Solar Flux Origins, Emergence, and Eruptions

Spectropolarimetric Inversion in Four Dimensions with Deep Learning (SPIn4D): II. A Physics-Informed Machine Learning Method for 3D Solar Photosphere Reconstruction

whawkins — Tue, 23 Dec 2025 16:21:35 +0000

Spectropolarimetric Inversion in Four Dimensions with Deep Learning (SPIn4D): II. A Physics-Informed Machine Learning Method for 3D Solar Photosphere Reconstruction whawkins Tue, 12/23/2025 - 09:21

Author:

whawkins

Dec 23, 2025

Astrophysical Journal: Inferring the three-dimensional (3D) solar atmospheric structures from observations is a critical task for advancing our understanding of the magnetic fields and electric currents that drive solar activity. In this work, we introduce a novel, Physics-Informed Machine Learning method to reconstruct the 3D structure of the lower solar atmosphere based on the output of optical depth sampled spectropolarimetric inversions, wherein both the fully disambiguated vector magnetic fields and the geometric height associated with each optical depth are returned simultaneously. Traditional techniques typically resolve the 180-degree azimuthal ambiguity assuming a single layer, either ignoring the intrinsic non-planar physical geometry of constant optical-depth surfaces (e.g., the Wilson depression in sunspots), or correcting the effect as a post-processing step. In contrast, our approach simultaneously maps the optical depths to physical heights, and enforces the divergence-free condition for magnetic fields fully in 3D. Tests on magnetohydrodynamic simulations of quiet Sun, plage, and a sunspot demonstrate that our method reliably recovers the horizontal magnetic field orientation in locations with appreciable magnetic field strength. By coupling the resolutions of the azimuthal ambiguity and the geometric heights problems, we achieve a self-consistent reconstruction of the 3D vector magnetic fields and, by extension, the electric current density and Lorentz force. This physics-constrained, label-free training paradigm is a generalizable, physics-anchored framework that extends across solar magnetic environments while improving the understanding of various solar puzzles.

Panel (a) shows the flowchart for training the model. The inputs are the 3D magnetic vector fields with azimuthal ambiguity, and an initial guess of the geometric heights associated with each optical-depth layer. The UNet3DB network predicts 3D vector magnetic field, and the UNet3DZ network provides the geometric heights. They are combined to compute a custom loss function that also considers physical constraints (divergence free magnetic field). Panel (b) shows the post-processing step that assembles the outputs from the neural networks (prediction) and the original input magnetic fields into the final output. Panel (c) shows an example of the 3D data, split with overlaps between nearby subfields. These individual subfields are used as the input for training. Panel (d) presents the UNet3D structure, reproduced from Figure 2 in Cicek et al. (2016).

Analysis Of Short-term Solar Activity Variability and Estimating Timings of Next Enhanced Bursts

whawkins — Tue, 11 Nov 2025 21:45:29 +0000

Analysis Of Short-term Solar Activity Variability and Estimating Timings of Next Enhanced Bursts whawkins Tue, 11/11/2025 - 14:45

Author:

whawkins

Nov 11, 2025

Zoomed-in burst-envelope forecasts from January 2024 to April 2026. Top: The Northern Hemisphere SSN with inferred RF (Random Forest) bursts properties. Middle: The Southern hemisphere counterpart. Bottom: Total (Northern Hemisphere + Southern Hemisphere) SSN, highlighting the same burst timings and amplitudes.

The Astrophysical Journal: A novel machine-learning-based hybrid forecasting strategy for predicting next enhanced burst of solar activity is presented. This hybrid forecast-system combines numerical, statistical, and machine-learning techniques to detect the occurrence of the next bursts of solar activity. These enhanced bursts are called “space weather seasons” that occur on intermediate timescales (6–18 months). Monthly smoothed sunspot number (SSN) data from 1878 to 2025 are analyzed using Gaussian fitting techniques to identify burst events and their properties such as amplitude and duration. The SSN data are divided into training, test, and forecast, which shows hindcast and forecast. Each hemisphere is modeled via a Seasonal Autoregressive Integrated Moving Average (SARIMA) approach, refined with an asymmetric Gaussian override to capture rapid burst rise and gradual decay, and burst amplitudes and duration are predicted using a Random Forest (RF) regression model. This hybrid approach successfully hindcasts burst timing in between November 2024 and May 2025, with a peak SSN of ∼70 around March 2025 for the Northern Hemisphere. The next burst in the Northern Hemisphere is forecast to be in December 2025 with a slightly lower SSN of 60. By contrast, the Southern Hemisphere shows relatively complicated behavior, where the bursts show multiple amplitudes starting approximately in October 2024 and ending in October 2025. The main burst shows an amplitude of 130 SSN. The next burst in the Southern Hemisphere is forecast to occur approximately in December 2025. Combining SSN properties in both hemispheres, we find that the total SSN is mainly influenced by a stronger cycle in the Southern Hemisphere.

The ASPIICS solar coronagraph aboard the Proba-3 formation flying mission. Scientific objectives and instrument design

whawkins — Tue, 11 Nov 2025 21:28:07 +0000

The ASPIICS solar coronagraph aboard the Proba-3 formation flying mission. Scientific objectives and instrument design whawkins Tue, 11/11/2025 - 14:28

Author:

whawkins

Nov 11, 2025

Astronomy and Astrophysics: We describe the scientific objectives and instrument design of the ASPIICS coronagraph launched aboard the Proba-3 mission of the European Space Agency (ESA) on 5 December 2024. Proba-3 consists of two spacecraft in a highly elliptical orbit around the Earth. One spacecraft carries the telescope, and the external occulter is mounted on the second spacecraft. The two spacecraft fly in a precise formation during 6 hours out of 19.63 hour orbit, together forming a giant solar coronagraph called ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun). Very long distance between the external occulter and the telescope (around 144 m) represents an increase of two orders of magnitude compared to classical externally occulted solar coronagraphs. This allows us to observe the inner corona in eclipse-like conditions, i.e. close to the solar limb (down to 1.099 Rs) and with very low straylight. ASPIICS will provide a new perspective on the inner solar corona that will help solve several outstanding problems in solar physics, such as the origin of the slow solar wind and physical mechanism of coronal mass ejections.

Two spacecraft of the Proba-3 mission. Left panel: the Coronagraph Spacecraft (CSC). Right panel: the Occulter Spacecraft (OSC). The annotations highlight key subsystems of the mission: the entrance door of the ASPIICS coronagraph (1), GNSS antennas (2), antennas of the Inter-Satellite Link (ISL, 3), some mires of the Visual-Based System (4), Corner Cube Retro-Reflector (5), which is a part of the Fine Lateral and Longitudinal Sensor (FLLS), the edge of the external occulter (6), three LEDs of the Occulter Position Sensor Emitter (OPSE, 7), wide-angle and narrow-angle cameras of the VBS (8), laser of the FLLS (9). The axes of the coordinate systems are shown in each panel, with the x-axis pointing away from the Sun, z-axis pointing towards the ecliptic north, and y-axis complementing the right-handed system. The theoretical formation corresponds to the perfect alignment of the respectively x, y, and z axes attached to the two spacecraft.

MHD simulations of CME with associated prominence eruption

whawkins — Tue, 16 Sep 2025 19:45:59 +0000

MHD simulations of CME with associated prominence eruption whawkins Tue, 09/16/2025 - 13:45

Author:

whawkins

Sep 16, 2025

Snapshots of the magnetic field lines (left column) and the synthetic SDO/AIA 304 Å images (right column) showing the development of a coronal mass ejection with associated prominence eruption in a MHD simulation of a prominence-forming coronal flux rope.

Solar Physics: We present an overview of magnetohydrodynamic (MHD) simulations of prominence-forming coronal flux ropes and the development of coronal mass ejection (CME) with associated prominence eruption. The simulations found the formation of a prominence-cavity system that qualitatively reproduces several observed features including the cavity, the prominence “horns”, and the central “cavity” enclosed in the “horns” above the prominence. We discuss the magnetic structure corresponding to these observed features and the effect of the prominence weight on the stability and eruption of the flux rope.

The Striated Solar Photosphere Observed at 0.″03 Resolution

whawkins — Wed, 13 Aug 2025 20:28:21 +0000

The Striated Solar Photosphere Observed at 0.″03 Resolution whawkins Wed, 08/13/2025 - 14:28

Author:

whawkins

Aug 13, 2025

Left: G-band intensity image observed with DKIST VBI showing striations with widths of approximately 20‑50 km. Right: Synthetic G-band intensity image computed from a MURaM simulation for an inclination of μ = 0.85, matching the observed inclination. The numerical simulation shows intensity striations on a comparable scale and confirms their association with photospheric magnetic flux concentrations that modulate the geometrical height where the emergent intensity forms.

The Astrophysical Journal Letters: Striated granular edges observed in the solar photosphere represent one of the smallest-scale phenomena on the Sun. They arise from the interaction of strongly coupled hydrodynamic, magnetic, and radiative properties of the plasma. In particular, modulations in the photospheric magnetic field strength cause variations in density and opacity along the line of sight, leading to their formation. Therefore, the striation patterns can be used as valuable diagnostics for studying the finest-scale structure of the photospheric magnetic field. The Daniel K. Inouye Solar Telescope (DKIST) allows observations of the solar atmosphere with a spatial resolution of better than 0 .″ 03 with its current instrumentation. We analyze images acquired with the Visible Broadband Imager using the G-band channel to investigate the characteristics of fine-scale striations in the photosphere and compare them with state-of-the-art radiation-MHD simulations at similar spatial resolution. Both observed and synthetic images reveal photospheric striae with widths of approximately 20‑50 km, suggesting that at least 4 m class solar telescopes are necessary to resolve this ultrafine structure. Analysis of the numerical simulations confirms that the striation observed in the filtergrams is associated with spatial variations in photospheric magnetic flux concentrations, which cause shifts in the geometrical height where the emergent intensity forms. Some fine-scale striations in the synthetic images originate from magnetic field variations of approximately 100 G, resulting in Wilson depressions as narrow as 10 km. This suggests that DKIST G-band images can trace the footprints of magnetic field variations and Wilson depressions at a similar scale.

The role of the Lorentz force in sunspot equilibrium

whawkins — Wed, 13 Aug 2025 19:50:25 +0000

The role of the Lorentz force in sunspot equilibrium whawkins Wed, 08/13/2025 - 13:50

Author:

whawkins

Aug 13, 2025

Scatter plots of the physical quantities in penumbra (extracted along an azimuthal arc) for GREGOR data (red squares), Hinode data (blue circles), and the MHD simulation (black triangles). Pearson correlations coefficients, c, for each of these pieces of data are provided in the legend. Linear fits to the data are shown with thick solid color lines. Upper left: γ − ∥B∥. Upper right: γ − Pg. Lower left: γ − ρ. Lower right: Lϕ − r−1∂Pg/∂ϕ. Each panel also includes three smaller subpanels in which the variations in the physical quantities along ϕ are displayed in purple and green colors. These subpanels are ordered as: GREGOR (left), Hinode (middle), and MHD simulations (right). This is also indicated by the arrows under the correlation coefficients for each data source. We note that the values of the ϕ components of the Lorentz force and of the gas pressure gradient in the simulations have been divided by five. The results demonstrate that, in the azimuthal ϕ direction, penumbral spines and intraspines are in almost perfect magnetohydrostatic equilibrium between the azimuthal components of Lorentz and pressure forces.

Astronomy & Astrophysics: Sunspots survive on the solar surface for timescales ranging from days to months. This requires them to be in an equilibrium involving magnetic fields and hydrodynamic forces. Unfortunately, theoretical models of sunspot equilibrium are very simplified as they assume that spots are static and possess a self-similar and axially symmetric magnetic field. These assumptions neglect the role of small-scale variations of the magnetic field along the azimuthal direction produced by umbral dots, light bridges, penumbral filaments, and so forth. Aims. We aim to study whether sunspot equilibrium is maintained once azimuthal fluctuations in the magnetic field, produced by the sunspot fine structure, are taken into account. Methods. We apply the FIRTEZ Stokes inversion code to spectropolarimetric observations to infer the magnetic and thermodynamic parameters in two sunspots located at the disk center and observed with two different instruments: one observed from the ground with the 1.5-meter German GREGOR Telescope and another with the Japanese spacecraft Hinode. We compare our results with three-dimensional radiative magnetohydrodynamic simulations of a sunspot carried out with the MuRAM code. Results. We infer clear variations in the gas pressure and density of the plasma directly related to fluctuations in the Lorentz force and associated with the filamentary structure in the penumbra. Similar results are obtained in the umbra despite its lack of an observed filamentary structure. Results from the two observed sunspots are in excellent qualitative and quantitative agreement with the numerical simulations. Conclusions. Our results indicate that the magnetic topology of sunspots along the azimuthal direction is very close to magnetohydrostatic equilibrium, thereby helping to explain why sunspots are such long-lived structures capable of surviving on the solar surface for days or even full solar rotations.

HAO research featured on AAS Nova

whawkins — Tue, 29 Jul 2025 21:03:34 +0000

HAO research featured on AAS Nova whawkins Tue, 07/29/2025 - 15:03

Mother's Day Superstorms: Pre- and Post-storm Evolutionary Patterns of AR 13664/8

whawkins — Tue, 24 Jun 2025 18:13:37 +0000

Mother's Day Superstorms: Pre- and Post-storm Evolutionary Patterns of AR 13664/8 whawkins Tue, 06/24/2025 - 12:13

Author:

whawkins

Jun 24, 2025

Top: Global-scale toroid patterns indicate ARs 13664 and 13668 were located in the south-toroid in such a way as to be sufficiently away from ARs in the north-toroid, indicating probability of their eruption; close proximity of ARs 13664 and 13668 indicates the possibility of complex interactions between them. Bottom: Small-scale evolution of AR13664/8 is shown with three snapshots from HMI continuum (left) and radial magnetic field(right). The active region at the right side of the first frame was denoted as AR13664 first, and AR 13668 emerged to the east of it. Multiple pairs of bipoles emerged with the positive and negative polarities seen in white and black, respectively.

The Astrophysical Journal: In the week including Mother's day 2024, active region (AR) 13664 became superactive when AR\,13668 emerged nearby, causing multiple X-class flares and CMEs, and activity level increased similar to that inferred from geomagnetic storms associated with the historic 1859 events. By analyzing bot global warped toroids on which the active regions are strung, and active-region-scale magnetic flux and helicity, we find: (i) North and South toroids have nearly identical warped patterns, with mostly longitudinal wave numbers $m=1-3$; (ii) in three longitude intervals North and South toroids were tipped away from each other in latitude, with a longitude phase-shift between them, creating locations most prone for AR eruptions; (iii) on active-region-scale, vector magnetic fields deviate far from potential fields, and therefore contain large amounts of magnetic 'free energy' available for conversion into kinetic energy and high temperature radiation; (iv) the positive and negative polarities converge toward each other, facilitating reconnection and magnetic energy release; (v) rapid changes in magnetic helicity caused by helicity injection from below that creates helicity imbalances. We conclude that the Mother's day superstorms were caused by enhanced magnetic complexity occurring due to intricate interactions among multiple active regions emerging at nearly the same locations. This suggests, predicting locations of magnetically complex ARs, and studying and tracking their eruptive states using different proxy parameters, can greatly improve our ability to forecast intense storms, not only hours but potentially weeks in advance.

A deep learning framework for instrument-to-instrument translation of solar observation data

whawkins — Tue, 06 May 2025 19:39:28 +0000

A deep learning framework for instrument-to-instrument translation of solar observation data whawkins Tue, 05/06/2025 - 13:39

Author:

whawkins

May 6, 2025

Nature Communications: The constant improvement of astronomical instrumentation provides the foundation for scientific discoveries. In general, these improvements have only implications forward in time, while previous observations do not benefit from this trend, and the joint use of data sets from different instruments is typically limited by differences in calibration and quality.
Researches from the High Altitude Observatory (NSF NCAR; USA), in collaboration with researchers from the University of Graz (Austria), and Skolkovo Institute of Science and Technology (Skoltech; Russia), recently developed a new deep learning framework for Instrument-To-Instrument translation of solar observation data, enabling homogenized data series across multi-instrument datasets. The approach uses unpaired domain translations with Generative Adversarial Networks, which eliminate the need for spatial or temporal overlap to relate instruments. The study demonstrates that the available data sets can directly profit from instrumental improvements, by applying the method to four different applications of ground- and space-based solar observations. The authors obtain a homogenized data series of 24 years of space-based observations of the solar EUV corona and line-of-sight magnetic field, solar full-disk observations with increased spatial resolution, real-time mitigation of atmospheric degradations in ground-based observations, and unsigned magnetic field estimates from the solar far-side based on EUV imagery. The direct comparison to simultaneous high-quality observations shows that the method produces images that are perceptually similar, and enables more homogeneous multi-instrument data sets without the requirement of spatial or temporal alignment.

Occasional overlapping observations between different instruments allow for direct comparison between AI-enhanced images and high-quality reference data. This figure presents side-by-side views of original space-based observations from SOHO/EIT, their AI-enhanced counterparts, and reference observations from SDO/AIA. The three rows highlight different solar features: the Extreme Ultraviolet observations of the solar limb (top), an active region (middle), and the magnetic field of a sunspot (bottom).

Jarolim et al., 2025

The results were published in Nature Communications (https://doi.org/10.1038/s41467-025-58391-4).

The Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) Code: A Global Corona Magnetohydrodynamic Code with the Yin-Yang grid

whawkins — Wed, 09 Apr 2025 20:43:41 +0000

The Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) Code: A Global Corona Magnetohydrodynamic Code with the Yin-Yang grid whawkins Wed, 04/09/2025 - 14:43

Author:

whawkins

Apr 9, 2025

The Astrophysical Journal Supplement: We describe the numerical algorithms of a global magnetohydrodynamic (MHD) code utilizing the Yin-Yang grid, called the Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) code, suitable for modeling the large-scale dynamical processes of the solar corona and the solar wind. It is a single-fluid MHD code taking into account the non-adiabatic effects of the solar corona, including the electron heat conduction, optically thin radiative cooling, and empirical coronal heating. We describe the numerical algorithms used to solve the set of MHD equations (with the semi-relativistic correction, or the Boris correction) in each of the partial spherical shell Yin Yang domains, and the method for updating the boundary conditions in the ghost-zones of the two overlapping domains with the code parallelized with the message passing interface (MPI). We validate the code performance with a set of standard test problems, and finally present a solar wind solution with a dipolar magnetic flux distribution at the solar surface, representative of solar minimum configuration.

The quasi-steady state solution from a global MHD simulation of the solar wind with a dipolar magnetic field, representative of the solar minimum condition. The magnetic field has reached a partially open configuration (top left panel) with open field lines (green and blue field lines) in the high latitude polar regions and closed field lines (red field lines) in the equatorial region under cusped field lines (orange field lines) which extend into an equatorial heliospheric current sheet (HCS). A transonic outflow reasonably close to the outflow in solar minimum coronal hole (Withbroe 1988) is obtained in the open field region. The synthetic white-light coronagraph image as would be observed from the equatorial earth view (top right panel) shows the bright equatorial helmet streamers made up by the closed and the cusped magnetic field lines and the dark coronal holes in the polar region made up by the open magnetic field, representative of the configuration typically seen in coronagraph (or eclipse) images during solar minimum. On the other hand, the synthetic coronagraph image as viewed from the pole (bottom right panel) shows striking dynamic features in the HCS due to the on-going 3D magnetic reconnection in the HCS. They show elongated dark (under-dense) wiggly features flowing sunward and truncate at the top of the helmet streamer. These features correspond to strong reconnection jets flowing sunward from the reconnection sites (see the red sunward flows of 𝑣𝑟 in the equatorial plane shown in the bottom left panel).

Solar Flux Origins, Emergence, and Eruptions

Spectropolarimetric Inversion in Four Dimensions with Deep Learning (SPIn4D): II. A Physics-Informed Machine Learning Method for 3D Solar Photosphere Reconstruction

Recent News

Analysis Of Short-term Solar Activity Variability and Estimating Timings of Next Enhanced Bursts

Recent News

The ASPIICS solar coronagraph aboard the Proba-3 formation flying mission. Scientific objectives and instrument design

Recent News

MHD simulations of CME with associated prominence eruption

Recent News

The Striated Solar Photosphere Observed at 0.″03 Resolution

Recent News

The role of the Lorentz force in sunspot equilibrium

Recent News

HAO research featured on AAS Nova

Recent News

Mother's Day Superstorms: Pre- and Post-storm Evolutionary Patterns of AR 13664/8

Recent News

A deep learning framework for instrument-to-instrument translation of solar observation data

Recent News

The Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) Code: A Global Corona Magnetohydrodynamic Code with the Yin-Yang grid

Recent News