Solar prominence

Sir Joseph Norman Lockyer, 1836-1920. Director of the solar physics observatory of The Royal College of Science at South Kensington. Pioneer in the spectroscopy of the sun and stars. In 1868 Lockyer and Janssen independently discovered a spectroscopic method of observing the solar prominences in daylight. Such observations had previously been made only at the time of total eclipses of the sun. 

Joseph Lockyer (1836-1920) was one of the pioneers of solar spectroscopy. In examining the spectra of solar prominences in 1869, Lockyer noticed an absorption line that he could not identify. Reasoning that it represented an element not present on Earth, he proposed a new element - helium, from the Greek word helios for Sun. This idea failed to achieve acceptance from Lockyer s scientific colleagues until a gas having the same mysterious spectral line was found 25 years later in rocks. The helium in terrestrial uranium ore formed as a decay product of radioactive uranium. Thus, this abundant element was first discovered in the Sun, rather than in the laboratory. Lockyer s cosmochemical discovery was recognized by the British government, which created a solar physics laboratory for him. Lockyer also founded the scientific journal Nature, which he edited for 50 years. 

Solar illumination Seasonal and diurnal patterns Solar prominence Solar system Solar wind... 

The sunspots move across the sun s face as the sun rotates, and when they are seen in profile at the edge of the sun they turn out to be tremendous eruptions which we call solar prominences. A prominence can be photographed—as on the following page—by using a coronagraph to artificially eclipse the sun s bright disk. 

In 1868, a total solar ecHpse provided a unique oppoitunity to apply the spectroscope to stellar chemistry. At the moment when the Sun was perfectly eclipsed, the solar prominences surrounding the dark disk provided discrete line-emission spectra. Among these was a series of lines that matched no known elements. The discoverer, Joseph Norman Lockyer (1836-1920), postulated the existence of a new chemical element, helium after Helios (or Sun). The names of most metals typically end in ium or um and since most elements are metals hehum was first assumed to be a metal and named accordingly. Some 27 years later, helium was identified as a gas emanating from the uranium-containing mineral cleveite by William Ramsay. 

The discoveries of helium and radon stand out as unusual. Radon was discovered as a result of radioactivity studies, or, more precisely, owing to the application of the radiometric method. Therefore, we shall deal with it in Chapter 11, which is devoted to the history of radioactive elements. The discovery of helium occupies an exceptional place in the history of chemistry. In 1868 a line was detected in the spectra of solar prominences, which could he assigned to none of the elements known on the earth. This line was attributed to a new element on the sun which was called helium . Twenty seven years later helium was first extracted on Earth. 

Another example is given by discoveries of three totally unrelated elements—bromine, yttrium, and helium. What is the meaning of their dates of discovery in Table 4 The date for bromine (1826) corresponds to the extraction of the element in a free form. The date for yttrium corresponds to the preparation of its oxide (1794). Forty years later it became clear that the yttrium of Gadolin had in fact been a mixture of rare earths, and a relatively clean yttrium oxide was prepared by Mosander. Thus, in 1794 a mixture of related elements was discovered rather than an individual element. The accepted date of discovery of helium (1868) corresponds to an event which had never before happened in the history of elements. For the first time a conclusion about the existence of a new element was made proceeding from an unknown line in the spectrum of solar prominences rather than from experiments with material terrestrial objects. This element remained a pure hypothesis until it was found on Earth (1895). 

In 1868, helium (He from Greek helios , the sun) was discovered due to a pale yellow line at 587.6 nm during the spectroanalytical examination of the solar prominences. In 1882, it was also detected in the spectral analysis of lava from the Vesuvius and as gas occlusion in the uranium mineral uraninite in 1889. Only in 1895, helium could be produced in its pure form in larger quantities from the mineral cleveite. And in 1908, H. Kamerlin -Onnes at Leiden succeeded for the first time in liquefying helium [4.1]. 

Sodium is present in fair abundance in the sun and stars. The D lines of sodium are among the most prominent in the solar spectrum. Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth s crust it is the most abundant of the alkali group of metals. 

In 1817, Josef Fraunhofer (1787-1826) studied the spectrum of solar radiation, observing a continuous spectrum with numerous dark lines. Fraunhofer labeled the most prominent of the dark lines with letters. In 1859, Gustav Kirchhoff (1824-1887) showed that the D line in the solar spectrum was due to the absorption of solar radiation by sodium atoms. The wavelength of the sodium D line is 589 nm. What are the frequency and the wavenumber for this line ... 

In addition to biogeochemical cycles (discussed in Section 6.5), the hydrosphere is a major component of many physical cycles, with climate among the most prominent. Water affects the solar radiation budget through albedo (primarily clouds and ice/snow), the terrestrial radiation budget as a strong absorber of terrestrial emissions, and global temperature distribution as the primary transporter of heat in the ocean and atmosphere. 

Helium is the second most abundant element in the visible Universe and accordingly there is a mass of data from optical and radio emission lines in nebulae, optical emission lines from the solar chromosphere and prominences and absorption lines in spectra of hot stars. Further estimates are derived more indirectly by applying theories of stellar structure, evolution and pulsation. However, because of the relative insensitivity of Tp to cosmological parameters, combined with the need to allow for additional helium from stellar nucleosynthesis in most objects, the requirements for accuracy are very severe better than 5 per cent to place cosmological limits on Nv and better still to place interesting constraints on t] or One can, however, assert with confidence that there is a universal floor to the helium abundance in observed objects corresponding to 0.23 < Fp < 0.25. 

Hydrogen in the uncombined state exists in enormous masses upon the sun, and is present in the "prominences observed in solar eclipses, while by optical means it may also be detected in many stars and nebulae. 

Lauretta, D. S. and McSween, H. Y., Jr., editors (2006) Meteorites and the Early Solar System II. Tucson University of Arizona Press, 943 pp. Another comprehensive, modem collection of reviews by prominent meteoriticists - everything you want to know about meteorites is here, but the chapters are at an advanced technical level. 

Additional models of FFMF for interstellar physics also postulated that the spiral arms of galaxies, as well as solar flares and prominences, could be constmcted of such force-free fields [17]. Similar Beltrami field structures have... 

Table 3.2. Elemental (atomicj abundance ratios of prominent noble gases in the solar system...

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