Modeling the quiet Sun cell and network emission with ALMA

Abstract

ALMA observations of the Sun at mm-$\lambda$ offer a unique opportunity to investigate the temperature structure of the solar chromosphere. In this article we expand our previous work on modeling the chromospheric temperature of the quiet Sun, by including measurements of the brightness temperature in the network and cell interiors, from high resolution ALMA images at 3 mm (Band 3) and 1.26 mm (Band 6). We also examine the absolute calibration of ALMA full-disk images. We suggest that the brightness temperature at the center of the solar disk in Band 6 is $\sim 440$ K above the value recommended by White et al. (2017) and we give improved results for the electron temperature variation of the average quiet Sun with optical depth, as well as the derived spectrum at the center of the disk. We found that the electron temperature in the network is considerably lower than predicted by model F of Fontenla et al. (1993) and that of the cell interior considerably higher than predicted by model A. Depending upon the network/cell segregation scheme, the electron temperature difference between network and cell at $\tau =1$ (100 GHz) is from $\sim$660 to $\sim$1550 K, compared to $\sim$3280 K predicted by the models; similarly, the $T_e$ ratio is from $\sim$1.10, to 1.24, against $\sim$1.55 of the model prediction. We also found that the network/cell $T_e(\tau )$ curves diverge as $\tau$ decreases, indicating an increase of contrast with height and possibly a steeper temperature rise in the network than in the cell interior.

Accepted, Astronomy & Astrophysics

References in corpus (9)

• Observing the Sun with the Atacama Large Millimeter-submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping
• Center-to-limb observations of the Sun with ALMA
• Inter-network regions of the Sun at millimetre wavelengths
• Observations of solar chromospheric oscillations at 3 mm with ALMA
• ALMA detection of dark chromospheric holes in the quiet Sun
• Transient brightenings in the quiet Sun detected by ALMA at 3 mm
• The Brightness Temperature of the Quiet Solar Chromosphere at 2.6 mm
• Solar Radius at Subterahertz Frequencies and its Relation to Solar Activity
• Measurement of the Height of the Chromospheric Network Emission from Solar Dynamics Observatory Images

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• Where is the base of the Transition Region? Evidence from TRACE, SDO, IRIS and ALMA observations