The 04 – 10 September 2017 Sun–Earth Connection Events: Solar Flares, Coronal Mass Ejections/Magnetic Clouds, and Geomagnetic Storms

dc.contributor.authorWu, Chin-Chun
dc.contributor.authorLiou, Kan
dc.contributor.authorLepping, Ronald P.
dc.contributor.authorHutting, Lynn
dc.description.abstractIn early September 2017, a series of solar flares and coronal mass ejections (CMEs) erupted from the Sun. The Cor2a coronagraph, a unit of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI), onboard the Solar Terrestrial Relations Observatory (STEREO)-A spacecraft recorded two Sun–Earth-directed CMEs on 4 September (referred to as CME04) and 6 September (referred to as CME06). A few days later, the Wind spacecraft ( ≈212.4 solar radii: R⊙ ) recorded two interplanetary shocks, presumably driven by CME04 and CME06, at ≈22:41 UT on 06 September 2017 (referred to as Shock06) and at ≈22:48 UT on 07 September 2017 (referred to as Shock07), respectively. The travel time of the CME04/Shock06 [ Δtshock-CME@18R⊙ ] and CME06/Shock07 from 18 R⊙ to the Wind spacecraft was 41.52 hours and 32.47 hours, respectively. The propagating speed [ VCME ] of the CME04 and CME06 at ≈18 R⊙ was determined with SECCHI/Cor2a as ≈886 kms−1 and ≈1368 kms−1 , respectively. Assuming a constant velocity after 18 R⊙ , the estimated Δtshock-CME@18R⊙ is 42.45 and 27.5 hours for CME04 and CME06, respectively. This simple estimate of the CME propagation speed provides a satisfactory result for the CME04 event (error ≈2.3% ) but not for the CME06 event (error ≈15.3% ). The second event, CME06, was delayed further due to an interaction with the preceding event (CME04). It is suggested that the CME speed estimated near the Sun with coronagraph images can be a good estimator for the interplanetary CME (ICME) transit time when there is no pre-event. A three-dimensional magnetohydrodynamic simulation is performed to address this issue by providing a panoramic view of the entire process not available from the observations. A southward interplanetary magnetic field [ Bs ] increased sharply to −31.6 nT on 7 September at Wind, followed by a severe geomagnetic storm ( Dst=−124 nT ). The sharp increase of the IMF [ Bs ] was a result of the interaction between Shock07 and the driver of Shock06 (CME04). This study suggests that a severe geomagnetic storm can be caused by the interaction between a MC, with an impinging IP shock from behind, and the Earth’s magnetosphere. The intensity of a geomagnetic storm will likely be stronger for an event associated with ICME–ICME interaction than for a geomagnetic event caused by only a single ICME.en_US
dc.description.sponsorshipAll data used in this study are obtained from the public domain. We thank the Wind PI teams and the National Space Science Data Center at NASA/Goddard Space Flight Center, for providing the solar wind plasma and magnetic-field data. The work of C.C. Wu was supported partially by the Chief of Naval Research and the NASA LWS 80HQTR18T0023 and HSWO2R17-0005 grants to the Naval Research Laboratory. The work of K. Liou was supported by the NSF grant 1743118 to the Johns Hopkins University Applied Physics Laboratory.en_US
dc.format.extent19 pagesen_US
dc.genrejournal articlesen_US
dc.identifier.citationWu, Chin-Chun; Liou, Kan; Lepping, Ronald P.; Hutting, Lynn; Solar Physics (2019) 294: 110;
dc.publisherSpringer Netherlandsen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Goddard Planetary Heliophysics Institute (GPHI)
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.rightsPublic Domain Mark 1.0*
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.subjectCoronal mass ejectionen_US
dc.subjectGeomagnetic stormen_US
dc.subjectInterplanetary shocken_US
dc.subjectInterplanetary magnetic fielden_US
dc.subjectSpace weather predictionen_US
dc.subjectICME-shock interactionen_US
dc.titleThe 04 – 10 September 2017 Sun–Earth Connection Events: Solar Flares, Coronal Mass Ejections/Magnetic Clouds, and Geomagnetic Stormsen_US


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