Upper atmosphere studies Observation of solar brightness oscillations ...
Upper atmosphere studies Observation of solar brightness oscillations at the South Pole R. STEBBINS, R. RONAN*, and M. ARRAMBIDE
Two members of the field team (Ronan and Stebbins) arrived at South Pole Station on 6 November, readied the telescope (figure 1), and commenced observations on 22 November. Arrambide replaced Stebbins in early December, and Stebbins returned to replace Arrambide on 18 January. Twelve-hour observing watches were continued until 31 January. The telescope was then dismantled and shipped back to Sunspot. The field team left Antarctica 5 February.
National Solar Observatory National Optical Astronomy Observatories** Sunspot, New Mexico 88349
The Sun is vibrating mechanically in a highly ordered, but complex, fashion. These acoustic resonances, called the "normal modes," reflect the internal structure of the star much as seismic data tell about the Earth's interior. The Sun's acoustic spectrum contains in excess of 10 million modes. To separate and identify the individual modes, continuous, multi-day observations are necessary; these are possible only at a South Pole site. A telescope specially designed for detecting the brightness manifestation of these solar oscillations and for operating in the south polar environment (Stebbins 1981) was set up at the Amundsen-Scott South Pole Station in the austral summer of 1982 - 1983. The telescope produced over 600 hours of data in that year. It was not operated the following austral summer. Left in place for 2 years, the telescope was run again through the austral summer of 1984 - 1985. In February 1985, it was dismantled and returned to the United States. Extensive data reduction software was produced for the 1982 - 1983 data, and much of the data was processed during 1983 and early 1984. We encountered problems correcting the data for detector idiosyncrasies. These problems appeared to be soluble but required additional calibration work at south polar ambient temperatures. As we prepared for the 1984 - 1985 season, we adjusted the detector electronics to prevent similar difficulties. During the summer of 1984, we also made several improvements to the hardware and operating software. The essential thrust of these was to take data on solar oscillations while scanning about the periphery of the Sun. The additional spatial information aids in the separation of modes in the acoustic spectrum. Enough electronic and mechanical parts of the telescope's solar detector had been returned to Sunspot to allow testing of these improvements. * Summer Research Assistant, presently at the Center for Astrophysics, Cambridge, Massachusetts 02138. ** Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 1985 REVIEW
I Figure 1. The telescope located near the Amundsen-Scott South Pole Station during the 1984 - 1985 season. (Photo courtesy of the National Solar Observatory Association of Universities for Research in Astronomy, Inc. Photograph number 850507.)
During the 1984-1985 austral summer, 932 hours of data were acquired comprising 55 percent of the entire season. Figure 2 shows the coverage. This excellent coverage is in contrast to the 1982– 1983 data (Stebbins and Mann 1983); the 1984– 1985 data contain many short data sets—none longer than 82 hours (fig219
ure 3). The earlier data consisted of fewer (16) and longer (up to 115 hours) data sets, covering 34 percent of the season. An extraordinarily long span of observing weather, nearly 2 weeks, occurred at about the time the telescope was starting up. The best solar observing weather seems to occur in November and late January.
20 Is I6 14 NUMBER 12 OF DATA SETS 10
0
0-10 10-20 20.3020-4040-0050-60
One problem with the instrument occurred during startup. We tried several shaft couplings in the solar perimeter-scanning drive before we found a suitable type. The only other instrument failure during the season was a blown fuse. We found that, with some care in design, moderately complex astronomical instrumentation can be made to run smoothly in the antarctic environment. Reduction of the data now on hand must begin with verification of the calibration of the 1984 - 1985 data. When this has been completed satisfactorily, the data reduction software developed for the 1982 - 1983 data has to be modified to account for the spatial information present in the newer data. This work is now in progress. The work reported here was supported in part by National Science Foundation grant DPP 80-01469. The National Solar Observatory is operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.
eo.0 70410 00-90
References
LENGTH OF DATA SETS (IN HRS)
Figure 3. Histogram showing the frequency of occurrence of data sets of certain lengths. (Photo courtesy of the National Solar Observatory Association of Universtities for Research in Astronomy, Inc. Photograph number 850505A.)
Stebbins, R.T. 1981. An antarctic telescope. In R.B. Dunn (Ed.), Solar instrumentation: What's next? Sunspot, N.M.: Sacramento Peak National Observatory. Stebbins, R. T., and G. R. Mann. 1983. Observations of solar oscillations at the South Pole. Antarctic Journal of the U.S., 18(5), 268 - 269.
DATA SET COVERAGE 84-85 I 2 3 4 5 6 CAt. 7 8 9 10 1112 I Ii I I II H I I Ni I HH
I-ff II
20 21 22 23 24 25 26 27 28 29 30 I 2 3 4 5 6 7 8 9 10 I I I I I I I I I I I I I I I I I DECEMBER NOVEMBER 13 1415 I— HH
16 I—I
17 18 19 I I H H
20 21 22 I I H I I
10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 I I I I I I I I I I I I I I I I I I I I DECEMBER
I
23 24 25 26 27 28 29 3031 32 33 34 35 N t I H I I I—I I—I I-4 HF-I H I I H I- -1
30 31 I 2 3 4 5 6 7 8 9 10 II 12 13 14 IS 16 17 IS 19 I I I I I I I I I I I I JANUARY 36 37 3839 40 41 42 43 I II-4I-411 II
9 20 21 22 23 24 25 26 27 28 29 30 31 I 2 3 4 5 6 7 8 I I I I I I I 1 I I I I I I I I I I I I I
FEBRUARY
Figure 2. Data set coverage during the 1984- 1985 austral summer. The data set numbers are shown above the bar indicating duration. (Photo courtesy of the National Solar Observatory Association of Universities for Research in Astronomy, Inc. Photograph number 850505B.) 220
ANTARCTIC JOURNAL
Two members of the field team (Ronan and Stebbins) arrived at South Pole Station on 6 November, readied the telescope (figure 1), and commenced observations on 22 November. Arrambide replaced Stebbins in early December, and Stebbins returned to replace Arrambide on 18 January. Twelve-hour observing watches were continued until 31 January. The telescope was then dismantled and shipped back to Sunspot. The field team left Antarctica 5 February.
National Solar Observatory National Optical Astronomy Observatories** Sunspot, New Mexico 88349
The Sun is vibrating mechanically in a highly ordered, but complex, fashion. These acoustic resonances, called the "normal modes," reflect the internal structure of the star much as seismic data tell about the Earth's interior. The Sun's acoustic spectrum contains in excess of 10 million modes. To separate and identify the individual modes, continuous, multi-day observations are necessary; these are possible only at a South Pole site. A telescope specially designed for detecting the brightness manifestation of these solar oscillations and for operating in the south polar environment (Stebbins 1981) was set up at the Amundsen-Scott South Pole Station in the austral summer of 1982 - 1983. The telescope produced over 600 hours of data in that year. It was not operated the following austral summer. Left in place for 2 years, the telescope was run again through the austral summer of 1984 - 1985. In February 1985, it was dismantled and returned to the United States. Extensive data reduction software was produced for the 1982 - 1983 data, and much of the data was processed during 1983 and early 1984. We encountered problems correcting the data for detector idiosyncrasies. These problems appeared to be soluble but required additional calibration work at south polar ambient temperatures. As we prepared for the 1984 - 1985 season, we adjusted the detector electronics to prevent similar difficulties. During the summer of 1984, we also made several improvements to the hardware and operating software. The essential thrust of these was to take data on solar oscillations while scanning about the periphery of the Sun. The additional spatial information aids in the separation of modes in the acoustic spectrum. Enough electronic and mechanical parts of the telescope's solar detector had been returned to Sunspot to allow testing of these improvements. * Summer Research Assistant, presently at the Center for Astrophysics, Cambridge, Massachusetts 02138. ** Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 1985 REVIEW
I Figure 1. The telescope located near the Amundsen-Scott South Pole Station during the 1984 - 1985 season. (Photo courtesy of the National Solar Observatory Association of Universities for Research in Astronomy, Inc. Photograph number 850507.)
During the 1984-1985 austral summer, 932 hours of data were acquired comprising 55 percent of the entire season. Figure 2 shows the coverage. This excellent coverage is in contrast to the 1982– 1983 data (Stebbins and Mann 1983); the 1984– 1985 data contain many short data sets—none longer than 82 hours (fig219
ure 3). The earlier data consisted of fewer (16) and longer (up to 115 hours) data sets, covering 34 percent of the season. An extraordinarily long span of observing weather, nearly 2 weeks, occurred at about the time the telescope was starting up. The best solar observing weather seems to occur in November and late January.
20 Is I6 14 NUMBER 12 OF DATA SETS 10
0
0-10 10-20 20.3020-4040-0050-60
One problem with the instrument occurred during startup. We tried several shaft couplings in the solar perimeter-scanning drive before we found a suitable type. The only other instrument failure during the season was a blown fuse. We found that, with some care in design, moderately complex astronomical instrumentation can be made to run smoothly in the antarctic environment. Reduction of the data now on hand must begin with verification of the calibration of the 1984 - 1985 data. When this has been completed satisfactorily, the data reduction software developed for the 1982 - 1983 data has to be modified to account for the spatial information present in the newer data. This work is now in progress. The work reported here was supported in part by National Science Foundation grant DPP 80-01469. The National Solar Observatory is operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.
eo.0 70410 00-90
References
LENGTH OF DATA SETS (IN HRS)
Figure 3. Histogram showing the frequency of occurrence of data sets of certain lengths. (Photo courtesy of the National Solar Observatory Association of Universtities for Research in Astronomy, Inc. Photograph number 850505A.)
Stebbins, R.T. 1981. An antarctic telescope. In R.B. Dunn (Ed.), Solar instrumentation: What's next? Sunspot, N.M.: Sacramento Peak National Observatory. Stebbins, R. T., and G. R. Mann. 1983. Observations of solar oscillations at the South Pole. Antarctic Journal of the U.S., 18(5), 268 - 269.
DATA SET COVERAGE 84-85 I 2 3 4 5 6 CAt. 7 8 9 10 1112 I Ii I I II H I I Ni I HH
I-ff II
20 21 22 23 24 25 26 27 28 29 30 I 2 3 4 5 6 7 8 9 10 I I I I I I I I I I I I I I I I I DECEMBER NOVEMBER 13 1415 I— HH
16 I—I
17 18 19 I I H H
20 21 22 I I H I I
10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 I I I I I I I I I I I I I I I I I I I I DECEMBER
I
23 24 25 26 27 28 29 3031 32 33 34 35 N t I H I I I—I I—I I-4 HF-I H I I H I- -1
30 31 I 2 3 4 5 6 7 8 9 10 II 12 13 14 IS 16 17 IS 19 I I I I I I I I I I I I JANUARY 36 37 3839 40 41 42 43 I II-4I-411 II
9 20 21 22 23 24 25 26 27 28 29 30 31 I 2 3 4 5 6 7 8 I I I I I I I 1 I I I I I I I I I I I I I
FEBRUARY
Figure 2. Data set coverage during the 1984- 1985 austral summer. The data set numbers are shown above the bar indicating duration. (Photo courtesy of the National Solar Observatory Association of Universities for Research in Astronomy, Inc. Photograph number 850505B.) 220
ANTARCTIC JOURNAL
