Solar Cycle Variation of the Interplanetary Forward Shock Drivers Observed at 1 AU

Oh, Sang‐Ha; Yi, Yu; Kim, Yong Ha

doi:10.1007/s11207-007-9042-2

Cited by 42 publications

(54 citation statements)

References 24 publications

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“…Moreover, the shock frequency has a cycle dependence closely related with the yearly mean sunspot number (see Fig. 2 of Oh et al 2007). A very similar frequency dependence is found for ICMEs (Robbrecht et al 2009;Boursier et al 2009).…”

Section: Introductionsupporting

confidence: 65%

“…At 1 AU and with in situ data, Berdichevsky et al (2000) found that only 43% (18/42) of shocks are associated to ICMEs during a solar minimum period (1994−1997). Analyzing seven years of data with Wind and ACE, Oh et al (2007) found that 79% (196/246) of shocks are associated to ICMEs (MCs and ejecta), while 21% (40/246) of shocks are associated to CIRs (or high speed streams, HSS). Moreover, the shock frequency has a cycle dependence closely related with the yearly mean sunspot number (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Mean shape of interplanetary shocks deduced from in situ observations and its relation with interplanetary CMEs

Janvier

Démoulin

Dasso

2014

A&A

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Context. Shocks are frequently detected by spacecraft in the interplanetary space. However, the in situ data of a shock do not provide direct information on its overall properties even when a following interplanetary coronal mass ejection (ICME) is detected. Aims. The main aim of this study is to constrain the general shape of ICME shocks with a statistical study of shock orientations. Methods. We first associated a set of shocks detected near Earth over 10 years with a sample of ICMEs over the same period. We then analyzed the correlations between shock and ICME parameters and studied the statistical distributions of the local shock normal orientation. Supposing that shocks are uniformly detected all over their surface projected on the 1 AU sphere, we compared the shock normal distribution with synthetic distributions derived from an analytical shock shape model. Inversely, we derived a direct method to compute the typical general shape of ICME shocks by integrating observed distributions of the shock normal. Results. We found very similar properties between shocks with and without an in situ detected ICME, so that most of the shocks detected at 1 AU are ICME-driven even when no ICME is detected. The statistical orientation of shock normals is compatible with a mean shape having a rotation symmetry around the Sun-apex line. The analytically modeled shape captures the main characteristics of the observed shock normal distribution. Next, by directly integrating the observed distribution, we derived the mean shock shape, which is found to be comparable for shocks with and without a detected ICME and weakly affected by the limited statistics of the observed distribution. We finally found a close correspondence between this statistical result and the leading edge of the ICME sheath that is observed with STEREO imagers. Conclusions. We have derived a mean shock shape that only depends on one free parameter. This mean shape can be used in various contexts, such as studies for high-energy particles or space weather forecasts.

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Section: Introductionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Mean shape of interplanetary shocks deduced from in situ observations and its relation with interplanetary CMEs

Janvier

Démoulin

Dasso

2014

A&A

View full text Add to dashboard Cite

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“…The larger values for our control sample may be due to the fact that it includes more shocks during the rise and solar maximum phases (1999–2002) than a random sample would have. Shocks at solar maximum tend to be faster and have larger Mach numbers and compression ratio [ Oh et al , ]. This may also reflect the fact that this sample excludes shocks inside CMEs which tend to have lower compression ratio and Mach numbers, as discussed below.…”

Section: Upstream Conditions and Properties Of Shocks Inside Cmesmentioning

confidence: 99%

Shocks inside CMEs: A survey of properties from 1997 to 2006

et al. 2015

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We report on 49 fast-mode forward shocks propagating inside coronal mass ejections (CMEs) as measured by Wind and ACE at 1 AU from 1997 to 2006. Compared to typical CME-driven shocks, these shocks propagate in different upstream conditions, where the median upstream Alfvén speed is 85 km s −1 , the proton = 0.08 and the magnetic field strength is 8 nT. These shocks are fast with a median speed of 590 km s −1 but weak with a median Alfvénic Mach number of 1.9. They typically compress the magnetic field and density by a factor of 2-3. The most extreme upstream conditions found were a fast magnetosonic speed of 230 km s −1 , a plasma of 0.02, upstream solar wind speed of 740 km s −1 and density of 0.5 cm −3 . Nineteen of these complex events were associated with an intense geomagnetic storm (peak Dst under −100 nT) within 12 h of the shock detection at Wind, and 15 were associated with a drop of the storm time Dst index of more than 50 nT between 3 and 9 h after shock detection. We also compare them to a sample of 45 shocks propagating in more typical upstream conditions. We show the average property of these shocks through a superposed epoch analysis, and we present some analytical considerations regarding the compression ratios of shocks in low regimes. As most of these shocks are measured in the back half of a CME, we conclude that about half the shocks may not remain fast-mode shocks as they propagate through an entire CME due to the large upstream and magnetosonic speeds.

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“…Certainly, CMEs play a very important role in formation of the coronal waves (Biesecker et al, 2002), and most of the interplanetary shocks are driven by CMEs (Reiner et al, 2001;Oh, Yi, and Kim, 2007). However, it remains unclear whether coronal shocks are CME driven (Cliver et al, 2004) or flare ignited (Vršnak, 2001).…”

Section: Introductionmentioning

confidence: 99%

A Flare-Generated Shock during a Coronal Mass Ejection on 24 December 1996

et al. 2008

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We present a multiwavelength study of the large-scale coronal disturbances associated with the CME -flare event recorded on 24 December 1996. The kinematics of the shock wave signature, the type II radio burst, is analyzed and compared with the flare evolution and the CME kinematics. We employ radio dynamic spectra, position of the Nançay Radioheliograph sources, and LASCO-C1 observations, providing detailed study of this limb event. The obtained velocity of the shock wave is significantly higher than the contemporaneous CME velocity (1000 and 235 km s −1 , respectively). Moreover, since the main acceleration phase of the CME took place 10 -20 min after the shock wave was launched, we Radio Physics and the Flare-CME Relationship Guest Editors: Karl-Ludwig Klein and Silja Pohjolainen J. Magdalenić is now also at SIDC, Royal Observatory

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Solar Cycle Variation of the Interplanetary Forward Shock Drivers Observed at 1 AU

Cited by 42 publications

References 24 publications

Mean shape of interplanetary shocks deduced from in situ observations and its relation with interplanetary CMEs

Mean shape of interplanetary shocks deduced from in situ observations and its relation with interplanetary CMEs

Shocks inside CMEs: A survey of properties from 1997 to 2006

A Flare-Generated Shock during a Coronal Mass Ejection on 24 December 1996

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