ALMA Discovery of Solar Umbral Brightness Enhancement at λ = 3 mm

  title={ALMA Discovery of Solar Umbral Brightness Enhancement at $\lambda$ = 3 mm},
  author={Kazumasa Iwai and Maria A. Loukitcheva and Masumi Shimojo and Sami K. Solanki and Stephen M. White},
  journal={The Astrophysical Journal Letters},
We report the discovery of a brightness enhancement in the center of a large sunspot umbra at a wavelength of 3 mm using the Atacama Large Millimeter/sub-millimeter Array (ALMA). Sunspots are among the most prominent features on the solar surface, but many of their aspects are surprisingly poorly understood. We analyzed a λ = 3 mm (100 GHz) mosaic image obtained by ALMA that includes a large sunspot within the active region AR12470, on 2015 December 16. The 3 mm map has a 300″ × 300″ field of… 

Figures from this paper

Solar ALMA Observations: Constraining the Chromosphere above Sunspots

We present the first high-resolution Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a sunspot at wavelengths of 1.3 and 3 mm, obtained during the solar ALMA Science Verification

ALMA Observations of the Solar Chromosphere on the Polar Limb

We report the results of the Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of the solar chromosphere on the southern polar limb. Coordinated observations with the Interface Region

First Spectral Analysis of a Solar Plasma Eruption Using ALMA

The aim of this study is to demonstrate how the logarithmic millimeter continuum gradient observed using the Atacama Large Millimeter/submillimeter Array (ALMA) may be used to estimate optical

First solar observations with ALMA

An ALMA Observation of Time Variations in Chromospheric Temperature of a Solar Plage Region

Nanoflares and the shock formation of magnetohydrodynamic waves in the solar chromosphere have been considered as key physical mechanisms of the heating of the chromosphere and corona. To investigate

He i Spectropolarimetry of a Supersonic Coronal Downflow Within a Sunspot Umbra

We report spectropolarimetric observations of a supersonic downflow impacting the lower atmosphere within a large sunspot umbra. This work is an extension of Schad et al. using observations acquired

A Study of Sunspot 3 Minute Oscillations Using ALMA and GST

Waves and oscillations are important solar phenomena, not only because they can propagate and dissipate energy in the chromosphere, but also because they carry information about the structure of the

Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy

Umbral flashes are periodic brightness increases routinely observed in the core of chromospheric lines within sunspot umbrae and are attributed to propagating shock fronts. In this work we quantify

The Submillimeter Active Region Excess Brightness Temperature during Solar Cycles 23 and 24

We report the temporal evolution of the excess brightness temperature ΔTb above solar active regions (ARs) observed with the Solar Submillimeter Telescope (SST) at 212 (λ = 1.4 mm) and 405 GHz (λ =

Thyr: a volumetric ray-marching tool for simulating microwave emission

Gyrosynchrotron radiation is produced by solar flares, and can be used to infer properties of the accelerated electrons and magnetic field of the flaring region. This microwave emission is highly



The chromosphere above sunspots at millimeter wavelengths

Aims. The aim of this paper is to demonstrate that millimeter wave data can be used to distinguish between various atmospheric models of sunspots, whose temperature structure in the upper photosphere


The brightness temperature of the radio free–free emission at millimeter range is an effective tool for characterizing the vertical structure of the solar chromosphere. In this paper, we report on

The Brightness Temperature of the Quiet Solar Chromosphere at 2.6 mm

The absolute brightness temperature of the Sun at millimeter wavelengths is an important diagnostic of the solar chromosphere. Because the Sun is so bright, measurement of this property usually

Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): High-Resolution Interferometric Imaging

Observations of the Sun at millimeter and submillimeter wavelengths offer a unique probe into the structure, dynamics, and heating of the chromosphere; the structure of sunspots; the formation and

Close Association of an Extreme-Ultraviolet Sunspot Plume with Depressions in the Sunspot Radio Emission

We obtained coordinated observations of the large sunspot in NOAA Region 8539 on 1999 May 9 and 13 with the Very Large Array and three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric

A closer look at a coronal loop rooted in a sunspot umbra

Extreme UV (EUV) and X-ray loops in the solar corona connect regions of enhanced magnetic activity, but they are not usually rooted in the dark umbrae of sunspots because the strong magnetic field

High-resolution millimeter-interferometer observations of the solar chromosphere

The use of millimeter-interferometer data for the study of chromospheric structure and dynamics is tested using 85 GHz observations with the 10-element Berkeley-Illinois-Maryland Array (BIMA).

Solar transition region above sunspots

Aims. We study the transition region (TR) properties above sunspots and the surrounding plage regions, by analyzing several sunspot reference spectra obtained by the SUMER (Solar Ultraviolet

The center-to-limb brightness variation of the sun at lambda = 850 microns

The 10.4 m submillimeter telescope of the Caltech Submillimeter Observatory was used to map the full disk of the Sun on 1991 July 9-10 at a wavelength λ=850 μm with an angular resolution of 20″.6. A

ALMA: status report on construction and early results from commissioning

The Atacama Large Millimeter/submillimeter Array (ALMA) is an international facility at an advanced stage of construction in the Atacama region of northern Chile. ALMA will consist of two arrays of