During the total solar eclipse of 11 July 2010, multi-slit spectroscopic observations of the solar corona were performed from Easter Island, Chile. To search for "high-frequency waves", observations were taken at a high cadence in the green line at 5303Å due to [Fe xiv] and the red line at 6374Å due to [Fe x].The data are analyzed to study the periodic variations in the intensity, Doppler velocity and line width using wavelet analysis. The data with high spectral and temporal resolution enabled us to study the rapid dynamical changes within coronal structures. We find that at certain locations each parameter shows significant oscillation with periods ranging from 6 -25 s. For the first time, we could detect damping of "high-frequency oscillations" with periods of the order of 10 s. If the observed damped oscillations are due to magnetohydrodynamic (MHD) waves then they can contribute significantly in the heating of the corona. From a statistical study we try to characterize the nature of the observed oscillations while looking at the distribution of power in different line parameters.

The analysis of the Ca-K line spectra as a function of latitude and integrated over the visible disk obtained during the period of 1989–2011 at the Kodaikanal Solar Tower Telescope shows that the FWHM of the K1 distribution at different latitudes varies by negligible amount at about 60° latitude whereas it varies significantly at other latitudes. Findings, especially the fewer variations in mid-latitude belts as compared to polar regions and complex variation in the shift in the activity around 60° latitude belt, will have important implications on the modeling of solar dynamos. Further, we have generated a uniform set of digitized Ca-K line images by selecting images considering the intensity distribution of the images corrected for the instrumental vignetting for the data obtained at Kodaikanal during the 20th century. Then, we have determined the percentage of plage and network areas by using the intensity and area threshold values.

The analysis of Ca-K line spectra as a function of solar latitude and integrated over longitudes taken during the period of 1989-2011 indicates that the K 1 width attains maximum amplitude at various latitude belts at different phases of the solar cycle. The FWHM of the K 1 distribution at different latitudes shows that its width varies by about 30% for the equatorial belt (<30 •) and 11% for the polar region (>70 •) latitudes. Interestingly, the K 1 width varies by ∼6% only in the 40-60 • latitude belts during the solar cycle. The analysis of cross-correlation coefficients of the K 1 width between the 35 • latitude and other latitude belts as a function of phase differences indicates that the activity representing toroidal field shifted at a uniform rate of about 5.1 m s −1 in the northern hemisphere from mid-latitudes toward the equator. In the southern hemisphere, activity shifted at a faster rate, ∼14 m s −1 , in the beginning of the cycle and the speed decreased with time, yielding an average speed of 7.5 m s −1 toward the equator. The shift of activity in the higher latitude belts showed complex behavior, indicating poleward and equatorward migration. These findings, especially the fewer variations in mid-latitude belts as compared to polar regions, asymmetry in the speed of the shift in the activity in both hemispheres, and complex variation in the direction of the shift in the activity representing poloidal fields in mid-latitude belts, will have an important implication on the modeling of the solar dynamo.

We present the observational properties of coronal mass ejection (CME) flux ropes (FRs) near the Sun based on a set of 35 events from solar cycle 24 (2010–2017). We derived the CME FR properties using the Flux Rope from Eruption Data technique. According to this technique, the geometrical properties are obtained from a flux-rope fit to CMEs and the magnetic properties from the reconnected flux in the source region. In addition, we use the magnetic flux in the dimming region at the eruption site. Geometric properties like radius of the FR and the aspect ratio are derived from the FR fitting. The reconnected flux exhibits a positive correlation with flare fluence in soft X-rays (SXRs), peak flare intensity in SXRs, CME speed, and kinetic energy, with correlation coefficients (cc) 0.78, 0.6, 0.48, and 0.55, respectively. We found a moderate positive correlation between magnetic flux in the core dimming regions and the toroidal flux obtained from the Lundquist solution for a force-free FR (cc = 0.43). Furthermore, we correlate the core dimming flux and CME mass (cc = 0.34). The area of the core dimming region shows a moderate correlation with the radius of the FR (cc = 0.4). Thus, we infer that greater magnetic content (poloidal and toroidal fluxes) indicates a more energetic eruption in terms of flare size, CME speed, kinetic energy, mass, and radius of the FR, suggesting important implications for space weather predictions.