Observing the Sun with the Atacama Large Millimeter-submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping

Abstract

The Atacama Large Millimeter-submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that utilizes the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions we derive quiet-Sun values at disk center of 7300 K at lambda=3 mm and 5900 K at lambda=1.3 mm. These values have statistical uncertainties of order 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of order 25 arcsec, the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range.

Solar Physics, accepted: 24 pages, 13 figures

References in corpus (15)

• The Atacama Large Millimeter/submillimeter Array
• A publicly available simulation of an enhanced network region of the Sun
• Dynamically Driven Evolution of the Interstellar Medium in M51
• Solar science with the Atacama Large Millimeter/submillimeter Array - A new view of our Sun
• The On The Fly Imaging Technique
• Observing the Sun with Atacama Large Millimeter/submillimeter Array (ALMA): High Resolution Interferometric Imaging
• Millimeter radiation from a 3D model of the solar atmosphere I. Diagnosing chromospheric thermal structure
• Phase Correction for ALMA with 183 GHz Water Vapour Radiometers
• Inter-network regions of the Sun at millimetre wavelengths
• Short Spacing Synthesis from a Primary Beam Scanned Interferometer
• Millimeter radiation from a 3D model of the solar atmosphere II. Chromospheric magnetic field
• The chromosphere above sunspots at millimeter wavelengths
• Observation of Chromospheric Sunspot at Millimeter Range with the Nobeyama 45 m Telescope
• How ALMA is calibrated: I Antenna-based pointing, focus and amplitude calibration
• Fast single-dish scans of the Sun using ALMA

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