{"id":"9b92e180-d9c2-4904-99c3-d9a585515b0d","arxiv_id":"2412.13444","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"Quiet Sun EUV upflow-like events, seen by Solar Orbiter, have average speeds of 62 km/s, lifetimes of 68.6 s, and lengths of 3.94 Mm, and may be spicule-like ejections that heat localized corona.","lead":"Using Solar Orbiter's high-resolution EUV images, the authors identify 59 small upflow-like events in the quiet Sun and measure their speed, lifetime, and length. The events look like hot fronts followed by cooler plasma and may be the EUV counterparts of spicules or network jets, with possible implications for heating the corona.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The inference that the 174 Å moving fronts are plasma outflows is not yet separated from propagating wave fronts, so the spicule/network-jet association rests on an untested kinematic interpretation.","rationale":"The reader's weakest assumption is exactly the interpretation of apparent 174 Å motions as plasma outflows, and my analysis sharpens this into a specific physical alternative: propagating wave fronts. The paper is careful in naming the events 'upflow-like' and in noting the absence of footpoint brightening, but the Discussion and Summary (items i, ii, and the coronal-heating statements) go beyond this hedge and treat the motions as ejections. Because EUI 174 Å is a broad filter containing Fe X and transition-region lines, an intensity front in that filter can be produced by a thermal or wave disturbance without net mass motion. The measured speeds are consistent with sound speeds at the derived temperatures, so the wave interpretation is not merely a conceptual possibility but a quantitative one. The dark trailing component could resolve this, but it is never temperature-diagnosed; the EM-loci analysis is restricted to the bright front. I therefore agree with the conditional verdict: the statistics are plausible and the observations are valuable, but the central physical conclusion should not be accepted as definitive until the wave-versus-flow ambiguity is tested with multi-passband timing or Doppler data. The proposed AIA multi-passband cross-correlation test is feasible with the existing dataset and would settle the concern directly. No independent evidence, such as machine-checked proofs or released code, is present in this manuscript, so the burden remains on the observational interpretation.","tokens_in":16899,"tokens_out":6393,"duration_ms":67509,"concrete_test":"Re-analyze the AIA 304, 171, 131, 193, and 211 Å time-distance cuts for the 29 dataset-2 events (Section 3.4, Figure 6). For each event, cross-correlate the leading bright front light curves along the same slit between passbands. If the front is a slow-mode wave, its arrival time should be temperature-ordered with delays consistent with the channel-dependent sound speed; if it is a mass ejection, the hot front and trailing dark component should be cospatial (within the 12-24 s AIA cadence) and the dark component should show a simultaneous darkening in 174 and 304 Å indicative of absorbing cool plasma, rather than a temperature-ordered lag. A wave-like lag or void-like dark signature would falsify the plasma-outflow interpretation and require the central claim to be substantially weakened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that the EUV upflow-like events are outward plasma ejections (and hence EUV counterparts of spicules/network jets that heat the localized corona) rests on interpreting the linear bright stripes in 174 Å time-distance plots as bulk plasma motion (Sections 3.2 and 3.4, Figures 2 and 6). The paper uses no Doppler spectroscopy; all velocities are plane-of-sky slopes of intensity features. In coronal/transition-region EUV imaging, propagating intensity fronts are commonly slow-mode magnetoacoustic waves, and the average measured speed of 62 km/s is close to the sound speed at the EM-derived front temperature of ~10^5.5 K (~85 km/s for μ=0.6), so a wave interpretation is quantitatively viable. The claimed 'cold plasma ejection' is the main discriminator, but it is inferred only from dark appearance in 174 Å and in some AIA channels; a dark trailing feature in broadband EUV can also be a density depletion or projection artifact, not cool chromospheric material. The EM-loci analysis is performed only on the bright front (Figure 7), not on the dark component. Therefore the physical identification of these features as real mass upflows, and everything built on it—lifetimes, lengths, recurrence, and coronal-heating contribution—is not yet established beyond the apparent-motion phenomenology.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports a statistical study of 59 small-scale EUV features observed by Solar Orbiter/EUI in the 174 Å channel, terming them “EUV upflow-like events.” Using time-distance plots, the authors derive average plane-of-sky velocities of 62 km/s, lifetimes of 68.6 s, and propagation distances of 3.94 Mm; 39% of the events are classified as recurrent. For a subset observed jointly with SDO/AIA, the events occur at network boundaries, often near mixed-polarity photospheric fields, and EM-loci analysis of the bright front gives an average temperature of about 10^5.5 K and EM of about 5.6×10^26 cm^-5. The paper interprets these features as outward plasma ejections—with a hot front followed by cool material—and suggests they may be EUV counterparts of chromospheric spicules and transition-region network jets, possibly contributing to localized coronal heating.","tokens_in":17146,"tokens_out":5625,"duration_ms":52054,"significance":"If the physical interpretation is established, this is a valuable observational result: high-resolution EUI imaging reveals a ubiquitous class of small-scale network-related features whose dynamics and recurrence are not well characterized in earlier work. The paper’s strengths include the use of standard time-distance and EM-loci methods, a modest sample with tabulated measurements, explicit use of the hedged term “upflow-like,” and comparison with prior spicule and network-jet observations. The main significance depends, however, on whether the moving 174 Å intensity features truly represent plasma outflows rather than propagating wave fronts or projection effects, and whether the “cold” trailing component is genuinely cool ejected plasma. These points are not yet demonstrated.","major_comments":[{"comment":"The central claim that the observed bright stripes in the 174 Å time-distance plots are bulk plasma outflows is not yet separated from propagating intensity fronts. All velocities are plane-of-sky slopes of brightness features, and no Doppler or spectroscopic diagnostic is used. The average speed of 62 km/s is comparable to the sound speed at the EM-derived front temperature of 10^5.5 K (about 85 km/s for μ=0.6), so a slow-mode magnetoacoustic wave interpretation is quantitatively viable. Because the subsequent “cold plasma ejection” is the paper’s main discriminator for mass motion, the authors should either provide quantitative evidence that the trailing dark feature is persistent, non-oscillatory, and moves in a way incompatible with waves, or explicitly restrict the conclusion to “apparent” motions and defer the physical interpretation.","section":"Section 3.2, Figures 2–3"},{"comment":"The identification of a “cold plasma ejection” is not supported by the radiative analysis as presented. The EM-loci calculation is performed only on the bright front, while the dark trailing component is characterized solely by its absence in 174 Å and in several AIA channels. In broadband EUV images, a dark trail can equally be a density depletion, a temperature-minimum region, or a projection artifact, and the paper does not provide a temperature or density constraint on the dark feature. Without such a constraint, the claim that cool chromospheric or transition-region plasma is being ejected, and the resulting spicule/network-jet analogy, is not established. The authors should attempt an EM or filter-ratio diagnostic on the dark component if possible, or present the ejection as a working hypothesis.","section":"Section 3.4, Figure 7"},{"comment":"The quantitative basis for the statistical claims is incomplete. Events are selected “by carefully checking all the regions” without a stated objective detection criterion, and the per-event velocities, lifetimes, and lengths from time-distance fits are reported without per-event uncertainties. Consequently, the histograms in Figure 3 show only sample scatter, not measurement error, and the positive correlation between velocity and propagation distance in Figure 3(d) may be influenced by the fitting and selection procedure. Please specify the detection and selection criteria, report uncertainties for each measured quantity (including errors from the linear fit, cadence, and pixel scale), and state clearly whether Table 1 values for recurrent events are averages over repetitions or values from a single event.","section":"Section 3.1, Table 1, Figure 3"},{"comment":"The conclusion that these events “play a role in heating localized corona above the network regions” is not quantitatively supported. The paper presents no energy budget, heat-input estimate, or event-rate per unit area and time; the claim rests mainly on the “haze-like” brightening and the recurrence fraction. If the authors wish to assert a heating role, they should provide at least an order-of-magnitude energy-flux estimate based on the measured velocities, densities, and occurrence rates; otherwise this statement should be explicitly labeled as a speculative extrapolation.","section":"Section 4, Summary"}],"minor_comments":[{"comment":"Please fix the numerous typos and grammatical errors (e.g., “high-resoltion” in the Abstract; “Diffierent,” “phenonema,” “brith place,” and “macorospicules” in Sections 1 and 4).","section":"Throughout"},{"comment":"The summary item (ii) lists the averaged quantities in an order that disagrees with the text: it reads “velocity, duration, and propagation distance … 68.6 s, 62 km/s, and 3.94 Mm,” which should be “62 km/s, 68.6 s, and 3.94 Mm”.","section":"Section 5, Summary item (ii)"},{"comment":"In the Discussion, the parenthetical for Type II spicule lifetimes reads “lifetimes (50-150 km s^-1),” which appears to be a unit error; lifetimes should be given in seconds.","section":"Section 4"},{"comment":"Please clarify how recurrent events are represented in Table 1: whether the listed duration, velocity, and length are averages over all repetitions, and how the “Start time” and “Time gap” columns are defined for recurrent events.","section":"Section 3.2, Table 1"},{"comment":"The “falling motion” of the bright front and dark body mentioned in Section 3.4 is not quantified; please either provide measurements of the falling phase or characterize this as a qualitative impression.","section":"Section 3.4, Figure 6"}],"recommendation":"major_revision","confidential_remarks":"The paper is likely of interest to the solar-physics community, and the observations are novel in their use of high-resolution EUI data. My main concern is that the central interpretation—that the apparent motions are plasma outflows with a cool trailing component—is not yet separated from propagating wave fronts or projection effects, and the only radiative diagnostic is applied to the bright front. This can be addressed by either adding discriminating evidence or softening the physical claims, so I do not recommend rejection. I would also encourage the editor to ask for explicit detection criteria and per-event uncertainties, as the current statistical presentation is difficult to evaluate quantitatively."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The useful thing here is the sample: 59 EUV upflow-like events, the first statistical set of these features after Schwanitz et al.'s two cases. The paper measures apparent velocities, lifetimes, lengths, finds 39% recurrence, describes blob/multi-strand fine structure and haze-like heating, places the events at network lanes, and gives an EM-loci temperature around 10^5.5 K. That is a real advance in phenomenology, and the authors are careful to call the features \"upflow-like\" and to label velocities as plane-of-sky. They also compare sensibly to network jets and type II spicules without overclaiming.\n\nThe soft spots are real but not fatal. Event selection is manual; I could not find stated criteria or a test of inter-observer agreement. Per-event measurement uncertainties are missing, so the histograms in Figure 3 have no error bars. The bigger issue is the one the stress-test note raises: everything rests on interpreting the bright 174 Å stripes as bulk plasma motion. At 62 km/s average, with a front temperature near 10^5.5 K (sound speed ~85 km/s), slow-mode waves are a quantitative alternative, and no Doppler data are used. The paper's main discriminator is the \"cold plasma ejection\" trailing the hot front, but that is inferred only from darkness in 174 Å and some AIA channels. A dark feature in broadband EUV can be a density depletion or projection effect. The EM-loci analysis is done only on the bright front, not on the dark component, so we never directly measure the temperature of the supposed cool material. These concerns do not sink the paper, but they mean the spicule/network-jet association and the coronal-heating inference are not yet established beyond apparent-motion phenomenology. A revision should add a wave-versus-flow discussion and, if possible, a differential emission measure or a test using the AIA 304/171 contrast of the dark component.\n\nTwo smaller things: the summary's item (ii) lists \"velocity, duration, and propagation distance\" but gives \"68.6 s, 62 km/s, 3.94 Mm,\" a simple ordering slip; and the 29-event magnetic context is a subset, so the 76% mixed-polarity fraction should be labeled as such (it is, in the text, but easy to miss).\n\nWho this is for: observers of quiet-Sun small-scale activity and anyone compiling the observational case for spicule/network-jet EUV counterparts. It deserves a serious referee; I would send it out. A moderate revision addressing the wave alternative and adding uncertainties would move it from conditional to solid.\n\nRecommendation: engage, referee it, and push on the wave/flow discrimination.","headline":"A useful first statistical sample of EUV upflow-like events, honestly labeled, but the plasma-vs-wave question is open and needs a dedicated test before spicule/coronal-heating conclusions harden.","tokens_in":17677,"tokens_out":3374,"would_cite":true,"duration_ms":32630,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The paper reports that 59 small-scale EUV upflow-like events in the quiet Sun, moving at an average apparent speed of 62 km s$^{-1}$ with lifetimes of 68.6 s, are outward plasma ejections from network regions that likely correspond to…","keywords":["Quiet Sun","EUV upflows","spicules","network jets","Solar Orbiter EUI","coronal heating","transition region","small-scale solar jets"],"falsifier":"A coordinated spectroscopic observation with a slit crossing one of these events in a transition-region line such as Si IV 1402 Å or Ne VIII 770 Å: if the bright front shows no corresponding Doppler outflow or shows oscillatory line shifts while the apparent transverse motion continues, the features are waves or projection artifacts rather than plasma ejections.","tokens_in":16722,"feed_emoji":"☀️","tokens_out":6406,"duration_ms":56247,"temperature":0.7,"pith_summary":"Using Solar Orbiter's 174 Å imager, the paper identifies 59 small-scale EUV upflow-like events in quiet-Sun network regions and argues that they are outward plasma ejections, not just brightness disturbances. The events move at an average apparent speed of 62 km s$^{-1}$, live about 69 s, and travel about 3.9 Mm, with many recurring every ~84 s. They show a bright leading front followed by cooler ejected plasma, no footpoint brightening, and some produce localized haze-like heating ahead of the ejection. The paper concludes that these events are likely the EUV counterparts of chromospheric spicules and transition-region network jets, and that their repetition may heat the localized corona above network lanes. If correct, they provide a direct observational link between small-scale quiet-Sun dynamics and coronal heating.","feed_headline":"59 tiny EUV jets erupt from quiet-Sun network lanes","feed_subtitle":"Fast, recurring ejections match spicule and network-jet behavior and may heat the nearby corona.","key_machinery":"The load-bearing observational objects are the EUV upflow-like events themselves: short-lived, collimated 174 Å brightness features with a bright leading front and a following dark ejection, moving along magnetic field lines. The analysis tools are time-distance (space-time) diagrams along the ejection direction, which yield velocity, lifetime, length, and recurrence intervals; the EM-loci emission-measure technique applied to SDO/AIA background-subtracted intensities to estimate bright-front temperature and emission measure; and co-aligned SDO/HMI magnetograms with AIA 1600 Å and Lyα images to establish the network and mixed-polarity environment. This combination lets the paper connect the EUI-only events to known lower-atmosphere phenomena by comparing speeds, lifetimes, lengths, and source-region magnetic settings.","core_discovery":"On its own terms, the paper claims that the quiet Sun is filled with small, collimated, outward-moving EUV features that originate at the boundaries of chromospheric network patches, carry plasma of transition-region or coronal temperature (averaging ~$10^{5.5}$ K) at their bright fronts, and often trail cooler material behind them. The measured averages over 59 events — 62 km s$^{-1}$ plane-of-sky speed, 68.6 s lifetime, and 3.94 Mm propagation distance — place these features in the same parameter range as network jets and type II spicules. Since 39% recur and at least 23 of the 29 events with SDO coverage show repeated activity, the paper suggests these are frequent, persistent mass and energy injections into the low corona. Their fine structure, including blob-like features, multi-strand evolution, and haze-like heating ahead of the spire, indicates small-scale heating processes that may contribute to heating the localized corona above network regions.","pith_inferences":["If the event rate seen in these two datasets is typical, the global quiet-Sun contribution of such events to coronal heating and solar-wind mass supply could be estimated by counting events over longer EUI campaigns; the paper does not make that extrapolation.","The haze-like heating ahead of the spire suggests the ejected plasma dissipates energy by colliding with or compressing the overlying corona; testing this would require simultaneous temperature and density diagnostics across the front.","A direct spectroscopic test, such as a slit crossing one of these events in Si IV or Ne VIII, could confirm that the apparent motions correspond to true line-of-sight outflows, separating them from wave-like disturbances.","The unipolar cases (24%) point to a second driver that does not require flux cancellation, such as p-mode leakage or ambipolar diffusion; comparing the two subpopulations could clarify whether they are one phenomenon with two triggers."],"forward_implications":["If these events are genuine ejections, quiet-Sun upflow-like activity is far more common than previously recognized, with dozens of events visible in just a few minutes of EUI imaging.","The ~84 s mean recurrence gap means repeated events deposit energy into the same network-field corona many times per hour, giving a natural mechanism for sustained localized heating.","Because the bright fronts reach ~$10^{5.5}$ K and the events arise mainly in mixed-polarity network regions with flux emergence or cancellation, the results link small-scale magnetic reconnection to plasma ejection and heating.","The similarity of measured speeds, lifetimes, and lengths to those of type II spicules and network jets supports identifying these EUV events as their coronal counterparts, connecting chromospheric and coronal observations of the same phenomenon."],"supporting_citations":[{"why":"Establishes network jets as on-disk counterparts of type II spicules, providing the interpretive framework for the EUV upflow-like events.","marker":"Tian et al. 2014b"},{"why":"Supplies quiet-region network jet speeds, lifetimes, and lengths that the paper's measured averages are compared against.","marker":"Kayshap et al. 2018"},{"why":"Provides quiet-region network jet velocities (20–70 km/s) used as a comparison for the measured event speeds.","marker":"Gorman et al. 2022"},{"why":"Offers the picture of bright coronal counterparts at spicule tops and the magnetic environment for spicule formation, used to interpret the bright fronts.","marker":"Samanta et al. 2019"},{"why":"Describes similar EUI quiet-Sun small-scale jets and microjets, which the paper distinguishes from its upflow-like events by the absence of footpoint brightening.","marker":"Hou et al. 2021"},{"why":"Earlier report of quiet-region upflow events that this paper extends into a larger statistical sample.","marker":"Schwanitz et al. 2023"},{"why":"Documents widespread weak upflows correlated with type II spicules, supporting the association of the observed events with spicules.","marker":"De Pontieu et al. 2009"},{"why":"Provides the EUI instrument context and quiet-Sun campfire observations that frame the new small-scale phenomena.","marker":"Berghmans et al. 2021"}],"fun_headline_variants":["Quiet Sun's tiny EUV jets: hot fronts, cool tails, recurring bursts","Small EUV upflows in quiet Sun may heat corona above network","EUV jets in quiet Sun mimic spicules, may heat corona","Recurring EUV upflows from quiet-Sun network heat the corona","Blobby EUV jets in quiet Sun reveal multi-strand nature"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The central assumption is that the moving 174 Å features are actual plasma blobs or fronts propagating outward along magnetic field lines, rather than apparent motions produced by waves or projection effects; all measured speeds, lifetimes, and distances, and the spicule and network-jet interpretation, rest on that.","fun_headline_variants_meta":{"raw":{"variants":["Quiet Sun's tiny EUV jets: hot fronts, cool tails, recurring bursts","Small EUV upflows in quiet Sun may heat corona above network","EUV jets in quiet Sun mimic spicules, may heat corona","Recurring EUV upflows from quiet-Sun network heat the corona","Blobby EUV jets in quiet Sun reveal multi-strand nature"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001133,"raw_usage":{"total_tokens":4756,"prompt_tokens":1042,"completion_tokens":3714,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":658,"completion_tokens_details":{"reasoning_tokens":3616}},"tokens_in":658,"tokens_out":3714,"duration_ms":24819,"temperature":1.0,"reasoning_tokens":3616,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T13:06:46.613262+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A coordinated spectroscopic observation with a slit crossing one of these events in a transition-region line such as Si IV 1402 Å or Ne VIII 770 Å: if the bright front shows no corresponding Doppler outflow or shows oscillatory line shifts while the apparent transverse motion continues, the features are waves or projection artifacts rather than plasma ejections.","supporting_citations":[{"cited_title":"P., & Peter , H","cited_arxiv_id":null,"evidence_quote":"Provides quiet-region network jet velocities (20–70 km/s) used as a comparison for the measured event speeds."},{"cited_title":"H., et al","cited_arxiv_id":null,"evidence_quote":"Earlier report of quiet-region upflow events that this paper extends into a larger statistical sample."}],"review_version":1}