Solar Cycle Telescope

The sun looks like a stable, static star. In reality, however, the sun possesses vigorous activity of magnetized plasma, as most dramatically seen as flare explosions. The magnetic activity of the sun has a periodicity; the activity maximum returns roughly every 11 years. At activity maxima, the sun produces numerous flares, which in turn produces aurorae and geomagnetic storms at the earth. Radio communications are disturbed, and sometimes orbiting satellites are damaged because of memory failure. It is also discovered recently that the radiative output from the sun varies in phase with the solar activity cycle, although small in amplitude. Therefore a quantitative evaluation of the effects of solar variability upon the environment around the earth is an urgent task to be undertaken. The periodicity sometimes becomes irregular; in the seventeenth century the solar activity was abnormally low and the climate on the earth was unusually cool for more than 50 years. Such irregularity might be predicted and cautioned only after the basic mechanisms of solar activity cycle is understood.

The activity of the sun is produced by the magnetic fields which are distributed all over the solar surface. The activity maximum is the period in which the largest amount of magnetic flux stays on the sun. The solar flares, which are the most violent manifestation of the sun's magnetic activity, are believed to be a process of liberating the magnetic stress stored in the solar atmosphere around sunspots. The time and magnitude of a flare might be forecasted by continuously monitoring the magnetic stress in the solar atmosphere.

The sun generates its magnetic fields by means of the so-called magnetohydrodynamic dynamo process, driven by the coupling between the rotation and the convection of the sun. The convective flow that is responsible for the dynamo process is expected to be of global scale and slow, of the order of 10 m/s. The detection of such a flow is still negative. To make the measurement conclusive, an order of magnitude improvement in measurement accuracy is required. The solar rotation, another constituent of the solar dynamo action, is easy to measure whereas its possible long-term variability is so far only argued based on historical records. We believe that the basic mechanisms of solar activity will be revealed through the observations of the following three items;
(1) accurate measurements of the solar surface magnetic fields,
(2) high precision measurements of convective flows, and
(3) long-term and high precision monitoring of solar rotation speed.
The Solar Cycle Telescope that we propose here is to investigate these items.

The magnetic fields are measured by spectroscopic polarimetry in the infrared H-band, at 1.56 micron. We will fully utilize high sensitivity, large-format infrared arrays, because the magnetic field measurement by means of the Zeeman effect is more sensitive as the wavelength increases. The measurement of flow speed and rotation speed will be given high absolute precision and long-term stability by adopting iodine absorption cells and stabilized lasers as the wavelength standards. The Solar Cycle Telescope is an instrument made of these advanced technology, and aims at the understanding of the basic driving mechanisms of solar activity cycle, by sustained observations of magnetic and velocity fields on the sun. It will also contribute to the study of the influence of solar variability upon the earth's environment.

- List of Publications

- Instrument Development and Tests

- Observation of Zeeman splitting of the infrared 1.56micron line (Hida Observatory, Kyoto University, 1999)

- Test observation through an iodine cell (Hida Observatory, Kyoto University, 2003)

- Experiment on ferroelectric liquid crystal retarders and polarization schemes

- Links:

SOLIS (Synoptic Optical Long-term Investigations of the Sun)

International Solar Cycle Studies

Intergovernmental Panel on Climate Change (IPCC)

NOAA Paleoclimatology Program

Past Global Changes (PAGES) Program

NASA Global Change Master Directory