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Feasibility of a reflecting coronagraph
Climate, Sundials, Telescopes, Magnetism, and Gravity Jokipii, J. E., H i g h A l t i t u d e O b s e r v a t o r y of the University of Colorado, "Diffusion of a-Particles i n the C o r o n a a n d Solar W i n d " , A s t r o - G e o p h y s i c a l M e m o r a n d u m No. 160, 14 A u g u s t 1963, 10 pgs. The mutual diffusion of a-particles and protons in the solar wind is analyzed. It is shown that this effect is sufficient to significantly lower the relative abundance of helium in the solar wind from that on the sun. In particular, the factor of ten reduction indicated by preliminary Mariner II data is shown to be consistent with the present estimates of coronal parameters. Chang, Ho-chi, a n d H a o Chiao-Suiu, P u r p l e M o u n t a i n O b s e r v a t o r y , N a n k i n g , " P h o t o m e t r y of Large Solar Flares", Scientia Sinica, Vol. X I I , No. 7, 1963, 13 pgs. Results of photometric and positional measurements of bright spots in three large solar flares are given. It is shown that these bright spots, being not stationary, move with velocities in the range of 10-20 km/sec for I I I and I I I flares. Tandberg-Hanssen, Einar, "Physical Conditions in L i m b Flares a n d Active P r o m i n e n c e s . VI. Selective E x c i t a t i o n C o n d i t i o n s " , T h e Astrophysical J o u r n a l , Vol. 137, No. 1, J a n u a r y , 1963, 15 pgs. The complex surge prominence of November 18, 1960, is studied spectroscopically. It is shown that the surge consists of different regions, where the physical conditions (temperature and/or internal motions) differ from one region to another. The metal and helium regions are shot out from an underlying flare in different directions. We notice that the emission from Fe II is considerably fainter than that from Ti II or Ba II. A finer spectroscopic classification of flares and prominences than that previously introduced is discussed. We find, as a general rule, that while Ti II lines are stronger than Fe II lines in prominences, the reverse holds true in flares. As a new classification criterion we introduce the line intensity ratio M = [I] (Fe II, 4584)/I(Ti II, 4572). Zirin, Harold, High A l t i t u d e O b s e r v a t o r y , B o u l d e r Colorado, " C o r o n a l O b s e r v a t i o n s a n d R o c k e t Solar U l t r a v i o l e t R e s u l t s " , A I A A J o u r n a l , Vol. 1, No. 6, J u n e , 1963, 4 pgs. Observations of the extreme ultraviolet (EUV) spectrum of the sun made from outside the earth's atmosphere have enabled astronomers to supplement knowledge of the solar corona obtained by observation in the visual and near infrared region with coronagraphs. Since the solar spectrum below 500 .~ arises primarily in the corona, EUV observations permit observation of the corona directly on the disk. On the basis of the knowledge of changes in the general temperature of the corona, the EUV spectrum is expected to change in the course of the solar cycle. Some short-term changes already have been observed at the time of solar flares. Particularly large effects are found in the near x-ray region. Observations of the EUV spectrum, combined with ground based observation give new information on the structure of the chromosphere-corona transition zone. A general outline is given of coronal problems which may be studied simultaneously from the ground and from above the atmosphere. Harris, Isadore, a n d W o l f g a n g Priester, G o d d a r d Space F l i g h t Center, " T i m e - D e p e n d e n t S t r u c t u r e of the U p p e r A t m o s p h e r e " , N A S A T N D-1443, J u l y 1962, 71 pp. The physical properties of the upper atmosphere are determined principally by heat conduction, heat sources, and the 72
barometric law. An analysis of the integro-differential equation describing these physical processes has been carried out. It is found that heating of the thermosphere due to absorption of the solar extreme ultraviolet (EUV) radiation alone cannot explain the observed diuranal variation of density and temperature, since it would yield a maximum of these properties at about 17h local time, instead of 14~ where it is observed. Secondly, if the EUV flux is adjusted to give the observed average temperature, than the amplitude of the diurnal density variation would be much too large compared to the observed amplitude. Thirdly, it would require an extremely high efficiency for the conversion of EUV radiation into heat (i.e., comparing the required flux with Hinteregger's measurements of the EUV flux). Thus, it is necessary to have another heat source in addition to the absorption of EUV radiation. If an additional heat source is used, with a maximum at about 9h local time and a flux of 1 erg/cm2-sec, a time-dependent model of the upper atmosphere is obtained that is in good agreement with the observed densities. There is evidence that this additional heat source derives its energy ultimately from the solar corpuscular radiation. The results of calculations are presented for a model in the equatorial and temperate zones of the earth for those times when the average solar activity corresponds to a solar radiation flux of 200 X 10-2~W/m2-cpsat 10.7 cm wavelength. The physical properties (temperature, density, pressure, scale height, mean molecular weight, and the number densities of N2, 02, He and H) are given as a function of local time and for the altitudes between 120 and 2050 kin. M a t s u s h i t a , S., High A l t i t u d e O b s e r v a t o r y , Boulder, Colorado, "On G e o m a g n e t i c S u d d e n C o m m e n c e ments, S u d d e n Impulses, a n d S t o r m D u r a t i o n s " , Journal of Geophysical Research, Sept., 1962, 25 pp. After a study of the morphology of geomagnetic sudden commencements during the IGY, their accompanying phem)mena, such as sudden increases of cosmic noise absorption, bursts of bremsstrahlung x rays, and commencements of geomagnetic micropulsations, are examined. Geomagnetic sudden impulses observed during the IGY are then studied similarly. Four types are found, three of which are completely analogous, both in their morphologies and in their accompanying phenomena, to the corresponding types of sudden commencements. The average duration of the storm depression of the horizontal geomagnetic field, usually attributed to the ring current, is also studied. Storms during years of great solar activity are found to be about three times longer than those during years of little solar activity. The spectrum of storm durations is found; it is concluded that even sudden impulses belong to the family of storms. Possible causes of all these related phenomena, including increases of cosmic noise absorption and micropulsations, are discussed. Newkirk, G o r d o n A., a n d J o h n A. E d d y , H i g h A l t i t u d e O b s e r v a t o r y , Boulder, Colorado, " D a y t i m e S k y R a d i a n c e F r o m F o r t y to E i g h t y T h o u s a n d F e e t " , Nature, Vol. 194, No. 4829, M a y , 1962, 3 pp. As part of a programme to investigate the feasibility of coronal observations from balloons, The High Altitude Observatory has flown an externally occulting corouagraph up to heigh'ts of 82,000 ft to measure the angular and the wavelength distribution of the daylight sky. The sky radiances were recorded in three ways: (1) photographically, at scattering angles ~ = 9.6 °, 20.7°, 31.4°, 40.6°, and 57.8° at X = 0.44~ with electric vector vibrating perpendicularly to the scattering plane; (2) photographically, at scattering angles from 1.67° to 2.8 ° with a low-dispersion spectrograph covering Xk0.37~).79~; (3) photoelectrically, at a scattering angle 10.3° at k = 0.52~. Zirin, H., a n d G o r d o n Newkirk, Jr., " F e a s i b i l i t y of a Reflecting C o r o n a g r a p h " , Applied Optics, S e p t e m b e r , 1963, 1 p. To overcome the one serious disadvantage of the Lyot Coronagraph--chromatic aberration--the authors explain that their tests indicate that the construction of a completely achromatic, reflecting coronagraph is feasible.
Solar Energy
barometric law. An analysis of the integro-differential equation describing these physical processes has been carried out. It is found that heating of the thermosphere due to absorption of the solar extreme ultraviolet (EUV) radiation alone cannot explain the observed diuranal variation of density and temperature, since it would yield a maximum of these properties at about 17h local time, instead of 14~ where it is observed. Secondly, if the EUV flux is adjusted to give the observed average temperature, than the amplitude of the diurnal density variation would be much too large compared to the observed amplitude. Thirdly, it would require an extremely high efficiency for the conversion of EUV radiation into heat (i.e., comparing the required flux with Hinteregger's measurements of the EUV flux). Thus, it is necessary to have another heat source in addition to the absorption of EUV radiation. If an additional heat source is used, with a maximum at about 9h local time and a flux of 1 erg/cm2-sec, a time-dependent model of the upper atmosphere is obtained that is in good agreement with the observed densities. There is evidence that this additional heat source derives its energy ultimately from the solar corpuscular radiation. The results of calculations are presented for a model in the equatorial and temperate zones of the earth for those times when the average solar activity corresponds to a solar radiation flux of 200 X 10-2~W/m2-cpsat 10.7 cm wavelength. The physical properties (temperature, density, pressure, scale height, mean molecular weight, and the number densities of N2, 02, He and H) are given as a function of local time and for the altitudes between 120 and 2050 kin. M a t s u s h i t a , S., High A l t i t u d e O b s e r v a t o r y , Boulder, Colorado, "On G e o m a g n e t i c S u d d e n C o m m e n c e ments, S u d d e n Impulses, a n d S t o r m D u r a t i o n s " , Journal of Geophysical Research, Sept., 1962, 25 pp. After a study of the morphology of geomagnetic sudden commencements during the IGY, their accompanying phem)mena, such as sudden increases of cosmic noise absorption, bursts of bremsstrahlung x rays, and commencements of geomagnetic micropulsations, are examined. Geomagnetic sudden impulses observed during the IGY are then studied similarly. Four types are found, three of which are completely analogous, both in their morphologies and in their accompanying phenomena, to the corresponding types of sudden commencements. The average duration of the storm depression of the horizontal geomagnetic field, usually attributed to the ring current, is also studied. Storms during years of great solar activity are found to be about three times longer than those during years of little solar activity. The spectrum of storm durations is found; it is concluded that even sudden impulses belong to the family of storms. Possible causes of all these related phenomena, including increases of cosmic noise absorption and micropulsations, are discussed. Newkirk, G o r d o n A., a n d J o h n A. E d d y , H i g h A l t i t u d e O b s e r v a t o r y , Boulder, Colorado, " D a y t i m e S k y R a d i a n c e F r o m F o r t y to E i g h t y T h o u s a n d F e e t " , Nature, Vol. 194, No. 4829, M a y , 1962, 3 pp. As part of a programme to investigate the feasibility of coronal observations from balloons, The High Altitude Observatory has flown an externally occulting corouagraph up to heigh'ts of 82,000 ft to measure the angular and the wavelength distribution of the daylight sky. The sky radiances were recorded in three ways: (1) photographically, at scattering angles ~ = 9.6 °, 20.7°, 31.4°, 40.6°, and 57.8° at X = 0.44~ with electric vector vibrating perpendicularly to the scattering plane; (2) photographically, at scattering angles from 1.67° to 2.8 ° with a low-dispersion spectrograph covering Xk0.37~).79~; (3) photoelectrically, at a scattering angle 10.3° at k = 0.52~. Zirin, H., a n d G o r d o n Newkirk, Jr., " F e a s i b i l i t y of a Reflecting C o r o n a g r a p h " , Applied Optics, S e p t e m b e r , 1963, 1 p. To overcome the one serious disadvantage of the Lyot Coronagraph--chromatic aberration--the authors explain that their tests indicate that the construction of a completely achromatic, reflecting coronagraph is feasible.
Solar Energy