[en] Far ultraviolet remote sensing from a high-altitude satellite is extensively used to image the global aurora, derive its energetics, and follow its dynamical morphology. It is generally assumed that the observed emissions are dominated by the interaction of the precipitated electrons with the thermospheric constituents. A model to calculate far ultraviolet emissions excited by auroral electrons and protons and the secondary electrons they generate has been used to calculate the volume excitation rate of the H I Ly-alpha, O I 1304 and 1356 Å, N I 1493 Å multiplets, and the N[SUB]2[/SUB] Lyman-Birge-Hopfield (LBH) bands. The characteristic energy and the energy flux are derived from the observed statistical distribution of precipitated protons and electrons. This model is applied to the midnight aurora, the noon cusp, and a proton-dominated aurora for moderately disturbed conditions. We show that in the first two cases, direct electron impact dominates the vertically integrated emission rate over the proton component, although proton excitation plays an important role at some altitudes in the daytime cusp. In afternoon regions of the auroral zone near the auroral boundary, secondary electrons due to proton ionization are the main source of FUV emissions. The energy dependence of the efficiency of LBH band emission viewed from high altitude is calculated for electron and proton precipitations. Maps of the N[SUB]2[/SUB] LBH emission excited by both components are obtained, and regions of proton-dominated auroral emission are identified. It is found that the distribution of the ratio of proton-induced to electron-induced brightness resembles maps of the ratio of the respective precipitated energy fluxes. Proton-dominated FUV emissions are thus located in a C-shaped sector extending from prenoon to midnight magnetic local times with a maximum proton contribution near the equatorward boundary of the statistical electron oval. The distribution of the Ly-alpha/LBH intensity ratio is found to mimic the ratio of the proton flux/total energy flux, although it is insufficient by itself to accurately determine the relative fraction of auroral energy carried by the protons.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Hubert, Benoît ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Gérard, Jean-Claude ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Bisikalo, D. V.
Shematovich, V. I.
Solomon, S. C.
Language :
English
Title :
The role of proton precipitation in the excitation of auroral FUV emissions
Publication date :
01 October 2001
Journal title :
Journal of Geophysical Research
ISSN :
0148-0227
eISSN :
2156-2202
Publisher :
American Geophysical Union (AGU), Washington, United States - District of Columbia
Ajello, J.M., and D.E. Shemansky, A reexamination of important N2 cross sections by electron impact with application to the dayglow: The Lyman-Birge-Hopfield band system and N I (119.99 nm), J. Geophys. Res., 90, 9845, 1985.
Banks, P.M., C.R. Chappell, and A.F. Nagy, A new model for the interaction of auroral electrons with the atmosphere: Spectral degradation, backscatter, optical emission and ionization, J. Geophys. Res., 79, 1459, 1974.
Basu, B., J.R. Jasperse, R.M. Robinson, R.R. Vondrak, and D.S. Evans, Linear transport theory of auroral proton precipitation: A comparison with observations, J. Geophys. Res., 92, 5920, 1987.
Basu, B., J.R. Jasperse, D.J. Strickland, and R.E. Daniell Jr., Transport-theoretic model for the electron-proton-hydrogen atom aurora, J. Geophys. Res., 98, 21,517, 1993.
Bilitza, D. (Ed.), International Reference Ionosphere IRI 90, World Data Cent. for Rockets and Satellites, 90-22, Greenbelt, Md., 1990.
Christon, S.P., D.J. Williams, D.G. Mitchell, C.Y. Huang, and L.A. Frank, Spectral characteristics of plasma sheet ion and electron populations during disturbed geomagnetic conditions, J. Geophys. Res., 96, 1, 1991.
Conway, R. R., Multiple fluorescent scattering of N2 ultraviolet emissions in the atmospheres of the Earth and Titan, J. Geophys. Res., 88, 4784, 1983.
Creutzberg, F., R. L. Gattinger, F. R. Harris, S. Wozniak, and A. Vallance Jones, Auroral studies with a chain of meridian scanning photometers, 2, Mean distributions of proton and electron aurora as a function of magnetic activity, J. Geophys. Res., 93, 14,591, 1988.
Crosswhite, H.M., and W.G. Fastie, Far-ultraviolet auroral spectra, J. Opt. Soc. Am., 52, 643, 1962.
Decker, D.T., B.V. Kozelov, B. Basu, J.R. Jasperse, and V.E. Ivanov, Collisional degradation of the proton-H atom fluxes in the atmosphere: A comparison of theoretical techniques, J. Geophys. Res., 101, 26,947, 1996.
Edgar, B.C., W.T. Miles, and A.E.S. Green, Energy deposition of protons in molecular nitrogen and applications to proton auroral phenomena, J. Geophys. Res., 78, 6595, 1973.
Edgar, B.C., H.S. Porter, and A.E.S. Green, Proton energy deposition in molecular and atomic oxygen and applications to polar cap, Planet. Space Sci., 25, 787, 1975.
Feldman, P.D., and E.P. Gentieu, The ultraviolet spectrum of an aurora 530-1520 Å, J. Geophys. Res., 87, 2453, 1982.
Frey, H.U., S.B. Mende, C.W. Carlson, J.-C. Gérard, B. Hubert, J. Spann, G.R. Gladstone, and T. J. Immel, The electron and proton aurora as seen by IMAGE-FUV and FAST, Geophys. Res. Lett. 28, 1135, 2001.
Galand, M., J. Lilensten, W. Kofman, and R.B. Sidje, Proton transport model in the ionosphere, 1, Multistream approach of the transport equations, J. Geophys. Res., 102, 22,261, 1997.
Gérard, J.C., and C.A. Earth, OGO-4 observations of the ultraviolet auroral spectrum, Planet. Space Sci., 24, 1059, 1976.
Gérard, J.C., B. Hubert, D.V. Bisikalo, and V.I. Shematovich, A model of the Lyman-α line profile in the proton aurora, J. Geophys. Res., 105, 15,795, 2000.
Germany, G.A., G.K. Parks, M. Brittnacher, J. Cumnock, D. Lummerzheim, J.F. Spann, L. Chen, P.G. Richards, and F.J. Rich, Remote determination of auroral energy characteristics during substorm activity, Geophys. Res. Lett, 24, 995, 1997.
Green, A.E.S., and R.S. Stolarski, Analytic models of electron impact excitation cross sections, J Atmos. Terr. Phys., 34, 1703, 1972.
Hardy, D.A., M.S. Gussenhoven, and E. Holeman, A statistical model of auroral electron precipitation, J. Geophys. Res., 90, 4229, 1985.
Hardy, D.A., M.S. Gussenhoven, and R. Raistrick, Statistical and functional representations of the pattern of auroral energy flux, number flux, and conductivity, J. Geophys. Res., 92, 12,275, 1987.
Hardy, D.A., M.S. Gussenhoven, and D. Brautigam, A statistical model of auroral ion precipitation, J. Geophys. Res., 94, 370, 1989.
Hardy, D.A., W. McNeil, M.S. Gussenhoven, and D. Brautigam, A statistical model of auroral ion precipitation, 2, Functional representation of the average patterns, J. Geophys. Res., 96, 5539, 1991.
Hedin, A.E., Extension of the MSIS thermosphere model into the middle and lower atmosphere, J. Geophys. Res., 96, 1159, 1991.
Ishimoto, M., C.I. Meng, G.J. Romick, and R.E. Huffman, Auroral electron energy and flux from molecular nitrogen ultraviolet emissions observed by the S3-4 satellite, J. Geophys. Res., 93, 9854, 1988.
Ishimoto, M., C.I. Meng, G.R. Romick, and R.E. Huffman, Doppler shift of auroral Lyman α observed from a satellite, Geophys. Res. Lett., 16, 143, 1989.
Jackman, C.H., R.H. Garvey, and A.E.S. Green, Electron impact on atmospheric gases, 1, Updated cross sections, J. Geophys. Res., 82, 5081, 1977.
Jasperse, J.R., and B. Basu, Transport theoretic solutions for auroral proton and H atom fluxes and related quantities, J. Geophys. Res., 87, 811, 1982.
Kozelov, B.V., and V.E. Ivanov, Monte-Carlo calculation of proton-hydrogen atom transport in N2, Planet. Space Sci., 40, 1503, 1992.
Lorentzen, D.A., F. Sigernes, and C.S. Deehr, Modeling and observations of dayside auroral hydrogen emission Doppler profiles, J. Geophys. Res., 103, 17,479, 1998.
Lummerzheim, D., and M. Galand, Profile of the Hβ emission line in proton aurora, J. Geophys. Res., 106, 23, 2001.
Lyons, L.R., and D.S. Evans, An association between discrete aurora and energetic particle boundaries, J. Geophys. Res., 89, 2395, 1984.
Marov, M. Y., V.I. Shematovich, D.V. Bisikalo, and J.C. Gérard, Nonequilibrium Processes in the Planetary and Cometary Atmospheres: Theory and Applications, Kluwer Acad., Norwell, Mass., 1997.
Mende, S.B., and R.H. Eather, Monochromatic all-sky observations and auroral precipitation patterns, J. Geophys. Res., 81, 3771, 1976.
Mende, S.B., et al., Far ultraviolet imaging from the IMAGE spacecraft, 1, System design, Space Sc. Rev., 91, 243, 2000.
Mende, S.B., H. Frey, S. B. Mende, H. U. Frey, M. Lampton, J.-C. Gérard, B. Hubert, S. Fuselier, R. Gladstone, and J. L. Burch, Global observations of proton and electron auroras in a substorm, Geophys. Res. Lett., 28, 1139, 2001.
Mumma, M.J., and E.C. Zipf, Dissociative excitation of vacuum-ultraviolet emission features by electron impact on molecular gases, II, N2, J. Chem. Phys., 55, 5582, 1971.
Ogawa, S., and M. Ogawa, Absorption cross sections of O2(α1Δg) and O2(X3Σg) in the region from 1087 to 1700 Å, Can. J. Phys., 53, 1845, 1975.
Rees, M.H., On the interaction of auroral protons with the Earth's atmosphere, Planet. Space Sci., 30, 463, 1982.
Rees, M.H., Physics and Chemistry of the Upper Atmosphere, Cambridge Univ. Press, New York, 1989.
Robinson, R.M., R.R. Vondrak, K. Miller, T. Dabbs, and D. Hardy, On calculating ionospheric disturbances from the flux and energy of precipitating electrons, J. Geophys. Res., 92, 2565, 1987.
Rudd, M.E., Energy and angular distribution of secondary electrons from 5-100 keV proton collisions with hydrogen and nitrogen molecules, Phys. Rev. A, 20, 787, 1979.
Sharber, J.R., R.A. Frahm, J.D. Winningham, J.C. Biard, D. Lummerzheim, M.H. Rees, D.L. Chenette, E.E. Gaines, R.W. Nightingale, and W.L. Imhof, Observations of the UARS particle environment monitor and computation of ionzation rates in the middle and upper atmosphere during a geomagnetic storm, Geophys. Res. Lett., 20, 1319, 1993.
Solomon, S.C., Auroral particle transport using Monte Carlo and Hybrid methods, J. Geophys. Res., 106, 107, 2001.
Solomon, S.C., P.B. Hays, and V. Abreu, The auroral 6300 A emission: Observation and modelling, J. Geophys. Res., 93, 9867, 1988.
Stenbaek-Nielsen, U.C., T.J. Hallinan, D.L. Osborne, J. Kimball, C. Chaston, J. McFadden, G. Delory, M. Temerin, and C.W. Carlson, Aircraft observations conjugate to FAST: Auroral arc thicknesses, Geophys. Res. Lett, 25, 2073, 1998.
Stone, E. J., and E. C. Zipf, Electron impact excitation on the 3S0 and 5S0 states of atomic oxygen, J. Chem. Phys., 60, 4237, 1974.
Strickland, D.J., and D.E. Anderson, Radiation transport effects on the OI 1356-Å limb intensity profile in the dayglow, J. Geophys. Res., 88, 9260, 1983.
Strickland, D.J., R.E. Daniell Jr., J.R. Jasperse, and B. Basu, Transport-theoretic model for the electron-proton-hydrogen atom aurora, 2, Model results, J. Geophys. Res., 98, 21,533, 1993.
Synnes, S.A., F. Soraas, and J.P. Hansen, Monte Carlo simulations of proton aurora, J. Atmos. Sol. Terr. Phys., 60, 1695, 1998.
Vallance-Jones, A., Aurora, D. Reidel, Norwell, Mass., 1974.
Van Zyl, B., and H. Neumann, Lyman α emission cross sections for low-energy H and H+ collisions with N2 and O2, J. Geophys. Res., 93, 1023, 1988.
Zipf, E.C., and P. Erdman, Electron impact excitation of atomic oxygen: Revised cross section, J. Geophys. Res., 90, 11087, 1985.
