Pith. sign in

REVIEW 5 major objections 5 minor 33 references

Vortex driven Schwinger pair creation in the magnetosphere of SgrA*

T0 review · 5 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash

Pith's one-line read Vortex-driven magnetic fields near equipartition would push Sgr A*'s magnetosphere past the Schwinger threshold and create electron-positron pairs at densities near 3e18 per cubic centimeter.

desk verdict A novel Sgr A* application of the centrifugal Schwinger mechanism with a strong vortex field, but the pair-density numbers are internally inconsistent and the detectability claim doesn't hold as written. read the letter →

arxiv 2501.00985 v4 pith:2MUB2WQ4 submitted 2025-01-02 astro-ph.HE

classification astro-ph.HE
keywords Schwingerpairproductionmagneto-centrifugalaccelerationSgrA*magnetosphereLangmuirinstabilityelectron-positronplasmaannihilationradiationvortex-drivenmagneticfieldGalacticcenterblackhole
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper tries to establish that the Milky Way's central black hole, Sgr A*, can turn into an efficient electron-positron pair factory if its magnetosphere carries a vortex-driven magnetic field near the equipartition limit, $B \simeq 6\times10^{12}$ G. At that field strength, magneto-centrifugal acceleration near the light cylinder is powerful enough to excite Langmuir waves whose electrostatic field reaches the Schwinger pair-creation threshold. The resulting electron-positron density, $n \simeq 3\times10^{18}\,\mathrm{cm^{-3}}$, is high enough that annihilation dominates the saturation and produces Doppler-shifted emission in the roughly 100 keV to 10 MeV range. If correct, this gives a concrete, observable channel linking extreme magnetic fields around black holes to pair creation, with a signature distinct from conventional pair-cascade models.

What carries the argument

The carrier of the argument is the vortex-driven equipartition field, $B \simeq c^4/(M G^{3/2}) \simeq 6\times10^{12}$ G, plus the chain it feeds: frozen-in motion along rotating magnetic field lines, centrifugal Lorentz-factor growth limited by curvature radiation or the bead-on-the-wire breakdown, parametric Langmuir instability with growth rate $\Gamma$, and the Schwinger rate $R = \frac{e^2 E^2}{4\pi^3 c \hbar^2} \sum_k k^{-2} \exp\!\left(-\frac{\pi m^2 c^3}{e\hbar E k}\right)$. Saturation is set by annihilation, $\Lambda \simeq 2\pi c r_e^2 n^2$, rather than by the electric field itself; equating production and annihilation yields the final pair density.

What would settle it

A numerical simulation of vortex-driven field growth in an accreting Kerr magnetosphere with Sgr A* parameters would settle the input premise: if the field saturates below $\sim 10^{12}$ G, the claimed chain from centrifugal acceleration to Langmuir instability to Schwinger pair production fails, even if each step in the chain is correct.

Watch

Extended reading notes

Core claim

The central claim is that Sgr A* can produce electron-positron pairs through a chain starting from a vortex-driven magnetic field $B \simeq 6\times10^{12}$ G. Because that field exceeds conventional estimates by orders of magnitude, protons and electrons remain frozen to the rotating field lines and are centrifugally accelerated to Lorentz factors near $10^{10}$--$10^{11}$; their charge separation parametrically drives Langmuir waves whose electrostatic field grows as $e^{\Gamma t}$ with $\tau = 1/\Gamma \simeq 5\times10^{-4}$ s. Once the field reaches the Schwinger threshold $E_S \simeq 1.4\times10^{14}$ statvolt cm$^{-1}$, the Schwinger rate supplies pairs until annihilation saturates the plasma at $n \simeq 3\times10^{18}$ cm$^{-3}$. The same chain with a conventional field gives $n \simeq 3\times10^{14}$ cm$^{-3}$, so the vortex field is what makes the magnetosphere a strong pair source and a potential source of Doppler-shifted annihilation lines in the 100 keV--10 MeV range.

Load-bearing premise

The load-bearing premise is that the magnetosphere actually confines a near-equipartition vortex field, $B \simeq 6\times10^{12}$ G, whose stored energy is a sizable fraction of the black hole's rest energy; the paper cites this field from the vortex literature, so if real vortex fields saturate far below that value, the Lorentz factors, instability growth, and pair densities all drop with it.

Editorial extensions

If this is right

  • If the vortex-driven field is present, the light-cylinder region of Sgr A* should contain an electron-positron plasma with $n \simeq 3\times10^{18}\,\mathrm{cm^{-3}}$, about four orders of magnitude denser than in the conventional-field case.
  • The pair annihilation should produce Doppler-shifted emission spanning roughly $100\,\mathrm{keV}$ to $10\,\mathrm{MeV}$ for Lorentz factors near 10, a band that distinguishes this mechanism from disk emission.
  • The Langmuir growth time, $\tau \simeq 5\times10^{-4}$ s, is far shorter than the rotation period $P \simeq 670$ s, so pair production should be a persistent feature rather than a transient burst.
  • Because dust can absorb the direct annihilation photons, the model also predicts efficient heating of the Sgr A* magnetosphere as a secondary signature.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Extending the setup, the equipartition scaling $B \sim M^{-1}$ suggests lower-mass black holes would be even more efficient pair sources per unit mass, but this application is not in the paper.
  • The paper leaves the annihilation-line luminosity uncomputed because it depends on magnetic-field topology; a dedicated model of the field-line geometry is the natural next step for making the prediction observable.
  • A clean observational discriminator would be Doppler modulation of the 100 keV--10 MeV feature at the rotation period, which would separate corotating pairs from stationary foreground emission.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

5 major / 5 minor

Summary. The paper proposes that in the magnetosphere of Sgr A*, a vortex-driven magnetic field of order 6e12 G, obtained by equating magnetic energy to the black hole rest energy, can make magneto-centrifugal acceleration so efficient that charge separation parametrically excites Langmuir waves. The associated electrostatic field is claimed to grow exponentially to the Schwinger threshold, producing electron-positron pairs with a saturated density of about 3e18 cm^-3 and Doppler-shifted annihilation emission in the 100 keV--10 MeV band. The calculation combines an equipartition field estimate, maximum Lorentz factors from energy-loss limits, an imported parametric growth rate from the author's previous work, and an annihilation-saturation balance to derive the final pair density.

Significance. If valid, the mechanism would offer an alternative and potentially much more efficient channel for electron-positron pair production in Sgr A* than conventional photon-photon or Penrose processes, with a distinctive annihilation-line signature. The manuscript is an analytic order-of-magnitude study and does not provide numerical simulations or machine-checked derivations. Its main strength is that it identifies a specific regime (ultra-strong vortex magnetic fields) and gives closed-form estimates that can be checked directly; however, the central quantitative results contain internal inconsistencies and rest on unproven assumptions about the field strength and the growth of the instability. As presented, the physical predictions are not sufficiently supported.

major comments (5)
  1. [Eq. (1), Sec. 2] The vortex-driven field B~6e12 G is asserted as an equipartition upper limit equating magnetic energy to the black hole rest energy. This is not a model: no vortex-generation mechanism, saturation level, or field-amplification timescale is given for Sgr A*, and the citations [19,22] describe more general settings that are not shown to apply to the accretion environment of Sgr A*. Since B controls the maximum Lorentz factors, the growth rate Gamma, the pair density n, and the annihilation luminosity, the entire quantitative prediction rests on an unvalidated input. The authors should either supply a concrete field-generation model or explicitly frame the results as a speculative upper-limit scenario with a sensitivity analysis over B.
  2. [Eq. (14), Sec. 2] The quoted vortex-field pair density does not follow from the paper's own parameters. With tau=5e-4 s, Gamma=1/tau=2e3 s^-1, c=3e10 cm/s, and r_e=2.82e-13 cm, Eq. (14) gives n=Gamma/(2*pi*c*r_e^2) about 1.3e17 cm^-3, not the quoted 3e18 cm^-3, a factor of about 23 discrepancy. The conventional-field value, 3e14 cm^-3, is correctly recovered, so the inconsistency is specific to the vortex case. Because the annihilation-line intensity scales as n^2, this numerical error changes the predicted signal by roughly two orders of magnitude and must be corrected.
  3. [Following Eq. (13), Sec. 2] The derivation of Eq. (14) is not reproducible. The text refers to 'Eq. (22)', which does not exist in the manuscript, and the instruction to neglect e^{Gamma*tau} relative to e^{2*Gamma*tau} does not connect to Eq. (13), which already contains the integrated density rather than an explicit exponential form. Moreover, the production-based density R(t0)*t0 about 1e30 cm^-3 quoted just before Eq. (11) is 12 orders of magnitude larger than the saturation density n obtained from Eq. (14). The manuscript never reconciles these two numbers. Since the observable annihilation signal is determined by the actual pair density, this inconsistency is load-bearing and requires a corrected, step-by-step calculation.
  4. [Eqs. (9), Sec. 2] The parametric growth rate Gamma is evaluated for hand-picked Lorentz factors gamma_1=10 and gamma_2=100, with the species assignment reversed between the conventional case (protons and electrons) and the vortex case (electrons and protons), and with inclination angles theta=90 degrees and theta=1-3 degrees respectively. No derivation or observational justification is provided for these choices, while the text itself notes that for larger inclination angles Landau damping suppresses the instability. Because the instability timescale tau and hence the final pair density are exponentially sensitive to these parameters, the central claim is not robust without a parameter-space scan or a first-principles calculation of the preferred Lorentz factors and angles.
  5. [Between Eqs. (10) and (11), Sec. 2] The claim that the exponentially growing electrostatic field 'will eventually reach' the Schwinger threshold is asserted rather than demonstrated. The paper introduces a saturation condition, Eq. (11), in which the power density of the pair plasma equals that of the electric field, but it never compares the saturation time t0 with the time required for the field to reach E_S. If saturation occurs before the Schwinger threshold, efficient pair production never begins. This is the central physical claim of the paper, and it needs an explicit comparison of the two timescales, or a bound showing that E_S is reached before the nonlinear saturation or other losses intervene.
minor comments (5)
  1. [Title] The title contains typos: 'Schwingrer' should be 'Schwinger' and 'magnetospher e' should be 'magnetosphere'.
  2. [Eq. (3)] The angular velocity Omega is expressed in units of 'rad sec^-2'; the correct unit for angular velocity is rad s^-1.
  3. [Eqs. (4)--(8)] The notation 'ctg' should be replaced by 'cot' for consistency with standard usage in English-language journals.
  4. [References] Reference [16] is incompletely formatted ('MNRAS, 2008, 490, 487' appears to lack volume or page details), and Reference [27] lacks a title; please check all bibliographic entries against the journal style.
  5. [Conclusions, Sec. 3] The concluding caveat that 'the total luminosity of the process strongly depends on the magnetic field topology and requires a dedicated analysis' is in tension with the paper's earlier quantitative claim of detectable annihilation lines; this dependence should be stated earlier and reflected in the abstract.

Circularity Check

3 steps flagged · score 6.0 of 10

The pair-density prediction reduces to the same author's imported growth rate via Eq. (14); missing Eq. (22) and a 12-order-of-magnitude inconsistency with the production density undermine the annihilation-line claim.

  1. fitted input called prediction [Section 2, Eq. (14)]
    "Taking the derivative of Eq. (22) with respect to τ and neglecting the term eΓτ relative to e2Γτ on the left-hand side of the equation straightforwardly yields an estimate for the electron and positron number densities n ≃ Γ/(2πcr2e), which for the conventional magnetic field and the vortex-driven magnetic field for θ = 1◦ equals 3 × 1014cm−3 and 3 × 1018cm−3 respectively."

    The headline quantitative result, n = 3e18 cm^-3, is nothing but a constant rescaling of Γ via n = Γ/(2π c r_e^2). Γ is not computed in this paper from an independent Sgr A* model; the numerical values τ ≃ 0.2 s and τ ≃ 5e-4 s are asserted after choosing γ1, γ2, and θ, and are imported from the same author's earlier work [16]. Thus the claimed density is a re-labeled version of the input growth rate, not an independent prediction. The reference to 'Eq. (22)' is also absent from the paper; the only reconstruction from Eq. (13) is the annihilation-balance identity, so the proportionality is imposed by construction.

  2. self citation load bearing [Section 2, Eq. (9) and the instability time-scale paragraph]
    "in [16] it has been shown that the growth rate, Γ, of the corresponding parametric process (electric field grows as eΓt), being very efficient on the LC zone is given by ... for a vortex-driven magnetic field and field-line inclination angles θ = 1◦ − 3◦, with γ1 = 10 (electrons) and γ2 = 100 (protons), the instability time-scale τ ≃ 5 × 10−4 s."

    The central parameter Γ, which through Eq. (14) fixes the pair density and the annihilation-line luminosity, is taken from Ref. [16], a same-author publication. The paper does not reproduce the derivation, supply code, or benchmark Γ against external data. Because the final observable is proportional to Γ, the load-bearing numerical content of the paper is re-exported from this self-citation. The vortex-field premise is similarly supported by Ref. [19] (Dvali, Osmanov, Zantedeschi), a submitted paper sharing the present author, making the self-citation chain extend from the magnetic field strength to the final pair density.

1 more flagged steps
  1. other [Section 2, Eq. (13) and the saturation paragraph]
    "R(τ ) ≃ Λ ≃ 2πcr2e (∫_0^τ R(t)dt)^2. ... Taking the derivative of Eq. (22) with respect to τ ... straightforwardly yields ... n ≃ Γ/(2πcr2e)."

    The derivation of Eq. (14) is presented as differentiating 'Eq. (22)', but no Eq. (22) exists in the manuscript. Reconstructing the step from Eq. (13) shows the result is just the equilibrium annuity relation for an exponential source, not a microphysical solution. Earlier in the same section the produced density is stated to reach R(t0)t0 ∼ 1e30 cm^-3 for both field cases, whereas Eq. (14) gives 3e14 and 3e18 cm^-3, a discrepancy of up to 12 orders of magnitude. Moreover, the quoted vortex value 3e18 cm^-3 disagrees with the paper's own Γ = 2e3 s^-1: inserting r_e = 2.82e-13 cm gives n ≃ 1.3e17 cm^-3, a factor of about 23 lower. This is not a cosmetic typo because the annihilation luminosity scales as n^2, but it does show the output is an imposed input, not a consistent prediction.

full rationale

The paper's derivation chain is not self-contained. The equipartition vortex field B ≃ 6e12 G (Eq. 1) is imported from [19,22], the Lorentz-factor limits come from [14] (same author), the instability growth rate Γ comes from [16] (same author), and the saturation formulas come from [8] (same author). The hinge is Eq. (14), n = Γ/(2π c r_e^2), which makes every later prediction—pair density, pair-creation rate, annihilation-line flux—a linear rescaling of Γ. Since Γ itself is not derived or tested in this paper but is quoted from prior work by the same author, the central quantitative claim reduces to a self-citation chain rather than an independent first-principles result. The manuscript also signals its own incompleteness: it refers to a nonexistent Eq. (22), gives production densities near 1e30 cm^-3 that are never reconciled with the saturation densities 3e14/3e18 cm^-3, and the quoted vortex density is inconsistent with its own Γ by a factor of about 23. These omissions would be non-circular errors if Γ were independently established, but because they occur in the exact step where the output is defined as Γ/(2π c r_e^2), they reinforce the conclusion that the 'prediction' is an imposed input. I do not claim the entire paper is definitionally circular: if the Γ result in Ref. [16] were independently machine-checked or externally benchmarked, the score would drop to 0–2. As submitted, however, the central observable is a rescaled version of the same author's imported growth rate, so a score of 6 is appropriate.

Assumptions & free parameters 5 free parameters · 5 assumptions · 0 invented entities

The central claim rests on an adopted near-equipartition magnetic field, an imported parametric instability rate, and several hand-picked parameters (gamma_1, gamma_2, theta). No parameters are fitted to observational data, but the choices are effectively free and control the output densities, so the ledger is dominated by assumptions rather than measured inputs.

free parameters (5)
  • Magnetic field strength B = approximately 6e12 G
    Equipartition upper limit B^2 R_g^3 approximately M c^2 is adopted as the actual field in Sgr A*; not derived from a magnetospheric model.
  • Lorentz factor of species 1 = 10
    Used in Eq. (9) for the parametric growth rate; conventional case protons, vortex case electrons. Chosen by hand, not derived from acceleration limits.
  • Lorentz factor of species 2 = 100
    Used in Eq. (9); conventional case electrons, vortex case protons. Chosen by hand.
  • Inclination angle theta = 1 to 3 degrees
    Only small angles are considered for the vortex case because larger angles lead to Landau damping; this selection maximizes the growth rate.
  • Spin parameter a = 0.65
    Intermediate value among 0.95, 0.5, and 0 from refs. [26,27]; angular velocity is only weakly sensitive to this choice.
assumptions (5)
  • ad hoc to paper Vortex-driven magnetic fields can reach the equipartition value B approximately 6e12 G in black hole magnetospheres.
    Invoked in Eq. (1) and attributed to refs. [19,22]; no derivation or model is given in this paper.
  • domain assumption Plasma is frozen-in and moves along straight, co-rotating field lines (bead-on-the-wire approximation).
    Used throughout Section 2; plausible for B = 6e12 G but not verified for the actual plasma conditions in Sgr A*.
  • domain assumption The parametric Langmuir instability growth rate from ref. [16], Eq. (9), applies with the chosen gamma and density values without modification.
    This is central to the exponential field growth; it is cited rather than re-derived in the present paper.
  • ad hoc to paper The exponentially growing electrostatic field reaches the Schwinger threshold before nonlinear saturation or other losses intervene.
    Asserted after Eq. (10); no energy budget or saturation analysis is provided.
  • domain assumption Energy equipartition across species, gamma_max n_GJ approximately gamma n, determines the particle densities.
    Stated in Section 2 but not used explicitly in the growth-rate examples, leaving the densities n_1 and n_2 unspecified.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Vortex driven Schwinger pair creation in the magnetosphere of SgrA*." pith.science (2026). https://pith.science/paper/2MUB2WQ4

@misc{pith2026250100985,
  author       = {Pith},
  title        = {Pith review of: Vortex driven Schwinger pair creation in the magnetosphere of SgrA*},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/2MUB2WQ4}},
  note         = {Machine review of arXiv:2501.00985}
}
read the original abstract

In this work, we explore the possibility of Schwinger pair creation triggered by magneto-centrifugal effects in the magnetosphere of SgrA*. We show that these effects become extremely efficient in the presence of a vortex-driven magnetic field, whose strength exceeds previous estimates by several orders of magnitude. The dynamics of magneto-centrifugally accelerated charged particles leads to charge separation, thereby parametrically exciting Langmuir waves. The associated electric field grows exponentially and upon reaching the Schwinger critical threshold, initiates efficient electron-positron pair production, which is ultimately saturated by annihilation processes.

Figures

Figures reproduced from arXiv: 2501.00985 by the authors.

Figure 1
Figure 1. Sketch of the model, with the centrifugally accelerated co-rotating particles moving along straight magnetic field lines in the nearby zone of the LC area . 2 Discussion and results It is straightforward to show that, even for the conventional magnetic field [14], B ≃  2L r 2c 1/2 ≃ 10 ×  Rg r 1/3 G, (2) which is much weaker than the vortex-driven magnetic field (see Eq. (1)), relativistic protons remain closely… view at source ↗

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

33 extracted references · 33 canonical work pages

  1. [1]

    Kazunori, . et al. (EHT collaboration), 2022, ApJL, 930, 1

  2. [2]

    et al., 2023, MNRAS, 525, 561 6/7

    Evans, F.A. et al., 2023, MNRAS, 525, 561 6/7

  3. [3]

    & Feng, Y., 2024, MNRAS, 531, 3136

    Xi, L. & Feng, Y., 2024, MNRAS, 531, 3136

  4. [4]

    & Linden, T., 2024, PhRvD, 109, 123041

    John, I., Leane, R.K. & Linden, T., 2024, PhRvD, 109, 123041

  5. [5]

    & Zdziarski, A.A., 1987, ApJ, 319, 643

    Lightman A.P. & Zdziarski, A.A., 1987, ApJ, 319, 643

  6. [6]

    & Leiter, D., 1979, ApJ, 229, 46

    Kafatos, M. & Leiter, D., 1979, ApJ, 229, 46

  7. [7]

    & Chkheidze, N., 2021, Universe, 7, 33 1

    Osmanov, Z., Machabeli, G. & Chkheidze, N., 2021, Universe, 7, 33 1

  8. [8]

    & Rossi, P., 2023, Universe, 9, 487

    Osmanov, Z.N., Bodo, G. & Rossi, P., 2023, Universe, 9, 487

Show all 33 references
  1. [9]

    & Euler, H., 1936, Zeitschrift f¨ ur Physik, 98, 71 4

    Heisenberg, W. & Euler, H., 1936, Zeitschrift f¨ ur Physik, 98, 71 4

  2. [10]

    Sauter, F., 1931, Zeitschrift f¨ ur Physik, 69, 742

  3. [11]

    Schwinger, J., 1951, PhRv, 82, 664

  4. [12]

    Gold, T., 1969, Nature, 221, 25

  5. [13]

    & Znajek, R.L., 1977, MNRAS, 179, 433

    Blandford, R.D. & Znajek, R.L., 1977, MNRAS, 179, 433

  6. [14]

    & Bodo, G., 2007, A&A, 470, 395

    Osmanov, Z., Rogava, A. & Bodo, G., 2007, A&A, 470, 395

  7. [15]

    Osmanov, Z., 2008, ApJ, 15, 351

  8. [16]

    Osmanov, Z., 2008, MNRAS, 2008, 490, 487

  9. [17]

    & Chkheidze, N., 2014, M NRAS, 445, 4155

    Osmanov, Z., Mahajan, S., Machabeli, G. & Chkheidze, N., 2014, M NRAS, 445, 4155

  10. [18]

    & Machabeli, 2017, ApJ, 835, 4

    Osmanov, Z., Mahajan, S. & Machabeli, 2017, ApJ, 835, 4

  11. [19]

    & Zantedeschi, M., 2025, (submitted to J CAP), arXiv: 2502.15510

    Dvali G., Osmanov, Z.N. & Zantedeschi, M., 2025, (submitted to J CAP), arXiv: 2502.15510

  12. [20]

    Lakes, R., 1998, Phys.Rev.L, 80, 1826-1829

  13. [21]

    et al., 2003, Phys.Rev.L, 90, 081801

    Luo, J. et al., 2003, Phys.Rev.L, 90, 081801

  14. [22]

    & Zantedeschi, M., 2021, PhRvL, 129, 06130 2

    Dvali G., Kuhnel, F. & Zantedeschi, M., 2021, PhRvL, 129, 06130 2

  15. [23]

    Abramowski, A., 2016, Nature, 531, 476-479

  16. [24]

    Kerr, R.P., 1963, Phys.Rev.L, 11, 237

  17. [25]

    Bardeen, J.M., Press, W.H., Teukolsky, S.A., 1972, ApJ, 178, 347

  18. [26]

    Dokuchaev, V.I., 2014, Gen.Rel.Grav., 46, 1832

  19. [27]

    EHT collaboration, 2022, ApJl, 930, 14

  20. [28]

    WorldvScientific Publishing Co

    Aharonian, F.A., Very High Energy Cosmic Gamma Radiation - A Cruc ial Window on the Extreme Universe. WorldvScientific Publishing Co. Pte. Ltd. 2004

  21. [29]

    Osmanov, Z.N., 2021, Galaxies, 9, 6

  22. [30]

    & Julian, W.H., 1969, ApJ, 157, 869

    Goldreich, P. & Julian, W.H., 1969, ApJ, 157, 869

  23. [31]

    & Popov, M.S., 1977, Fortschritte der Physik, 25, 373-400

    Marinov, V.S. & Popov, M.S., 1977, Fortschritte der Physik, 25, 373-400

  24. [32]

    Svensson, R.,1982, ApJ, 258, 335

  25. [33]

    & Ostlie, Dale A.,An introduction to modern astr ophysics and cosmology, Pearson (2010) 7/7

    Carroll, Bradley W. & Ostlie, Dale A.,An introduction to modern astr ophysics and cosmology, Pearson (2010) 7/7

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.