arXiv subjects

Richard Morton

Publications and source records attributed to Richard Morton.

7 recordsLinked to original sources

arXiv2026

Synthetic Fe XIII 1074.7 nm Observations of Torsional Alfv\'{e}n Waves in Coronal Waveguides

Torsional Alfv\'{e}n waves are a promising mechanism for transporting energy through the solar atmosphere, with implications for coronal heating and solar wind acceleration. Recently, signatures of torsional Alfv\'{e}n waves have been observed with the Daniel K. Inouye Solar Telescope. We aim to investigate the effects of line of sight integration and plasma conditions on the observable properties of the torsional mode. Here we present three-dimensional magnetohydrodynamic simulations of multiple coronal waveguides, driven by a combination of transverse kink and torsional wave drivers, considering two plasma regimes representative of active region (AR) and quiet Sun (QS) conditions. Synthetic observables of the Fe~\textsc{xiii}~1074.7~nm coronal emission line are produced using the pyCELP forward-modelling framework to enable direct comparison with spectroscopic observations. In the QS regime, red-blue Doppler asymmetries are associated with the driven torsional waves, though their observed amplitudes are substantially reduced by line-of-sight integration. In contrast, the AR regime exhibits red-blue Doppler asymmetries even in the absence of an imposed torsional driver, which may be misidentified as the $m=0$ torsional Alfv\'{e}n mode. In the AR setup, the red-blue Doppler asymmetries arise from strong phase mixing, generating shear flows and localised vorticity between waveguides where emission is strongest. The differences between the two regimes are governed by the location of peak emission, which is determined by the degree of density inhomogeneity. Our results support the identification of torsional Alfv\'{e}n wave signatures in the quiet Sun (a weakly inhomogeneous environment), but caution should be exercised when interpreting spectroscopic observations in strongly inhomogeneous environments such as active regions.

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arXiv2026

High-Frequency Magnetohydrodynamic Waves with Substantial Energy in the Solar Polar Corona

The acceleration and heating of the fast solar wind remain long-standing challenges in space physics. One type of leading theoretical models requires high-frequency magnetohydrodynamic (MHD) waves to transport and dissipate sufficient energy in the corona. However, such high-frequency waves with energetically significant amplitudes have never been unambiguously observed, leaving a key gap between theories and observations. Using high-cadence, high-resolution extreme-ultraviolet imaging from Solar Orbiter's Extreme Ultraviolet Imager, we identify a previously hidden population of high-frequency MHD waves in coronal plumes of the solar polar region. An analysis of the detected propagating kink waves shows that over one-third have periods shorter than 100 s, a population largely undetected by earlier instruments. Power spectral analysis demonstrates that these high-frequency waves carry substantial energy flux, which are significantly underestimated in lower-cadence data. These results suggest that high-frequency MHD waves may contribute importantly to the energy budget of the solar polar corona and could play a role in solar wind acceleration, highlighting the value of high-resolution observations for probing energy transport in magnetized space and astrophysical plasmas.

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arXiv2026

A Robust Deep Learning Framework for Prominence Detection through Composite Feature Representations

Solar prominences are dynamic structures suspended within the solar corona and are manifestation of solar activity. Their evolution includes eruptions linked to coronal mass ejections, making their detection critical for space weather monitoring and forecasting. The vast amounts of high-cadence data provided by missions such as SDO/AIA motivate the application of deep learning frameworks capable of assimilating large-scale datasets. However, previous studies have reported poor model performance caused by contamination from hot coronal emission from the EUV HeII 304 {\AA} channel. Using an existing labeled prominence dataset, we find that trained YOLOv5 object detection models exhibit a strong bias towards the 304 {\AA} colormap, rather than physically meaningful prominence features. We develop a further two models comprising three-channel images constructed through an original dataset preprocessing pipeline: (i) full-disk grayscale, full-disk enhanced corona, and disk-removed, (ii) same as (i) with all disk-removed images. Our pipeline corrects instrument degradation to maintain more consistent feature representations across the solar cycle. The composite model (i) achieves a mAP@50 of 0.749 and a recall of $78\%$ on the test set, outperforming previous bounding box methods. Visual analysis of the composite models reveals that many apparent false positives are valid unlabeled prominences. We additionally demonstrate cross-instrument generalization by testing the composite model on SUVI image data. By examining dataset biases that propagate into model predictions, we provide recommendations for robust dataset construction. We present a reliable, physically-motivated, and versatile deep learning model to automatically detect prominences in EUV images, providing a framework beneficial for space weather applications.

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arXiv2025

Ubiquitous high-frequency waves and disturbances in the active region corona observed with DKIST/Cryo-NIRSP

The plasma of the solar corona harbors a multitude of coronal wave modes, some of which could be dissipated to provide the required energy and momentum to heat the corona and accelerate the solar wind. We present observations of the corona acquired with the newly commissioned infrared slit spectropolarimeter Cryo-NIRSP at the Daniel K. Inouye Solar Telescope (DKIST), Haleakala, Hawaii to study the high frequency wave behavior in closed, active-region structures. Cryo-NIRSP observes the corona off the limb in the Fe XIII 1074 and 1079 nm forbidden atomic lines. The large aperture of DKIST allows us to explore the active region corona with temporal resolution faster than a second with an achieved spatial resolution of 2-5 arcseconds. Enhanced wave power is observed in the power spectra up to 100 mHz. Furthermore, we report on a statistically significant anti-correlation between the Fe XIII 1074 nm peak line intensity and line width in our data, possibly pointing to the presence of compressive magnetohydrodynamic (MHD) wave modes. These observations show how the powerful spectropolarimetric capabilities of DKIST offer great promise for furthering our knowledge of coronal MHD waves.

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arXiv2020

Mapping the magnetic field in the solar corona through magnetoseismology

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe xiii 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

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arXiv2020

Global maps of the magnetic field in the solar corona

Understanding many physical processes in the solar atmosphere requires determination of the magnetic field in each atmospheric layer. However, direct measurements of the magnetic field in the Sun's corona are difficult to obtain. Using observations with the Coronal Multi-channel Polarimeter, we have determined the spatial distribution of the plasma density in the corona, and the phase speed of the prevailing transverse magnetohydrodynamic waves within the plasma. We combine these measurements to map the plane-of-sky component of the global coronal magnetic field. The derived field strengths in the corona from 1.05 to 1.35 solar radii are mostly 1-4 Gauss. These results demonstrate the capability of imaging spectroscopy in coronal magnetic field diagnostics.

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arXiv2020

The drivers of active region outflows into the slow solar wind

Plasma outflows from the edges of active regions have been suggested as a possible source of the slow solar wind. Spectroscopic measurements show that these outflows have an enhanced elemental composition, which is a distinct signature of the slow wind. Current spectroscopic observations, however, do not have sufficient spatial resolution to distinguish what structures are being measured or to determine the driver of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a sounding rocket in May, 2018, and observed areas of active region outflow at the highest spatial resolution ever achieved (250 km). Here we use the Hi-C data to disentangle the outflow composition signatures observed with the Hinode satellite during the flight. We show that there are two components to the outflow emission: a substantial contribution from expanded plasma that appears to have been expelled from closed loops in the active region core, and a second contribution from dynamic activity in active region plage, with a composition signature that reflects solar photospheric abundances. The two competing drivers of the outflows may explain the variable composition of the slow solar wind.

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