High-Resolution Imaging of the Solar Chromosphere in the Centimetre-Millimetre Band Through Single-Dish Observations

摘要

Solar observations offer both a rich interdisciplinary laboratory on fundamental astrophysics and precious tools for Space Weather applications. The involved plasma processes determine a complex and partially unknown radio emission picture that could be efficiently explored through single-dish imaging at high frequencies. In particular, mapping the brightness temperature of the free-free radio emission in the centimetre and millimetre range is an effective tool for characterising the vertical structure of the solar chromosphere. We are planning to perform continuum imaging of the solar chromosphere in K-band (18-26.5 GHz) with the 32-m diameter Medicina radio telescope and with the 64-m diameter Sardinia Radio Telescope (SRT), as a first scientific demonstration test for the potentialities of Italian single-dish antennas in this field. This will also be useful for the assessment of observation parameters aiming at studying in detail the chromospheric brightness temperature of the quiet Sun, the solar flares and the sunspots. In perspective, this study will contribute to Space Weather monitoring networks and forecast, filling different gaps that presently exist in the worldwide observing scenario. We present preliminary tests of single-dish solar imaging at 24 GHz with the Medicina 32-m radio telescope. These observations proved that our antenna and K-band receiver are stable during solar pointing and could provide full mapping of the solar disk in ～1 hour exposure using state-of-the-art imaging techniques.