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R. Schwenn B. Inhester S. P. Plunkett A. Epple B. Podlipnik D. K. Bedford C. J. Eyles G. M. Simnett S. J. Tappin M. V. Bout P. L. Lamy A. Llebaria G. E. Brueckner K. P. Dere R. A. Howard M. J. Koomen C. M. Korendyke D. J. Michels J. D. Moses N. E. Moulton S. E. Paswaters D. G. Socker O. C. St. Cyr D. Wang 《Solar physics》1997,175(2):667-684
The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft
has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line
emission corona can be made visible throughout the instrument's full field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured
from Sun center). Quantitative evaluations based on calibrations cannot yet be performed, but some basic signatures show up
even now: (1) There are often bright and apparently closed loop systems centered at latitudes of 30° to 45° in both hemispheres.
Their helmet-like extensions are bent towards the equatorial plane. Farther out, they merge into one large equatorial ‘streamer
sheet’ clearly discernible out to 32 R⊙. (2) At mid latitudes a more diffuse pattern is usually visible, well separated from
the high-latitude loops and with very pronounced variability. (3) All high-latitude structures remain stable on time scales
of several days, and no signature of transient disruption of high-latitude streamers was observed in these early data. (4)
Within the first 4 months of observation, only one single ‘fast’ feature was observed moving outward at a speed of 70 km s-1 close to the equator. Faster events may have escaped attention because of data gaps. (5) The centers of high-latitude loops
are usually found at the positions of magnetic neutral lines in photospheric magnetograms. The large-scale streamer structure
follows the magnetic pattern fairly precisely. Based on our observations we conclude that the shape and stability of the heliospheric
current sheet at solar activity minimum are probably due to high-latitude streamers rather than to the near-equatorial activity
belt.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004948913883 相似文献
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Küveler G. Wiehr E. Thomas D. Harzer M. Bianda M. Epple A. Sütterlin P. Weisshaar E. 《Solar physics》1998,182(1):247-255
The primary image reflected from the field stop of solar Gregory telescopes is used for automatic guiding. This new system
avoids temporal varying influences from the bending of the telescope tube by the main mirror's gravity and from offsets between
the telescope and a separate guiding refractor. The required stiffness of the guider mechanics and the small areas of the
sensors demand small f numbers for the guider optics, which cause problems with the image quality and with heat. Problems
also arise from the pinhole in the telescope's field stop which is imaged as a dark dot on the sensor. Pointing errors introduced
by the telescope affect shifts of the solar image on the sensor. These are numerically determined by Fourier methods which
are found to be less sensitive to noise than profile centering methods. Several types of guiders are tested, the final equipment,
now installed at the Gregory telescopes at Tenerife and at Locarno, is described. 相似文献
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