Abstract

The forward scattering of sunlight by atmospheric aerosols causes a bright glow to appear around the Sun. This phenomenon, the simplest manifestation of the solar corona, is called the solar aureole. Simple methods can be used to photograph the solar aureole with conventional and digital cameras. Aureole images permit both a visually qualitative and an analytically quantitative comparison of aureoles caused by dust, smoke, haze, pollen, and other aerosols. Many hundreds of aureole photographs have been made at Geronimo Creek Observatory in Texas, including a regular time series since September 1998. These images, and measurements extracted from them, provide an important supplement to studies of atmospheric aerosols.

© 2003 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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Bishop, S. E.

S. E. Bishop, “The remarkable sunsets,” Nature (London) 29, 259–260 (1884).
[CrossRef]

Coulson, K. L.

K. L. Coulson, Polarization and Intensity of Light in the Atmosphere (Deepak, Hampton, Va., 1988), pp. 350–362.

Fiske, R. S.

T. Simkin, R. S. Fiske, Krakatau 1883 (Smithsonian Institution Press, Washington, D.C., 1983), pp. 154–159.

Linacre, E.

E. Linacre, Climate and Data Resources (Routledge, London, 1992), pp. 152–153.

Livingston, W.

L. Lynch, W. Livingston, Color and Light in Nature (Cambridge U. Press, Cambridge, 1995), p. 32.

Lynch, L.

L. Lynch, W. Livingston, Color and Light in Nature (Cambridge U. Press, Cambridge, 1995), p. 32.

Meinel, A.

A. Meinel, M. Meinel, Sunsets, Twilights, and Evening Skies (Cambridge U. Press, Cambridge, 1983), pp. 79–81.

Meinel, M.

A. Meinel, M. Meinel, Sunsets, Twilights, and Evening Skies (Cambridge U. Press, Cambridge, 1983), pp. 79–81.

Miller, J. R.

Mims, F. M.

Mims, S. A.

S. A. Mims, “Stuff in the air: Sahara dust and other aerosols collected in South Texas,” presented at the Texas Junior Academy of Science, Texas AM University, College Station, Texas, 17 April 2002.

Minnaert, M. G. J.

M. G. J. Minnaert, Light and Color in the Outdoors, revised edition, L. Seymour, ed. (Springer-Verlag, Berlin, 1993), pp. 238–245.

Nakajima, T.

O’Neil, N. T.

Shiobara, M.

Simkin, T.

T. Simkin, R. S. Fiske, Krakatau 1883 (Smithsonian Institution Press, Washington, D.C., 1983), pp. 154–159.

Tanaka, M.

Appl. Opt. (4)

Nature (London) (1)

S. E. Bishop, “The remarkable sunsets,” Nature (London) 29, 259–260 (1884).
[CrossRef]

Other (7)

T. Simkin, R. S. Fiske, Krakatau 1883 (Smithsonian Institution Press, Washington, D.C., 1983), pp. 154–159.

A. Meinel, M. Meinel, Sunsets, Twilights, and Evening Skies (Cambridge U. Press, Cambridge, 1983), pp. 79–81.

S. A. Mims, “Stuff in the air: Sahara dust and other aerosols collected in South Texas,” presented at the Texas Junior Academy of Science, Texas AM University, College Station, Texas, 17 April 2002.

L. Lynch, W. Livingston, Color and Light in Nature (Cambridge U. Press, Cambridge, 1995), p. 32.

E. Linacre, Climate and Data Resources (Routledge, London, 1992), pp. 152–153.

M. G. J. Minnaert, Light and Color in the Outdoors, revised edition, L. Seymour, ed. (Springer-Verlag, Berlin, 1993), pp. 238–245.

K. L. Coulson, Polarization and Intensity of Light in the Atmosphere (Deepak, Hampton, Va., 1988), pp. 350–362.

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Figures (3)

Fig. 1
Fig. 1

(a) Aureole-free Sun photographed from the 4.3-km summit of Mauna Kea in Hawaii on 24 June 2000 (AOT820 nm ≤ 0.02). The solar disk here and in (c)–(f) is blocked by a small black sphere mounted on a stiff wire. (b) Bishop’s ring around the Sun caused by volcanic aerosols in the stratosphere photographed from the summit of Mauna Kea on 4 August 1992 (AOT820 nm = 0.37). The solar disk is blocked by an antenna mast. (c) Solar aureole on a very clear day at Geronimo Creek Observatory, Texas, 14 February 1999 (AOT820 nm = 0.04). (d) Extraordinarily rare pollen corona on a clear day at Geronimo Creek Observatory, 17 January 1999 (AOT820 nm = 0.07). (e) Broadly diffuse aureole and bluish sky caused by smoke from Mexico advected over Texas on 5 May 2000 (AOT820 nm = 0.36). (e) Disk-shaped aureole and grayish sky formed by Sahara dust blown from Africa to Texas on 4 July 2000 (AOT820 nm = 0.24).

Fig. 2
Fig. 2

Digitized scan of the intensity of blue light from the edge of the solar disk to 16° away from the Sun for the solar aureoles in Figs. 1(a) (Mauna Kea summit), 1(d) (Clear sky over Texas), 1(e) (Mexican smoke over Texas), and 1(f) (Sahara dust over Texas).

Fig. 3
Fig. 3

Ratios of the red/blue intensities of the aureoles plotted in Fig. 2. The high color ratio caused by the Sahara dust implies that it comprises larger particle sizes than does smoke.

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