The Earth’s magnetosphere is the outermost layer of the geospace system deflecting energetic charged particles from the Sun and solar wind. The solar wind has major impacts on the Earth’s magnetosphere, but it is unclear whether the same holds for solar flares—a sudden eruption of electromagnetic radiation on the Sun. Here we use a recently developed whole geospace model combined with observational data from the 6 September 2017 X9.3 solar flare event to reveal solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and its adjacent ionosphere, the ionized part of Earth’s upper atmosphere. We observe a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 km and 150 km. This reduces the efficiency of mechanical energy conversion in the dayside solar wind–magnetosphere interaction, resulting in less Joule heating of the Earth’s upper atmosphere, a reconfiguration of magnetosphere convection, as well as changes in dayside and nightside auroral precipitation. This work thus demonstrates that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited—as previously believed—to the atmospheric region where radiation energy is absorbed1.
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Source data are provided with this paper. All other used data are available from the corresponding author upon reasonable request. The GNSS TEC and AMPERE FACs datasets are available from http://millstonehill.haystack.mit.edu/ and http://ampere.jhuapl.edu/. EISCAT radar and Inuvik high-frequency radar data are available from https://portal.eiscat.se/madrigal/ and http://vt.superdarn.org/tiki-index.php?page=DaViT+RTP, respectively. THEMIS data are available from http://themis.ssl.berkeley.edu. OMNI solar wind data are available from the CDAWeb website (https://cdaweb.gsfc.nasa.gov/index.html/). Solar irradiance data are provided by the NOAA National Geophysical Data Center (NGDC) GOES website (https://www.ngdc.noaa.gov/stp/satellite/goes/index.html).
The computer code (LTR) to simulate the geospace response to solar flares is available from the corresponding author upon request.
Tsurutani, B. T. et al. A brief review of ‘solar flare effects’ on the ionosphere. Radio Sci. 44, RS0A17 (2009).
Liu, J. Y. et al. Solar flare signatures of the ionospheric GPS total electron content. J. Geophys. Res. 111, A05308 (2006).
Le, H., Ren, Z., Liu, L., Chen, Y. & Zhang, H. Global thermospheric disturbances induced by a solar flare: a modeling study. Earth Planets Space 67, 3 (2015).
Liu, H., Lühr, H., Watanabe, S., Köhler, W. & Manoj, C. Contrasting behavior of the thermosphere and ionosphere in response to the 28 October 2003 solar flare. J. Geophys. Res. 112, A07305 (2007).
Sutton, E. K., Forbes, J. M., Nerem, R. S. & Woods, T. N. Neutral density response to the solar flares of October and November, 2003. Geophys. Res. Lett. 33, L22101 (2006).
Qian, L., Burns, A. G., Chamberlin, P. C. & Solomon, S. C. Variability of thermosphere and ionosphere responses to solar flares. J. Geophys. Res. 116, A10309 (2011).
Zhang, D. H. et al. Impact factor for the ionospheric total electron content response to solar flare irradiation. J. Geophys. Res. 116, A04311 (2011).
Pembroke, A. et al. Initial results from a dynamic coupled magnetosphere-ionosphere-ring current model. J. Geophys. Res. 117, A02211 (2012).
Glocer, A. et al. CRCM + BATS-R-US two-way coupling. J. Geophys. Res. 118, 1635–1650 (2013).
Lyon, J. G., Fedder, J. A. & Mobarry, C. M. The Lyon–Fedder–Mobarry (LFM) global MHD magnetospheric simulation code. J. Atmos. Sol. Terr. Phys. 66, 1333–1350 (2004).
De Zeeuw, D. L. et al. Coupling of a global MHD code and an inner magnetospheric model: initial results. J. Geophys. Res. 109, A12219 (2004).
Berdermann, J. et al. Ionospheric response to the X9.3 flare on 6 September 2017 and its implication for navigation services over Europe. Space Weather 16, 1604–1615 (2018).
Qian, L. et al. Solar flare and geomagnetic storm effects on the thermosphere and ionosphere during 6–11 September 2017. J. Geophys. Res. 124, 2298–2311 (2019).
Yamauchi, M. et al. Ionospheric response observed by EISCAT during the 6–8 September 2017 space weather event: overview. Space Weather 16, 1437–1450 (2018).
Ridley, A., Gombosi, T. & Dezeeuw, D. Ionospheric control of the magnetosphere: conductance. Ann. Geophys. 22, 567–584 (2004).
Wiltberger, M., Weigel, R. S., Lotko, W. & Fedder, J. A. Modeling seasonal variations of auroral particle precipitation in a global-scale magnetosphere-ionosphere simulation. J. Geophys. Res. 114, A01204 (2009).
Merkin, V. G. et al. Global evolution of Birkeland currents on 10 min timescales: MHD simulations and observations. J. Geophys. Res. 118, 4977–4997 (2013).
Borovsky, J. E., Lavraud, B. & Kuznetsova, M. M. Polar cap potential saturation, dayside reconnection, and changes to the magnetosphere. J. Geophys. Res. 114, A03224 (2009).
Lotko, W. et al. Ionospheric control of magnetotail reconnection. Science 345, 184–187 (2014).
Förster, M., Doornbos, E. & Haaland, S. in Dawn–Dusk Asymmetries in Planetary Plasma Environments (eds Haaland, S. et al.) Ch. 10, 125–142 (Geophysical Monograph Series, John Wiley Publications, 2017).
Paschmann, G. et al. Plasma acceleration at the Earth’s magnetopause: evidence for magnetic reconnection. Nature 282, 243–246 (1979).
Chen, L. et al. Electron bulk acceleration and thermalization at Earth’s quasiperpendicular bow shock. Phys. Rev. Lett. 120, 225101 (2018).
Fedder, J. A. & Lyon, J. G. The solar wind-magnetosphere-ionosphere current-voltage relationship. Geophys. Res. Lett. 14, 880–883 (1987).
Kozyra, J. U. et al. Effects of a high-density plasma sheet on ring current development during the November 2–6, 1993, magnetic storm. J. Geophys. Res. 103, 26285–26305 (1998).
Turner, N. E., Cramer, W. D., Earles, S. K. & Emery, B. A. Geoefficiency and energy partitioning in CIR-driven and CME-driven storms. J. Atmos. Sol. Terr. Phys. 71, 1023–1031 (2009).
Clausen, L. B. N., Baker, J. B. H., Ruohoniemi, J. M., Milan, S. E. & Anderson, B. J. Dynamics of the region 1 Birkeland current oval derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). J. Geophys. Res. 117, A06233 (2012).
Roble, R. G., Ridley, E. C., Richmond, A. D. & Dickinson, R. E. A coupled thermosphere/ionosphere general circulation model. Geophys. Res. Lett. 15, 1325–1328 (1988).
Richmond, A. D., Ridley, E. C. & Roble, R. G. A thermosphere/ionosphere general circulation model with coupled electrodynamics. Geophys. Res. Lett. 19, 601–604 (1992).
Toffoletto, F., Sazykin, S., Spiro, R. & Wolf, R. Inner magnetospheric modeling with the Rice Convection Model. Space Sci. Rev. 107, 175–196 (2003).
Merkin, V. G. & Lyon, J. G. Effects of the low-latitude ionospheric boundary condition on the global magnetosphere. J. Geophys. Res. 115, A10202 (2000).
Wang, W. et al. Initial results from the coupled magnetosphere–ionosphere–thermosphere model: thermosphere–ionosphere responses. J. Atmos. Sol. Terr. Phys. 66, 1425–1441 (2004).
Lin, D. et al. SAPS in the 17 March 2013 storm event: initial results from the coupled magnetosphere–ionosphere–thermosphere model. J. Geophys. Res. 124, 6212–6225 (2019).
Wang, W. et al. Ionospheric electric field variations during a geomagnetic storm simulated by a coupled magnetosphere ionosphere thermosphere (CMIT) model. Geophys. Res. Lett. 35, L18105 (2008).
Zhang, B. et al. Electron precipitation models in global magnetosphere simulations. J. Geophys. Res. 120, 1035–1056 (2015).
Cnossen, I. & Förster, M. North–south asymmetries in the polar thermosphere-ionosphere system: solar cycle and seasonal influences. J. Geophys. Res. 121, 612–627 (2016).
Chamberlin, P. C., Woods, T. N. & Eparvier, F. G. Flare Irradiance Spectral Model (FISM): daily component algorithms and results. Space Weather 5, S05001 (2007).
Chamberlin, P. C., Woods, T. N. & Eparvier, F. G. Flare Irradiance Spectral Model (FISM): flare component algorithms and results. Space Weather 6, S05001 (2008).
Woods, T. N. et al. The Solar EUV Experiment (SEE): mission overview and first results. J. Geophys. Res. 110, A01312 (2005).
Solomon, S. C. & Qian, L. Solar extreme-ultraviolet irradiance for general circulation models. J. Geophys. Res. 110, A10306 (2005).
Coster, A. & Komjathy, A. Space weather and the global positioning system. Space Weather 6, S06D04 (2008).
Lotko, W. The unifying principle of coordinated measurements in geospace science. Space Weather 15, 553–557 (2017).
Anderson, B. J. et al. Development of large-scale Birkeland currents determined from the Active Magnetosphere and Planetary Electrodynamics Response Experiment. Geophys. Res. Lett. 41, 3017–3025 (2014).
Shepherd, S. G. Altitude-adjusted corrected geomagnetic coordinates: definition and functional approximations. J. Geophys. Res. 119, 7501–7521 (2014).
Knipp, D. et al. Comparison of magnetic perturbation data from LEO satellite constellations: statistics of DMSP and AMPERE. Space Weather 12, 2–23 (2014).
This work is supported by the Strategic Priority Research Program of Chinese Academy of Sciences grant no. XDB 41000000, NSF of China 42074188 and 42030202, and US NSF Awards 1739188, 1522133 and AGS1452309. We acknowledge the use of data from the Chinese Meridian Project. We thank Q. Shi and W. Shang for helpful discussions.
The authors declare no competing interests.
Peer review information Nature Physics thanks Matthias Förster and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
a, Interplanetary magnetic field components, Bx, By, and Bz in nT; b, solar wind number density in cm−3; c, solar wind velocity components, Vx, Vy, and Vz in km/s; and (d) X-ray intensity on September 6, 2017 integrated over wavelengths from 0.1 to 0.8 nm observed by the GOES satellite (red line), calculated from FISM (blue line), and without solar flare effects (black line). Horizontal dotted lines represent zero Y-axis reference lines in panels a and c.
Universal time and altitude variations of electron density (Ne), electron temperature (Te), and ion temperature (Ti) from LTR flare simulations (left panels) and EISCAT Tromsø VHF radar (right panels) on 6 September 2017. Since the VHF radar was pointing at geographic north with 30° elevation angle, the latitudinal coverage is about 69°–72° for 80–400 km altitude.
Comparison of 10-minute average LTR simulated Hall ∑H conductance for pre-flare (11:44–11:53 UT, a, flare-peak (12:10–12:19 UT, b, intervals on September 6, 2017. Polar plots are in magnetic latitude-local time (MLT) coordinates as in panel a.
From top to bottom are magnitude of magnetic field a, e, ion density b, f, bulk flow c, g, and ion spectra d, h. The four horizontal axes in the bottom panels stand for X (Xgsm), Y (Ygsm), and Z (Zgsm) components in the Geocentric Solar Magnetospheric System coordinate, and universal time (UT).
Numerical simulated TEC used to generate Fig. 1.
Numerical simulated FACs used to generate Fig. 2.
Numerical simulated velocity used to generate Fig. 3.
Numerical simulated CPCP and Joule heating rate used to generate Fig. 4.
Numerical simulated Ne, Te and Ti used to generate Extended Data Fig. 2.
Numerical simulated Hall conductance used to generate Extended Data Fig. 3.
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Liu, J., Wang, W., Qian, L. et al. Solar flare effects in the Earth’s magnetosphere. Nat. Phys. 17, 807–812 (2021). https://doi.org/10.1038/s41567-021-01203-5