Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Direct in situ observations of eruption-associated magnetic reconnection in the solar corona

Nature Astronomy volume 9, pages 1444–1454 (2025)Cite this article

Subjects

Abstract

Magnetic reconnection is a fundamental process within highly conductive plasmas. Oppositely oriented field lines are reconfigured, releasing stored magnetic energy. It plays a vital role in shaping the dynamics of the solar corona and provides one of the main mechanisms for releasing the stored energy that powers solar eruptions. Reconnection at the Sun has been studied using remote-sensing observations, but the Parker Solar Probe (PSP) now permits in situ sampling of reconnection-related plasma in the corona. Here we report on a PSP fly-through of a reconnecting current sheet in the corona during a major solar eruption on 5–6 September 2022. We find that even 24 h after the flare peak, PSP detected the reconnection exhaust, indicating continuing fast reconnection, which we confirmed using remote-sensing observations made by the Solar Orbiter. This reconnection persisted much longer than typical timescales of a few minutes to hours. Plasma parameters measured by PSP within the reconnection region match numerical simulations. These new observations provide a key bridge between theory and measurements of plasmas in the solar atmosphere, laboratory experiments and astrophysical systems, generating new constraints required for the refinement of models and for the strengthening of their links to observations at many scales.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to the full article PDF.

USD 39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: WISPR images of CME and post-eruptive flows in the corona.
Fig. 2: Evolution of flare ribbons observed by the full Sun imager onboard SolO/FSI.
Fig. 3: In situ measurements of plasma and magnetic field compared to trajectory of PSP through the corona.
Fig. 4: Comparison of observed in situ parameters with the output from a numerical model.

Similar content being viewed by others

Data availability

The PSP mission data used in this study are openly available at the CDAWeb of the NASA Space Physics Data Facility (https://cdaweb.gsfc.nasa.gov/). The SolO mission data are openly available in the ESA Solar Orbiter Archive (https://soar.esac.esa.int/soar/). The simulation data will be shared upon request to author X.X. (xiaoyan.xie@cfa.harvard.edu).

Code availability

The codes used for reducing and analysing the data are available as part of the SolarSoft library (https://www.lmsal.com/solarsoft/sswdb_description.html). The public version of the NIRVANA code is available on the GitLab repository (https://gitlab.aip.de/ziegler/NIRVANA). Python packages Astropy (v.5.1, https://github.com/astropy/astropy), Astrospice (v.0.2, now archived, https://github.com/astrospice/astrospice/tree/main/astrospice), Pyspedas (v.4.1.0, https://github.com/spedas/pyspedas), Matplotlib (v3.5.2, https://github.com/matplotlib/matplotlib) and Sunpy (v.5.0, https://github.com/sunpy/sunpy) were used in creating some of the figures.

References

  1. Sweet, P. A. Electromagnetic phenomena in cosmical physics. In Proc. IAU Symposium No 6 (ed. Lehnert, B.) 123 (Cambridge University Press, 1958).

  2. Parker, E. N. Sweet’s mechanism for merging magnetic fields in conducting fluids. J. Geophys. Res. 62, 509–520 (1957).

    ADS  Google Scholar 

  3. Petschek, H. E. Magnetic field annihilation. In Proc. AAS-NASA Symposium on the Physics of Solar Flares (ed. Hess, W. N.) 425–439 (NASA, 1964).

  4. Sturrock, P. A. Model of the high-energy phase of solar flares. Nature 211, 695–697 (1966).

    ADS  Google Scholar 

  5. Kopp, R. A. & Pneuman, G. W. Magnetic reconnection in the corona and the loop prominence phenomenon. Sol. Phys. 50, 85–98 (1976).

    ADS  Google Scholar 

  6. Shibata, K. & Tanuma, S. Plasmoid-induced-reconnection and fractal reconnection. Earth Planets Space 53, 473–482 (2001).

    ADS  Google Scholar 

  7. Bhattacharjee, A. Impulsive magnetic reconnection in the Earth’s magnetotail and the solar corona. Annu. Rev. Astron. Astrophys. 42, 365–384 (2004).

    ADS  Google Scholar 

  8. Cassak, P. A. & Shay, M. A. Magnetic reconnection for coronal conditions: reconnection rates, secondary islands and onset. Space Sci. Rev. 172, 283–302 (2012).

    ADS  Google Scholar 

  9. Su, Y. et al. Imaging coronal magnetic-field reconnection in a solar flare. Nat. Phys. 9, 489–493 (2013).

    Google Scholar 

  10. Reeves, K. K., McCauley, P. I. & Tian, H. Direct observations of magnetic reconnection outflow and CME triggering in a small erupting solar prominence. Astrophys. J. 807, 7 (2015).

    ADS  Google Scholar 

  11. Patel, R., Pant, V., Chandrashekhar, K. & Banerjee, D. A statistical study of plasmoids associated with a post-CME current sheet. Astron. Astrophys. 644, A158 (2020).

    ADS  Google Scholar 

  12. Chen, B. et al. Measurement of magnetic field and relativistic electrons along a solar flare current sheet. Nat. Astron. 4, 1140–1147 (2020).

    ADS  Google Scholar 

  13. Yan, X. et al. Fast plasmoid-mediated reconnection in a solar flare. Nat. Commun. 13, 640 (2022).

    ADS  Google Scholar 

  14. Gosling, J. T., Skoug, R. M., McComas, D. J. & Smith, C. W. Direct evidence for magnetic reconnection in the solar wind near 1 au. J. Geophys. Res.: Space Phys. 110, A01107 (2005).

    ADS  Google Scholar 

  15. Gosling, J. T., Skoug, R. M., McComas, D. J. & Smith, C. W. Magnetic disconnection from the Sun: observations of a reconnection exhaust in the solar wind at the heliospheric current sheet. Geophys. Res. Lett. 32, L05105 (2005).

    ADS  Google Scholar 

  16. Phan, T. D. et al. Parker Solar Probe in situ observations of magnetic reconnection exhausts during Encounter 1. Astrophys. J. Suppl. Ser. 246, 34 (2020).

    ADS  Google Scholar 

  17. Lin, J. & Forbes, T. G. Effects of reconnection on the coronal mass ejection process. J. Geophys. Res. 105, 2375–2392 (2000).

    ADS  Google Scholar 

  18. Øieroset, M., Phan, T. D., Fujimoto, M., Lin, R. P. & Lepping, R. P. In situ detection of collisionless reconnection in the Earth’s magnetotail. Nature 412, 414–417 (2001).

    ADS  Google Scholar 

  19. Burch, J. L. et al. Electron-scale measurements of magnetic reconnection in space. Science 352, aaf2939 (2016).

    ADS  Google Scholar 

  20. Torbert, R. B. et al. Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space. Science 362, 1391–1395 (2018).

    ADS  MathSciNet  Google Scholar 

  21. Eastwood, J. P. et al. Evidence for collisionless magnetic reconnection at Mars. Geophys. Res. Lett. 35, L02106 (2008).

    ADS  Google Scholar 

  22. Zhang, T. L. et al. Magnetic reconnection in the near Venusian magnetotail. Science 336, 567 (2012).

    ADS  Google Scholar 

  23. Arridge, C. S. et al. Cassini in situ observations of long-duration magnetic reconnection in Saturn’s magnetotail. Nat. Phys. 12, 268–271 (2016).

    Google Scholar 

  24. Hanasz, M. & Lesch, H. Conditions for fast magnetic reconnection in astrophysical plasmas. Astron. Astrophys. 404, 389–395 (2003).

    ADS  Google Scholar 

  25. Weżgowiec, M., Ehle, M. & Beck, R. Hot gas and magnetic arms of NGC 6946: indications for reconnection heating? Astron. Astrophys. 585, A3 (2016).

    ADS  Google Scholar 

  26. Ripperda, B., Bacchini, F. & Philippov, A. A. Magnetic reconnection and hot spot formation in black hole accretion disks. Astrophys. J. 900, 100 (2020).

    ADS  Google Scholar 

  27. Shukla, A. & Mannheim, K. Gamma-ray flares from relativistic magnetic reconnection in the jet of the quasar 3C 279. Nat. Commun. 11, 4176 (2020).

    ADS  Google Scholar 

  28. Aimar, N. et al. Magnetic reconnection plasmoid model for Sagittarius A* flares. Astron. Astrophys. 672, A62 (2023).

    Google Scholar 

  29. Bhattacharjee, A., Huang, Y.-M., Yang, H. & Rogers, B. Fast reconnection in high-Lundquist-number plasmas due to the plasmoid Instability. Phys. Plasmas 16, 112102 (2009).

    ADS  Google Scholar 

  30. Forbes, T. G., Seaton, D. B. & Reeves, K. K. Reconnection in the post-impulsive phase of solar flares. Astrophys. J. 858, 70 (2018).

    ADS  Google Scholar 

  31. Yamada, M. et al. Study of driven magnetic reconnection in a laboratory plasma. Phys. Plasmas 4, 1936–1944 (1997).

    ADS  Google Scholar 

  32. Bolaños, S. et al. Laboratory evidence of magnetic reconnection hampered in obliquely interacting flux tubes. Nat. Commun. 13, 6426 (2022).

    ADS  Google Scholar 

  33. Zhang, Y., Pree, S. & Bellan, P. M. Generation of laboratory nanoflares from multiple braided plasma loops. Nat. Astron. 7, 655–661 (2023).

    ADS  Google Scholar 

  34. Ji, H. et al. Laboratory study of collisionless magnetic reconnection. Space Sci. Rev. 219, 76 (2023).

    ADS  Google Scholar 

  35. Fox, N. J. et al. The Solar Probe Plus Mission: humanity’s first visit to our star. Space Sci. Rev. 204, 7–48 (2016).

    ADS  Google Scholar 

  36. Patel, R. et al. The closest view of a fast coronal mass ejection: how faulty assumptions near perihelion lead to unrealistic interpretations of PSP/WISPR observations. Astrophys. J. Lett. 955, L1 (2023).

    ADS  Google Scholar 

  37. García Marirrodriga, C. et al. Solar Orbiter: mission and spacecraft design. Astron. Astrophys. 646, A121 (2021).

    Google Scholar 

  38. West, M. J. & Seaton, D. B. SWAP observations of post-flare giant arches in the long-duration 14 October 2014 solar eruption. Astrophys. J. Lett. 801, L6 (2015).

    ADS  Google Scholar 

  39. French, R. J., Matthews, S. A., van Driel-Gesztelyi, L., Long, D. M. & Judge, P. G. Dynamics of late-stage reconnection in the 2017 September 10 solar flare. Astrophys. J. 900, 192 (2020).

    ADS  Google Scholar 

  40. Long, D. M. et al. The eruption of a magnetic flux rope observed by Solar Orbiter and Parker Solar Probe. Astrophys. J. 955, 152 (2023).

    ADS  Google Scholar 

  41. Vourlidas, A. et al. The Wide-Field Imager for Solar Probe Plus (WISPR). Space Sci. Rev. 204, 83–130 (2016).

    ADS  Google Scholar 

  42. Howard, R. A. et al. Overview of the remote sensing observations from PSP Solar Encounter 10 with perihelion at 13.3 R⊙. Astrophys. J. 936, 43 (2022).

    ADS  Google Scholar 

  43. Romeo, O. M. et al. Near-Sun in situ and remote-sensing observations of a coronal mass ejection and its effect on the heliospheric current sheet. Astrophys. J. 954, 168 (2023).

    ADS  Google Scholar 

  44. Rochus, P. et al. The Solar Orbiter EUI instrument: the extreme ultraviolet imager. Astron. Astrophys. 642, A8 (2020).

    Google Scholar 

  45. de Jager, C. & Svestka, Z. 21 May 1980 flare review. Sol. Phys. 100, 435 (1985).

    ADS  Google Scholar 

  46. Noglik, J. B., Walsh, R. W. & Ireland, J. Indirect calculation of the magnetic reconnection rate from flare loops. Astron. Astrophys. 441, 353–360 (2005).

    ADS  Google Scholar 

  47. Savage, S. L., McKenzie, D. E., Reeves, K. K., Forbes, T. G. & Longcope, D. W. Reconnection outflows and current sheet observed with Hinode/XRT in the 2008 April 9 ‘cartwheel CME’ flare. Astrophys. J. 722, 329–342 (2010).

    ADS  Google Scholar 

  48. Cheng, X. et al. Observations of turbulent magnetic reconnection within a solar current sheet. Astrophys. J. 866, 64 (2018).

    ADS  Google Scholar 

  49. Solanki, S. K. et al. The polarimetric and helioseismic imager on Solar Orbiter. Astron. Astrophys. 642, A11 (2020).

    Google Scholar 

  50. Badman, S. T. et al. Prediction and verification of Parker Solar Probe Solar wind sources at 13.3 R⊙. J. Geophys. Res.: Space Phys. 128, e2023JA031359 (2023).

    ADS  Google Scholar 

  51. Bale, S. D. et al. The FIELDS instrument suite for Solar Probe Plus. Measuring the coronal plasma and magnetic field, plasma waves and turbulence, and radio signatures of solar transients. Space Sci. Rev. 204, 49–82 (2016).

    ADS  Google Scholar 

  52. Kasper, J. C. et al. Solar Wind Electrons Alphas and Protons (SWEAP) investigation: design of the solar wind and coronal plasma instrument suite for Solar Probe Plus. Space Sci. Rev. 204, 131–186 (2016).

    ADS  Google Scholar 

  53. Rivera, Y. J. et al. In situ observations of large-amplitude Alfvén waves heating and accelerating the solar wind. Science 385, 962–966 (2024).

    ADS  Google Scholar 

  54. Gosling, J. T. et al. Bidirectional solar wind electron heat flux events. J. Geophys. Res. 92, 8519–8535 (1987).

    ADS  Google Scholar 

  55. Chen, Y. et al. Can the Parker Solar Probe detect a CME-flare current sheet? Astrophys. J. Suppl. Ser. 269, 22 (2023).

    ADS  Google Scholar 

  56. Liu, Y.-H. et al. First-principles theory of the rate of magnetic reconnection in magnetospheric and solar plasmas. Commun. Phys. 5, 97 (2022).

    Google Scholar 

  57. Daughton, W. et al. Role of electron physics in the development of turbulent magnetic reconnection in collisionless plasmas. Nat. Phys. 7, 539–542 (2011).

    Google Scholar 

  58. Carcaboso, F. et al. Characterisation of suprathermal electron pitch-angle distributions. Bidirectional and isotropic periods in solar wind. Astron. Astrophys. 635, A79 (2020).

    Google Scholar 

  59. Mei, Z. X., Keppens, R., Roussev, I. I. & Lin, J. Magnetic reconnection during eruptive magnetic flux ropes. Astron. Astrophys. 604, L7 (2017).

    ADS  Google Scholar 

  60. Mei, Z. et al. Numerical simulation on the leading edge of coronal mass ejection in the near-Sun region. Astrophys. J. 958, 15 (2023).

    ADS  Google Scholar 

  61. Forbes, T. G. & Lin, J. What can we learn about reconnection from coronal mass ejections? J. Atmos. Sol.-Terr. Phys. 62, 1499–1507 (2000).

    ADS  Google Scholar 

  62. Liu, Y. D. et al. Direct in situ measurements of a fast coronal mass ejection and associated structures in the corona. Astrophys. J. 963, 85 (2024).

    ADS  Google Scholar 

  63. Thernisien, A. F. R., Howard, R. A. & Vourlidas, A. Modeling of flux rope coronal mass ejections. Astrophys. J. 652, 763–773 (2006).

    ADS  Google Scholar 

  64. Moore, R. L., Sterling, A. C., Hudson, H. S. & Lemen, J. R. Onset of the magnetic explosion in solar flares and coronal mass ejections. Astrophys. J. 552, 833–848 (2001).

    ADS  Google Scholar 

  65. Huang, J. et al. Parker Solar Probe observations of high plasma β solar wind from the streamer belt. Astrophys. J. Suppl. Ser. 265, 47 (2023).

    ADS  Google Scholar 

  66. Yokoyama, T. & Shibata, K. Magnetohydrodynamic simulation of a solar flare with chromospheric evaporation effect based on the magnetic reconnection model. Astrophys. J. 549, 1160–1174 (2001).

    ADS  Google Scholar 

  67. Ni, L., Kliem, B., Lin, J. & Wu, N. Fast magnetic reconnection in the solar chromosphere mediated by the plasmoid instability. Astrophys. J. 799, 79 (2015).

    ADS  Google Scholar 

  68. Isobe, H. et al. Reconnection rate in the decay phase of a long duration event flare on 1997 May 12. Astrophys. J. 566, 528–538 (2002).

    ADS  Google Scholar 

  69. Ramesh, R., Narayanan, A. S., Kathiravan, C., Sastry, C. V. & Shankar, N. U. An estimation of the plasma parameters in the solar corona using quasi-periodic metric type III radio burst emission. Astron. Astrophys. 431, 353–357 (2005).

    ADS  Google Scholar 

  70. Czaykowska, A., Alexander, D. & De Pontieu, B. Chromospheric heating in the late phase of two-ribbon flares. Astrophys. J. 552, 849–857 (2001).

    ADS  Google Scholar 

  71. Ziegler, U. The NIRVANA code: parallel computational MHD with adaptive mesh refinement. Comput. Phys. Commun. 179, 227–244 (2008).

    ADS  MathSciNet  Google Scholar 

  72. Forbes, T. G. Magnetic reconnection in solar flares. Geophys. Astrophys. Fluid Dyn. 62, 15–36 (1991).

    ADS  Google Scholar 

  73. Sittler Jr, E. C. & Guhathakurta, M. Semiempirical two-dimensional magnetohydrodynamic model of the solar corona and interplanetary medium. Astrophys. J. 523, 812–826 (1999).

    ADS  Google Scholar 

  74. Xie, X. et al. Numerical experiments on dynamic evolution of a CME-flare current sheet. Mon. Not. R. Astron. Soc. 509, 406–420 (2022).

    ADS  Google Scholar 

Download references

Acknowledgements

We thank T. G. Forbes, N. E. Raouafi and Z. Mei for helpful discussions while we carried out the analysis for this paper. This work originally developed during the team meetings of the Connect programme of NASA’s Heliophysics System Observatory: Energetics of solar eruptions from the chromosphere to the inner heliosphere project, supported by Grant No. 80NSSC20K1283. The WISPR, FIELDS and SWEAP suites were designed, developed and are operated under NASA contract NNN06AA01C. We acknowledge the extraordinary contributions of the PSP mission operations and spacecraft engineering team at the Johns Hopkins University Applied Physics Laboratory. The PSP was designed, built and is now operated by the Johns Hopkins University Applied Physics Laboratory as part of NASA’s Living with a Star programme (Contract No. NNN06AA01C). The EUI instrument was built by CSL, IAS, MPS, MSSL/UCL, PMOD/WRC, ROB, LCF/IO with funding from the Belgian Federal Science Policy Office (Grant Nos. BELSPO/PRODEX PEA 4000134088, 4000112292, 4000117262 and 4000134474); the Centre National d’Etudes Spatiales (CNES); the UK Space Agency; the Bundesministerium für Wirtschaft und Energie (BMWi) through the Deutsches Zentrum für Luft- und Raumfahrt (DLR); and the Swiss Space Office. The space mission SolO is the result of an international collaboration between ESA and NASA, and it is operated by ESA. The NIRVANA code was developed by U. Ziegler at the Leibniz Institute for Astrophysics Potsdam. We are grateful to the ESA SOC and MOC teams for their support. The German contribution to SO/PHI is funded by the BMWi through DLR and by MPG central funds. The Spanish contribution is funded by AEI/MCIN/10.13039/501100011033/ and the European Union Next Generation EU/PRTR (Grant Nos. RTI2018-096886-C5, PID2021-125325OB-C5, PCI2022-135009-2 and PCI2022-135029-2) and ERDF – A way of making Europe; Center of Excellence Severo Ochoa awards to IAA-CSIC (SEV-2017-0709, CEX2021-001131-S); and a Ramón y Cajal fellowship awarded to D.O.S. The French contribution is funded by CNES. R.P., D.B.S., M.J.W., K.K.R., S.R., X.X. and T.N. were supported by the Connect programme of NASA’s Heliophysics System Observatory (Grant No. 80NSSC20K1283). S.T.B. and Y.J.R. were supported by the PSP project through the SAO/SWEAP (Subcontract No. 975569). G.S. was supported by WISPR Phase-E funds. P.H. is funded by the Office of Naval Research. This project has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 101097844 for project WINSUN).

Author information

Authors and Affiliations

  1. Department of Solar and Heliospheric Physics, Southwest Research Institute, Boulder, CO, US

    Ritesh Patel, Daniel B. Seaton & Matthew J. West

  2. Center for Astrophysics ∣ Harvard & Smithsonian, Cambridge, MA, US

    Tatiana Niembro, Xiaoyan Xie, Samuel T. Badman, Soumya Roy, Yeimy J. Rivera & Katharine K. Reeves

  3. Inter-University Centre for Astronomy and Astrophysics, Pune, India

    Soumya Roy

  4. Johns Hopkins Applied Physics Laboratory, Laurel, MD, US

    Guillermo Stenborg

  5. US Naval Research Laboratory, Washington, DC, US

    Phillip Hess

  6. Max Planck Institute for Solar System Research, Göttingen, Germany

    Alex Feller, Johann Hirzberger, Sami K. Solanki & Gherardo Valori

  7. Instituto de Astrofísica de Andalucía (IAA-CSIC), Granada, Spain

    David Orozco Suárez & Hanna Strecker

Authors
  1. Ritesh Patel
    View author publications

    Search author on:PubMed Google Scholar

  2. Tatiana Niembro
    View author publications

    Search author on:PubMed Google Scholar

  3. Xiaoyan Xie
    View author publications

    Search author on:PubMed Google Scholar

  4. Daniel B. Seaton
    View author publications

    Search author on:PubMed Google Scholar

  5. Samuel T. Badman
    View author publications

    Search author on:PubMed Google Scholar

  6. Soumya Roy
    View author publications

    Search author on:PubMed Google Scholar

  7. Yeimy J. Rivera
    View author publications

    Search author on:PubMed Google Scholar

  8. Katharine K. Reeves
    View author publications

    Search author on:PubMed Google Scholar

  9. Guillermo Stenborg
    View author publications

    Search author on:PubMed Google Scholar

  10. Phillip Hess
    View author publications

    Search author on:PubMed Google Scholar

  11. Matthew J. West
    View author publications

    Search author on:PubMed Google Scholar

  12. Alex Feller
    View author publications

    Search author on:PubMed Google Scholar

  13. Johann Hirzberger
    View author publications

    Search author on:PubMed Google Scholar

  14. David Orozco Suárez
    View author publications

    Search author on:PubMed Google Scholar

  15. Sami K. Solanki
    View author publications

    Search author on:PubMed Google Scholar

  16. Hanna Strecker
    View author publications

    Search author on:PubMed Google Scholar

  17. Gherardo Valori
    View author publications

    Search author on:PubMed Google Scholar

Contributions

R.P. led the work, carried out the analysis of the remote-sensing data and led the preparation of the paper. T.N. carried out the analysis of PSP in situ data. X.X. carried out the numerical simulation and provided its results. D.B.S. contributed towards the interpretation of the data, models and results and worked on improving the figures. S.T.B. performed the ballistic projection of the magnetogram data. S.R. interpreted the flare energetics. Y.J.R. helped interpretation of in situ signatures and results. K.K.R. interpreted the data, models and results. G.S. processed the WISPR data and provided its outputs. P.H. and M.J.W. helped in interpreting the WISPR and EUI data, respectively. A.F., J.H., D.O.S., S.K.S., H.S. and G.V. processed and provided SO/PHI data. All authors participated in discussing the results and writing the draft.

Corresponding author

Correspondence to Ritesh Patel.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Astronomy thanks Philippa Browning and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Additional plasma parameters based on PSP measurements.

(a) PSP in situ measurement of BR on 6 September 2022 from 17:25 to 17:45 UT, the time period used for generating PSP data plots in Fig. 4, right panel, shown in red for consistency with Figs. 3 and 4. Derived parameters in panels (b - e) are Alfvén speed (VA), total pressure (PTOTAL), proton plasma beta (ß) and Alfvén Mach number (MA) respectively during this period. The vertical dashed line at 17:35 UT is the same reference time as in Fig. 3.

Extended Data Fig. 2 Schematic of the September 5, 2022 CME.

The dimensions are not to scale and have been exaggerated to visualize the extent of the CME, current sheet and PSP orbit plane in the context of the CME source region. Even though the source region (shown with the red-blue pair of filled circles) is in the southern hemisphere, the CME is wide enough that PSP crosses its associated current sheet. The light blue triangle shows the part of the current sheet lying above the plane along the vector radial to the source region, whereas the magenta region is below that plane. The black arrow at the top of the sphere and the solid black curve near the center represent the solar north pole and equator, respectively. The gray shaded region bound by a dashed line shows PSP’s orbit plane. Note that in the real scenario, the active region is more complex (Fig. 3b), and the flare loops arcade shows inclined orientation as shown in Fig. 2. For simplicity, here we only show a portion of the complicated arcade system, which should not be confused with the loops orientation seen in EUI images. Further, the flux rope structure has traveled well out into interplanetary space.

Extended Data Fig. 3 Spatial distributions and parameter profiles from the 2.5D magnetohydrodynamic models.

The left panel shows a snapshot of the distributions of density (color shading) and magnetic field (solid curves) at 1641 s. Reference coordinates in R and T direction with respect to PSP are shown in the top left corner of this panel. Magnetic field, speed, density, temperature and current density as a function of distance are plotted from left to right panels along inclined cuts marked with black arrows at different heights for comparison. Note that the distance in these panels from 0 to 20 Mm in the horizontal axis corresponds to x = 10 Mm to x = -10 Mm in the left panel, that is from right to left along the black arrow. The same is applicable to the right panel based on PSP measurements, where the time axis is converted to distance.

Supplementary information

Supplementary Video 1

Imaging observation from 12:00 ut on 5 September 2022 to 23:14 ut on 6 September 2022 by the WISPR-I telescope of PSP. Snapshots of this video at various timestamps are shown in Fig. 1.

Supplementary Video 2

The evolution of the active region of interest. The left panel shows SO/PHI observations that are related to Fig. 3b. The middle and right panels show FSI observations of the same region at 174 and 304 Å, respectively. Stills from these two panels are shown in Fig. 2b,c and 2e,f, respectively.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Patel, R., Niembro, T., Xie, X. et al. Direct in situ observations of eruption-associated magnetic reconnection in the solar corona. Nat Astron 9, 1444–1454 (2025). https://doi.org/10.1038/s41550-025-02623-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • Version of record:

  • Issue date:

  • DOI: https://doi.org/10.1038/s41550-025-02623-6

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing