Abstract
A detector sharing the orbital rate of Venus has a unique perspective on solar periodicities. Fourier analysis of the 8.6 year record of solar EUV output gathered by the Langmuir probe on Pioneer Venus Orbiter shows the influences of global oscillation modes located in the convective envelope and in the radiative interior. Seven of the eight lowest angular harmonic r-mode families are detected by their rotation rates which differ almost unmeasurably from ideal theoretical values. This determines a mean sidereal rotation rate for the envelope of 457.9 ± 2.0 nHz which corresponds to a period of 25.3 days. Many frequencies are aliased at ± 106 nHz by modulation from the lowest angular harmonic r-mode in the envelope. The rotation of this mode seems slightly retrograde, -1.5 ± 2.0 nHz, but small positive values are not excluded. We confirm that the rotation of the radiative interior, 381 nHz, is slower than the envelope by detecting g-mode frequencies for angular harmonics, 2 ≤ l ≤ 6, and a possible first detection of the rotation rate for the l = 1 case. Solar EUV lacks the sudden darkenings (dips) shown by visible irradiance; vortex cores in the photosphere and below are again suggested as a possible explanation.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aizenman, M. L. and Smeyers, P.: 1977, Astrophys. Space Sci. 48, 123.
Antonucci, E., Azzarelli, L., Casalini, P., Cerri, S., and Denoth, F.: 1979, Solar Phys. 61, 9.
Brace, L. H., Hoegy, W. R., and Theis, R. F.: 1988, J. Geophys. Res. 93, 7282.
Chandrasekhar, S. and Lebovitz, N. R.: 1962, Astrophys. J. 135, 248.
Chapman, S. and Bartels, J.: 1940, Geomagnetism, Clarendon, Oxford, p. 181.
Cox, J. P.: 1976, Ann. Rev. Astron. Astrophys. 14, 247.
Cowling, T. G.: 1941, Monthly Notices Roy. Astron. Soc. 101, 367.
Hickey, J. R., Major, E. R., and Kyle, H. L.: 1984, User's Guide for Nimbus 7 ERB Solar Analysis Tape (ESAT), NASA Technical Memo 86143.
Hickey, J. R., Stowe, L. L., Jacobowitz, H., Peligrino, P., Maschoff, R. H., House, F., and Von der Haar, T. H.: 1980, Science 208, 281.
Hoegy, W. R. and Wolff, C. L.: 1989, J. Geophys. Res. (in press).
Kiepenheuer, K. O.: 1953, in G. P. Kuiper (ed.), The Sun, Univ. Chicago Press, Chicago, p. 338.
Krehbiel, J. P., Brace, L. H., Theis, R. F., Cutler, J. R., Pinkus, W. H., and Kaplan, R. B.: 1980, IEEE Trans. Geosci. Remote Sensing GE-18, 49.
Lean, J.: 1987, J. Geophys. Res. 92, No. D1, 839.
Ledoux, P.: 1974, in P. Ledoux et al. (eds.), ‘Stellar Instability and Evolution’, IAU Symp. 59.
McIntosh, P. S. and Wilson, P. R.: 1985, Solar Phys. 97, 59.
Papaloizou, J. and Pringle, J. E.: 1978, Monthly Notices Roy. Astron. Soc. 182, 423.
Provost, J., Berthomieu, G., Rocca, A.: 1981, Astron. Astrophys. 94, 126.
Rottman, G. J.: 1985, C. S. Zerefos and A. Ghazi (eds.), Proc. Quadrennial Ozone Sympos., Halkidiki, Greece, D. Reidel Publ. Co., Dordrecht, Holland, p. 656.
Saio, H.: 1982, Astrophys. J. 256, 717.
Smeyers, P., Craeynest, D., and Martens, L.: 1981, Astrophys. Space Sci. 78, 483.
Spruit, H. C.: 1977, Astron. Astrophys. 55, 151.
Sýkora, J.: 1971, Solar Phys. 18, 72.
Vernazza, J. E., Avrett, E. H., and Loeser, R.: 1973, Astrophys. J. 184, 605.
Wagner, W. J.: 1976, in V. Bumba and J. Kleczek (eds.), Basic Mechanisms of Solar Activity, D. Reidel Publ. Co., Dordrecht, Holland.
Willson, R. C.: 1982, J. Geophys. Res. 87, 4319.
Wolff, C. L.: 1974, Astrophys. J. 194, 489.
Wolff, C. L.: 1983, Astrophys. J. 264, 667.
Wolff, C. L.: 1984, Solar Phys. 93, 1.
Wolff, C. L. and Blizard, J. B.: 1986, Solar Phys. 105, 1.
Wolff, C. L. and Hickey, J. R.: 1987a, Science 235, 1631 (Paper I).
Wolff, C. L. and Hickey, J. R.: 1987b, Solar Phys. 109, 1 (Paper II).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Wolff, C.L., Hoegy, W.R. Periodic solar EUV flux monitored near Venus. Sol Phys 123, 7–20 (1989). https://doi.org/10.1007/BF00150008
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00150008