Real-time prediction of two geomagnetic storms using Solar Orbiter as a far upstream solar wind monitor

2); (2) Institute of Physics; (3) Blackett Laboratory; Alastair Crabtree (3) ((1) Austrian Space Weather Office; Austria; Christian M\"ostl (1); Emma E. Davies (1); Eva Weiler (1; GeoSphere Austria; Graz

arxiv: 2508.13892 · v3 · submitted 2025-08-19 · ⚛️ physics.space-ph

Real-time prediction of two geomagnetic storms using Solar Orbiter as a far upstream solar wind monitor

Emma E. Davies (1) , Eva Weiler (1 , 2) , Christian M\"ostl (1) , Satabdwa Majumdar (1) , Hannah T. R\"udisser (1 , Timothy S. Horbury (3) , Helen O'Brien (3)

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Jean Morris (3) Alastair Crabtree (3) ((1) Austrian Space Weather Office GeoSphere Austria Graz Austria (2) Institute of Physics University of Graz (3) Blackett Laboratory Imperial College London South Kensington Campus London UK)

This is my paper

Pith reviewed 2026-05-18 22:49 UTC · model grok-4.3

classification ⚛️ physics.space-ph

keywords geomagnetic stormscoronal mass ejectionssolar wind monitoringspace weather forecastingSolar Orbiterin situ observationsdrag-based models

0 comments

The pith

Far-upstream Solar Orbiter observations enable real-time predictions of CME magnetic structure and geomagnetic impact at Earth for two March 2024 events.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that in situ magnetic field data from Solar Orbiter at 0.53 and 0.60 au can be used to forecast the magnetic structure of coronal mass ejections and the resulting geomagnetic indices at Earth. Predictions were issued 15.3 and 4.3 hours before the CME shocks reached L1 and 33.9 and 10.3 hours before peak storm intensity, well ahead of current L1-based nowcasts. Constraining simple drag-based propagation models with the upstream measurements improved arrival-time estimates, although several-hour errors remained. The work demonstrates that radial evolution effects can dominate over longitudinal separation up to 10 degrees when making these forecasts.

Core claim

Real-time predictions of coronal mass ejection magnetic structure and resulting geomagnetic impact at Earth can be made using far-upstream in situ magnetic field observations from Solar Orbiter, yielding lead times of 15.3 and 4.3 hours before shock arrival at L1 and 33.9 and 10.3 hours before peak storm time for two events, even across heliocentric distances of 0.53 and 0.60 au and with longitudinal separations up to 10 degrees.

What carries the argument

Far-upstream in situ magnetic field measurements from Solar Orbiter used to observationally constrain simple drag-based CME propagation models for predicting magnetic structure and geomagnetic indices at Earth.

If this is right

Observationally constraining drag-based models with upstream data improves arrival time estimates compared with unconstrained runs.
Actionable geomagnetic forecasts remain possible with longitudinal separations up to 10 degrees when radial evolution dominates.
Different expansion behaviors for individual CMEs and internal regions limit prediction accuracy.
Continuous upstream measurements that also include plasma parameters could account for preexisting disturbed solar wind conditions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Dedicated missions stationed continuously far upstream could supply routine early warnings for geomagnetic storms.
Extending the method to include plasma density and speed measurements would likely reduce errors arising from disturbed background solar wind.
The same upstream-constrained modeling approach could be tested on other space-weather parameters such as radiation belt enhancements.

Load-bearing premise

Radial evolution effects dominate over longitudinal effects and simple drag-based models can adequately capture the expansion behavior of individual CMEs.

What would settle it

A subsequent CME event where the predicted geomagnetic index at Earth deviates substantially from the observed value despite the availability of far-upstream magnetic field data from a similar heliocentric distance.

read the original abstract

We present the first real-time predictions of coronal mass ejection (CME) magnetic structure and resulting geomagnetic impact at Earth for two events using far-upstream observations from Solar Orbiter during March 2024. While our approach assumes idealized conditions for CME propagation and scaling, in situ magnetic field data from upstream monitors still produced realistic predictions despite the large heliocentric distance between Solar Orbiter and L1 (0.53 and 0.60 au). Geomagnetic index predictions were made 15.3 and 4.3 hours before the CME shock arrival at L1, and 33.9 and 10.3 hours ahead of peak storm time; a large improvement over current L1-based nowcasting capabilities. We find that observationally constraining the simple drag-based models using the upstream in situ observations improved arrival time estimates for the two events in this study, although arrival time errors of several hours still remain. Our results show that good predictions of CME magnetic structure and geomagnetic indices with actionable lead-times can be made with far upstream spacecraft, even with longitudinal separations up to 10{\deg} from the Sun-Earth line, over heliocentric distance ranges where radial evolution effects dominate over longitudinal effects. Limitations include different expansion behaviors for individual CMEs and regions within. Future missions providing continuous data, including solar wind plasma parameters alongside magnetic field measurements, could account for preexisting disturbed conditions and improve geomagnetic prediction accuracy. Our findings demonstrate the substantial value of real-time upstream solar wind measurements for enhancing geomagnetic forecasting accuracy at Earth and provide critical validation for future dedicated upstream space weather missions.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This shows real lead-time gains for two March 2024 storms from Solar Orbiter at 0.5-0.6 AU, but the idealized drag-model scaling and small sample keep the results preliminary.

read the letter

The main thing to know is that the authors used Solar Orbiter magnetic field data from well upstream to make real-time forecasts of CME structure and geomagnetic indices for two specific events, beating L1 nowcasts by hours to a day. They constrained simple drag-based propagation models with the upstream observations and got arrival-time improvements, even with up to 10 degrees of longitudinal offset. That is the concrete advance: an actual demonstration rather than a simulation study. The paper is clear that radial evolution dominated in these cases and that the predictions were realistic enough to be useful for storm timing. It also flags the missing plasma parameters and varying expansion as limits, which is honest. The work is aimed squarely at the space-weather forecasting and mission-design crowd. Anyone thinking about dedicated upstream monitors or how to stretch warning times beyond the current one-hour L1 window will see direct value in the reported lead times of 15 and 4 hours to shock arrival and 34 and 10 hours to peak storm time. A serious referee should see this. The central claim rests on only two events and explicit idealized assumptions about propagation and scaling, with several-hour residuals still present and no broader statistical test. That is a real but proportionate weakness rather than a fatal one; the data are real and the comparison to L1 is straightforward. The citation pattern looks standard for the field. I would send it to review so the assumptions can be stress-tested and the authors can add error bars or more cases if available.

Referee Report

3 major / 3 minor

Summary. The manuscript claims to present the first real-time predictions of coronal mass ejection (CME) magnetic structure and resulting geomagnetic impact at Earth for two March 2024 events using far-upstream in situ observations from Solar Orbiter at 0.53 and 0.60 au. It reports geomagnetic index predictions with lead times of 15.3 and 4.3 hours before CME shock arrival at L1 and 33.9 and 10.3 hours before peak storm time. The approach employs observationally constrained drag-based models for propagation and magnetic field scaling, claiming improved arrival time estimates (despite several-hour residuals) and demonstrating the value of upstream monitoring with up to 10° longitudinal separation where radial evolution dominates.

Significance. If the results hold, this provides a valuable proof-of-concept for far-upstream monitors in space weather forecasting, offering actionable lead times beyond L1 nowcasting and validation for future dedicated upstream missions. The reported lead times and realistic geomagnetic predictions highlight operational potential, though the two-event sample and idealized assumptions limit broader claims of generalizability.

major comments (3)

[Results (Event 1 and Event 2)] Results sections for the two events: The claim that observationally constraining drag-based models with upstream data 'improved arrival time estimates' is load-bearing for the forecasting value, but the parameters appear post-hoc adjusted to the same observations used for prediction. This risks circularity; an explicit comparison to unconstrained or baseline models (with quantitative metrics) is needed to substantiate the improvement.
[Discussion] Discussion section: The central generalization that 'radial evolution effects dominate over longitudinal effects' at 10° separation underpins the magnetic structure scaling to L1 and Bz predictions. However, no quantitative test or sensitivity analysis to longitudinal variations is provided, despite the abstract noting 'different expansion behaviors for individual CMEs and regions within'. This assumption is load-bearing for the 'realistic predictions' claim.
[Abstract and Conclusions] Abstract and conclusions: The assertions of 'good predictions' and 'substantial value' for upstream monitoring rest on two events with several-hour arrival errors and no error bars or statistical validation across a larger sample. This small-N limitation directly affects the strength of the recommendation for future missions.

minor comments (3)

[Abstract] Abstract: The statement of 'a large improvement over current L1-based nowcasting capabilities' would benefit from explicit quantification (e.g., typical L1 lead times for comparison).
[Methods] Methods: Clarify the exact procedure for scaling |B| and clock angle from Solar Orbiter to L1, including any assumptions on expansion or distortion of the Bz component.
[References] References: Ensure inclusion of key prior works on drag-based CME propagation models and upstream monitoring concepts for context.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their insightful comments on our manuscript. We address each of the major comments in detail below and indicate where revisions will be made to the manuscript.

read point-by-point responses

Referee: [Results (Event 1 and Event 2)] Results sections for the two events: The claim that observationally constraining drag-based models with upstream data 'improved arrival time estimates' is load-bearing for the forecasting value, but the parameters appear post-hoc adjusted to the same observations used for prediction. This risks circularity; an explicit comparison to unconstrained or baseline models (with quantitative metrics) is needed to substantiate the improvement.

Authors: We thank the referee for highlighting this important point about potential circularity. Upon reflection, the model parameters were tuned using the upstream data to optimize the fit for these events. To substantiate the improvement, we will add to the revised manuscript a direct comparison between the observationally constrained drag-based model and an unconstrained baseline model using typical parameters from the literature. We will provide quantitative metrics, including the predicted arrival times and errors for both methods for each event. This will allow readers to assess the added value of the upstream constraints. revision: yes
Referee: [Discussion] Discussion section: The central generalization that 'radial evolution effects dominate over longitudinal effects' at 10° separation underpins the magnetic structure scaling to L1 and Bz predictions. However, no quantitative test or sensitivity analysis to longitudinal variations is provided, despite the abstract noting 'different expansion behaviors for individual CMEs and regions within'. This assumption is load-bearing for the 'realistic predictions' claim.

Authors: We agree that the assumption regarding the dominance of radial evolution over longitudinal effects at ~10° separation is central to our scaling approach. With only two events available, a full quantitative sensitivity analysis varying the longitudinal separation is not possible within this study. In the revised discussion, we will expand on this assumption, reference supporting literature on CME propagation, and more clearly acknowledge the limitations due to potential different expansion behaviors. We will also note that future work with additional events or MHD simulations could provide such sensitivity tests. revision: partial
Referee: [Abstract and Conclusions] Abstract and conclusions: The assertions of 'good predictions' and 'substantial value' for upstream monitoring rest on two events with several-hour arrival errors and no error bars or statistical validation across a larger sample. This small-N limitation directly affects the strength of the recommendation for future missions.

Authors: We accept the referee's critique regarding the strength of claims based on a limited sample of two events. We will revise the abstract and conclusions to use more cautious language, framing our results as a proof-of-concept demonstration rather than broadly asserting 'good predictions' or 'substantial value'. We will emphasize the specific lead times achieved and the remaining arrival time uncertainties, and include a stronger statement on the need for larger statistical samples to validate the approach for operational use. Error bars on predictions will be discussed where applicable. revision: yes

Circularity Check

0 steps flagged

No significant circularity: forward propagation from upstream observations

full rationale

The paper's central chain takes in-situ magnetic field data from Solar Orbiter at 0.53–0.60 AU, constrains standard drag-based propagation models with those upstream measurements, and produces forward forecasts of arrival time, magnetic structure, and geomagnetic indices at Earth/L1. This constitutes an extrapolation across heliocentric distance rather than a fit or renaming of the target quantities themselves. The abstract and skeptic notes explicitly flag idealized radial-dominance assumptions and remaining arrival-time residuals of several hours, but these do not reduce the reported predictions to the input data by construction. No load-bearing self-citations, uniqueness theorems, or ansatzes imported from prior author work are required for the derivation; the lead-time improvements over L1 nowcasting provide an independent external benchmark. The result is therefore self-contained against the upstream observations.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on idealized CME propagation and scaling assumptions plus the dominance of radial over longitudinal evolution effects. No new physical entities are introduced. Free parameters appear in the drag-based model fits constrained by the two events.

free parameters (1)

drag-based model parameters
Parameters in the simple drag-based models are observationally constrained using the upstream in-situ data for each event.

axioms (2)

domain assumption Idealized conditions for CME propagation and scaling hold sufficiently for the two events studied.
Stated explicitly in the abstract as the basis for the predictions.
domain assumption Radial evolution effects dominate over longitudinal effects up to 10 degrees separation.
Invoked to justify applicability despite longitudinal separation.

pith-pipeline@v0.9.0 · 5925 in / 1568 out tokens · 29533 ms · 2026-05-18T22:49:25.630032+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

We use an α value of -1.64 to scale the magnetic field values... ζ≈0.8... drag-based model... Temerin & Li model
IndisputableMonolith/Foundation/DimensionForcing.lean alexander_duality_circle_linking unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

radial evolution effects dominate over longitudinal effects... arrival time errors of several hours

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

Towards a Fully Automated Pipeline for Short-Term Forecasting of In Situ Coronal Mass Ejection Magnetic Field Structure
astro-ph.SR 2026-02 unverdicted novelty 6.0

An automated pipeline forecasts CME magnetic fields at L1 using initial magnetic obstacle data, achieving errors of roughly 5 hours in timing and 10 nT in strength comparable to full-event reconstructions.