Chinese sunspot drawings and their digitization - (V) the phase relation between Hα flare index and sunspot activity
Abstract
Hα flare index is one of the solar activity indicators to describe the physical properties of the active regions in the solar atmosphere. Sunspot number is a representative indicator of the magnetic activity in the photosphere, which is associated with the energy supply rate to the corona. Thus, it is significant to investigate the phase relationship between Hα flare activity and sunspot activity. In the present work, monthly Hα flare index (FIm), monthly sunspot activity (sunspot numbers (Rs) and group sunspot numbers (Rg)) compiled from the Purple Mountain Observatory are used to find their phase relationship using the cross-correlation analysis. For solar cycles 20-23, there is a very pronounced time lag of about 9, 4, 4.5 and 10 months between the monthly FIm and Rs, respectively. Furthermore, there is a noticeable time lag of about 7, 8, 4.5 and 9 months between FIm and Rg for the same cycles, respectively. If we take the whole time series together, we notice that FIm has a time lag of about 4 months with regard to both Rs and Rg. The possible physical mechanisms for their observed phase lag are discussed.
- Publication:
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Journal of Astrophysics and Astronomy
- Pub Date:
- December 2022
- DOI:
- 10.1007/s12036-022-09831-w
- Bibcode:
- 2022JApA...43...41L
- Keywords:
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- Sun: activity;
- Sun: solar cycle;
- Sun: Hα flare index;
- Method: cross-correlation analysis