arxiv: 2604.13670 · v1 · submitted 2026-04-15 · 🌌 astro-ph.SR · astro-ph.IM· eess.SP· physics.plasm-ph· physics.space-ph

Recognition: unknown

Probing Coronal Activity Using Radio Signals Based on the 2021 superior conjunction of Mars: the Downlink Data from Tianwen-1

Yu-Chen Liu , De-Qing Kong , Song Tan , Zi-Han Zhao , Zan Wang , Dong-Hao Liu , Xin-Ying Zhu , Yan su

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Hong-Bo Zhang

Authors on Pith no claims yet

Pith reviewed 2026-05-10 12:33 UTC · model grok-4.3

classification 🌌 astro-ph.SR astro-ph.IMeess.SPphysics.plasm-phphysics.space-ph

keywords solar coronafrequency scintillationsolar windcoronal mass ejectionscoronal streamersradio signalsspacecraft downlinksolar activity

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The pith

A characteristic frequency scintillation parameter extracted from a Mars spacecraft downlink signal identifies coronal streamers, high-speed solar wind, and CMEs through temporal and spatial correlations.

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

The paper examines the Doppler frequency variations recorded in a spacecraft radio signal whose path passed within 4.53 solar radii of the Sun. From the scintillation spectrum it extracts one characteristic parameter whose magnitude grows as the path nears the Sun and shows distinct spikes on three specific days. Those spikes align in time with solar features observed independently, and the parameter also tracks changes in solar wind speed with a measurable delay. A sympathetic reader would care because the result indicates that ordinary interplanetary communication links can serve as a probe for mapping activity in the inner solar corona.

Core claim

Analysis of the Doppler frequency scintillation spectrum within 10 solar radii yields a characteristic frequency scintillation parameter. This parameter increases with decreasing solar distance and exhibits anomalies on October 5, 13, and 15 that display strong spatio-temporal correlations with coronal activity. The parameter thereby identifies phenomena including coronal streamers, high-speed solar wind, and coronal mass ejections, while the observed temporal correlation and delay with solar wind speed changes confirms the feasibility of spatially localizing the responsible solar activity.

What carries the argument

The characteristic frequency scintillation parameter derived from the Doppler frequency scintillation spectrum of the solar wind.

If this is right

The parameter increases as the signal path approaches the Sun.
Anomalies in the parameter correspond to the passage of coronal streamers, high-speed solar wind, and CMEs.
A distinct temporal correlation and delay exists between frequency scintillation and solar wind speed changes.
The approach validates the feasibility of spatially localizing solar activity using spacecraft radio signals.

Where Pith is reading between the lines

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

Routine downlink signals from any interplanetary probe could supply similar coronal diagnostics during future superior conjunctions.
The scintillation parameter supplies an independent data stream that could cross-check models of solar wind acceleration derived from imaging alone.
Multiple simultaneous spacecraft links at different solar longitudes might allow tomographic reconstruction of coronal structures.

Load-bearing premise

The observed frequency scintillation anomalies are produced by specific coronal structures rather than other propagation effects, instrumental artifacts, or coincidental timing.

What would settle it

Absence of any increase in the parameter as the signal path approaches the Sun, or complete lack of correspondence between the dates of parameter anomalies and independent records of coronal streamers or CMEs on those dates.

Figures

Figures reproduced from arXiv: 2604.13670 by De-Qing Kong, Dong-Hao Liu, Hong-Bo Zhang, Song Tan, Xin-Ying Zhu, Yan su, Yu-Chen Liu, Zan Wang, Zi-Han Zhao.

**Figure 2.** Figure 2: Schematic Diagram of Doppler Change Trend Fitting Algorithm [PITH_FULL_IMAGE:figures/full_fig_p010_2.png] view at source ↗

**Figure 3.** Figure 3: A comparison with the commonly used integration interval is also conducted. The theoretical up [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗

**Figure 4.** Figure 4: The normalized RMS frequency fluctuation measure(FM) Statistics of Frequency Fluctuations [PITH_FULL_IMAGE:figures/full_fig_p012_4.png] view at source ↗

**Figure 4.** Figure 4: represent data from the same day. To clearly illustrate the trend of FM variation σFM in the figure, the spacing between consecutive σFM data points on the x-axis is not proportional to the actual time intervals. Instead, the data are arranged at equal intervals along the x-axis in chronological order to generate [PITH_FULL_IMAGE:figures/full_fig_p013_4.png] view at source ↗

**Figure 5.** Figure 5: The normalized RMS frequency fluctuation measure Variation with Solar offset during the 2021 [PITH_FULL_IMAGE:figures/full_fig_p014_5.png] view at source ↗

**Figure 6.** Figure 6: Relationship between FM fluctuations σFMand CMEs.(a):The frequency scintillation power spectrum observed on 2021 October 13. (b):Comparison between solar wind speed variations and variations in the σFM. (c):A CME eruption observed on the right-hand side of the Sun on October 15, 2021. 13 that the data on that day were anomalous [PITH_FULL_IMAGE:figures/full_fig_p015_6.png] view at source ↗

**Figure 7.** Figure 7: Relationship between FM fluctuations σFM and High-Speed Solar Wind Streams.(a):The frequency scintillation power spectrum observed on October 13. (b):Comparison between solar wind speed estimated from SOHO C2 and σFM variations. (c):From the inner to the outer region, the image is a composite of the SOHO C2 coronagraph and the SOHO C3 coronagraph. Calculations indicate that the velocity of this jet around … view at source ↗

**Figure 8.** Figure 8: Relationship between FM fluctuations σFM and Coronal Streamer. (a):The frequency scintillation power spectrum observed on October 05. (b):Comparison between solar wind speed estimated from SOHO C2 and FM variations σFM. (c):From the inner to the outer region, the image is a composite of SDO AIA 193 A, the SOHO C2 coronagraph. ˚ reliability of the temporal correlation between the σFM anomaly peaks and the S… view at source ↗

**Figure 9.** Figure 9: Relationship between σFM and spatially mismatched CMEs. (a):The frequency scintillation power spectrum observed on October 02. (b):Comparison between solar wind speed estimated from SOHO C2 and FM variations σFM. (c):From the inner to the outer region, the image is a composite of SDO AIA 193 A, the SOHO /LASCO C2 coronagraph and the SOHO C3 coronagraph. ˚ This yields an observed time delay of approximately… view at source ↗

read the original abstract

During the first superior conjunction of the Tianwen-1 Mars probe in October 2021, its downlink signal received by the Wuqing 70-m radio telescope passed within 4.53 solar radii of the Sun. The signal was significantly perturbed by the solar wind, providing a mechanism to probe coronal activity. We analyze the Doppler frequency scintillation spectrum of the solar wind within 10 solar radii to derive a characteristic frequency scintillation parameter. Statistical analysis indicates this parameter increases as the signal path approaches the Sun, with notable anomalies observed on October 5, 13, and 15. Comparisons with SOHO and SDO data reveal strong spatio-temporal correlations between these scintillation anomalies and coronal activity. We demonstrate that this parameter effectively identifies solar phenomena, including coronal streamers, high-speed solar wind, and coronal mass ejections (CMEs). Quantitative analysis confirms a distinct temporal correlation and delay between frequency scintillation and solar wind speed changes, validating the feasibility of spatially localizing solar activity.

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

Tianwen-1 radio data yields a usable scintillation parameter that tracks coronal activity via correlations, but line-of-sight integration undercuts the spatial localization claims.

read the letter

This paper shows a workable radio scintillation parameter from the Tianwen-1 2021 conjunction that correlates with coronal activity, but the claim of spatially localizing specific features like streamers and CMEs is weakened by the integrated nature of the line-of-sight measurements. They took the Doppler frequency data from the Wuqing telescope during the superior conjunction when the signal grazed within 4.53 solar radii. From the scintillation spectrum they define a characteristic parameter and track how it behaves as the path gets closer to the Sun. On three dates they note spikes that coincide with known solar wind structures seen in SOHO and SDO data, and they measure a time offset between the radio signal changes and in-situ wind speed shifts. The strength here is the straightforward application to a fresh dataset. Using an existing Mars probe link avoids the need for dedicated solar missions, and the reported correlations give a sense that the parameter picks up real solar wind variations. The temporal delay analysis adds a quantitative angle that could help with timing predictions. The main limitation is that scintillation integrates density fluctuations along the entire path from Earth to the closest approach and back. Without a calculation that maps the known positions of streamers, high-speed streams, and CMEs onto that specific geometry and predicts the expected spectrum, it's difficult to pin the anomalies to the near-Sun features rather than to other segments of the path or to unrelated effects. The abstract mentions strong spatio-temporal correlations, but that alone does not rule out geometry or coincidence. This kind of work is useful for the solar physics community that already does radio occultation studies. Readers who want practical examples of spacecraft-based coronal diagnostics will find the data handling and the specific dates interesting. It is solid enough to go to peer review, though the referees will likely ask for more on the forward modeling or error analysis to support the localization statements.

Referee Report

2 major / 2 minor

Summary. The manuscript analyzes Doppler frequency scintillation spectra in the Tianwen-1 Mars probe downlink signal received at the Wuqing 70-m telescope during the October 2021 superior conjunction, when the line of sight passed within 4.53 Rs of the Sun. From these spectra the authors derive a characteristic frequency scintillation parameter, report that it increases as the path approaches the Sun, identify anomalies on 5, 13 and 15 October, and show spatio-temporal correlations between those anomalies and coronal streamers, high-speed wind streams, and CMEs visible in contemporaneous SOHO and SDO imagery. They conclude that the parameter can identify these solar-wind structures and that the observed temporal delays validate the feasibility of spatially localizing coronal activity.

Significance. If the reported correlations survive quantitative scrutiny, the work demonstrates a practical, ground-based radio technique for monitoring inner-coronal structures using existing planetary-mission downlinks. The cross-instrument comparison with independent EUV and white-light imagery is a constructive element. However, the absence of forward modeling of the line-of-sight integral and of uncertainty estimates on the scintillation parameter limits the immediate scientific impact.

major comments (2)

[Abstract / quantitative analysis] Abstract and quantitative-analysis section: the central claim that the frequency-scintillation parameter 'validates the feasibility of spatially localizing solar activity' is not supported by any forward-model calculation that folds the known three-dimensional locations of streamers, high-speed streams, or CMEs into the exact Earth–Tianwen-1 ray-path geometry. Without such modeling, the reported temporal offset between scintillation anomalies and in-situ solar-wind speed changes could arise from integration along distant path segments or from geometric projection effects rather than from the specific coronal features invoked.
[Statistical analysis] Statistical-analysis section: no error bars, formal uncertainty propagation, or explicit data-selection criteria are supplied for the scintillation parameter or for the identification of the October 5, 13, and 15 anomalies. This omission prevents assessment of whether the claimed 'strong spatio-temporal correlations' exceed the level expected from random fluctuations or post-hoc choices.

minor comments (2)

[Methods] The explicit mathematical definition of the 'characteristic frequency scintillation parameter' (including any windowing or fitting procedure applied to the Doppler spectrum) should be stated in the methods section with an equation number.
[Figures] Figure captions should indicate the precise time intervals and frequency ranges used to compute the scintillation parameter for each plotted point.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed review. The comments highlight important areas for strengthening the quantitative interpretation and statistical rigor of our analysis. We address each major comment below, indicating the revisions incorporated into the manuscript.

read point-by-point responses

Referee: [Abstract / quantitative analysis] Abstract and quantitative-analysis section: the central claim that the frequency-scintillation parameter 'validates the feasibility of spatially localizing solar activity' is not supported by any forward-model calculation that folds the known three-dimensional locations of streamers, high-speed streams, or CMEs into the exact Earth–Tianwen-1 ray-path geometry. Without such modeling, the reported temporal offset between scintillation anomalies and in-situ solar-wind speed changes could arise from integration along distant path segments or from geometric projection effects rather than from the specific coronal features invoked.

Authors: We agree that a full forward-modeling calculation incorporating the precise 3D geometry of the coronal structures along the Earth–Tianwen-1 line of sight would provide more definitive support for the spatial-localization interpretation. Our analysis instead relies on direct spatio-temporal correlations between the observed scintillation anomalies and the independently imaged coronal streamers, high-speed streams, and CMEs in contemporaneous SOHO and SDO data, together with the measured temporal delays that are consistent with expected propagation distances. We have revised the quantitative-analysis section to include an expanded discussion of line-of-sight integration effects, possible projection ambiguities, and the limitations of the current approach. We note, however, that performing a complete forward simulation lies beyond the scope of this observational study. revision: partial
Referee: [Statistical analysis] Statistical-analysis section: no error bars, formal uncertainty propagation, or explicit data-selection criteria are supplied for the scintillation parameter or for the identification of the October 5, 13, and 15 anomalies. This omission prevents assessment of whether the claimed 'strong spatio-temporal correlations' exceed the level expected from random fluctuations or post-hoc choices.

Authors: We concur that explicit uncertainty estimates and transparent data-selection criteria are necessary to evaluate the robustness of the reported correlations. In the revised manuscript we have added error bars to the frequency-scintillation parameter derived from the Doppler spectral fitting uncertainties and the standard deviation across frequency bins. We have also documented the anomaly-identification criteria (deviations exceeding three standard deviations from the smoothed background trend) and included a brief statistical assessment demonstrating that the spatio-temporal correlations with the coronal features exceed the 95 % confidence level relative to randomized time series. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation remains self-contained

full rationale

The frequency scintillation parameter is extracted directly from the observed Doppler spectrum of the Tianwen-1 downlink. Anomalies are identified via statistical analysis of the parameter's behavior as the ray path approaches the Sun, then cross-checked against independent SOHO/SDO imagery for spatio-temporal correlations. The claim that the parameter identifies specific phenomena (streamers, high-speed wind, CMEs) and supports spatial localization rests on these external data matches and observed time delays, not on any internal redefinition, fitted subset renamed as prediction, or self-citation chain. No equations reduce the output to the input by construction, and the analysis is benchmarked against separate observational datasets.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The work is observational data analysis. No new free parameters, axioms, or invented entities are introduced beyond standard assumptions of radio propagation through plasma. The characteristic frequency scintillation parameter is defined from the Doppler spectrum but its exact construction is not visible in the abstract.

pith-pipeline@v0.9.0 · 5522 in / 1242 out tokens · 24533 ms · 2026-05-10T12:33:28.112768+00:00 · methodology

discussion (0)

Reference graph

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