The size of fine structures in the quiescent prominence that appeared on August 16, 1992 has been estimated using power spectra generated from intensity variations of Ha images of the lower part of the prominence, which were taken with a G1 CCD camera attached to 25cm coronagraph at Norikura Coronal Station in Japan. The lower part of the prominence has shown a distinct intensity variation with optical thickness of τ=1~5. Our analysis yields a mean size of fine structures ranging from 350 km to 1,000 km, in good agreement with Hirayama(1985) and Zirker & Koutchmy(1989, 1991).

To study kinematics of solar prominences, we have made Ha spectrographic study of an eruptive prominence which appeared on the 27th of August, 1992 with a position angle of 270 deg. The observation was carried out by a Littrow type spectrograph and a G1 CCD camera attached to the 25cm coronagraph at Norikura Coronal Station. In taking the spectral data the slit was placed in parallel to the solar limb at 7 different heights, each being separated by 5 arcsec with a time step of 30 sec. The observed eruptive prominence shows a wide range of line of sight Doppler velocity, spanning from Vdopp=−17.5km/stoVdopp=58.2km/s Vdopp=−17.5km/stoVdopp=58.2km/s . It is also found that the velocity increases with height at the rate of ΔV=0.86km/s/arcsec ΔV=0.86km/s/arcsec .

A quantitative analysis has been made to estimate the horizontal variation of physical parameters in a loop type active prominence by analyzing Call H&K and Hε… Hε… spectra taken from such an active prominence (appeared on May 23, 1981 with position angle 251 degree) with Littrow type spectrograph attached to 25cm coronagraph at Norikura Coronal Station of National Astronomical Observatory of Japan. The spectral resolution is 1.12A/mm and the spatial resolution is 25'/mm for Call H&K lines. The present study shows that the turbulent velocity ranges from 10km/s to 20 km/s in the loop prominence, which are in good agreement with those of Hirayama (1989). It is also found that the temperature of the loop prominence is higher than that of quiescent prominences(\~8,000K) (\~8,000K) by about 4,000 K, whose temperature deviation seems very high.

To derive coronal temperature, electron density and nonthermal velocity, we have analyzed high resolution spectra (e.g., Fe XII 338.3, Fe XII 352.1, Fe XIV 334.2, Fe XIV 353.8, Fe XV 284.2, Fe XV 321.8, Fe XV 327.0, Fe XVI 335.4, and Fe XVI 360.8) taken from AR 6615 by SERTS (Solar Extreme Ultraviolet Rocket Telescope and Spectrograph). Important findings emerging from the present study are as follows: (1) Temperature estimated from Fe XVI 335.4 and Fe XIV, 334.2 is ~2.4 × 106 K and no systematic difference in temperature is found between the active region and its adjacent quiet region; (2) Mean electron density estimated from Fe XV is ~3 × 109 cm -3 and ~10 10 cm-3 from Fe XII and Fe XIV; (3) Mean density of the active region is found to be higher than that of the quiet region by a factor of 2; (4) Nonthermal velocity estimated from Fe XV and Fe XVI is 20 ~ 25 km s-l which decreases with increasing ionization temperatures. This supports the notion that the nonthermal velocity declines outwards above the transition region.

To examine relations between stellar activity and rotation we estimated parameters of stellar activity such as R′ H K , R′ M g I I , R′ C I I , R′ C I V and R′ X − r a y from the published data which measure the activity levels of stellar chromospheres, transition regions and coronae. In the present study we considered only the main sequence stars in an attempt to minimize the influence of other stellar parameters such as radius, age and stellar convection on stellar activity since they are also known to affect the magnetic field generation. In the present analysis we selected only those stars that satisfy the following conditions: (1) flux measurements are available together with Ca II fluxes and (2) rotation periods are determined by Ca II observations. We derived relations between the ¯Rossby number Ro and stellar activity R′ H K , R′ M g I I , R′ C I I , R′ C I V and R′ X − r a y and assessed the relations by plotting R′ H K , R′ M g I I and R′ X − r a y against rotation period P rot for comparison with observations. From the comparison it is found that as far as the rotation-activity relation is concerned, (1) normalized surface flux R′ H K is better than the surface flux F′ H K , in the sense that R′ H K differentiates the color dependence better and (2) R′ H K defined by Rutten (1984) describes the observations notably better than R′ H K of Noyes et al. (1984).

Making use of a relation proposed by Wielen (1977), a new empirical relation between Call emission flux and stellar age is derived by analyzing Wilson and Woolley's spectroscopic data (1970) of late type main sequence stars (K0-M5) and kinematic properties of those stars given by Gliese (1969). The proposed relation shows that the emission flux excess of the Call H-K lines, F ′ k + F ′ k introduced by Linsky et al. (1979) decreases with stellar age τ as τ − 0.51 , consistent with the inverse square law as noted by Skumanich (1972).