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  • richardmitnick 11:21 am on March 18, 2016 Permalink | Reply
    Tags: , , , Universe of Spectroscopy   

    From NAOJ Universe of Spectroscopy: “Spectra of the Solar Corona” 

    NAOJ

    NAOJ

    Universe of Spectroscopy
    Universe of Spectroscopy

    To observe the corona surrounding the Sun, we have to wait for an opportunity to view a total solar eclipse when the Moon fully blocks the solar disk. In visible light, the bright solar surface hampers observation of the faint corona.

    Observations at shorter wavelength light such as ultraviolet and X-ray are appropriate to investigate the corona in detail. The high-temperature corona emits more radiation at shorter wavelength. However, ultraviolet and X-ray radiation cannot penetrate the Earth’s atmosphere. That is the reason why we need a space observatory.

    The observational satellite Hinode’s onboard instrument, called Extreme-ultraviolet Imaging Spectrometer (EIS), was designed for obtaining spectra of the solar corona. The extreme-ultraviolet is a wavelength range of the shorter wavelength region of ultraviolet radiation. We can find many spectral lines radiating from high temperature (higher than one million Kelvin) plasma.

    JAXA HINODE spacecraft
    JAXA HINODE spacecraft

    The extreme-ultraviolet is a wavelength range of the shorter wavelength region of ultraviolet radiation. We can find many spectral lines radiating from high temperature (higher than one million Kelvin) plasma.

    The most frequent lines are emission lines originating in ionized iron. Iron, with the symbol Fe, is atomic number 26 and will have 26 electrons. In such a hot corona, a part of the electrons is removed from iron atoms, and more electrons are removed at higher temperature. Analysis of the emission lines of the ionized iron yields information on the temperature of the corona.

    1
    A part of the extreme-ultraviolet spectrum obtained by the EIS installed on Hinode. Many emission lines caused by ionized iron are visible. For example, “Fe X” means an iron ion removed nine electrons from a neutral iron atom. Combining ratios between other iron charge states yields the temperature of the corona. In addition, analyzing the wavelength shift of emission lines, we will derive the corona’s motion velocity.

    Is the corona’s temperature one million Kelvin?

    It is generally believed that the corona’s temperature is one million Kelvin. However, plasma of various temperatures is distributed throughout the corona. “Warm” plasma has a temperature of about one million Kelvin, while “hot” plasma is higher than two million Kelvin. Moreover, super hot plasma with a temperature of higher than ten million Kelvin is observed when a giant solar flare erupts. Studying the solar spectra at extreme-ultraviolet is essential to developing an understanding of the temperature distribution and the dynamics of the solar corona that has such a diversity of temperatures.

    2
    The solar corona’s image in the extreme-ultraviolet emission line of an ionized iron. The typical temperature of each iron charge state is indicated.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
    Subaru

    ALMA Array
    ALMA

    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

     
  • richardmitnick 11:54 am on March 3, 2016 Permalink | Reply
    Tags: , , Fraunhofer lines of the sun, , Universe of Spectroscopy   

    From NAOJ: “Fraunhofer Lines of the Sun” 

    NAOJ

    NAOJ

    Universe of Spectroscopy

    November 16, 2011 [Presented by NAOJ March 3, 2016]
    Yukio Katsukawa

    Fraunhofer Lines of the Sun Norikura Solar Observatory
    Solar spectra observed by 25cm Cornagraph at Norikura Solar Observatory. The Fraunhofer lines (C, D, E, F, G, H,and K lines) are indicated.

    When you let sunlight pass through a prism, you can see that the light is broken up into the colors of the rainbow (a spectrum). If you observe the spectrum more carefully, you will find countless dark features. These are absorption lines caused by impurities such as calcium, sodium, magnesium, iron, and so on. The chief element of the Sun is hydrogen, and the impurities in minuscule quantities absorb the light coming from the inside at specific wavelengths, resulting in the dark features.

    The Fraunhofer lines are a set of famous absorption lines named after a German physicist. Fraunhofer designated the principal features with the letters A through K from longer wavelength (redder) to shorter (bluer). For example, the D line is caused by sodium, and the H and K lines are caused by calcium. Some Fraunhofer lines were known to originate in absorption in the Earth’s atmosphere.

    The Fraunhofer lines are, indeed, a lifeline of solar physicists. The depths of the absorption lines provide information about temperature, and the wavelength shifts of the lines tell us the motion of gas. If the Sun consisted only of pure hydrogen, there would be no absorption line. This would mean that the researchers could not study the temperature or the motion of the Sun’s atmosphere. This would be the end for them. Thanks to the impurities, we can investigate the Sun in detail.

    3-D Structure of the Sun’s atmosphere

    A dark feature in a spectrum results from absorption of light at a given wavelength. This means a low degree of transparency of the atmosphere at this wavelength. Therefore, we can only observe the outer region of the Sun at this wavelength. We utilize this to study the atmosphere outside the region where we usually observe. The degree of the transparency of the Sun’s atmosphere depends on the absorption lines. Thus, we combine several absorption lines to observe several layers and to study the 3D structure of the Sun’s atmosphere.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
    Subaru

    ALMA Array
    ALMA

    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

     
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