8 research outputs found
Developing Information System on Lunar Crescent Observations
We present a progress report on the development of information system of lunar crescent astronomical observations which will be largely accessible for public domain. This consists of calculations of the Moon's ephemeris as well as systematic real-time lunar crescent observations. A well suited small telescope, equipped with a simple digital detector, is connected to a server to provide information on lunar crescent observations. The system has been used and worked well. The only constraint is poor weather condition. Network of small telescopes, installed at various locations in Indonesia, are currently planned to provide plethora of data. In the long term, this will be used to help to determine the astronomical visibility criteria of lunar crescent for Islamic calendar
Emergence of a Twisted Magnetic Flux Bundle as a Source of Strong Flare Activity
Sunspot proper motions and flares of a super active region NOAA 5395, which
was the biggest and the most flare-active region in the 22nd sunspot cycle,
were analyzed in details. We measured sunspot proper motions by using the
H-alpha - 5.0 A images obtained with the 60-cm Domeless Solar Telescope (DST)
at Hida Observatory, Kyoto University and found some peculiar vortex-like
motions of small satellite spots successively emerged from the leading edge of
this sunspot group. To explain these motions of small sunspots, we proposed a
schematic model of the successive emergence of twisted and winding magnetic
flux ropes coiling around a trunk of magnetic flux tube. The location of the
strongest flare activity was found to coincide with very the site of the
vortex-like motions of sunspots. We conclude that the flare-productive magnetic
shear is produced by the emergence of the twisted magnetic flux bundle.
Magnetic energy is stored in the twisted flux tubes which are originally formed
in the convection zone and released as flares in the course of the emergence of
the twisted flux tubes above the photosphere.Comment: 19 pages LaTeX, 8 figures, ApJ accepted high resolution figures :
e-mail to [email protected]
Clear sky fraction above Indonesia: an analysis for astronomical site selection
We report a study of cloud cover over Indonesia based on meteorological
satellite data, spanning over the past 15 years (from 1996 to 2010) in order to
be able to select a new astronomical site capable to host a multi-wavelength
astronomical observatory. High spatial resolution of meteorological satellite
data acquired from {\it Geostationary Meteorological Satellite 5} ({\it GMS
5}), {\it Geostationary Operational Environmental Satellite 9} ({\it GOES 9}),
and {\it Multi-functional Transport Satellite-1R} ({\it MTSAT-1R}) are used to
derive yearly average clear fractions over the regions of Indonesia. This
parameter is determined from temperature measurement of the IR3 channel (water
vapor, 6.7 m) for high altitude clouds (cirrus) and from the IR1 channel
(10.7 m) for lower altitude clouds. Accordingly, an algorithm is developed
to detect the corresponding clouds. The results of this study are then adopted
to select the best possible sites in Indonesia to be analysed further by
performing in situ measurements planned for the coming years. The results
suggest that regions of East Nusa Tenggara, located in south-eastern part of
Indonesia, are the most promising candidates for such an astronomical site.
Yearly clear sky fraction of this regions may reach better than 70 per cent
with an uncertainty of 10 per cent.Comment: 15 pages, 13 figures, and 4 table