NIGHTGLOW

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NIGHTGLOW

• Light of the Night Sky
• EUSO Background (cf. J.ADAMS report)
• VARIABILITY (Airglow)
• Extrapolation from Balloon experiments
• Other light sources and their variability
• Nightglow toy model

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Light of the Night Sky

• IAU COMMISSION 21LIGHT OF THE NIGHT SKY /
  LUMIERE DU CIEL NOCTURNE
• President Philippe Lamy
• Vice President M. Greenburg
• Organizing Committee S. Bowyer (USA), E. Dwek
  (USA), M. Greenburg (Netherlands), Bo A.
  Gustafson (USA), P. Lamy (France), R. Henry
  (USA), I. Mann (Germany), T. Mukai (Japan), W.
  Reach (USA), A. Witt (USA).
• Overview
• The diffuse components of the light of the night
  sky encompass a variety of physical phenomena
  over the full range of cosmic distance scales.
  From the Earth outward they include airglow in
  the Earth's atmosphere, scattering and thermal
  emission from the interplanetary dust cloud
  (zodiacal light), emission from the interstellar
  medium, integrated starlight, diffuse galactic
  light, diffuse emission in other galaxies and
  extragalactic background radiation. The purpose
  of Commission 21 is to facilitate research in
  these areas among the worldwide astronomical
  community. The Commission sponsors colloquia and
  symposia on these topics and supports related
  efforts in other commissions in the IAU. For
  historical and programmatic reasons, the
  Commission's main emphasis is in the ultraviolet,
  optical, and infrared bands of the spectrum.
• Commission 21 is part of Division III, Planetary
  Systems Science, which also includes Commissions
  15, 16, 20, 22, and 51.
• NEWS (Updated 28 June, 2001)
• Message from the Ex-President
• Commision 21 Members
• How to join the IAU and Commission 21
• Division III information
• Page last updated 28 June, 2001Please e-mail any
  questions or comments to IAU Commission 21

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The 1997 reference of diffuse Night Sky
BrightnessCh.Leinert et al. Astron.Astrophys.
Suppl.Ser. 127,1-99 (1998)
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Night sky Brightness in U Band (360 nm)From
Ground

• Airglow 6. 10-7 W/m2.sr.s
  300 f .m-2 sr-1 ns-1
• Zodiacal light 2. 10-7
  100
• Integrated Star Light 1.6 10-7
  80
• Diffuse Galactic Light 2. 10-9
  1
• Total 9.6 10-7 W/m2.sr.s
  480 f/m2.sr.ns

Site IB Max IBMin (440nm)
Mag / q W / m2.sr.s ESO 22.74 22.97 9.9
8.0 Kitt Peak 22.65 22.98
10.8 8. Hawaii 22.27 23.03
15. 7.6
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Earth Albedo at NightObserved above 90 km
Background Earth albedo Airglow direct view
Airglow Volume emission profile
BISS BBABY IAIRGLOW BBABY 300
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Airglow Spectrum
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Airglow variability

• Cosmic rays activity
• Sun position (variation with time)
• Solar activity (follow 10.7cm intensity)
• Geomagnetic location
• O2 Hertzberg band spectrum
• Discrete spectrum
• Peaks around 315,337,357,391
• N2 band 391nm seen

Factor x 2
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Diffuse Night Sky Brightness variation
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Diffuse Night Sky Brightness variationwith solar
activity
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Earth albedo at nightObserved below 90 km
(Balloon)
Earth albedo Atmosphere (clouds) Surface
reflectivity
Source Isotropic Night Sky Observer below 90
km at Nadir Atmosphere Standard (No clouds)
Transmission from ground T0.6
Integrated Atmospheric Backscattering KBS 1/2
(Rayleigh) BA480.1/2.0.4 100 f .m-2 sr-1 ns-1
Transmission to Ground Surface Reflectivity
R BG I.T2.R 4800.36R 175R
Upward reflected flux must be less than incoming
flux
BABY above sea B400 BABY above
Ground B500
Other sources ?
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Other sources of Night sky

• In the estimated 480 photons of incoming flux
  some sources are not accounted for in the
  Reference in the night sky brightness
• Airglow variations (solar cycle)
• Stars and planets
• Moon phases
• Light pollution

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Solar activity
I x 1.5-2
BABY2001
BABY1998
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Stars and planets

• Individual stars are not counted in reference of
  diffuse night sky ..

Flux 10-3 Full Moon --- I 230
photons/m2.sr.ns
I
Planets (if any) are not counted Venus mag
-4.4 i.e 5.10-4 Full Moon 70 photons Jupiter
mag -2.7 15

• A physically-BasedNight sky model, H.W.Jensen
  et al http/graphics.stanford.edu/henrik/papers/n
  ightsky/
• in opposition

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Moon phases

• Magnitude
• Full Moon -12.7 Sun -26.8
• Full Moon 2.3 10-6 Sun
• Bandwitdh 300-400nm
• ISun1014 ph/cm2.s.sr.nm
• I Full Moon 2.3 105 ph/m2.sr.ns
• Moon phases
• I Half Moon 0.1 x I Full Moon
• New Moon 1 day 100 ph/..
• New Moon 3.5 days 3000 ph/..

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Light pollution from cities
Line of 20 increase of Night Sky Background
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Conclusions

• BISS BBABY IAIRGLOW
• 400 300
  above sea
• But
• Airglow varies up to factor 3
• BABY data implies other sources than the diffuse
  night sky brightness reference
• Extrapolation from balloon needs more parameters
• Moon phases have to be included

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Example