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ALMA and IRIS Observations of the Solar Chromosphere. I. An On-disk Type II Spicule
Martínez-Sykora, Juan; De Pontieu, Bart; Chintzoglou, Georgios +7 more
We present observations of the solar chromosphere obtained simultaneously with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph. The observatories targeted a chromospheric plage region of which the spatial distribution (split between strongly and weakly magnetized regions) allowed the study of l…
Measurements of Photospheric and Chromospheric Magnetic Field Structures Associated with Chromospheric Heating over a Solar Plage Region
Kitai, Reizaburo; Kleint, Lucia; Schad, Thomas A. +6 more
In order to investigate the relation between magnetic structures and the signatures of heating in plage regions, we observed a plage region with the He I 1083.0 nm and Si I 1082.7 nm lines on 2018 October 3 using the integral field unit mode of the GREGOR Infrared Spectrograph (GRIS) installed at the GREGOR telescope. During the GRIS observation, …
Emergence of Internetwork Magnetic Fields through the Solar Atmosphere
Gošić, M.; De Pontieu, B.; Bellot Rubio, L. R. +2 more
Internetwork (IN) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. Since they emerge all over the Sun, these small-scale fields bring a substantial amount of flux, and therefore energy, to the solar surface. Because of this, IN fields are crucial for understanding the quiet Sun …
Exploring Mutual Information between IRIS Spectral Lines. I. Correlations between Spectral Lines during Solar Flares and within the Quiet Sun.
Kleint, Lucia; Panos, Brandon; Voloshynovskiy, Sviatoslav
Spectral lines allow us to probe the thermodynamics of the solar atmosphere, but the shape of a single spectral line may be similar for different thermodynamic solutions. Multiline analyses are therefore crucial, but computationally cumbersome. We investigate correlations between several chromospheric and transition region lines to restrain the th…
High-frequency Wave Power Observed in the Solar Chromosphere with IBIS and ALMA
Kowalski, Adam F.; Cranmer, Steven R.; Reardon, Kevin P. +3 more
We present observational constraints on the chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We use observations from the Dunn Solar Telescope in New Mexico, complemented with observations from the Atacama Large Millimeter Array collected on 2017 April 23. The properties of the power spectra of the vari…
ALMA and IRIS Observations of the Solar Chromosphere. II. Structure and Dynamics of Chromospheric Plages
Martínez-Sykora, Juan; De Pontieu, Bart; Chintzoglou, Georgios +7 more
We propose and employ a novel empirical method for determining chromospheric plage regions, which seems to better isolate a plage from its surrounding regions than other methods commonly used. We caution that isolating a plage from its immediate surroundings must be done with care in order to successfully mitigate statistical biases that, for inst…
Coronal Heating and Solar Wind Formation in Quiet Sun and Coronal Holes: A Unified Scenario
Solanki, Sami K.; Tripathi, Durgesh; Nived, V. N.
Coronal holes (CHs) are darker than the quiet Sun (QS) when observed in coronal channels. This study aims to understand the similarities and differences between CHs and QS in the transition region using the Si IV 1394 Å line, recorded by the Interface Region Imaging Spectrograph, by considering the distribution of magnetic field measured by the He…
Is Flare Ribbon Fine Structure Related to Tearing in the Flare Current Sheet?
Wyper, P. F.; Pontin, D. I.
Observations of solar flare ribbons show significant fine structure in the form of breaking wavelike perturbations and spirals. The origin of this structure is not well understood, but one possibility is that it is related to the tearing instability in the flare current sheet. Here we study this connection by constructing an analytical 3D magnetic…
Unsupervised Machine Learning for the Identification of Preflare Spectroscopic Signatures
De Pontieu, Bart; Sainz Dalda, Alberto; Woods, Magnus M.
The study of the preflare environment is of great importance to understanding what drives solar flares. k-means clustering, an unsupervised machine-learning technique, has the ability to cluster large data set in a way that would be impractical or impossible for a human to do. In this paper we present a study using k-means clustering to identify p…
Exploring Mutual Information between IRIS Spectral Lines. II. Calculating the Most Probable Response in all Spectral Windows
Kleint, Lucia; Panos, Brandon
A three-dimensional picture of the solar atmosphere's thermodynamics can be obtained by jointly analyzing multiple spectral lines that span many formation heights. In Paper I, we found strong correlations between spectral shapes from a variety of different ions during solar flares in comparison to the quiet Sun. We extend these techniques to addre…