Other team members:
Maria Kazachenko National Solar Observatory 
Serena Criscuoli National Solar Observatory

Scientific Focus of Data Sets: Solar system and beyond

Description of Data Sets:

To understand physical properties of the so-called “Quiet Sun,” high-resolution imagery of the solar surface must be obtained. Thus, our team selected data from the Swedish Solar 1m Telescope (SST). The analyzed data have a spatial resolution close to the diffraction limit of the telescope, (0.15 arcsec at 557 nm) thus allowing to resolve the small, transient, and chaotic magnetism on the quiet Sun photosphere. The field of view was 57”.5 x 57”.3 and the pixel resolution was 0”.059 pixel-1 (43.2 km) To analyze the magnetic flux changes and plasma velocities of magnetic polarities on the solar surface, a series of 100 images were taken at a cadence of 28 seconds with the CRisp SpectroPolarimeter (CRISP) observing three Fe I lines at 630.1, 630.2 and 557.6 nm at the solar disk center and at a spectral resolution of 4 pm. Doppler velocities of the plasma captured by CRISP were obtained by applying a Gaussian fit to the Fe I line profile at 557.6 nm. Magnetic flux density was derived by applying the COG method to the left and right-hand circularly polarized light observed at the Fe I 630.1 nm spectral range.
The data from the SST was acquired in August 2011 during a coordinated campaign involving the SST, DOT, and HINODE facilities awarded by the OPTICON to my mentor, Dr. Serena Criscuoli. As such, she has the right to use the acquired datasets as well as to authorize its use for scientific purposes to students and other collaborators.

Scientific Potential of Presentation:

The so-called “Quiet Sun” is one of the final frontiers of solar physics. Responsible for the majority of the Sun’s energy output, it is generally defined as the areas of the solar surface not occupied by active regions (sunspots), and until recently, it has widely been regarded as boring, insignificant, quiet. Within the past decade, however, advancements in solar optics and observing techniques have allowed scientists to scrutinize the solar surface in greater and greater detail, and what they discovered was truly astonishing. Unlike its name suggests, the “quiet” Sun is not quiet at all, but is instead writhing with intricate webs and patterns of magnetic fields, evolving and shifting rapidly. These magnetic fields come in all shapes and typical sizes of a few hundred kilometers or less, but come in two flavors of magnetic polarity: positive and negative. Due to the chaotic nature of the convective plasma that drives the motion of quiet Sun magnetism, positive and negative-polarity magnetic elements frequently cancel. Previous research has revealed these magnetic cancellations to play an important role in the dynamics and energetics of the upper solar atmosphere. Since technology has only improved recently, magnetic cancellations have not been documented well and their fundamental characteristics are still relatively unknown.
Utilizing high-resolution datasets from the SST, myself and my team were able to make novel discoveries and conclusions regarding magnetic cancellation. From the original SST dataset we derived three data-products: longitudinal magnetograms showing line-of-sight magnetic field strengths (b-los), white light frames showing surface features, and dopplergrams showing line-of-sight velocities (v-los) of plasma. The variety of datasets allowed me to study every aspect of magnetic cancellation, tracking the magnetic fluxes of the polarities as they converged, deriving values for the amount and rate of flux cancellation, and even observing plasma downflows that may be related to magnetic reconnection, an enigma scientists have been trying to understand for decades. Aside from the quantification of magnetic cancellation, the very visual process of two polarities converging and interacting made the datasets themselves a unique research and learning tool.
Because the datasets were so visually oriented, captivating, and self-evident, they could be easily incorporated as a learning tool and observing them in parallel was useful to study correlations and relationships between different solar phenomena. The time-series datasets of magnetograms show a network of magnetism characteristic of small-scale quiet Sun environments while the white-light and dopplergram imagery shoes a patchwork of granules, by-products of solar convection, rippling and pulsating. When viewed as a movie, the datasets become a tool to reveal the beauty and strange nature of the Sun to non-scientists, and I have incorporated this technique into talks, presentations, and my research blog (http://www.quietsun.weebly.com). Furthermore, because of the number of “angles” we have, relationships previously neglected can be explored or expanded upon. For example, by comparing results obtained from the analysis of the b-los dataset and a the v-los dataset, we were able to establish a relationship between cancellations and downflow velocity; an important discovery.