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Gordon A. MacDonald

Publications and source records attributed to Gordon A. MacDonald.

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The Sunspot Solar Observatory Data Archive: Continuing Operations at the Dunn Solar Telescope

The Sunspot Solar Observatory Data Archive (SSODA) stores data acquired with the suite of instruments at the Richard B. Dunn Solar Telescope (DST) from February 2018 to the present. The instrumentation at the DST continues to provide high cadence imaging, spectroscopy, and polarimetry of the solar photosphere and chromosphere across a wavelength range from 3500Å to 11,000Å. At time of writing, the archive contains approximately 374 TiB of data across more than 520 observing days (starting on February 1, 2018). These numbers are approximate as the DST remains operational, and is actively adding new data to the archive. The SSODA includes both raw and calibrated data. A subset of the archive contains the results of photospheric and chromospheric spectropolarimetric inversions using the Hazel-2.0 code to obtain maps of magnetic fields, temperatures, and velocity flows. The SSODA represents a unique resource for the investigation of plasma processes throughout the solar atmosphere, the origin of space weather events, and the properties of active regions throughout the rise of Solar Cycle 25.

astro-ph.SR

Properties of 16 Sunspots Observed with Hinode Solar Optical Telescope

We studied 16 sunspots with different sizes and shapes using the observations with the Hinode Solar Optical Telescope. The ratio of G-band and CaII H images reveal rich structures both within the umbra and penumbra of most spots. The striking features are the compact blob at the foot point of the umbra side of the penumbral fibrils with disk center-limb side asymmetry. In this paper, we present properties of these features using the spectropolarimetry and images in G-band, CaII and blue filters. We discuss the results using the contemporary models of the sunspots.

astro-ph.SR

Stokes Profiles at the Narrow Magnetic Lanes of Sun Spots

It has been previously observed that narrow lanes of transverse and longitudinal magnetic field with opposite polarity are the site of large solar flares. We performed a comprehensive examination of the stokes asymmetries of active region NOAA 10930. The active region was observed just before, during and after an X-class flare, which occurred during December 13, 2006 from 02:20 to 06:18 UT. We observe a static fibril interacting with a rotating penumbra of opposite polarity in the hours prior to the flare. Above the fibril were several small sites of hot gas in the chromosphere. During and after the flare, the fibril and its corresponding flow and profiles were much less pronounced. We present a full analysis of magnetic and plasma properties of this active region.

astro-ph.SR