arXiv subjects

Simone Di Matteo

Publications and source records attributed to Simone Di Matteo.

6 recordsLinked to original sources

arXiv2026

UK White Paper on Space-based total solar eclipse observations: structure and dynamics of the solar atmosphere

Our Sun is uniquely placed to enable a detailed study of astrophysical plasmas and how they are governed by the magnetic fields that thread through them. On the one hand, magnetic fields confine plasma and determine plasma heating, flows, and energisation. On the other hand, magnetic fields and their evolution give rise to the most violent eruptions in the Solar System. Understanding the details of how energy is built up and released, and the impact of these physical processes on the plasma, remain key open questions that directly map to UKRI's science strategy through the STFC Solar System Advisory Panel's roadmap for Solar System research goals: What are the causes, consequences and predictability of solar magnetic variability and the solar cycle? What are the structures, dynamics and energetics of the Sun? What are the underlying processes that drive Sun-planet connections? And what are the fundamental processes at work in the Solar System? As laid out in this White Paper, the Moon-Enabled Sun Occultation Mission (MESOM) directly addresses these questions and in doing so delivers several Pillars of the National Space Strategy.

astro-ph.IM↗

arXiv2026

Tracking the Evolution of Plasma Instabilities from the Prominence-Corona Transition Region into Interplanetary Space with Total Solar Eclipse and WISPR/PSP White Light Images

High-resolution total solar eclipse (TSE) white light (WL) images are the only observations at present to capture coronal structures over an uninterrupted field of view (FoV) of at least 10 solar radii (Rs) starting from the solar limb. They were the first to report the presence of vortex rings originating within the prominence-corona transition region (PCTR). They also captured CMEs and Kelvin-Helmholtz (KH) instabilities at different phases of their evolution. While the evolution of CMEs and KH waves is relatively well-documented, little is known about the survivability of vortex rings beyond the FoV of the TSE images. In this study, we use seven TSE images and non-contemporaneous WL images acquired by the Wide-Field Imager for Parker Solar PRobe (WISPR) to track the spatial evolution of vortex rings, KH waves, and CMEs. The size trend versus radial distance for vortex rings and KH waves are found to be shallower below 1.5 Rs than beyond 3 Rs, while the CMEs observed beyond 3 Rs show a unique slope. The WISPR time series yield an average speed of 249.02 +/- 25.3 km/s for the vortex rings beyond 3 Rs, that when combined with their size yields a speed of 19.39 +/- 3.20 km/s below 1 Rs. These values are remarkably consistent with the acceleration profile of the slow solar wind over the same distance. This study provides strong empirical evidence that vortex rings, which originate at the PCTR with complex magnetic structures, do not dissipate as they expand away from the Sun with the solar wind.

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arXiv2025

Periodic Variations in Visible Light Brightness as Tracers of Fine Coronal Structures

The quiescent or dynamic nature of fine scale ray-like features in the sun corona, observed in visible light, is still an open question. Here, we show that most of daily and hourly periodic variations in visible light brightness of the high corona (up to 15 Rs) are aligned to the tip of streamers and are consistent with the periodicity of plasma release from simulations of tearing-induced magnetic reconnection at the heliospheric current sheet. The areas in which we detect periodicities can be used as tracers of non-quiescent fine coronal rays. This also allows their distinction from coronal rays more likely to be real quiescent features or associated with smaller and/or faster unresolved brightness variations. In the low- and middle-corona (down to 1.4 Rs) similar brightness variations are observed along loop-like and cusp-like features marking boundaries of streamers which then connect to radial features in the high corona. This suggests the presence of additional mechanisms in the low- and middle-corona periodically releasing density structures in the solar wind. The periodicity distributions show a solar cycle modulation with shorter periods (smaller structures) during solar maximum. Periodicities are observed within streamers during solar minimum, but are visible at all latitudes, even extending radially from the poles, during solar maximum.

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arXiv2025

Coronal Cells in Coronal Holes: Systematic Analysis and Implications for Coronal Evolution

Using advanced processing techniques, we analyze high-cadence, high-resolution extreme ultraviolet images and show that, throughout the solar cycle, mid-latitude coronal holes (CHs) are made up of ubiquitous and space-filling funnel-shaped structures (or cells) anchored to unipolar magnetic flux concentrations in network lanes. We demonstrate that the coronal cells, previously documented in the magnetically closed regions, as well as coronal plumes, inside CHs, are a particular manifestation of ubiquitous cells. The cell properties depend on the magnetic field intensity at their footpoint and connectivity in the corona, either closing in opposite polarity regions (CF-cells) or extending to form open-field (OF-cells). The OF-cells reach size scales on the order of super-granules and are characterized by dark lanes delimiting ray-like features both showing, at different levels, persistent jet-like ejections. The cells' lifetime mirrors that of magnetic flux concentrations revealed by magnetograms, slowly emerging and then disappearing in a matter of a few hours to a few days in a one-to-one correspondence. When a cell forms along the CH boundary, it can alter the CH boundary by shrinking or expanding the CH by an approximately supergranular cell unit. Therefore, coronal cells can contribute to the dynamics of CH boundary. We contextualize these observations in a "coronal cell" theory potentially able to provide an explanation for fine scale coronal structures and jetting activity in polar coronal holes.

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arXiv2024

Connecting the Low to High Corona: Propagating Disturbances as Tracers of the Near-Sun Solar Wind

We revisit a quiet 14-day period of solar minimum during January 2008 and track sub-streamer propagating disturbances (PDs) from low heights in STEREO/EUVI to the extended corona through STEREO/COR1 and into STEREO/COR2 along nonradial paths that trace the structure of the underlying streamers. Using our recently developed method for generating nonradial Height-Time profiles of outward PDs (OPDs) and inward PDs (IPDs), we obtained their velocities along the radial and position angle directions. Our analysis of 417 unique OPDs revealed two classes: slow and fast OPDs. Slow OPDs form preferentially at $\approx$1.6 $R_\odot$ closer to the streamer boundaries, with asymmetric occurrence rates, and show speeds of $16.4_{-8.4}^{+26.6}km/s$ at 1.5 $R_\odot$ and accelerate up to $200.1_{-57.9}^{+71.1}km/s$ at 7.5 $R_\odot$. Fast OPDs form preferentially at $\approx$ 1.6 $R_\odot$ and at $\approx$3.0 $R_\odot$ both at the streamer boundaries and slightly more often within them. They show speeds of $87.8_{-24.8}^{+59.1}km/s$ at 1.5 $R_\odot$ up to $197.8_{-46.7}^{+61.8}km/s$ at 7.5 $R_\odot$. IPDs are observed forming at $\approx$1.8 $R_\odot$ with speeds of tens of $km/s$, mostly concentrated in the aftermath of a CME eruption. We present an example in which we show that periodic brightness variations related to OPDs remained in the range of 98 to 128 min, down to $\approx$2.0 $R_\odot$, well within the field of view of COR1. The velocity profiles of slow OPDs for heliocentric height below 3.0 $R_\odot$ show good agreement with speeds more closely related to the bulk solar wind obtained via interplanetary scintillation.

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arXiv2023

Tracking Non-Radial Outflows in Extreme Ultraviolet and White Light Solar Images

Understanding the solar corona requires knowledge of its dynamics through its various layers and subsequent connectivity to the heliosphere. This requires understanding the nature of the outflows and the physical transitions through the middle corona (~1.5-6.0 Rs). While this region is still inaccessible to in situ measurements, remote sensing observations are available, but their interpretation can be controversial due to line-of-sight effects and the non-radial motion of outflowing structures close to the Sun (<3.0 Rs). In this work, we describe a method to mitigate these challenges by generating non-radial Height-Time profiles of outflows by using advanced image processing techniques. The North and South boundaries of a large equatorial streamer during the 2008 solar minimum were identified in STEREO/SECCHI solar images, using two different methodologies based on thresholds of brightness and piece-wise polynomial function fitting. To address line-of-sight issues, we used tomographic reconstruction of the 3D distribution of the coronal electron density based on SECCHI/COR2 images. Spectral analysis of the time series of the position angle of the streamer boundary revealed its oscillatory nature at some heights at 36-48 hours and 10.5-14.6 hours. Dividing the distance between the North and South streamer boundaries in equal parts at each height, we obtained non-radial Height-Time paths from which we generated non-radial profiles of corona/solar wind plasma outflow. We tracked outflows as they moved uninterruptedly from the Sun in EUVI, through COR1 and into COR2. Finally, we discuss preliminary results of non-radial plane-of-sky velocities for a CME and two small-scale features.

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