A numerical study of the interaction between two ejecta in the interplanetary medium: one- and two-dimensional hydrodynamic simulations

Abstract

Abstract.We studied the heliospheric evolution in one and two dimensions of the interaction between two ejecta-like disturbances beyond the critical point: a faster ejecta 2 overtaking a previously launched slower ejecta 1. The study is based on a hydrodynamic model using the ZEUS-3-D code. This model can be applied to those cases where the interaction occurs far away from the Sun and there is no merging (magnetic reconnection) between the two ejecta. The simulation shows that when the faster ejecta 2 overtakes ejecta 1 there is an interchange of momentum between the two ejecta, where the leading ejecta 1 accelerates and the tracking ejecta 2 decelerates. Both ejecta tend to arrive at 1 AU having similar speeds, but with the front of ejecta 1 propagating faster than the front of ejecta 2. The momentum is transferred from ejecta 2 to ejecta 1 when the shock initially driven by ejecta 2 passes through ejecta 1. Eventually the two shock waves driven by the two ejecta merge together into a single stronger shock. The 2-D simulation shows that the evolution of the interaction can be very complex and there are very different signatures of the same event at different viewing angles; however, the transferring of momentum between the two ejecta follows the same physical mechanism described above. These results are in qualitative agreement with in-situ plasma observations of "multiple magnetic clouds" detected at 1 AU.

Numerical Investigation of the Homologous Coronal Mass Ejection Events from Active Region 9236

“…The inclusion of the first CME was needed to match observed values of the hydrodynamic parameters at 1 AU, even though the two CMEs have not fully interacted by 1 AU. The propagation and interaction of two ejecta from 18 R to 1 AU have also been recently modeled using a two-dimensional hydrodynamic code (Gonzalez-Esparza et al 2004). Schmidt & Cargill (2004) studied the interaction of two CMEs in the LASCO coronographs' fields of view (1.7Y32 R ) using 2.5-dimensional MHD simulations; the authors investigated different scenarios with and without direct magnetic interactions between the flux ropes.…”

Magnetohydrodynamic simulation of the interaction between interplanetary strong shock and magnetic cloud and its consequent geoeffectiveness: 2. Oblique collision

“…Dynamical response and ensuing geoeffectiveness of these structures are directly associated with the interaction during their formation and evolution. Numerical simulations have been applied to study most of the complex structures: e.g., the interaction of a shock wave with an MC [ Vandas et al , 1997; Odstrcil et al , 2003; Xiong et al , 2006], and the interaction of two MCs [ Odstrcil et al , 2003; Gonzalez‐Esparza et al , 2004; Lugaz et al , 2005; Wang et al , 2005].…”

Comment on “Interplanetary origin of intense geomagnetic storms (Dst < −100 nT) during solar cycle 23” by W. D. Gonzalez et al.

“…[2] However, the interaction between two CMEs close to the Sun [Gopalswamy et al, 2001[Gopalswamy et al, , 2002 and between magnetic clouds near the Earth [see, e.g., Burlaga et al, 2001;Berdichevsky et al, 2003;Gonzalez-Esparza et al, 2004;Farrugia et al, 2006a;and ' Xie et al [2006] studied 37 long-lived geomagnetic storms (LLGMS events) with Dst < À100 nT and the associated CMEs which occurred during 1998-2002 and found that 24 of 37 events were caused by successive CMEs and number of interacting magnetic clouds was observed from 2 up to 4.…”

“…[2] However, the interaction between two CMEs close to the Sun [Gopalswamy et al, 2001[Gopalswamy et al, , 2002 and between magnetic clouds near the Earth [see, e.g., Burlaga et al, 2001;Berdichevsky et al, 2003;Gonzalez-Esparza et al, 2004;Farrugia et al, 2006a; and references therein] has been reported. A number of papers showed that several strong magnetic storms (see, for instance, events on 31 March, 2001, minimum Dst value of À387 nT, 11 -13 April, 2001, Dst min = À271 nT [Wang et al, 2003]; 28-30 October, 2003, Dst min = À363 nT [Veselovsky et al, 2004;Skoug et al, 2004];20 November, 2003, Dst min = À472 nT [Ermolaev et al, 2005]; 8 -10 November, 2004, Dst min = À373 nT [Yermolaev et al, 2005]) have been generating by multiple interacting magnetic clouds.…”