Relations estimated at shock discontinuities excited by coronal mass ejections

Еселевич, М.; Еселевич, В. Г.

doi:10.1134/s1063772911020028

Cited by 21 publications

(16 citation statements)

References 13 publications

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“…For this, we use the following assumptions: (1) κ dcr ranges from 0.78 to 1.1 corresponding to spherical and ellipsoid shapes of the CMEs (Seiff 1962;Spreiter et al 1966;Savani et al 2012); (2) γ ranges from 1 (isothermal) to 5/3 (adiabatic for monoatomic gas) (Liu et al 2005;Wang et al 2009;Eselevich & Eselevich 2011); and (3) M CME is estimated using the following simple relation…”

Section: Relationships Under Gasdynamic Theorymentioning

confidence: 99%

“…V A is the local Alfvén speed determined by using Mann's magnetic field distribution (1999) and Saito's density distribution (1970) in the equatorial plane, which assumptions have been widely used for the calculation of local characteristic speeds (Cho et al 2005(Cho et al , 2008Eselevich & Eselevich 2011). In addition to this, we also determine V A under Mann's magnetic field distribution and coronal electron density distributions (CEDDs), which are estimated around MPAs of CMEs using polarized brightness (pB) measurements of SOHO/LASCO-C2 (see Section 2.3 of Lee et al 2016 for details).…”

Section: Relationships Under Gasdynamic Theorymentioning

confidence: 99%

“…We determine the theoretical stand-off distance ratios of 18 CMEs (R MHD ) using Equation (8) because shock conditions near MPAs of CMEs are approximated as quasi-parallel shocks (Bemporad et al 2014;Susino et al 2015). For this, we use the following assumptions: (1) γ ranges from 1 (isothermal) to 5/3 (adiabatic for monoatomic gas) (Liu et al 2005;Wang et al 2009;Eselevich & Eselevich 2011); and (2) θ CME ranges from 0°to 26°. If θ CME is 26°and γ=5/3, the result of Equation (8) is consistent with that based on GD theory (Spreiter et al 1966).…”

Section: Relationships Under Magnetohydrodynamic Theorymentioning

confidence: 99%

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Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

Lee

Moon

Lee

et al. 2017

ApJ

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It is generally believed that fast coronal mass ejections (CMEs) can generate their associated shocks, which are characterized by faint structures ahead of CMEs in white-light coronagraph images. In this study, we examine whether the observational stand-off distance ratio, defined as the CME stand-off distance divided by its radius, can be explained by bow shock theories. Of 535 SOHO/LASCO CMEs (from 1996 to 2015) with speeds greater than 1000 km s −1 and angular widths wider than 60°, we select 18 limb CMEs with the following conditions: (1) their Alfvénic Mach numbers are greater than one under Mann's magnetic field and Saito's density distributions; and (2) the shock structures ahead of the CMEs are well identified. We determine observational CME stand-off distance ratios by using brightness profiles from LASCO-C2 observations. We compare our estimates with theoretical stand-off distance ratios from gasdynamic (GD) and magnetohydrodynamic (MHD) theories. The main results are as follows. Under the GD theory, 39% (7/18) of the CMEs are explained in the acceptable ranges of adiabatic gamma (γ) and CME geometry. Under the MHD theory, all the events are well explained when we consider quasiparallel MHD shocks with γ=5/3. When we use polarized brightness (pB) measurements for coronal density distributions, we also find similar results: 8% (1/12) under GD theory and 100% (12/12) under MHD theory. Our results demonstrate that the bow shock relationships based on MHD theory are more suitable than those based on GD theory for analyzing CME-driven shock signatures.

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Section: Relationships Under Gasdynamic Theorymentioning

confidence: 99%

Section: Relationships Under Gasdynamic Theorymentioning

confidence: 99%

Section: Relationships Under Magnetohydrodynamic Theorymentioning

confidence: 99%

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Which Bow Shock Theory, Gasdynamic or Magnetohydrodynamic, Better Explains CME Stand-off Distance Ratios from LASCO-C2 Observations ?

Lee

Moon

Lee

et al. 2017

ApJ

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“…Although there have been attempts to search for white-light features of the shocks in the past (Sheeley et al 2000;Vourlidas et al 2003), the diffuse feature has been recognized as a shock manifestation only recently (Gopalswamy 2009;Gopalswamy et al 2009a;Ontiveros & Vourlidas, 2009;Eselevich & Eselevich, 2011). In coronagraphic difference images, one observes a diffuse feature surrounding the bright feature identified as the CME flux rope.…”

Section: White-light Signatures Of Cme-driven Shocks: Four-part Cme Smentioning

confidence: 94%

“…The shock strength can be measured in terms of the density compression ratio downstream to upstream using brightness jump in the diffuse feature (Ontiveros & Vourlidas 2009;Eselevich & Eselevich 2011;Bemporad & Mancuso 2011). Bemporad & Mancuso (2011) used the compression ratio to infer the Alfvén Mach number at various locations of the shock front.…”

Section: White-light Signatures Of Cme-driven Shocks: Four-part Cme Smentioning

confidence: 99%

Commission 49: Interplanetary Plasma and Heliosphere

Gopalswamy¹,

Mann²,

Bougeret³

et al. 2011

Proc. IAU

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Commission 49 (Interplanetary Plasma and Heliosphere) is part of IAU Division II (Sun and Heliosphere). The research topics include large-scale solar disturbances such as coronal mass ejections (CMEs), shocks, and corotating interaction regions (CIRs) propagating into the heliosphere. The disturbances propagate through the solar wind, which essentially defines the heliosphere. The solar disturbances provide large-scale laboratory to study plasma processes over various time and spatial scales, the highest spatial scale being the size of the heliosphere itself (~100 AU). These solar disturbances are related to solar activity in the form of active regions and coronal holes. Solar eruptions are accompanied by particle acceleration and the particles can be hazardous to life on earth in various ways from modifying the ionosphere to damaging space technology and increasing lifetime radiation dosage to astronauts and airplane crew. Particle acceleration in solar eruptions poses fundamental physics questions because the underlying mechanisms are not fully understood. One of important processes is the particle acceleration by shocks, which occurs throughout the heliosphere. The heliosphere has both neutral and ionized material, with interesting interaction between the two components.

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