Sarah Gibson

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.

SynCOM: An Empirical Model for High-Resolution Simulations of Transient Solar Wind Flows

whawkins — Thu, 18 Jul 2024 15:24:22 +0000

SynCOM: An Empirical Model for High-Resolution Simulations of Transient Solar Wind Flows whawkins Thu, 07/18/2024 - 09:24

Author:

whawkins

Jul 18, 2024

Comparison between a COR2 and a SynCOM simulated image; (a) Training data set from STEREO-A/COR2 instrument. (b) SynCOM simulation using solar constraints with 5,000 blobs. The blob sizes are doubled, making the image appear more natural compared to COR2 images. (c) SynCOM simulation using solar constraints with 5,000 blobs. The smaller blob sizes highlight its fine-scale structures.

Astrophysical Journal— (Published: November 2024) The Synthetic Corona Outflow Model (SynCOM), an empirical model, simulates the solar corona's dynamics to match high-resolution observations, providing a useful resource for testing velocity measurement algorithms. SynCOM generates synthetic images depicting radial variability in polarized brightness and includes stochastic elements for plasma outflows and instrumental noise. It employs a predefined flow velocity probability distribution and an adjustable signal-to-noise ratio to evaluate different data analysis methods for coronal flows. By adjusting parameters to match specific coronal and instrumental conditions, SynCOM offers a platform to assess these methods for determining coronal velocity and acceleration. Validating these measurements would help to understand solar wind origins and support missions such as the Polarimeter to Unify the Corona and Heliosphere (PUNCH). In this study, we demonstrate how SynCOM can be employed to assess the precision and performance of two different flow tracking methods. By providing a ground-truth based on observational data, we highlight the importance of SynCOM in confirming observational standards for detecting coronal flows.

A Study on the Nested Rings CME Structure Observed by the WISPR Imager Onboard Parker Solar Probe

whawkins — Wed, 12 Jun 2024 20:30:52 +0000

A Study on the Nested Rings CME Structure Observed by the WISPR Imager Onboard Parker Solar Probe whawkins Wed, 06/12/2024 - 14:30

Author:

whawkins

Jun 12, 2024

Astrophysical Journal— (Published: December 2024) Despite the significance of coronal mass ejections (CMEs) in space weather, a comprehensive understanding of their interior morphology remains a scientific challenge, particularly with the advent of many state-of-the-art solar missions such as the Parker Solar Probe (Parker) and Solar Orbiter (SO). In this study, we present an analysis of a CME and its interior structure observed during the seventh solar encounter of the Parker Solar Probe, utilizing the data from its Wide-Field Imager for Solar PRobe (WISPR) heliospheric imager. We observe a complex CME structure consisting of non-concentric nested rings, which we argue is a signature of the embedded helical magnetic flux rope (MFR) of the CME. This CME exhibits a general three-part density structure but with no significantly bright front and core, revealing its overall configuration with a highly structured intensity pattern. We demonstrate the dynamical properties and morphology of these nested density structures, indicating that they outline the magnetic field geometry and the projection of the three-dimensional structure of the flux rope along the lines of sight of the WISPR imager. Comparisons of observations from various viewpoints suggest that these CME substructures can be discerned owing to the ideal viewing perspective, close proximity, and spatial resolution of the observing instrument.

Despite the significance of coronal mass ejections (CMEs) in space weather, a comprehensive understanding of their interior morphology remains a scientific challenge, particularly with the advent of many state-of-the-art solar missions such as the Parker Solar Probe (Parker) and Solar Orbiter (SO). In this study, we present an analysis of a CME and its interior structure observed during the seventh solar encounter of the Parker Solar Probe, utilizing the data from its Wide-Field Imager for Solar PRobe (WISPR) heliospheric imager. We observe a complex CME structure consisting of non-concentric nested rings, which we argue is a signature of the embedded helical magnetic flux rope (MFR) of the CME. This CME exhibits a general three-part density structure but with no significantly bright front and core, revealing its overall configuration with a highly structured intensity pattern. We demonstrate the dynamical properties and morphology of these nested density structures, indicating that they outline the magnetic field geometry and the projection of the three-dimensional structure of the flux rope along the lines of sight of the WISPR imager. Comparisons of observations from various viewpoints suggest that these CME substructures can be discerned owing to the ideal viewing perspective, close proximity, and spatial resolution of the observing instrument.

Observing the evolution of the Sun’s global coronal magnetic field

whawkins — Tue, 14 May 2024 19:48:54 +0000

Observing the evolution of the Sun’s global coronal magnetic field whawkins Tue, 05/14/2024 - 13:48

Author:

whawkins

May 14, 2024

Science: The energy powering the hot solar corona and driving solar eruptions lies in the coronal magnetic field. Monitoring the field evolution in the global corona is crucial but has not been achieved before. With daily observations from the Upgraded Coronal Multi-channel Polarimeter, we have obtained magnetograms of the global corona above the solar limb over approximately eight months. We have obtained magnetic field distributions on spherical shells with different solar radii in the corona, and monitored evolution of the field at nearly all latitudes and across different heights throughout multiple solar rotations. A comparison of observational results with coronal models reveals general consistency yet distinct discrepancies particularly in high-latitude regions, suggesting the potential of model improvement through constraints from these observations.

Examples of global coronal magnetic field maps and simultaneously taken coronal intensity images. (A) Composite GOES/SUVI 19.5 nm intensity image generated using observations from 19:48 UT to 19:52 UT on 21 February 2022. (B and C) UCoMP maps of coronal magnetic field strength and direction (POS component) on 21 February 2022. A median filter of 3×3 pixels was applied to reduce noise. (D) Similar to (A) but for observations from 20:48 UT to 20:52 UT on 1 June 2022. (E and F) Similar to (B) and (C) but on 1 June 2022. (G) Similar to (A) but for observations from 19:48 UT to 19:52 UT on 5 August 2022. (H and I) Similar to (B) and (C) but on 5 August 2022. The reference direction in (C), (F) and (I) is the local radial direction. Wave propagation direction that is counterclockwise to the local radial direction is defined as a positive angle and otherwise negative.

EUV polarimetric diagnostics of the solar corona: the Hanle effect of Ne viii 770 A

whawkins — Tue, 30 Apr 2024 16:16:15 +0000

EUV polarimetric diagnostics of the solar corona: the Hanle effect of Ne viii 770 A whawkins Tue, 04/30/2024 - 10:16

Author:

whawkins

Apr 30, 2024

Top row: Rising phase (CR2104) of SC24: (a) PSIMAS model map of magnetic field, (b) LOS-integrated Stokes L/I in the presence of magnetic fields, (c) LOS-integrated linear polarization azimuth (relative to radial direction on the plane-of-sky), and (d) synthesized ratio between LOS integrated L/I in presence and (L/I)0 in absence of model magnetic fields. Only on-disk information within 1 Rsun is shown here. Middle row and bottom row illustrate the same maps, but during the maximum phase (CR2171) and the minimum phase (CR2225), respectively. Contours of a particular color in a given map represent iso-curves of the depicted physical quantity shown in logarithmic scale. Note that collisional excitation has been included here.

Astrophysical Journal: Magnetic fields are the primary driver of the plasma thermodynamics in the upper solar atmosphere, especially in the corona. However, magnetic field measurements in the solar corona are sporadic, thereby limiting us from the complete understanding of physical processes occurring in the coronal plasma. In this paper, we explore the diagnostic potential of a coronal emission line in the extreme-ultraviolet (EUV), i.e., Ne viii 770 AA to probe the coronal magnetic fields. We utilize 3D 'Magneto-hydrodynamic Algorithm outside a Sphere' (MAS) models as input to the FORWARD code to model polarization in Ne viii line produced due to resonance scattering, and interpret its modification due to collisions and the magnetic fields through the Hanle effect. The polarization maps are synthesized both on the disk as well as off-the-limb. The variation of this polarization signal through the different phases of solar cycle 24 and the beginning phase of solar cycle 25 is studied in order to understand the magnetic diagnostic properties of this line owing to different physical conditions in the solar atmosphere. The detectability of the linear polarization signatures of the Hanle effect significantly improves with increasing solar activity, consistently with the increase in the magnetic field strength and the intensity of the mean solar brightness at these wavelengths. We finally discuss the signal-to-noise ratio (SNR) requirements by considering realistic instrument designs.

Magnetohydrodynamic turbulence simulations as a testing ground for PUNCH

whawkins — Tue, 30 Apr 2024 15:56:00 +0000

Magnetohydrodynamic turbulence simulations as a testing ground for PUNCH whawkins Tue, 04/30/2024 - 09:56

Author:

whawkins

Apr 30, 2024

Solar Physics: The Polarimeter to UNify the Corona and Heliosphere (PUNCH) will image macroscopic features of the inner heliosphere and also admit sufficiently high spatial resolution to probe scales of turbulence within the upper end of the inertial range, close to the integral scale. Because PUNCH is an imager, the measurements it will make relate differently to the underlying turbulent environment of the outer corona and inner heliosphere than do more familiar in situ samples. We present a numerical study that combines magnetohydrodynamic simulations of turbulence together with forward-modeling synthesis of white- light data via the FORWARD code. We show that (i) the “usual” turbulence scalings are modified by the integration along the line of sight in an optically thin medium, and (ii) those scalings are still linked to the original properties of the turbulent field. This study is a first step in the process of analyzing and understanding the unprecedented information that PUNCH will provide.

(a) Density field snapshot in a 2D plane of the simulation ρ(x = 0, y, z), (b) 2D density obtained by integrating the 3D simulation domain in one direction ⟨ρ(x, y, z)⟩x, (c) normalized correlation functions obtained from these two fields. the red curve refers to ρ(x = 0, y, z), while the blue to ⟨ρ(x, y, z)⟩x. The horizontal line marks the 1/e level at which the correlation lengths are estimated (vertical lines). The averaging procedure dilutes the sharp gradients and the correlation length almost doubles from 1.9Rsun to 4.1Rsun. Notice that the density features in (a) can almost identically be observed in Fig. 5(c) because the NEAR FOV almost exactly matches the information on the TS with little to no stretching.

WHPI repository of 2024 Total Solar Eclipse activities

whawkins — Tue, 19 Mar 2024 16:14:43 +0000

WHPI repository of 2024 Total Solar Eclipse activities whawkins Tue, 03/19/2024 - 10:14

Author:

whawkins

Mar 19, 2024

HAO is leading the effort through the Whole Heliosphere and Planetary Interactions (WHPI) initiative to support the 2024 Total Solar Eclipse by providing a platform for gathering information on ongoing eclipse activities. The WHPI Eclipse Campaign website aims to be a one-stop repository for existing or ongoing eclipse efforts.

The Total Solar Eclipse on April 8, 2024 offers ideal conditions for eclipse science, unique opportunities for cross-disciplinary collaborations, and an excellent occasion for public engagement. HAO is leading the effort through the Whole Heliosphere and Planetary Interactions (WHPI) initiative to support the 2024 Total Solar Eclipse by providing a platform for gathering information on ongoing eclipse activities. The WHPI Eclipse Campaign website aims to be a one-stop repository for existing or ongoing eclipse efforts. We welcome any and all contributions, no effort is too small! Please contact us at whpi_help@hao.ucar.edu if you have any questions or would like to be included.

The repository is currently:

Linking to model prediction outputs of what to expect on the eclipse day;
Providing information on planned dedicated observations by ground and space-based assets that will pursue and support eclipse science;
Compiling a list of eclipse science experiments that will be deployed on or flown into the eclipse path;
Providing information on Citizen Science projects those interested can join in;
Listing planned outreach and public engagement efforts.

We hope our repository will promote interactions between the different efforts and foster collaboration across disciplines. We wish everyone a clear sky and happy observing of the eclipse!

Comprehensive analysis of a filament-embedding solar active region at different stages of evolution

whawkins — Fri, 09 Feb 2024 16:11:31 +0000

Comprehensive analysis of a filament-embedding solar active region at different stages of evolution whawkins Fri, 02/09/2024 - 09:11

Author:

whawkins

Feb 9, 2024

Astrophysical Journal Letters: Active regions are the brightest structures seen in the solar corona, so their physical properties hold important clues to the physical mechanisms underlying coronal heating. In this work, we present a comprehensive study for a filament-embedding active region as determined from observations from multiple facilities including the Chinese Hα Solar Explorer (CHASE). The spectral resolution of CHASE is as high as 0.024 ̊A pixel−1, which enables an accurate determination of the chromospheric Doppler velocity that is especially crucial for probing the relative stable structure investigated here. We find three types of dynamic features which correspond to different thermal and magnetic properties during the investigated time period, i.e., the overlying loops – 1MK cool loops, the moss region – 2∼3 MK hot loops, and the sigmoidal filament. The overlying cool loops,which have potential field, always show Doppler blue shifts at the east footprint and Doppler red shifts at the west, indicating a pattern of ‘siphon flow‘. The moss brightening region – the hot loops in the vicinity of the filament, which have moderate sheared field, always shows downward Doppler red shifts at the chromosphere, which could be a signature of plasma condensing into the inner region adjacent to the filament. The sigmoidal filament, which have severe sheared field lines along the polarity inversion line, however shows a different Doppler velocity pattern in its middle part, i.e., an upward Doppler blue shift at the double-J shaped stage and then a downward red shift after the sigmoidal filament forms. The present work shows overall properties of the filament-embedding active region, constraining the heating mechanisms of different parts of the active region and providing hints regarding the mass loading of the embedded filament.

Overview of the observations at Feb 14 (panels (a1)-(f1)) and 15 (panels (a2)-(f2)) is shown in the lower panels. Hα line center images from NVST and CHASE are displayed in panels (a1)-(a2) and (b1)-(b2), respectively. Panels (c1)-(c2) show the images from AIA/304 ̊A, and Doppler velocities obtained from CHASE are displayed in panels (d1)-(d2). The contours show the LOS magnetic field (Blos) with threshold values of ±100 G. Doppler velocity and AIA/171 ̊A with a larger FOV are shown in panels (e1)-(e2) and (f1)-(f2), respectively. Panels (g1)-(g2) show the vector magnetic field, with vertical magnetic field (Bver) in the background and the horizontal field (Bhor) overlaid on top as arrows. Red arrows show Bhor at positive polarity and blue arrows show Bhor at negative polarity. Pink and grey contours of ±5 G of the Bver are overlaid. Horizontal flows at the photosphere obtained from DAVE4VM are displayed in panels (h1)-(h2) with purple arrows showing the velocity at positive polarity and green arrows at the negative polarity. Grey and black contours of ±100 G of the Bver are also overlaid.

Mapping the Sun’s Alfvén Surface with PUNCH

whawkins — Tue, 05 Dec 2023 21:56:46 +0000

Mapping the Sun’s Alfvén Surface with PUNCH whawkins Tue, 12/05/2023 - 14:56

Author:

whawkins

Dec 5, 2023

Solar Physics: The solar wind is the extension of the Sun’s hot and ionized corona, and it exists in a state of continuous expansion into interplanetary space. The radial distance at which the wind’s outflow speed exceeds the phase speed of Alfvénic and fast-mode magnetohydrodynamic (MHD) waves is called the Alfvén radius. In one-dimensional models, this is a singular point beyond which most fluctuations in the plasma and magnetic field cannot propagate back down to the Sun. In the multi-dimensional solar wind, this point can occur at different distances along an irregularly shaped “Alfvén surface.” In this paper, we review the properties of this surface and discuss its importance in models of solar wind acceleration, angular momentum transport, MHD waves and turbulence, and the geometry of closed coronal loops. We also review the results of simulations and data analysis techniques that aim to determine the location of the Alfvén surface. Combined with recent perihelia of Parker Solar Probe, these studies seem to indicate that the Alfvén surface spends most of its time at heliocentric distances between about 10 and 20 solar radii. It is becoming increasingly apparent that this region of the heliosphere is sufficiently turbulent that there often exist multiple (stochastic and time-dependent) crossings of the Alfv´en surface along any radial ray. Thus, in many contexts, it is more useful to make use of the concept of a frothy “Alfvén zone” rather than one closed surface. This paper also reviews how the Polarimeter to UNify the Corona and Heliosphere (PUNCH) will measure the properties of the Alfvéen surface and provide key constraints on theories of solar wind acceleration.

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Inflows towards Bipolar Magnetic Active Regions and Their Nonlinear Impact on a Three-Dimensional Babcock-Leighton Solar Dynamo Model

whawkins — Thu, 28 Sep 2023 18:03:45 +0000

Inflows towards Bipolar Magnetic Active Regions and Their Nonlinear Impact on a Three-Dimensional Babcock-Leighton Solar Dynamo Model whawkins Thu, 09/28/2023 - 12:03

Author:

whawkins

Sep 28, 2023

Solar Physics: The changing magnetic fields of the Sun are generated and maintained by a solar dynamo, the exact nature of which remains an unsolved fundamental problem in solar physics. K. Teweldebirhan, M. Miesch, and S. Gibson investigate the role and impact of converging flows toward Bipolar Magnetic Regions (BMR inflows) on the Sun’s global solar dynamo. These flows are large-scale physical phenomena that have been observed and so should be included in any comprehensive solar dynamo model. We have augmented the Surface flux Transport And Babcock–LEighton (STABLE) dynamo model to study the nonlinear feedback effect of BMR inflows with magnitudes varying with surface magnetic fields. This fully-3D realistic dynamo model produces the sunspot butterfly diagram and allows a study of the relative roles of dynamo saturation mechanisms such as tilt-angle quenching and BMR inflows. The results of our STABLE simulations show that magnetic field dependent BMR inflows significantly affect the evolution of the BMRs themselves and result in a reduced buildup of the global poloidal field due to local flux cancellation within the BMRs, to an extent that is sufficient to saturate the dynamo. As a consequence, for the first time, we have achieved fully 3D solar dynamo solutions in which BMR inflows alone regulate the amplitudes and periods of the magnetic cycles.

Cycling magnetic behavior for a solar dynamo saturated by bipolar-magnetic-region inflows. (a) Butterfly diagram of the longitudinally-averaged radial field ⟨Br ⟩ at the surface (r = R) as a function of latitude and time, highlighting fourteen magnetic cycles. Polar amplitudes can exceed 300 G but the color table saturates at ± 100G. (b) Diagram of longitudinally-averaged toroidal field 〈Bφ〉near the base of the convection zone (r = 0.72R). Red and blue denote eastward and westward field respectively. (c) ⟨Br ⟩ averaged over the north (blue) and south (red) polar regions, above latitudes of ± 70◦, plotted vs. time.Vertical dotted lines mark polar field reversals in the NH (blue) and SH (red). (d) is similar to (c) but for〈Bφ〉in the lower convection zone and averaged over the entire NH (blue) and SH (red), as opposed to just the polarregions as in (c), with a saturation level for the color table of 90 kG.

Sarah Gibson

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

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