Numerical studies of the interplanetary "shock overtaking magnetic cloud (MC)" event are continued by a 2.5 dimensional magnetohydrodynamic (MHD) model in heliospheric meridional plane. Interplanetary direct collision (DC)/oblique collision (OC) between an MC and a shock results from their same/different initial propagation orientations. For radially erupted MC and shock in solar corona, the orientations are only determined respectively by their heliographic locations. OC is investigated in contrast with the results in DC \citep{Xiong2006}. The shock front behaves as a smooth arc. The cannibalized part of MC is highly compressed by the shock front along its normal. As the shock propagates gradually into the preceding MC body, the most violent interaction is transferred sideways with an accompanying significant narrowing of the MC's angular width. The opposite deflections of MC body and shock aphelion in OC occur simultaneously through the process of the shock penetrating the MC. After the shock's passage, the MC is restored to its oblate morphology. With the decrease of MC-shock commencement interval, the shock front at 1 AU traverses MC body and is responsible for the same change trend of the latitude of the greatest geoeffectiveness of MC-shock compound. Regardless of shock orientation, shock penetration location regarding the maximum geoeffectiveness is right at MC core on the condition of very strong shock intensity. An appropriate angular difference between the initial eruption of an MC and an overtaking shock leads to the maximum deflection of the MC body. The larger the shock intensity is, the greater is the deflection angle. The interaction of MCs with other disturbances could be a cause of deflected propagation of interplanetary coronal mass ejection (ICME).
Deep Dive into Magnetohydrodynamic Simulation of the Interaction between Interplanetary Strong Shock and Magnetic Cloud and its Consequent Geoeffectiveness 2: Oblique Collision.
Numerical studies of the interplanetary “shock overtaking magnetic cloud (MC)” event are continued by a 2.5 dimensional magnetohydrodynamic (MHD) model in heliospheric meridional plane. Interplanetary direct collision (DC)/oblique collision (OC) between an MC and a shock results from their same/different initial propagation orientations. For radially erupted MC and shock in solar corona, the orientations are only determined respectively by their heliographic locations. OC is investigated in contrast with the results in DC \citep{Xiong2006}. The shock front behaves as a smooth arc. The cannibalized part of MC is highly compressed by the shock front along its normal. As the shock propagates gradually into the preceding MC body, the most violent interaction is transferred sideways with an accompanying significant narrowing of the MC’s angular width. The opposite deflections of MC body and shock aphelion in OC occur simultaneously through the process of the shock penetrating the MC. After
with the results in DC [Xiong et al., 2006]. The shock front behaves as a smooth arc. The cannibalized part of MC is highly compressed by the shock front along its normal. As the shock propagates gradually into the preceding MC body, the most violent interaction is transferred sideways with an accompanying significant narrowing of the MC's angular width. The opposite deflections of MC body and shock aphelion in OC occur simultaneously through the process of the shock penetrating the MC. After the shock's passage, the MC is restored to its oblate morphology. With the decrease of MC-shock commencement interval, the shock front at 1 AU traverses MC body and is responsible for the same change trend of the latitude of the greatest geoeffectiveness of MC-shock compound. Regardless of shock orientation, shock penetration location regarding the maximum geoeffectiveness is right at MC core on the condition of very strong shock intensity. An appropriate angular difference between the initial eruption of an MC and an overtaking shock leads to the maximum deflection of the MC body. The larger the shock intensity is, the greater is the deflection angle. The interaction of MCs with other dis-D R A F T November 7, 2018, 10:10am D R A F T X -3
turbances could be a cause of deflected propagation of interplanetary coronal mass ejection (ICME).
D R A F T November 7, 2018, 10:10am D R A F T
Interplanetary (IP) space is permeated by highly fluctuating solar wind with magnetic field frozen in its plasma [Parker, 1963]. The relatively quiet equilibrium of IP space is frequently interrupted by the solar disturbances, especially during solar maximum. Giant clouds of ionized gas with magnetic flux of 10 23 maxwell and plasma mass of 10 16 g, called coronal mass ejection (CME), are regularly emitted from the sun [Gosling, 1990;Webb et al., 1994]. IP CME (ICME) generally causes strong perturbation in the space environment as it passes by. Several models have already been applied in space weather forecasting, such as (1) HAF (Hakamada-Akasofu-Fry) [Fry et al., 2001[Fry et al., , 2005]];
(2) STOA (Shock Time of Arrival) [Smart and Shea, 1985];
(3) ISPM (Interplanetary Shock Propagation
Model) [Smith and Dryer, 1990]; (4) an ensemble of HAF, STOA and ISPM models [Dryer et al., 2001[Dryer et al., , 2004]]; (5) SWMF (Space Weather Modeling Framework) [Groth et al., 2000;Gombosi et al., 2001;Toth et al., 2005]; (6) HHMS (Hybrid Heliospheric Modeling System) [Detman et al., 2006] , and so on. Great challenges are still faced to improve the prediction performance of space weather to satisfy the ever-increasing demands from human civilization [Baker, 2002].
Magnetic clouds (MCs) are an important subset of ICMEs, whose fraction decreases from ∼ 100% (though with low statistics) at solar minimum to ∼ 15% at solar maximum [Richardson andCane, 2004, 2005]. Identified by their characteristics including enhanced magnetic field, large and smooth rotation of magnetic field and low proton temperature [Burlaga et al., 1981], MCs have been the subject of increasingly intense study. The MCs with long interval of large southward magnetic field B s are widely considered to
be the major IP origin of moderate to intense geomagnetic storms, especially during the solar maximum [Tsurutani, 1988;Gosling et al., 1991;Gonzalez et al., 1999] and, hence, play a crucial role in space weather prediction. An MC should probably be a curved loop-like structure with its feet connecting to the solar surface [Larson et al., 1997]. The force-free magnetic flux rope models have been proven to be very valuable to interpret in situ observations of MCs [Lundquist, 1950;Goldstein, 1983;Burlaga, 1988;Farrugia et al., 1993]. For the study of evolution of an individual MC during its anti-sunward propagation, many sophisticated models are developed based on these initial flux rope models: (1) Analytical models [Osherovich et al., 1993a[Osherovich et al., , b, 1995;;Hidalgo, 2003Hidalgo, , 2005]];
(2)
Kinematic models [Riley and Crooker, 2004;Owens et al., 2006];
(3) Numerical models [Vandas et al., 1995[Vandas et al., , 1996[Vandas et al., , 1997[Vandas et al., , 2002;;Groth et al., 2000;Odstrcil et al., 2002;Schmidt and Cargill, 2003;Manchester et al., 2004a, b]. Especially numerical simulations in (3) on a single MC have been exhaustive under the condition of various magnetic field strengths, axis orientations and speeds.
ICME is not an absolutely self-isolated entity during IP propagation. It may interact with other solar transients (e.g., shock, ejecta) and heterogenous medium (e.g., corotating interacting region). With less defined characteristics, some IP complex structures are reported recently, such as complex ejecta [Burlaga et al., 2002], multiple MCs [Wang et al., 2002a[Wang et al., , 2003a]], shock-penetrated MC [Wang et al., 2003b;Berdichevsky et al., 2005], non-pressure-balanced “MC boundary layer” associated with magnetic reconnection [Wei et al., 2003[Wei e
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