1. Solar Soft X-Rays Data Periodic Analysis Pu Wang Department of Astronomy, Nanjing University Department of Astronomy, Nanjing University July 9, 2005 Pwang@nju.edu.cn The First Chinese-Korean Solar Physics Workshop

2. Outline of Presentation 1. Introduction 5. Future Works 2. Data and Analysis Methods 3. Periodicity Analysis Results 4. Discussion and Summary

3. 1. Introduction As a long-term periodicity, the Sun exhibits the 11-year sunspot cycle, which has been known for a long time. For short terms, the Sun often exhibits 27-d and 13.5-d periodicities, which tell more about spatial organization of the solar activity than its temporal organization. The regime between these extremes of time scales (between 27 d and 11 y) is called the “mid range.” Periodicities in this mid range have been explored, starting with the discovery of a 153-d periodicity in -ray flare occurrence (Rieger et al. 1984). Since then, many researchers investigated mid-range periodicities, using various solar activity indicators. Many researchers studied periodicities in sunspot areas and numbers. Analysis of flare data of different solar cycles found other periodicities.

4. 1. Introduction 51-d period in flares selected by CFI (comprehensive flare index) during cycle 19 (Bai 1987) The 77 day periodicity in the flare rate of cycle 22 (Astrophysical Journal) 78-d period in flares selected by microwave-peak flux during cycle 20 (Bogart & Bai 1985) 84-d period in CFI-selected flares during cycle 20 (Bai 1992b) 127-d period in flares selected by CFI and flares selected by 10-cm radio peak flux The ~150 day quasi-periodicity in interplanetary and solar phenomena during cycle 23 Evidence for a fundamental period of the sun and its relation to the 154 day complex of periodicities On the 24- and 155-day periodicity observed in solar Hα flares

5. 1. Introduction It is important to detect mid-range flare periodicities and to calculate accurately their statistical significances because flare periodicities can provide information on properties of the Sun. Flare periodicities can provide information on properties of the Sun. Using X-ray flux to analyze the Flare periodicities can provide accurate information on properties of the Sun. Flare periodicities in earlier cycles (19–22) have been studied by many authors, but it seems necessary reanalyze them with the different methods so that we can compare statistical significances of several periodicities analyzed previously with different methods.

6. 2. Data and Analysis Methods GOES SPACE ENVIRONMENT MONITOR 1-Minute & 5- Minute Averages Data 1986.01.01-2005.05.31 XL 1 - 8 Å X-rays (Watts/m 2 ) XS 0.5 - 3 Å X-rays, or 0.5 – 4 Å prior to GOES-8 (Watts/m 2 ) The GOES X-ray Sensor (XRS) data have recently been used in new ways for forecasting and specifying conditions.

7. The Wavelet Transform Continuous wavelet transform of the signal x(t) using the analysis wavelet  (.) Translation parameter, measure of time Scale parameter, measure of frequency The mother wavelet. All kernels are obtained by translating (shifting) and/or scaling the mother wavelet A normalization constant Signal to be analyzed Scale = 1/frequency

8. 2. Data and Analysis Methods 24-hours integrated soft x-ray flux. Using Morlet mother wavelet function This wavelet has no scaling function, but is explicit.

9. 1986.01.01- 1996.12.31 XL Day 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77 New periodicity: 230

10. 1986.01.01- 1996.12.31 XS day 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77,127

11. 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77,152 New periodicity: 230 1999.02.05- 2003.02.10 XL day

12. 1999.02.05-2003.02.10 XS day 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77,127 New periodicity: 230

13. 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77,152 New periodicity: 230 1997.01.01-2005.05.31 XL day

14. 1997.01.01-2005.05.31 XS day 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77,152

15. 1986.01.01-2005.05.31 XL day 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77 New periodicity: 230

16. 1986.01.01- 2005.05.31 XS day 3. Periodicity Analysis Results Confirmed periodicity: 25.5,77,127,152 New periodicity: 230

17. 4. Discussion and Summary By using soft x-ray flux data, we can also find 25.5, 77, 127, 152-d Periodicities. Interesting probably 230-d Periodicity have been found by analyzing soft x-ray flux data. Different time scale show different Periodicity. Using soft x-ray flux data also can accurately describe the solar activity Periodicity The results presented may provide useful information for the space weather forecast

18. 5. Future Works The results may provide useful information for the space weather forecast, and the validity needs to be verified by observations. The observational examples and statistical results will be devoted to our Future works. Some solar flare occurrence periodicities should be confirmed by other ideas.

19. Thank you! The First Chinese-Korean Solar Physics Workshop

20. Thank you! The First Chinese-Korean Solar Physics Workshop

21. Signal Processing Structure Signal Processing Time-domain techniques Freq.-domain techniques Filters Fourier T. Non/Stationary Signals Stationary Signals TF domain techniques WAVELET TRANSFORMS STFT CWT DWT MRA 2-D DWTSWT Applications Denoising Compression Signal Analysis Disc. Detection BME / NDE Other…