Atmospheric Composition and Structure: Airglow and aurora; Atmospheric Composition and Structure: Planetary atmospheres (5210; 5405; 5704); Atmospheric Composition and Structure: Thermosphere: energy deposition (3369); Atmospheric Composition and Structure: Instruments and techniques; Magnetospheric Physics: Auroral phenomena (2407)
Abstract :
[en] The STIS and ACS instruments onboard HST are widely used to study the giant planet's aurora. Several assumptions have to be made to convert the instrumental counts into meaningful physical values (type and bandwidth of the filters, definition of the physical units, etc…), but these may significantly differ from one author to another, which makes it difficult to compare the auroral characteristics published in different studies. We present a method to convert the counts obtained in representative ACS and STIS imaging modes/filters used by the auroral scientific community to brightness, precipitated power and radiated power in the ultraviolet (700-1800 Å). Since hydrocarbon absorption may considerably affect the observed auroral emission, the conversion factors are determined for several attenuation levels. Several properties of the auroral emission have been determined: the fraction of the H[SUB]2[/SUB] emission shortward and longward of the HLy-α line is 50.3% and 49.7% respectively, the contribution of HLy-α to the total unabsorbed auroral signal has been set to 9.1% and an input of 1 mW m[SUP]-2[/SUP] produces 10 kR of H[SUB]2[/SUB] in the Lyman and Werner bands. A first application sets the order of magnitude of Saturn's auroral characteristics in the total UV bandwidth to a brightness of 10 kR and an emitted power of ˜2.8 GW. A second application uses published brightnesses of Europa's footprint to determine the current density associated with the Europa auroral spot: 0.21 and 0.045 μA m[SUP]-2[/SUP] assuming no hydrocarbon absorption and a color ratio of 2, respectively. Factors to extend the brightnesses observed with Cassini-UVIS to total H[SUB]2[/SUB] UV brightnesses are also provided.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Gustin, Jacques ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Physique des atmosphères et des environnements planétaires
Bonfond, Bertrand ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Grodent, Denis ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Physique des atmosphères et des environnements planétaires
Gérard, Jean-Claude ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Language :
English
Title :
Conversion from HST ACS and STIS auroral counts into brightness, precipitated power, and radiated power for H2 giant planets
Publication date :
01 July 2012
Journal title :
Journal of Geophysical Research. Space Physics
ISSN :
2169-9380
eISSN :
2169-9402
Publisher :
American Geophysical Union (AGU), Washington, United States - District of Columbia
Bonfond, B., M. F. Vogt, J.-C. Geacute;rard, D. Grodent, A. Radioti, and V. Coumans (2011), Quasi-periodic polar flares at Jupiter: A signature of pulsed dayside reconnections?, Geophys. Res. Lett., 38, L02104, doi:10.1029/ 2010GL045981.
Broadfoot, A. L., et al. (1979), Extreme ultraviolet observations from Voyager 1 encounter with Jupiter, Science, 204, 979-982, doi:10.1126/ science.204.4396.979.
Broadfoot, A. L., et al. (1981), Extreme ultraviolet observations from Voyager 1 encounter with Saturn, Science, 212, 206-211, doi:10.1126/ science.212.4491.206.
Dols, V., J.-C. Geacute;rard, J. T. Clarke, J. Gustin, and D. Grodent (2000), Diagnostics of the Jovian aurora deduced from ultraviolet spectroscopy: Model and HST/GHRS observation, Icarus, 147, 251-266, doi:10.1006/ icar.2000.6415.
Dziczek, D., J. M. Ajello, G. K. James, and D. L. Hansen (2000), A study of the cascade contribution to the H2 Lyman band system from electron impact, Phys. Rev. A, 61, 064702, doi:10.1103/PhysRevA.61.064702.
Geacute;rard, J.-C., and V. Singh (1982), A model of energetic electrons and EUV emission in the Jovian and Saturnian atmospheres and implications, J. Geophys. Res., 87, 4525-4532, doi:10.1029/JA087iA06p04525.
Geacute;rard, J.-C., J. Gustin, D. Grodent, P. Delamere, and J. T. Clarke (2002), The excitation of the FUV Io tail on Jupiter: Characterization of the electron precipitation, J. Geophys. Res., 107(A11), 1394, doi:10.1029/ 2002JA009410.
Geacute;rard, J. C., B. Bonfond, J. Gustin, D. Grodent, J. T. Clarke, D. Bisikalo, and V. Shematovich (2009), Altitude of Saturn's aurora and its implications for the characteristic energy of precipitated electrons, Geophys. Res. Lett., 36, L02202, doi:10.1029/2008GL036554.
Gladstone, G. R., M. Allen, and Y. L. Yung (1996), Hydrocarbon photochemistry in the upper atmosphere of Jupiter, Icarus, 119, 1-52, doi:10.1006/icar.1996.0001. (Pubitemid 126161853)
Grodent, D., J. H. Waite Jr., and J. C. Geacute;rard (2001), A self-consistent model of the Jovian auroral thermal structure, J. Geophys. Res., 106, 12,933-12,952, doi:10.1029/2000JA900129. (Pubitemid 33729406)
Grodent, D., J.-C. Geacute;rard, J. Gustin, B. H. Mauk, J. E. P. Connerney, and J. T. Clarke (2006), Europa's FUV auroral tail on Jupiter, Geophys. Res. Lett., 33, L06201, doi:10.1029/2005GL025487.
Gustin, J., et al. (2004), Jovian auroral spectroscopy with FUSE: Analysis of self-absorption and implications for electron precipitation, Icarus, 171, 336-355, doi:10.1016/j.icarus.2004.06.005. (Pubitemid 39238580)
Gustin, J., S. W. H. Cowley, J.-C. Geacute;rard, G. R. Gladstone, D. Grodent, and J. T. Clarke (2006), Characteristics of Jovian morning bright FUV aurora from Hubble Space Telescope/Space Telescope Imaging Spectrograph imaging and spectral observations, J. Geophys. Res., 111, A09220, doi:10.1029/ 2006JA011730.
Kharchenko, V., A. Dalgarno, D. R. Schultz, and P. C. Stancil (2006), Ion emission spectra in the Jovian X-ray aurora, Geophys. Res. Lett., 33, L11105, doi:10.1029/2006GL026039. (Pubitemid 44123098)
Kimble, R. A., et al. (1998), The on-orbit performance of the Space Telescope Imaging Spectrograph, Astrophys. J., 492, L83-L93, doi:10.1086/ 311102. (Pubitemid 128716121)
Liu, W., and D. R. Schultz (2000), Ultraviolet emission from oxygen precipitating into Jovian aurora, Astrophys. J., 530, 500-503, doi:10.1086/ 308367.
Liu, X., D. E. Shemansky, S. M. Ahmed, G. K. James, and J. M. Ajello (1998), Electron-impact excitation and emission cross sections of the H2 Lyman and Werner systems, J. Geophys. Res., 103, 26,739-26,758, doi:10.1029/98JA02721. (Pubitemid 128664960)
Maybhate, A., and A. Armstrong (2010), ACS Instrument Handbook, 10th ed., Space Telescope Sci. Inst., Baltimore, Md.
Moses, J. I., T. Fouchet, B. Beacute;zard, G. R. Gladstone, E. Lellouch, and H. Feuchtgruber (2005), Photochemistry and diffusion in Jupiter's stratosphere: Constraints from ISO observations and comparisons with other giant planets, J. Geophys. Res., 110, E08001, doi:10.1029/ 2005JE002411.
Radioti, A., J.-C. Gerard, D. Grodent, B. Bonfond, N. Krupp, and J. Woch (2008), Discontinuity in Jupiter's main auroral oval, J. Geophys. Res., 113, A01215, doi:10.1029/2007JA012610.
Sandel, B. R., and A. L. Broadfoot (1981), Morphology of Saturn's aurora, Nature, 292, 679-682, doi:10.1038/292679a0.
Shematovich, V. I., D. V. Bisikalo, and J. C. Geacute;rard (1994), A kinetic model of the formation of the hot oxygen geocorona: 1. Quiet geomagnetic conditions, J. Geophys. Res., 99, 23,217-23,228, doi:10.1029/ 94JA01769.
Trafton, L. M., V. Dols, J.-C. Geacute;rard, J. H. Waite, G. R. Gladstone, and G. Munhoven (1998), HST spectra of the Jovian ultraviolet aurora: Search for heavy ion precipitation, Astrophys. J., 507, 955-967, doi:10.1086/306338. (Pubitemid 128158827)
Waite, J. H., Jr., T. E. Cravens, J. U. Kozyra, A. F. Nagy, S. K. Atreya, and R. H. Chen (1983), Electron precipitation and related aeronomy of the Jovian thermosphere and ionosphere, J. Geophys. Res., 88, 6143-6163, doi:10.1029/JA088iA08p06143. (Pubitemid 14455611)
Waite, J. H., Jr., F. Bagenal, F. Seward, C. Na, G. R. Gladstone, T. E. Cravens, K. C. Hurley, J. T. Clarke, R. Elsner, and S. A. Stern (1994), ROSAT observations of the Jupiter aurora, J. Geophys. Res., 99(A8), 14,799-14,809, doi:10.1029/94JA01005.
Yung, Y. L., G. R. Gladstone, K. M. Chang, J. M. Ajello, and S. K. Srivastava (1982), H2 fluorescence spectrum from 1200 to 1700 A by electron impact: Laboratory study and application to jovian aurora, Astrophys. J., 254, L65-L69, doi:10.1086/183757.
