Rotation of the solar interior
20
modeling of the International Cometary Explorer data indicates that the coronal mean-free path at the lower energies was 3 times larger than at neutron monitor energies, while the escape time was 10 times larger. This observed energy dependence of coronal transport parameters provides an important constraint for theoretical models of charged particle transport in the solar corona. This research was supported in part b y National Science Foundation grant DPP 83-00544 and by National Aeronautics and Space Administration grant NAG5-374.
0) ci
L (0
C
C
0 U U) U)
References
04)
C) X w
Axford, W.I. 1965. Anisotropic diffusion of solar cosmic rays.
Planetary
and Space Science, 13, 1301-1309.
0 2 4 6 8 Distance Traveled (Astronomical Units) Figure 2. Counting rate (above background) of the South Pole neutron monitor (data points) is well described by a combination of coronal diffusion and interplanetary focused transport (broad curve). Also shown is the response of the interplanetary propagation model to impulsive injection at the Sun (spike-like curve).
Rotation of the solar interior T.L. DUVALL, JR.
Laboratory for Astronomy and Solar Physics National Aeronautics and Space Administration Goddard Space Flight Center Greenbelt, Maryland 20771 J.W. HARVEY
National Solar Observatory Tucson, Arizona 85726
M.A. POMERANTZ Bartol Research Foundation of the Franklin Institute University of Delaware Newark, Delaware 19716
Although no helioseimological campaign was conducted during the 1985-1986 austral summer, progress has been made in the mammoth analytical program that is required for processing and interpreting the vast amount of data recorded in the 280
Bieber, J.W., P.A. Evenson, and M.A. Pomerantz. 1985. Exponential anisotropy of solar cosmic rays. Proceedings, 19th international Cosmic Ray Conference (La Jolla), 4, 335-338. Bieber, J.W., P.A. Evenson, and M.A. Pomerantz. 1986. Focusing anisotropy of solar cosmic rays. Journal of Geophysical Research, 91,8713-8724.
Bieber, J.W., J.A. Earl, C. Green, H. Kunow, R. Muller-Mellin, and C. Wibberenz. 1980. Interplanetary pitch angle scattering and coronal transport of solar energetic particles: New information from Helios. Journal of Geophysical Research, 85, 2313-2323. Duggal, S.P. 1979. Relativistic solar cosmic rays. Reviews of Geophysics and Space Physics, 17, 1021-1058. Reid, G.C. 1964. A diffusive model for the initial phase of a solar proton event. Journal of Geophysical Research, 69, 2659-2667.
spatially resolved experiment conducted several years ago (Pomerantz, Harvey, and Duvall 1982; Harvey. Pomerantz, and Duvall 1982). In particular, one of the major objectives—to derive information about the latitude and depth dependence of solar rotation—has already been achieved in a study using only one-third of the data. The bottom line is that the rotation averaged over the outer half of the Sun, probed by our measurements of normal modes of oscillation with degree 1 greater than 20 (where 1 is the number of nodes around the Sun of trapped acoustical waves) is essentially identical with that of the surface. Figure 1 shows one way of representing the spectra of solar oscillations as a function of frequency v, azimuthal order rn (which determines the surface pattern), and degree!. The depth in the Sun that is probed by a particular mode depends upon the value of 1, with the waves characterized by higher! values being confined to shallower regions. Without rotation, the frequencies corresponding to each of the ridges would be independent of rn—i.e., the lines would be vertical. This degeneracy is removed by rotation, however, causing the ridges to tilt. A complicated analysis is required for reaching quantitative conclusions about how the rotation rate varies with depth and latitude (Duvall, Harvey, and Pomerantz 1986). The essence of the results is displayed by figure 2. Coefficients a, of Legendre polynomials that enter into the description of the various eigenmodes are plotted against 1. The dashed lines are computed from measurements of the well-known surface differential rotaANTARCTIC JOURNAL
al445_
I
jic 20 15
a9 -
10-
5.
0
I
I I
a^ 15
Figure 1. Spectra of p,-mode oscillations with 5 values of I. The ordinate is m, ranging from m = + I (retrograde sectoral harmonics) to m = 0 (zonal harmonics) to m = -I(prograde sectoral harmonics). The tilt is produced by solar rotation, which removes the degeneracy of m.
tion rate, which decreases with heliolatitude. Within the variations in the latitude dependence of the angular velocity of surface features during the solar activity cycle, the odd-indexed coefficients, which carry information about rotation, do not vary with 1. The even-indexed coefficients provide information about the latitude variation of sound speed versus depth. If the internal structure of the Sun were independent of latitude, the even coefficients should be zero. The fact that they differ significantly indicates that the structure of the convection zone is different near the equator compared with higher latitudes. These unexpected results could have profound implications for theories of the origin of the solar magnetic field and solar activity. More surprises are likely to unfold as the analysis of the data in hand continues. This work was supported in part by National Science Foundation grant DPP 81-19627.
Stellar photometry at the South Pole K.Y. CHEN, J.P. OLIVER, and F.B. WOOD Department of Astronomy University of Florida Gainesville, Florida 32611
The south pole optical telescope (SPOT) was designed, constructed, and tested in Gainesville, Florida in 1985. The design is modified somewhat from the telescope operated at the pole in 1986 REVIEW
_+-
a5:rITH
20 30 40 50 60 70 80 90 100
Figure 2. Comparison of coefficients a i determined from the spatially resolved solar oscillation measurements with the values calculated from observations of the rotation of surface features. These results provide information about the latitude and depth dependence of the rotation rate and the Sun's internal structure.
References Duvall, T.L., Jr., J.W. Harvey and M.A. Pomerantz. 1986. Latitude and depth variation of solar rotation. Nature, 321, 500-501. Harvey, J. , M. Pomerantz, and T. Duvall, Jr. 1982. Astronomy on ice. 64(6), 520-523. Pomerantz, MA., J.W. Harvey, and T. Duvall, Jr. 1982. Large-scale motions and structure of the Sun. Antarctic Journal of the U.S., 17(5),
232-233.
the winter of 1984 (Giovanne et al. 1983; Wood et al. 1984). The telescope is a twin-mirror siderostat with a 8-centimeter achromatic lens which collects and brings the light to focus at the field stop. After passing an optical filter and a Fabry lens, the light reaches a photomultiplier which measures the brightness of a selected star or sky. The function of SPOT is controlled by an AIM-65 computer. Data are recorded on floppy disk. The telescope and computer were installed in January 1986 by Oliver and McNeil! after Wood's December 1985 trip to the pole to review site preparation and station nighttime lighting plans. The telescope system is housed in a special insulated building, 12 foot x 8 foot X 8 foot, constructed by the carpenters of ITT Antarctic Services. Only the optical head of SPOT is exposed to the harsh outside environment. The telescope is in a separate 281
modeling of the International Cometary Explorer data indicates that the coronal mean-free path at the lower energies was 3 times larger than at neutron monitor energies, while the escape time was 10 times larger. This observed energy dependence of coronal transport parameters provides an important constraint for theoretical models of charged particle transport in the solar corona. This research was supported in part b y National Science Foundation grant DPP 83-00544 and by National Aeronautics and Space Administration grant NAG5-374.
0) ci
L (0
C
C
0 U U) U)
References
04)
C) X w
Axford, W.I. 1965. Anisotropic diffusion of solar cosmic rays.
Planetary
and Space Science, 13, 1301-1309.
0 2 4 6 8 Distance Traveled (Astronomical Units) Figure 2. Counting rate (above background) of the South Pole neutron monitor (data points) is well described by a combination of coronal diffusion and interplanetary focused transport (broad curve). Also shown is the response of the interplanetary propagation model to impulsive injection at the Sun (spike-like curve).
Rotation of the solar interior T.L. DUVALL, JR.
Laboratory for Astronomy and Solar Physics National Aeronautics and Space Administration Goddard Space Flight Center Greenbelt, Maryland 20771 J.W. HARVEY
National Solar Observatory Tucson, Arizona 85726
M.A. POMERANTZ Bartol Research Foundation of the Franklin Institute University of Delaware Newark, Delaware 19716
Although no helioseimological campaign was conducted during the 1985-1986 austral summer, progress has been made in the mammoth analytical program that is required for processing and interpreting the vast amount of data recorded in the 280
Bieber, J.W., P.A. Evenson, and M.A. Pomerantz. 1985. Exponential anisotropy of solar cosmic rays. Proceedings, 19th international Cosmic Ray Conference (La Jolla), 4, 335-338. Bieber, J.W., P.A. Evenson, and M.A. Pomerantz. 1986. Focusing anisotropy of solar cosmic rays. Journal of Geophysical Research, 91,8713-8724.
Bieber, J.W., J.A. Earl, C. Green, H. Kunow, R. Muller-Mellin, and C. Wibberenz. 1980. Interplanetary pitch angle scattering and coronal transport of solar energetic particles: New information from Helios. Journal of Geophysical Research, 85, 2313-2323. Duggal, S.P. 1979. Relativistic solar cosmic rays. Reviews of Geophysics and Space Physics, 17, 1021-1058. Reid, G.C. 1964. A diffusive model for the initial phase of a solar proton event. Journal of Geophysical Research, 69, 2659-2667.
spatially resolved experiment conducted several years ago (Pomerantz, Harvey, and Duvall 1982; Harvey. Pomerantz, and Duvall 1982). In particular, one of the major objectives—to derive information about the latitude and depth dependence of solar rotation—has already been achieved in a study using only one-third of the data. The bottom line is that the rotation averaged over the outer half of the Sun, probed by our measurements of normal modes of oscillation with degree 1 greater than 20 (where 1 is the number of nodes around the Sun of trapped acoustical waves) is essentially identical with that of the surface. Figure 1 shows one way of representing the spectra of solar oscillations as a function of frequency v, azimuthal order rn (which determines the surface pattern), and degree!. The depth in the Sun that is probed by a particular mode depends upon the value of 1, with the waves characterized by higher! values being confined to shallower regions. Without rotation, the frequencies corresponding to each of the ridges would be independent of rn—i.e., the lines would be vertical. This degeneracy is removed by rotation, however, causing the ridges to tilt. A complicated analysis is required for reaching quantitative conclusions about how the rotation rate varies with depth and latitude (Duvall, Harvey, and Pomerantz 1986). The essence of the results is displayed by figure 2. Coefficients a, of Legendre polynomials that enter into the description of the various eigenmodes are plotted against 1. The dashed lines are computed from measurements of the well-known surface differential rotaANTARCTIC JOURNAL
al445_
I
jic 20 15
a9 -
10-
5.
0
I
I I
a^ 15
Figure 1. Spectra of p,-mode oscillations with 5 values of I. The ordinate is m, ranging from m = + I (retrograde sectoral harmonics) to m = 0 (zonal harmonics) to m = -I(prograde sectoral harmonics). The tilt is produced by solar rotation, which removes the degeneracy of m.
tion rate, which decreases with heliolatitude. Within the variations in the latitude dependence of the angular velocity of surface features during the solar activity cycle, the odd-indexed coefficients, which carry information about rotation, do not vary with 1. The even-indexed coefficients provide information about the latitude variation of sound speed versus depth. If the internal structure of the Sun were independent of latitude, the even coefficients should be zero. The fact that they differ significantly indicates that the structure of the convection zone is different near the equator compared with higher latitudes. These unexpected results could have profound implications for theories of the origin of the solar magnetic field and solar activity. More surprises are likely to unfold as the analysis of the data in hand continues. This work was supported in part by National Science Foundation grant DPP 81-19627.
Stellar photometry at the South Pole K.Y. CHEN, J.P. OLIVER, and F.B. WOOD Department of Astronomy University of Florida Gainesville, Florida 32611
The south pole optical telescope (SPOT) was designed, constructed, and tested in Gainesville, Florida in 1985. The design is modified somewhat from the telescope operated at the pole in 1986 REVIEW
_+-
a5:rITH
20 30 40 50 60 70 80 90 100
Figure 2. Comparison of coefficients a i determined from the spatially resolved solar oscillation measurements with the values calculated from observations of the rotation of surface features. These results provide information about the latitude and depth dependence of the rotation rate and the Sun's internal structure.
References Duvall, T.L., Jr., J.W. Harvey and M.A. Pomerantz. 1986. Latitude and depth variation of solar rotation. Nature, 321, 500-501. Harvey, J. , M. Pomerantz, and T. Duvall, Jr. 1982. Astronomy on ice. 64(6), 520-523. Pomerantz, MA., J.W. Harvey, and T. Duvall, Jr. 1982. Large-scale motions and structure of the Sun. Antarctic Journal of the U.S., 17(5),
232-233.
the winter of 1984 (Giovanne et al. 1983; Wood et al. 1984). The telescope is a twin-mirror siderostat with a 8-centimeter achromatic lens which collects and brings the light to focus at the field stop. After passing an optical filter and a Fabry lens, the light reaches a photomultiplier which measures the brightness of a selected star or sky. The function of SPOT is controlled by an AIM-65 computer. Data are recorded on floppy disk. The telescope and computer were installed in January 1986 by Oliver and McNeil! after Wood's December 1985 trip to the pole to review site preparation and station nighttime lighting plans. The telescope system is housed in a special insulated building, 12 foot x 8 foot X 8 foot, constructed by the carpenters of ITT Antarctic Services. Only the optical head of SPOT is exposed to the harsh outside environment. The telescope is in a separate 281
