Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
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SOLAR CYCLE VARIATION OF MICROWAVE POLAR BRIGHTENING AND EUV CORONAL HOLE OBSERVED BY NOBEYAMA RADIOHELIOGRAPH AND SDO/AIA

  • Received : 2016.12.06
  • Accepted : 2017.07.25
  • Published : 2017.08.31
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Abstract

We investigate the solar cycle variation of microwave and extreme ultraviolet (EUV) intensity in latitude to compare microwave polar brightening (MPB) with the EUV polar coronal hole (CH). For this study, we used the full-sun images observed in 17 GHz of the Nobeyama Radioheliograph from 1992 July to 2016 November and in two EUV channels of the Atmospheric Imaging Assembly (AIA) $193{\AA}$ and $171{\AA}$ on the Solar Dynamics Observatory (SDO) from 2011 January to 2016 November. As a result, we found that the polar intensity in EUV is anti-correlated with the polar intensity in microwave. Since the depression of EUV intensity in the pole is mostly owing to the CH appearance and continuation there, the anti-correlation in the intensity implies the intimate association between the polar CH and the MPB. Considering the report of Gopalswamy et al. (1999) that the enhanced microwave brightness in the CH is seen above the enhanced photospheric magnetic field, we suggest that the pole area during the solar minimum has a stronger magnetic field than the quiet sun level and such a strong field in the pole results in the formation of the polar CH. The emission mechanism of the MPB and the physical link with the polar CH are not still fully understood. It is necessary to investigate the MPB using high resolution microwave imaging data, which can be obtained by the high performance large-array radio observatories such as the ALMA project.

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References

  1. Altrock, R. 2014, Forecasting the Maxima of Solar Cycle 24 with Coronal Fe xiv Emission, Sol. Phys., 289, 623 https://doi.org/10.1007/s11207-012-0216-1
  2. Babcock, H. W. 1961, The Topology of the Sun's Magnetic Field and the 22-Year Cycle, ApJ, 133, 572 https://doi.org/10.1086/147060
  3. Brajsa, R., Benz, A. O., Temmer, M., Jurdana-Sepic, R., Saina, B., & Wohl, H. 2007, An Interpretation of the Coronal Holes Visibility in the Millimeter Wavelength Range, Sol. Phys., 245, 167 https://doi.org/10.1007/s11207-007-9008-4
  4. Dulk, A. G. 1985, Radio emission from the sun and stars, ARAA, 23, 169 https://doi.org/10.1146/annurev.aa.23.090185.001125
  5. Gopalswamy, N., Shibaski, K., Thompson, B. J., Gurman, J., & DeForest, C. 1999, Microwave Enhancement and Variability in the Elephant'S Trunk Coronal Hole: Comparison with SOHO Observations, JGR, 104, 9767 https://doi.org/10.1029/1998JA900168
  6. Gopalswamy, N., Yashiro, S., Makela, P., Michalek, G., Shibasaki, K., & Hathaway, D. H. 2012, Behavior of Solar Cycles 23 and 24 Revealed by Microwave Observasions, ApJL, 750, L42 https://doi.org/10.1088/2041-8205/750/2/L42
  7. Ito, H., Tsuneta, S., Shiota, D., Tokumaru, M., & Fujiki, K. 2010, Is the Polar Region Different from the Quiet Region of the Sun, ApJ, 719, 131 https://doi.org/10.1088/0004-637X/719/1/131
  8. Karachik, N. V., & Pevtsov, A. A. 2014, Properties of Magnetic Neutral Line Gradients and Formation of Filament, Sol. Phys., 289, 821 https://doi.org/10.1007/s11207-013-0362-0
  9. Kosugi, T., Ishiguro, M., & Shibasaki, K. 1986, Polar-Cap and Coronal-Hole-Associated Brightenings of the Sun at Millimeter Wavelengths, PASJ, 38, 1
  10. Lemen, J. R., Title, A. M., Akin, D. J., et al. 2012, The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO), Sol. Phys., 175, 17
  11. Nakajima, H., Nishio, M., Enome, S., et al. 1994, The Nobeyama Radioheliograph, Proc. of IEEEP, 82, 701
  12. Selhorst, C. L., Silva, A. V., Costa, J. E. R., & Shibasaki, K. 2003, Temporal and Angular Variation of the Solar Limb Brightening at 17 GHz, A&A, 401, 1143 https://doi.org/10.1051/0004-6361:20030071
  13. Selhorst, C. L., Gimenex de Castro, C. G., Varela Saraiva, A. C., & Costa, J. E. R. 2010, How Are the EUV and Radio Polar Limb-Brightenings Correlated?, A&A 463, 551
  14. Shibasaki, K. 1998, Radio Synoptic Maps and Polar Cap Brightening, ASP Conference Series, 140, 373
  15. Shibasaki, K. 2013, Long-Term Global Solar Activity Observed by the Nobeyama Radioheliograph, PASJ, 65, S17 https://doi.org/10.1093/pasj/65.sp1.S17
  16. Shimojo, M. 2013, Unusual Migration of Prominence Activities in the Southern Hemisphere during Cycles 23-24, PASJ, 65, S16 https://doi.org/10.1093/pasj/65.sp1.S16
  17. Oliveira e Silva, A. J., Selhorst, C. L., Simoes, P. J. A., & Gimenez de Castro, C. G. 2016, Comparison of Solar Radio and Extreme Ultraviolet Synoptic Limb Charts during the Present Solar Maximum, A&A, 592, A91 https://doi.org/10.1051/0004-6361/201527792
  18. Svalgaard, L., Cliver, E. W., & Kamide, Y. 2005, Sunspot Cycle 24: Smallest Cycle in 100 Years?, GRL, 32, L01104
  19. Svalgaard, L., & Kamide, Y. 2013, Asymmetric Solar Polar Field Reversals, ApJ, 763, 23 https://doi.org/10.1088/0004-637X/763/1/23