Advertisement

Solar Physics

, 294:175 | Cite as

The Solar Radius at 37 GHz Through Cycles 22 to 24

  • Caius L. SelhorstEmail author
  • Juha Kallunki
  • C. Guillermo Giménez de Castro
  • Adriana Valio
  • Joaquim E. R. Costa
Article

Abstract

To better understand the influence of the activity cycle on the solar atmosphere, we report the time variation of the radius observed at 37 GHz (\(\lambda=8.1\mbox{ mm}\)) obtained by the Metsähovi Radio Observatory (MRO) through Solar Cycles 22 to 24 (1989 – 2015). Almost 5800 maps were analyzed, however, due to instrumental setup changes the dataset showed four distinct behaviors, which required a normalization process to allow for the whole interval analysis. When the whole period was considered, the results showed a positive correlation index of 0.17 between the monthly means of the solar radius at 37 GHz and solar flux obtained at 10.7 cm (F10.7). This correlation index increased to 0.44, when only the data obtained during the last period without instrumental changes were considered (1999 – 2015). The solar radius correlation with the solar cycle agrees with the previous results obtained at mm/cm wavelengths (17 and 48 GHz), nevertheless, this result is the opposite of that reported at submillimeter wavelengths (212 and 405 GHz).

Keywords

Sun: radio radiation Solar cycle Sun: radius 

Notes

Acknowledgements

C.L.S. acknowledges financial support from the São Paulo Research Foundation (FAPESP), grant number 2019/03301-8. C. L. S. and C. G. G. C. are thankful to CNPq by the support through grants 306638/2018-5 and 305203/2016-9, respectively. The authors also thank Niko Lavonen for help with the data reduction.

Disclosure of Potential Conflicts of Interest

The authors declare that they have no conflicts of interest.

References

  1. Andrei, A.H., Boscardin, S.C., Chollet, F., Delmas, C., Golbasi, O., Jilinski, E.G., Kiliç, H., Laclare, F., Morand, F., Penna, J.L., Reis Neto, E.: 2004, Comparison of CCD astrolabe multi-site solar diameter observations. Astron. Astrophys.427, 717. DOI. ADS. ADSCrossRefGoogle Scholar
  2. Bachurin, A.F.: 1983, Variation in solar radio radius with the phase of the solar activity cycle at wavelengths of 2.25 and 3.5 cm. Izv. Ordena Trud. Krasn. Znam. Krym. Astrofiz. Obs.68, 68. ADS. ADSGoogle Scholar
  3. Basu, D.: 1998, Radius of the Sun in relation to solar activity. Solar Phys.183, 291. ADS. ADSCrossRefGoogle Scholar
  4. Battaglia, M., Hudson, H.S., Hurford, G.J., Krucker, S., Schwartz, R.A.: 2017, The solar X-ray limb. Astrophys. J.843(2), 123. DOI. ADS. ADSCrossRefGoogle Scholar
  5. Bush, R.I., Emilio, M., Kuhn, J.R.: 2010, On the constancy of the solar radius. III. Astrophys. J.716, 1381. DOI. ADS. ADSCrossRefGoogle Scholar
  6. Chapman, G.A., Dobias, J.J., Walton, S.R.: 2008, On the variability of the apparent solar radius. Astrophys. J.681, 1698. DOI. ADS. ADSCrossRefGoogle Scholar
  7. Costa, J.E.R., Silva, A.V.R., Makhmutov, V.S., Rolli, E., Kaufmann, P., Magun, A.: 1999, Solar radius variations at 48 GHz correlated with solar irradiance. Astrophys. J. Lett.520, L63. DOI. ADS. ADSCrossRefGoogle Scholar
  8. Emilio, M., Leister, N.V.: 2005, Solar diameter measurements at São Paulo Observatory. Mon. Not. Roy. Astron. Soc.361, 1005. DOI. ADS. ADSCrossRefGoogle Scholar
  9. Emilio, M., Kuhn, J.R., Bush, R.I., Scherrer, P.: 2000, On the constancy of the solar diameter. Astrophys. J.543, 1007. DOI. ADS. ADSCrossRefGoogle Scholar
  10. Gilliland, R.L.: 1981, Solar radius variations over the past 265 years. Astrophys. J.248, 1144. DOI. ADS. ADSCrossRefGoogle Scholar
  11. Giménez de Castro, C.G., Varela Saraiva, A.C., Costa, J.E.R., Selhorst, C.L.: 2007, The solar radius in the EUV during the cycle XXIII. Astron. Astrophys.476, 369. DOI. ADS. ADSCrossRefGoogle Scholar
  12. Kallunki, J., Tornikoski, M.: 2018, Measurements of the quiet-Sun level brightness temperature at 8 mm. Solar Phys.293, 156. DOI. ADS. ADSCrossRefGoogle Scholar
  13. Kilic, H., Golbasi, O.: 2011, Comparison of long-term trend of solar radius with sunspot activity and flare index. Astrophys. Space Sci.334, 75. DOI. ADS. ADSCrossRefzbMATHGoogle Scholar
  14. Kosovichev, A., Rozelot, J.-P.: 2018a, Cyclic changes of the Sun’s seismic radius. Astrophys. J.861(2), 90. DOI. ADS. ADSCrossRefGoogle Scholar
  15. Kosovichev, A.G., Rozelot, J.P.: 2018b, Solar cycle variations of rotation and asphericity in the near-surface shear layer. J. Atmos. Solar-Terr. Phys.176, 21. DOI. ADS. ADSCrossRefGoogle Scholar
  16. Kuhn, J.R., Bush, R.I., Emilio, M., Scherrer, P.H.: 2004, On the constancy of the solar diameter. II. Astrophys. J.613, 1241. DOI. ADS. ADSCrossRefGoogle Scholar
  17. Laclare, F., Delmas, C., Coin, J.P., Irbah, A.: 1996, Measurements and variations of the solar diameter. Solar Phys.166, 211. DOI. ADS. ADSCrossRefGoogle Scholar
  18. Lefebvre, S., Bertello, L., Ulrich, R.K., Boyden, J.E., Rozelot, J.P.: 2006, Solar radius measurements at Mount Wilson Observatory. Astrophys. J.649, 444. DOI. ADS. ADSCrossRefGoogle Scholar
  19. Menezes, F., Valio, A.: 2017, Solar radius at subterahertz frequencies and its relation to solar activity. Solar Phys.292, 195. DOI. ADS. ADSCrossRefGoogle Scholar
  20. Noël, F.: 2004, Solar cycle dependence of the apparent radius of the Sun. Astron. Astrophys.413, 725. DOI. ADS. ADSCrossRefGoogle Scholar
  21. Rozelot, J.P.: 1998, The correlation between the Calern solar diameter measurements and the solar irradiance. Solar Phys.177, 321. ADS. ADSCrossRefGoogle Scholar
  22. Rozelot, J.P., Kosovichev, A., Kilcik, A.: 2015, Solar radius variations: an inquisitive wavelength dependence. Astrophys. J.812, 91. DOI. ADS. ADSCrossRefGoogle Scholar
  23. Scargle, J.D.: 1982, Studies in astronomical time series analysis. II – Statistical aspects of spectral analysis of unevenly spaced data. Astrophys. J.263, 835. DOI. ADS. ADSCrossRefGoogle Scholar
  24. Selhorst, C.L., Silva, A.V.R., Costa, J.E.R.: 2004, Radius variations over a solar cycle. Astron. Astrophys.420, 1117. ADS. ADSCrossRefGoogle Scholar
  25. Selhorst, C.L., Giménez de Castro, C.G., Válio, A., Costa, J.E.R., Shibasaki, K.: 2011, The behavior of the 17 GHz solar radius and limb brightening in the spotless minimum XXIII/XXIV. Astrophys. J.734, 64. DOI. ADS. ADSCrossRefGoogle Scholar
  26. Selhorst, C.L., Simões, P.J.A., Brajša, R., Valio, A., Giménez de Castro, C.G., Costa, J.E.R., Menezes, F., Rozelot, J.P., Hales, A.S., Iwai, K., White, S.: 2019, Solar polar brightening and radius at 100 and 230 GHz observed by ALMA. Astrophys. J.871(1), 45. DOI. ADS. ADSCrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.NAT – Núcleo de AstrofísicaUniversidade Cruzeiro do Sul/Universidade Cidade de São PauloSão PauloBrazil
  2. 2.Metsähovi Radio ObservatoryAalto UniversityKylmäläFinland
  3. 3.CRAAMUniversidade Presbiteriana MackenzieSão PauloBrazil
  4. 4.IAFEUniversidad de Buenos Aires/CONICETBuenos AiresArgentina
  5. 5.CEAInstituto Nacional de Pesquisas EspaciaisSão José dos CamposBrazil

Personalised recommendations