MHD shock interactions in coronal structures

Grib, S. A.; Koutchmy, S.; Sazonova, V. N.

doi:10.1007/bf00153838

Cited by 12 publications

(4 citation statements)

References 27 publications

(3 reference statements)

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“…Refraction of coronal shocks into low Alfven speed regions has been discussed before [ Uchida , 1968]. The shock may also become a slow shock inside the CH if it can penetrate [see, e.g., Grib et al , 1996].…”

Section: Discussionmentioning

confidence: 99%

CME interactions with coronal holes and their interplanetary consequences

et al. 2009

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[1] A significant number of interplanetary shocks ($17%) during cycle 23 were not followed by drivers. The number of such ''driverless'' shocks steadily increased with the solar cycle with 15%, 33%, and 52% occurring in the rise, maximum, and declining phase of the solar cycle. The solar sources of 15% of the driverless shocks were very close the central meridian of the Sun (within $15°), which is quite unexpected. More interestingly, all the driverless shocks with their solar sources near the solar disk center occurred during the declining phase of solar cycle 23. When we investigated the coronal environment of the source regions of driverless shocks, we found that in each case there was at least one coronal hole nearby, suggesting that the coronal holes might have deflected the associated coronal mass ejections (CMEs) away from the Sun-Earth line. The presence of abundant low-latitude coronal holes during the declining phase further explains why CMEs originating close to the disk center mimic the limb CMEs, which normally lead to driverless shocks due to purely geometrical reasons. We also examined the solar source regions of shocks with drivers. For these, the coronal holes were located such that they either had no influence on the CME trajectories, or they deflected the CMEs toward the Sun-Earth line. We also obtained the open magnetic field distribution on the Sun by performing a potential field source surface extrapolation to the corona. It was found that the CMEs generally move away from the open magnetic field regions. The CME-coronal hole interaction must be widespread in the declining phase and may have a significant impact on the geoeffectiveness of CMEs.

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Section: Discussionmentioning

confidence: 99%

CME interactions with coronal holes and their interplanetary consequences

et al. 2009

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“… Wu [2003] obtained the same results from the 2‐D MHD simulation. A similar problem of the FS‐TD interaction was studied in the supersonic solar wind [ Neubauer , 1976] and in the solar corona [ Grib et al , 1996]. The existence of the rarefaction wave reflected from the magnetopause was indicated by the schematic plot of Figure 11 of Zhuang et al [1981].…”

Section: Introductionmentioning

confidence: 99%

Numerical MHD modeling of propagation of interplanetary shock through the magnetosheath

Samsonov¹,

Němeček²,

Šafránková³

2006

J. Geophys. Res.

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[1] Propagation of an interplanetary (IP) shock through the bow shock and magnetosheath is studied using numerical results of a three-dimensional MHD model of the magnetosheath. According to already published theoretical studies, a fast forward shock passing through the bow shock would generate a train of new discontinuities including a slow expansion wave, a contact discontinuity, and a slow reversed shock. We have found that these particular discontinuities propagate with similar velocities and thus they cannot be distinguished in our calculations, and we observe one discontinuity that combines properties of all of them. We suggest that the same would be true for an analysis of experimental data. We have simulated three different ways of the magnetopause response to the IP shock. A comparison of these runs reveals that the magnetopause reaction defines the mode of reflected waves. Assuming a fast earthward motion of the magnetopause, about 240 km s À1 or more, we obtain that a fast rarefaction wave would propagate from the magnetopause toward the bow shock, while a slower magnetopause motion would result in a fast reversed shock. On the other hand, the speed of the IP shock propagation does not depend on the magnetopause response, and all three model runs confirm a deceleration of the modeled IP shock front in the magnetosheath in course of its motion from the subsolar region to the magnetosheath flanks.

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“…Slow shocks are expected mainly in low beta plasmas in the corona, particularly if the temperature of ions is lower than the electron (Hada & Kennel 1985). These shocks decay faster than fast-mode shocks and thus are unlikely to be found beyond 0.4 au (Grib et al 1996). At 1 au, a few slow-mode shocks were observed among hundreds of fast-mode ones (see, e.g., the Harvard Smithsonian Center for Astrophysics' shock database, https://www.cfa.harvard.…”

Section: Cme Coherencementioning

confidence: 99%

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

Braga

Vourlidas

Liewer

et al. 2022

ApJ

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Although coronal mass ejections (CMEs) resembling flux ropes generally expand self-similarly, deformations along their fronts have been reported in observations and simulations. We present evidence of one CME becoming deformed after a period of self-similar expansion in the corona. The event was observed by multiple white-light imagers on 2021 January 20–22. The change in shape is evident in observations from the heliospheric imagers from the Wide-Field Imager for Solar Probe Plus (WISPR), which observed this CME for ∼44 hr. We reconstruct the CME using forward-fitting models. In the first hours, observations are consistent with a self-similar expansion, but later on the front flattens, forming a dimple. Our interpretation is that the CME becomes deformed at ∼0.1 au owing to differences in the background solar wind speeds. The CME expands more at higher latitudes, where the background solar wind is faster. We consider other possible causes for deformations, such as loss of coherence and slow-mode shocks. The CME deformation seems to cause a time-of-arrival error of 16 hr at ∼0.5 au. The deformation is clear only in the WISPR observations; thus, it would have been missed by 1 au coronagraphs. Such deformations may help explain the time-of-arrival errors in events where only coronagraph observations are available.

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MHD shock interactions in coronal structures

Cited by 12 publications

References 27 publications

CME interactions with coronal holes and their interplanetary consequences

CME interactions with coronal holes and their interplanetary consequences

Numerical MHD modeling of propagation of interplanetary shock through the magnetosheath

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

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