Abstract
THE solar chromosphere is a thin layer of gas that is several thousand degrees hotter than the underlying photosphere, and responsible for most of the Sun's ultraviolet emission. The mechanism by which it is heated to temperatures exceeding 10,000 K is not understood. Millimetre and submillimetre radiometry can be used to obtain the chromospheric temperature profile, but the diffraction-limited resolution for the largest telescopes is at best 17 arcsec, or ∼12,500 km at the Sun's distance. This is greater than the thickness of the quiet chromosphere itself. The total eclipse of July 1991, which passed over the Mauna Kea Observatory in Hawaii, provided a rare opportunity to make limb occultation observations with a large submillimetrewavelength telescope, the 15-m James Clerk Maxwell Telescope, and in this way we obtained a temperature profile in 1.3-mm radiation with ∼300 km resolution at the Sun. Our observations indicate that spicules (magnetically entrained funnels of gas) reach a temperature of 8,000 K at 3,000–4,000 km above the photosphere, a temperature lower than those of many spicule models.
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Lindsey, C., Jefferies, J., clark, T. et al. Extreme-infrared brightness profile of the solar chromosphere obtained during the total eclipse of 1991. Nature 358, 308–310 (1992). https://doi.org/10.1038/358308a0
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DOI: https://doi.org/10.1038/358308a0
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