Twin Telescope observations of the Sun at Kodaikanal Observatory

We report the design, fabrication and installation of a 'Twin Telescope' at Kodaikanal Observatory intended to augment the ongoing synoptic observations of the Sun that has been carried out since 1904. The telescope uses a 15 cm objective capable of taking Ca-K line filtergrams and photoheliograms in continuum of the full disk of the Sun simultaneously, at a frequency of 0.1 Hz using 2kx2k format CCD cameras. The telescope has been in operation since February 2008 and images are being obtained at a cadence of 5 min during normal observing periods. In case of solar activity, images of the active regions can be taken at a frequency of 1 Hz by restricting the field of view and spatial resolution. In this paper, we describe the telescope, instruments, image acquisition, data calibration and image processing. We also discussed a method of determining the network element and plage area index. The preliminary results show that while the network element covers about 30% of the disk, the percentage of the network element area index varies marginally with the seeing conditions during the day.Comment: 17 pages, 10 Figures, to appear in the 2012 March issue of the Bulletin of the Astronomical Society of Indi

A study of solution crystal growth in LOW-g (2-IML-1)

During the International Microgravity Laboratory-1 (IML-1) mission it is planned to grow triglycine sulfate (TGS) crystals from aqueous solution using the modified Fluids Experiment System (FES). A special cooled sting technique will be used for solution crystal growth. The objectives of the experiment are as follows: (1) to grow crystals of TGS using the modified FES; (2) to perform holographic interferometric tomography of the fluid field in three dimensions; (3) to study the fluid motion due to g-jitter by multiple exposure holography of tracer particles; and (4) to study the influence of g-jitter on the growth rate

Prominence eruption initiated by helical kink-instability of an embedded flux rope

We study the triggering mechanism of a limb-prominence eruption and the associated coronal mass ejection near AR 12342 using SDO and LASCO/SOHO observations. The prominence is seen with an embedded flux thread (FT) at one end and bifurcates from the middle to a different footpoint location. The morphological evolution of the FT is similar to an unstable flux rope (FR), which we regard as prominence embedded FR. The FR twist exceeds the critical value. In addition, the morphology of the prominence plasma in 304\AA~images marks the helical nature of the magnetic skeleton with a total of 2.96 turns along arc length. The potential field extrapolation model indicates that the critical height of the background magnetic field gradient falls within the inner corona (105Mm) consistent with the extent of coronal plasma loops. These results suggest that the helical kink instability in the embedded FR caused the slow rise of the prominence to a height of the torus instability domain. Moreover, the differential emission measure analysis unveils heating of the prominence plasma to coronal temperatures during eruption, suggesting a reconnection-related heating underneath the upward rising embedded FR. The prominence starts with a slow rise motion of 10km/s, followed by fast and slow acceleration phases having an average acceleration of $28.9m/s^2$, $2.4m/s^2$ in C2, C3 field of view respectively. As predicted by previous numerical simulations, the observed synchronous kinematic profiles of the CME leading edge and the core supports the involved FR instability in the prominence initiation.Comment: Accepted in ApJ, 13 pages, 9 figure