With the aim of investigating the resonance system of NO, equivalent width calculations have been made for the 213.575 nm, O1(31.5) line of the 1-0 band of y-system of NO for the photospheric HSRA model, and for the line 214.012 nm, O1(25.5) line of the same band system for Zwaan's (1974) sunspot model.Calculations show that 3,-band system would not show up in the photospheric spectrum whereas a sunspot model yields an equivalent width of 72 m~, suggesting that sunspots may provide relatively more favourable conditions for the detections of the resonance systems of some abundant molecules in the inaccessible ultraviolet region.

In the present investigation, we have carried out power spectrum analysis of sunspot number and great hard X-ray (GHXR) burst (equal to or greater than i0,000 counts per second) for a period of about 6 years. The GHXR bursts show a periodicity of about 155 days. On the other hand, sunspot numbers do not show any periodicity. The GHXR burst periodicity confirms the existence of a 152-158 days periodicity in the occurrence of solar energetic events. Further, the GHXR bursts are showing periodicity independently indicating that the GHXR bursts are a separate class of X-ray flares.

No abstract

No abstract

Here we have carried out a power-spectrum analysis of solar nuclear gamma-ray (NGR) flares observed by SMM and HINOTORI satellites. The solar NGR flares show a periodicity of 152 days, confirming the existence of a 152-158 days periodicity in the occurrence of solar activity phenomena and also indicating that the NGR flares are a separate class of solar flares . The power-spectrum analysis of the daily sunspot areas on the Sun for the period 1980-1982 shows a peak around 159 days while sunspot number data do not show any periodicity (Verma and Joshi, 1987). Therefore, only sunspot area data should be treated as an indicator of solar activity and not the daily sunspot number data. l.IntroductionDuring the solar cycle 21, 152-158 day periodicity was detected in the rate of occurrence of energetic solar flares. This periodicity was first pointed out by Rieger et al. (1984) from the occurrence rate of solar gamma-ray (GR) bursts detected above 300 keY . Rieger et al. (1984) found that soft X-ray bursts also show a 152 day periodicity in the rate of GOES events with classification > M 2.5. Kiplinger et al. (1984) studied larger sample of 6775 solar hard X-ray (HXR) bursts above 30 key and found a 158 day periodicity. Ichimoto et al. (1985) found similar periodicity from H-alpha flare data observed during solar cycles 20 and 21.Bogart and Bai (1985) carried out a power-spectrum study of microwave (MW) emission bursts observed on 1 GHz for the period 1966-1983 and found a 152 day periodicity. Verma and Joshi (1987) analysed strong HXRbursts and sunspot number data for the period 1980-1984 and found a 155 day periodicity in case of strong HXR events and no periodicity in case of sunspot number data. Wolff (1983) carried out Fourier analysis of the variation of the mean monthly sunspot numbers for the period 1799-1979 and found that the most prominent peak below 200 days is 155.4 days, remarkbly close to the period for flares in cycle 21.In the present work, we have carried out a power-spectrumanalysis of daily solar NGR flares, sunspot area data and umbral area data. Observational Data, Analysis and ResultsIn the present investigation we have used data of flares observed by SMM satellite during the period 1980-1985 and HINOTORI satellite during 1981 -1982 The SMM satellite recorded 92 NGR flares (Cliver et ai.,1989).