z&e during magnetospheric substorms. Radio Sci. 3, 715. Retzler, J. and Simpson, J. A. (1969). Relativistic electrons confined within the neutral sheet of the geomagnetic tail. J. geophys. Res. 74, 2149. Roederer, J. G. and Hones, E. W., Jr. (1974). Motion of magnetospheric particle clouds in a time-dependent electric field model. J. geophys. Res. 79, 1432. Sarris, E. T., Krimigis, S. M. and Armstrong, T. P. (1976). Observations of magnetospheric bursts of high energy protons and electrons at 35 RE with IMP-7. .I. geophys. Res. 81, 2341. Scarf, F. L., Frank, L. A., Ackerson, K. L. and Lepping, R. P. (1974). Plasma wave turbulence at distant crossing of the plasma sheet boundaries and at the neutral sheet. Geophys. Res. L&t. 1,189. Sentman, D. D. and Van Allen, J. A. (1975). Recirculation of energetic particles in Jupiter’s magnetosphere. Geophy; Res. ken. 2, 465. _ Simuson. J. A.. Eraker, J. H., Lamuort, J. E. and Walpole, P. H. (1974). Electrons and protons accelerated in Mercury’s magnetic field. Science 185, 160. Siscoe, G. L., Ness, N. F. and Yeates, C. M. (1975). Substorms on Mercury? J. geophys. Res. 80, 4359. Speiser, T. W. (1967). Particle trajectories in model current sheets. 2. Applications to auroras using a geomagnetic tail moddl. J. geophys. Res. 72, 3919: Stansberrv, K. G. and White. R. S. (1974). Juniter’s radiation belts. J. geophys. R&. 79, 2331. ’ L Trainor, J. H., McDonald, F. B., Teegarden, B. J., Webber, W. R. and Roelof, E. C. (1974). Energetic particles in the Jovian magnetosphere. j. geiphys. ges. 79,360O. Tsurutani. B. and Boaott. F. (1972). Onset of maanetospheric &storms. i geephy;. Rei. 77, 4677. Van Allen, J. A., Baker, D. N., Randall, B. A. and Sentman, D. D. (1974). The mannetosnhere of Jupiter as observed withPioneer 10, 1. &r&rent and p&ciDal findinas. .I. neoohvs. Res. 79. 3559. Va’syliunas, i. M.71975). Theoretical models of magnetic field line merging, 1. Reo. Geophys. Space Phys. 13, 303.
in Northern
1NG
Ireland
BANDS
OBSERVED
IN AURORA
(Received in final form 2 March 1976) Abstract-Synthetic spectral band profiles of the Os+ 1NG system are presented for use in the analysis of aurora1 observations. Observed profiles are used to check the accuracy of the simulation. In the preparation of numerical models simulating aurora1 processes many sources of data are used, one of which is the aurora1 spectrum (Valiance Jones, 1974). The successful analysis of the spectrum is based initially on the correct identification of the emission features plus careful measurements of their relative intensities. Since many of these features actually consist of blends of various atomic lines and molecular band systems it is impossible to determine accurately the relative intensities of the compo-
nents unless their spectral shapes are known. This problem may be overcome in most cases by preparing synthetic spectra of the relevant band systems (e.g. Gattinger and Valiance Jones, 1974). However, not only is the synthesis time-consuming for some systems, but also, the information required is not always readily available. Such is the case for the Ozc 1NG bands. This band system was identified in the aurora by Nicolet and Dogniaux (1950) by employing the synthetic
1000
Research notes The relative intensity of the individual rotational lines (photon units) in a vibrational band is given by I(S, J”) = Cv(J’,S?3S(.Y, .P)e-F”cJ’)
5500
5550
5600
5650
WAVELENGTH-i FIG. 1. SYNTHETIC OF THE
300K
SPECTRUM
OF THE Au=1 SEQUENCE A TEMFERATURE OF (DASHED LINE) Cow SPECTRUM (SOLID LINE-
G,+iNG BAND SYSTEM AT AND A s~rr WIDTH OF 4A
PARED
WITH
AN
OBSERVED BIRELY, 1975).
The relative band intensities in the synthetic spectrum are from Gattinger and Vallance Jones (1974). The observed spectrum was shifted 2 A to the red to match the wavelength scafe of the synthetic spectrum.
spectrum comparison technique on the 2-O band in the 5275 A region of the aurorai spectrum. However, since their 5 A synthetic O-O band profife differs somewhat from those observed for the 1-O and 2-O bands (e.g. Chamberlain, 1941), it appears likely that their method of deriving the intensities of the individual rotational lines was not sufficiently accurate. Gattinger and Vatlance Jones (1974) pursued the problem and arrived at a more satisfactory band profile which is presented here in greater detail.
-
4-2
where v(.J’, S’) is the wavenumber of the transition, S(S, J”) is the line strength factor, and the exponential term is related to the rotational population distribution in the upper state as discussed below. Although the band structure is relatively complex (4&--4Jf,) with 48 possible branches (Nevin, 1939), there is in principle no difficulty in determining the wavenumbers of all the important transitions in the system (Her&erg, 1950 and references therein). U~o~unateiy, this is not the case for the line strength factors. Formulas for Hund’s case (a) and case (b) coupiing are available (Kovacs, 1969), but they are not applicable since the coupling is intermediate between the two. Zare (1972) extended the theoretical treatment and also by private ~rnrnu~~tion provided the individual line strengths necessary for the present analysis. Since the coupling constants for the first few vibrational levels of the a‘%, state are nearly identical, the same set of line strength factors can be used for al1 bands. 6
5
g2 F z! WI a
SUM ---2 - 0 BAND . -.. 3 , S*pJD > c ‘07
j$ ,
0
BAND
5200
5250
WAVELENGTH
5300
-ii
5 lZ -
FIG. 3. SYNTHE~C SPECI-RA OF THE bu=2 SEQUENCE OF THE&+lNGBAND SYSTBMAT200K(DAsHEDLINE)AND 400K (SOLID LINE)WITH ASLITWIDTH OF 2A.
W > F: d: ii a
WAVELENGTH
- ANGSTROMS
Fro. 2.
SYNTHETIC SPECTRA OFTHE BANDS IN THE Au==2 SEQUENCE OF THE G,+lNG SYSTEM AT A ~~PE~TU~ OF 300K ANDASLI-TWIDTHOF 2ii.
The relative
band intensities are from Gattinger Valiance Jones (1974).
and
In determining the rotational population distribution in the upper state it is assumed that simultaneous ionization and excitation from the 0zX3P,- state occurs with no change in the rotational state of the molecule. Consequently, the rotational term values of the 0,X3&- VI”= 0 state, F”, have been used to calculate an assumed Boltzmann distribution in the upper state rotational levels designated by J’ (Valiance Jones, 1974, p. 158). The accuracy of the synthesis technique can be determined only if suitable observed band profiles are available for comparison. Gattinger and Valiance Jones (1974) analyzed the Au = 2 sequence but at a spectral resolution somewhat too low to make a critical assessment of the accuracy of the model. However, comparisons between
1001
Research notes laboratory observations of the Au = 1 sequence at higher resolution (Birely, 1975) and the corresponding synthetic spectrum (Fig. 1) indicate that the simulated profile is sufficiently accurate for normal analysis of the aurora1 spectrum. Since the easily observable AD = 2 sequence at 5250 8, is not as badly blended in the aurora1 spectrum as the other sequences, it is probably the most convenient feature for future observations. The synthetic spectra of the bands in the sequence (2-O 3-l and 4-2) for a triangular instrumental function of 2 x and a temperature of 300 K are given for reference in Fig. 2. The relative vibrational intensities are those determined by Gattinger and Vallance Jones (1974) for a best fit to the observed aurora1 spectrum. Synthetic band profiles of this sequence and others at various temperatures and instrumental slit widths can be readily generated with the model discussed here. As another example, an indication of the sensitivity of the profile of the Au = 2 sequence to temperature changes is contained in Fig. 3 for 200 and 400 K. Band profiles for slit widths less than about 0.5 8, cannot be accurately generated with the model since the error in the calculated wavelengths is of the order of 0.25 A; this is usually sufficiently accurate for generation of aurora1 comparison spectra. The synthetic reference spectra presented here provide much of the information required to properly calibrate photometric systems designed to measure the aurora1 brightness of the 02+ 1NG bands, and especially those in the Au = 2 sequence.
Acknowledgements-I wish to thank Dr. A. Valiance Jones for his assistance in dealing with this problem.
R. L. Gattinger Herzbern Institute of Astrophysics, National Research kouncii oj Canada, Ottawa, Canada KlA OR6
REFERENCES
Birely, J. H. (1975). Chamberlain, J. W. airglow. Academic Gattinger, R. L. and
Phys. Rev. (A) 11,79.
(1961). Physics of the aurora and Press, N.Y. Vallancc Jones, A. (1974). Can. J.
Phys. 52, 2343.
Herzberg, G. (1950). Spectra of diatomic molecues. Van Nostrand, N.Y. Kovacs, I. (1969). Rotational structure in the spectra of diatomic molecules Elsevier, N.Y. Nevin, T. E. (1939). Phil. Trans. R. Sot. Land. (A), 237, 471. Nicolet, M. and Dogniaux, R. (1950). J. geophys. Res. 55, 21. Valiance Jones, A. (1974). The Aurora. Reidel, Dordrecht, Holland. Zare, R. N. (1972). In Molecular Specrroscopy: Modem Research (Ed. K. N. Rao and C. W. Mathews), p. 207. Academic Press, N.Y.