Extreme geomagnetic disturbances due to shocks within CMEs

Lugaz, Noé; Farrugia, Charles J.; Huang, C. L.; Spence, H. E.

doi:10.1002/2015gl064530

Cited by 57 publications

(42 citation statements)

References 29 publications

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“…This can be seen as the increase in the dynamic pressure and the temperature spike at the shock (Figure , panels 2 and 3). Such shock‐in‐a‐cloud configuration has been reported in Lugaz et al (). The duration of MC 1 is very short, despite that, β remains below 1 until 01:18 UTC on 8 September.…”

Section: Event Overviewsupporting

confidence: 72%

Modeling the Multiple CME Interaction Event on 6–9 September 2017 with WSA‐ENLIL+Cone

et al. 2019

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A series of coronal mass ejections (CMEs) erupted from the same active region between 4–6 September 2017. Later, on 6–9 September, two interplanetary (IP) shocks reached L1, creating a complex and geoeffective plasma structure. To understand the processes leading up to the formation of the two shocks, we model the CMEs with the Wang‐Sheeley‐Arge (WSA)‐ENLIL+Cone model. The first two CMEs merged already in the solar corona driving the first IP shock. In IP space, another fast CME presumably interacted with the flank of the preceding CMEs and caused the second shock detected in situ. By introducing a customized density enhancement factor (dcld) in the WSA‐ENLIL+Cone model based on coronagraph image observations, the predicted arrival time of the first IP shock was drastically improved. When the dcld factor was tested on a well‐defined single CME event from 12 July 2012 the shock arrival time saw similar improvement. These results suggest that the proposed approach may be an alternative to improve the forecast for fast and simple CMEs. Further, the slowly decelerating kilometric type II radio burst confirms that the properties of the background solar wind have been preconditioned by the passage of the first IP shock. This likely caused the last CME to experience insignificant deceleration and led to the early arrival of the second IP shock. This result emphasizes the need to take preconditioning of the IP medium into account when making forecasts of CMEs erupting in quick succession.

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Section: Event Overviewsupporting

confidence: 72%

Modeling the Multiple CME Interaction Event on 6–9 September 2017 with WSA‐ENLIL+Cone

et al. 2019

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“…Shocks inside CMEs as a potential source of intense geomagnetic storms were also discussed by Wang et al (2003a) and further investigated in Wang et al (2003b). Specific examples were also discussed in Lugaz et al (2015a), who argued that the combination of high dynamic pressure and compressed magnetic field just behind the shock may be particularly efficient in pushing Earth's magnetopause earthwards and, therefore, in driving energetic electron losses in Earth's radiation belt. An example of such an event is given in Figure 10d for a shock inside a magnetic ejecta that occurred on 19 February 2014 and resulted in an intense geomagnetic storm.…”

Section: The Geoeffectiveness Of Interacting Cmesmentioning

confidence: 99%

The Interaction of Successive Coronal Mass Ejections: A Review

et al. 2017

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We present a review of the different aspects associated with the interaction of successive coronal mass ejections (CMEs) in the corona and inner heliosphere, focusing on the initiation of series of CMEs, their interaction in the heliosphere, the particle acceleration associated with successive CMEs, and the effect of compound events on Earth's magnetosphere. The two main mechanisms resulting in the eruption of series of CMEs are sympathetic eruptions, when one eruption triggers another, and homologous eruptions, when a series of similar eruptions originates from one active region. CME-CME interaction may also be associated with two unrelated eruptions. The interaction of successive CMEs has been observed remotely in coronagraphs (with the Large Angle and Spectrometric Coronagraph Experiment -LASCO-since the early 2000s) and heliospheric imagers (since the late 2000s), and inferred from in situ measurements, starting with early measurements in the 1970s. The interaction of two or more CMEs is associated with complex phenomena, including magnetic reconnection, momentum exchange, the propagation of a fast magnetosonic shock through a magnetic ejecta, and changes in the CME expansion. The presence of a preceding CME a few hours before a fast eruption has been found to be connected with higher fluxes of solar energetic particles (SEPs), while CME-CME interaction occurring in the corona is often associated with unusual radio bursts, indicating electron acceleration. Higher suprathermal population, enhanced turbulence and wave activity, stronger shocks, and shock-shock or shock-CME interaction have been proposed as potential physical mechanisms to explain the observed associated SEP events. When measured in situ, CME-CME interaction may be associated with relatively well organized multiple-magnetic cloud events, instances of shocks propagating through a previous magnetic ejecta or more complex ejecta, when the characteristics of the individual eruptions cannot be easily distinguished. CME-CME interaction is associated with some of the most intense recorded geomagnetic storms. The compression of a CME by another and the propagation of a shock inside a magnetic ejecta can lead to extreme values of the southward magnetic field component, sometimes associated with large values of the dynamic pressure. This can result in intense geomagnetic storms, but also trigger substorms and large earthward motions of the magnetopause, potentially associated with changes in the outer radiation belts. Future in situ measurements in the inner heliosphere by Solar Probe+ and Solar Orbiter may shed light on the evolution of CMEs as they interact, by providing opportunities for conjunction and evolutionary studies.

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“…For 70% of the events (65/92), the magnetopause reached geosynchronous orbit (6.6 R E ). In Lugaz et al [], we discussed how the combination of large dynamic pressures and southward IMF behind shocks within transients can simultaneously compress and erode the magnetosphere, pushing the magnetopause down to below geosynchronous orbit and in some instances, resulting in electron losses through magnetopause shadowing [ Turner et al , ; Alves et al , ]. Enhanced wave‐particle acceleration and Dst effect [ Kim et al , ] are two other mechanisms which can contribute to energetic electron losses during this type of events [e.g., see Shprits et al , ; Kilpua et al , ].…”

Section: Studymentioning

confidence: 99%

“…The possibility that a shock overtaking a magnetic ejecta may result in intense geomagnetic activities was raised in Ivanov [1982] and Burlaga et al [1987] and discussed in greater detail in Wang et al [2003]. Dedicated studies of in situ measurements of shocks propagating within a preceding magnetic ejecta were reported in Collier et al [2007] and Lugaz et al [2015b]; an example of their interplanetary formation was discussed in Liu et al [2014]; an example of their potential effects on the radiation belt has been described in Lugaz et al [2015a]; and simulations of such events was performed in Vandas et al [1997], Lugaz et al [2005], Xiong et al [2006], and Lugaz et al [2013]. This type of event can be thought as an ongoing CME-CME interaction event.…”

Section: Introductionmentioning

confidence: 99%

Factors affecting the geoeffectiveness of shocks and sheaths at 1 AU

et al. 2016

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We identify all fast‐mode forward shocks, whose sheath regions resulted in a moderate (56 cases) or intense (38 cases) geomagnetic storm during 18.5 years from January 1997 to June 2015. We study their main properties, interplanetary causes, and geoeffects. We find that half (49/94) such shocks are associated with interacting coronal mass ejections (CMEs), as they are either shocks propagating into a preceding CME (35 cases) or a shock propagating into the sheath region of a preceding shock (14 cases). About half (22/45) of the shocks driven by isolated transients and which have geoeffective sheaths compress preexisting southward Bz. Most of the remaining sheaths appear to have planar structures with southward magnetic fields, including some with planar structures consistent with field line draping ahead of the magnetic ejecta. A typical (median) geoeffective shock‐sheath structure drives a geomagnetic storm with peak Dst of −88 nT pushes the subsolar magnetopause location to 6.3 RE, i.e., below geosynchronous orbit and is associated with substorms with a peak AL index of −1350 nT. There are some important differences between sheaths associated with CME‐CME interaction (stronger storms) and those associated with isolated CMEs (stronger compression of the magnetosphere). We detail six case studies of different types of geoeffective shock‐sheaths, as well as two events for which there was no geomagnetic storm but other magnetospheric effects. Finally, we discuss our results in terms of space weather forecasting and potential effects on Earth's radiation belts.

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Extreme geomagnetic disturbances due to shocks within CMEs

Cited by 57 publications

References 29 publications

Modeling the Multiple CME Interaction Event on 6–9 September 2017 with WSA‐ENLIL+Cone

Modeling the Multiple CME Interaction Event on 6–9 September 2017 with WSA‐ENLIL+Cone

The Interaction of Successive Coronal Mass Ejections: A Review

Factors affecting the geoeffectiveness of shocks and sheaths at 1 AU

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