Long-Term Trends in Ionospheric Indices оf Solar Activity

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Abstract

The results of identifying trends in the annual average ionospheric indices ΔIG and ΔT are presented, which were obtained after excluding from IG and T the dependence of these indices on the annual average solar activity indices. The solar activity indices were F10, Ly-a and MgII – solar radiation fluxes at 10.7 cm, in the Lyman-alpha line of hydrogen (121.567 nm) and the ratio of the central part to the flanks in the magnesium emission band 276-284 nm. Two-time intervals (in years), 1980–2012 and 2013–2023, are considered. It was found that for the interval 1980–2012 all analyzed linear trends were negative, i.e. ΔIG and ΔT values decreased over time. They were very weak and insignificant. Fluctuations of ΔIG and ΔT relative to trends for Ly-a were almost twice as large as for F10 and MgII. In the interval 2013–2023, all analyzed linear trends intensified and became significant, i.e. the rate of decrease in ΔIG and ΔT over time increased. For MgII this rate was almost twice as high as for F10. For the interval 2013–2023, the MgII index overestimated the contribution of solar radiation to ionospheric indices, especially during the growth phase of solar cycle 25, which began at the end of 2019. As a result, in the growth phase of solar cycle 25, the F10 index became a more adequate indicator of solar activity for ionospheric indices than MgII. In the interval 1980–2012, the F10 and MgII indices changed almost synchronously. The growth phase of solar cycle 25 was the first time this synchrony was disrupted for the entire period of MgII measurements.

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M. G. Deminov

Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences

Author for correspondence.
Email: deminov@izmiran.ru
Russian Federation, Troitsk

References

  1. Данилов А.Д., Константинова А.В. Долговременные вариации параметров средней и верхней атмосферы и ионосферы (обзор) // Геомагнетизм и аэрономия. Т. 60. № 4. С. 411–435. 2020. https://doi.org/10.31857/S0016794020040045
  2. Bilitza D. IRI the international standard for the ionosphere // Adv. Radio Sci. V. 16. P. 1–11. 2018. https://doi.org/10.5194/ars-16-1-2018
  3. Caruana J. The IPS monthly T index / Proc. Solar-Terrestrial Prediction Workshop. Leura, Australia. October 16–20, 1989. V. 2. Ed. R.J. Thompson. Boulder, CO: Environmental Research Lab. P. 257–263. 1990.
  4. Danilov A.D., Berbeneva N.A. Statistical analysis of the critical frequency foF2 dependence on various solar activity indices // Adv. Space Res. V. 72. № 6. P. 2351–2361. 2023. https://doi.org/10.1016/j.asr.2023.05.012
  5. Deminov M.G. Trends in ionospheric indices of solar activity // Geomagn. Aeron. (Engl. Transl.) V. 64. № 5. 2024.
  6. Jones W.B., Gallet R.M. The representation of diurnal and geographic variations of ionospheric data by numerical methods // Telecommun. J. V. 29. № 5. P. 129–149. 1962.
  7. Jones W.B., Gallet R.M. The representation of diurnal and geographic variations of ionospheric data by numerical methods. 2 // Telecommun. J. V. 32. № 1. P. 18–28. 1965.
  8. Laštovička J. Long-term changes in ionospheric climate in terms of foF2 // Atmosphere. V. 13. № 1. ID 110. 2022. https://doi.org/10.3390/atmos13010110
  9. Laštovička J., Burešova D. Relationships between foF2 and various solar activity proxies // Space Weather. V. 21. № 4. ID e2022SW003359. 2023. https://doi.org/10.1029/2022SW003359
  10. Laštovička J. Dependence of long-term trends in foF2 at middle latitudes on different solar activity proxies // Adv. Space Res. V. 73. № 1. P. 685–689. 2024. https://doi.org/10.1016/j.asr.2023.09.047
  11. Liu R., Smith P., King J. A new solar index which leads to improved foF2 predictions using the CCIR atlas // Telecommun. J. V. 50. № 8. P. 408–414. 1983.
  12. Machol J., Snow M., Woodraska D., Woods T., Viereck R., Coddington O. An improved Lyman-alpha composite // Earth and Space Science. V. 6. № 12. P. 2263–2272. 2019. https://doi.org/10.1029/2019EA000648
  13. Snow M., Machol J., Viereck R., Woods T., Weber M., Woodraska D., Elliott J. A revised Magnesium II core-to-wing ratio from SORCE SOLSTICE // Earth and Space Science. V. 6. № 11. P. 2106–2114. 2019. https:// doi.org/10.1029/2019EA000652
  14. Upton L.A., Hathaway D.H. Solar cycle precursors and the outlook for cycle 25 // J. Geophys. Res. – Space. V. 128. N 10. ID e2023JA031681. 2023. https://doi.org/10.1029/2023JA031681

Supplementary files

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2. Fig. 1. Dependences of ionospheric indices T12 and IG12 on solar activity indices MgII12 and Ly-α12 according to the measurement data and regression equations (4) - points and solid lines; K and σ - correlation coefficients and standard deviations of these equations.

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3. Fig. 2. Changes in the ΔIG12(X) index with time in years from experimental data (dots) and linear interpolations (trends) of these data - solid lines.

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4. Fig. 3. Changes in the ΔT12(X) index with time in years from experimental data (dots) and linear interpolations (trends) of these data - solid lines.

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5. Fig. 4. Changes with time in years of the IG12 index (thick line) and models of this index IGmod(F1012) - thin line and IGmod(MgII12) - dashed line.

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