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arxiv: 1907.07884 · v1 · pith:C64UQW3Anew · submitted 2019-07-18 · 🌌 astro-ph.SR · physics.space-ph

Corrugated Features in Coronal-mass-ejections-driven Shocks: A Discussion on the Predisposition to Particle Acceleration

A. P\'aez , V. Jatenco-Pereira , D. Falceta-Gon\c{c}alves , M. Opher This is my paper

Pith reviewed 2026-05-24 19:55 UTC · model grok-4.3

classification 🌌 astro-ph.SR physics.space-ph
keywords CME-driven shocksparticle accelerationcorrugated shocksshock normal anglessolar coronaquasi-parallel shocksquasi-perpendicular shocksCME expansion
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The pith

Disturbances from irregular CME expansion produce corrugated shocks with uneven normal angles that favor particle acceleration.

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

The paper models three initial smooth shock shapes from fast CMEs in the low corona using polar Gaussian profiles. It then adds combinations of wave-like functions to create corrugated versions that represent disturbances from the bimodal solar wind, CME deflection, irregular expansion, and coronal fluctuations. For both smooth and corrugated shocks the normal angle between the shock surface and the radial upstream magnetic field is computed to map quasi-parallel and quasi-perpendicular regions. The resulting irregular angle distributions on corrugated shocks are taken to create conditions for multiple particle-acceleration processes. The authors conclude that irregular CME expansion is likely a decisive driver of such acceleration.

Core claim

Corrugated features imposed on CME-driven shocks by disturbances, especially irregular expansion, generate irregular distributions of shock normal angles that classify different portions of the shock as quasi-parallel or quasi-perpendicular and thereby predispose those shocks to particle acceleration.

What carries the argument

Corrugated shock surfaces formed by superposing wave-like functions on polar Gaussian profiles, from which the distribution of angles between the local shock normal and the radial magnetic field is calculated.

If this is right

  • Corrugated shocks support different particle-acceleration processes than smooth shocks because of their irregular normal-angle distributions.
  • Irregular CME expansion is a decisive factor in the origin of particle acceleration at these shocks.
  • Modeling these features opens investigation of downstream jets, instabilities, shock thermalization, shock stability, and the injection process.
  • Smooth Gaussian shocks produce more uniform normal-angle classifications than their corrugated counterparts.

Where Pith is reading between the lines

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

  • Spacecraft observations of normal-angle statistics at actual CME shocks could test whether the modeled irregularity matches reality.
  • The same corrugation mechanism might explain event-to-event differences in energetic-particle production efficiency.
  • The approach could be extended to ask how corrugations affect downstream turbulence or thermalization rates.
  • Similar modeling might apply to other expanding astrophysical shocks where piston irregularities are present.

Load-bearing premise

The chosen wavelengths and amplitudes of the added wave-like functions faithfully represent actual physical disturbances in the solar wind and CME piston.

What would settle it

In-situ or remote measurements of a real CME-driven shock that show uniform rather than irregular normal-angle distributions around the front would falsify the claimed predisposition to acceleration.

Figures

Figures reproduced from arXiv: 1907.07884 by A. P\'aez, D. Falceta-Gon\c{c}alves, M. Opher, V. Jatenco-Pereira.

Figure 1
Figure 1. Figure 1: Scheme of a meridional view of CME 1, CME 2, and CME 3 and their shocks. We show three different CMEs, structured in core; cavity; and frontal loop (Illing & Hundhausen 1985). For all situations we considered a sheath structure (green shadow) formed behind the shocks. The CME-pause and coronal magnetic field lines (MFL) are indicated by the blue and black thin lines, respectively. Panels (a), (b), and (c) … view at source ↗
Figure 2
Figure 2. Figure 2: Reconstruction of the shocks presented in [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Corrugated function k(φ) (R ), Equation (7) (black line), and its contributions k1(φ), Equation (8) (blue line), k2(φ), Equation (9) (red line); and k3(φ), Equation (10) (green line) in function of polar angle coordinate, φ. With k1(φ) > k2(φ) > k3(φ) amplitudes, we scale the effect of the bimodal SW, CME irregular expansion and fluctuations of solar corona as large, medium and small scales for ∼ 3.0 R dis… view at source ↗
Figure 4
Figure 4. Figure 4: Schematic comparative between smooth, panel (a), and corrugated shocks, panel (b). In order to show the contrast between two shocks types, we use the parabolic shock morphology, i.e., like the shock 1. We illustrate the differences between CME piston (gray shadow), CME-pause (blue line), downstream or sheath (green shadow), upstream (yellow shadow) of the shock (red lines), and distribution of the shock no… view at source ↗
Figure 5
Figure 5. Figure 5: Plots of shock normal angles for smooth, θ Sm Bn (φ), and corrugated θ Cm Bn (φ) shocks, with m = 1, 2, 3, see [PITH_FULL_IMAGE:figures/full_fig_p013_5.png] view at source ↗
read the original abstract

The study of the acceleration of particles is an essential element of research in the heliospheric science. Here, we discuss the predisposition to the particle acceleration around coronal mass ejections (CMEs)-driven shocks with corrugated wave-like features. We adopt these attributes on shocks formed from disturbances due to the bimodal solar wind, CME deflection, irregular CME expansion, and the ubiquitous fluctuations in the solar corona. In order to understand the role of a wavy shock in particle acceleration, we define three initial smooth shock morphologies each one associated with a fast CME. Using polar Gaussian profiles we model these shocks in the low corona. We establish the corrugated appearance on smooth shock by using combinations of wave-like functions that represent the disturbances from medium and CME piston. For both shock types, smooth and corrugated, we calculate the shock normal angles between the shock normal and the radial upstream coronal magnetic field in order to classify the quasi-parallel and quasi-perpendicular regions. We consider that corrugated shocks are predisposed to different process of particle acceleration due to irregular distributions of shock normal angles around of the shock. We suggest that disturbances due to CME irregular expansion may be a decisive factor in origin of particle acceleration. Finally, we regard that accepting these features on shocks may be the start point for investigating some questions in the sheath and shock, like downstream-jets, instabilities, shock thermalization, shock stability, and injection particle process.

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.

Referee Report

2 major / 1 minor

Summary. The manuscript models three smooth CME-driven shock morphologies in the low corona using polar Gaussian profiles, then superposes combinations of wave-like functions to introduce corrugations representing disturbances from the bimodal solar wind, CME deflection, irregular expansion, and coronal fluctuations. Shock normal angles relative to the radial upstream magnetic field are computed for both smooth and corrugated cases to classify quasi-parallel and quasi-perpendicular regions; the resulting irregular angle distributions are argued to predispose corrugated shocks (especially those affected by irregular CME expansion) to different particle acceleration processes.

Significance. If the modeling choices prove representative of real coronal conditions, the work would draw attention to shock morphology as a factor modulating particle acceleration at CME-driven shocks. The absence of quantitative outputs, error estimates, or direct comparisons to observations or MHD simulations, however, leaves the central suggestion dependent on untested premises about wave parameters, limiting its current impact on heliospheric science.

major comments (2)
  1. [Section 3] Section 3 (model construction): the amplitudes, wavelengths, and phases of the added wave-like functions are selected without calibration against observed coronal fluctuation spectra (e.g., from LASCO or SDO) or self-consistent MHD shock simulations; if these scales do not match actual disturbances, the computed normal-angle distributions and the inferred predisposition to acceleration do not follow from the physical mechanisms invoked.
  2. The manuscript supplies neither quantitative outputs (e.g., angle histograms, fractions of quasi-parallel regions, or statistical measures of irregularity) nor error estimates for the smooth versus corrugated cases, so the claim that corrugated shocks are predisposed to different acceleration processes rests on qualitative description alone.
minor comments (1)
  1. [Abstract] Abstract: several grammatical issues (e.g., “around of the shock”, “regard that accepting these features”) reduce clarity; these should be corrected in revision.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments. We address the major points below, defending the conceptual scope of the work while agreeing to strengthen the presentation where the criticism is valid.

read point-by-point responses

  1. Referee: [Section 3] Section 3 (model construction): the amplitudes, wavelengths, and phases of the added wave-like functions are selected without calibration against observed coronal fluctuation spectra (e.g., from LASCO or SDO) or self-consistent MHD shock simulations; if these scales do not match actual disturbances, the computed normal-angle distributions and the inferred predisposition to acceleration do not follow from the physical mechanisms invoked.

    Authors: The wave parameters are chosen as representative illustrations of disturbances from the bimodal solar wind, CME deflection, irregular expansion, and coronal fluctuations, as stated in the manuscript. The goal is a conceptual discussion showing that any such corrugations generically produce irregular normal-angle distributions, rather than a data-calibrated or MHD-matched simulation. We have added clarifying text in Section 3 stating that the scales are illustrative examples chosen to demonstrate the effect, not fitted values. revision: partial

  2. Referee: The manuscript supplies neither quantitative outputs (e.g., angle histograms, fractions of quasi-parallel regions, or statistical measures of irregularity) nor error estimates for the smooth versus corrugated cases, so the claim that corrugated shocks are predisposed to different acceleration processes rests on qualitative description alone.

    Authors: We agree the original version relies on qualitative comparison. The revised manuscript will include quantitative outputs: histograms of shock-normal angles and the fractions of quasi-parallel versus quasi-perpendicular regions for each smooth and corrugated case. Because the model is deterministic (not statistical), formal error estimates are not applicable; the differences follow directly from the imposed wave functions. revision: yes

Circularity Check

0 steps flagged

No significant circularity; forward modeling of assumed morphologies

full rationale

The paper defines smooth shock profiles via polar Gaussian functions, superposes explicit wave-like perturbations to represent disturbances, computes normal angles directly from the resulting geometry, and infers predisposition to acceleration from the angle distributions. No equation or result reduces by construction to a fitted input, self-citation, or prior ansatz; the workflow is a self-contained demonstration of morphological effects under stated assumptions. This matches the default expectation of non-circularity for modeling studies.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The modeling rests on several ad-hoc choices for wave amplitudes and wavelengths that are not constrained by independent coronal observations; the mapping from normal-angle statistics to acceleration predisposition is treated as an untested domain assumption.

free parameters (1)
  • wave amplitudes and wavelengths
    Chosen by hand to represent disturbances from solar wind and CME piston; no fitting procedure or observational constraint is stated in the abstract.
axioms (1)
  • domain assumption The chosen wave-like functions accurately reproduce the statistical distribution of shock-normal angles produced by real coronal disturbances.
    Invoked when the authors conclude that corrugated shocks are predisposed to different acceleration processes.

pith-pipeline@v0.9.0 · 5814 in / 1305 out tokens · 19773 ms · 2026-05-24T19:55:26.871331+00:00 · methodology

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