Cross Helicity of the 2018 November Magnetic Cloud Observed by the Parker Solar Probe

Good, Simon; Kilpua, Emilia; Ala‐Lahti, Matti; Osmane, Adnane; Bale, S. D.; Zhao, Lingling

doi:10.3847/2041-8213/abb021

Cited by 18 publications

(26 citation statements)

References 47 publications

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“…2. The total magnetic fluctuation power is dominated by the transverse fluctuations, which is consistent with nearly incompressible MHD turbulence models (Zank & Matthaeus 1992, 1993Zank et al 2017;Adhikari et al 2017) and reported also in previous studies of downstream regions of interplanetary shocks (e.g., Moissard et al 2019;Good et al 2020). 3.…”

Section: Summary and Discussionsupporting

confidence: 90%

“…The highly negative σ r indicates that the energy of the fluctuating magnetic field b 2 dominates compared to the kinetic fluctuation energy u 2 . These two turbulent properties of the ICME flux rope structures have been widely studied (Telloni et al 2020b;Zhao et al 2020Zhao et al , 2021Good et al 2020). After the passage of the ICME, Wind tends to measure slightly faster solar wind with an increased σ c .…”

Section: Observation Of the Icme And Its Driven Shockmentioning

confidence: 96%

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Turbulence and wave transmission at an ICME-driven shock observed by the Solar Orbiter and Wind

Zhao

Zank

et al. 2021

A&A

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Aims. An interplanetary coronal mass ejection (ICME) event was observed by the Solar Orbiter at 0.8 AU on 2020 April 19 and by Wind at 1 AU on 2020 April 20. Futhermore, an interplanetary shock wave was driven in front of the ICME. Here, we focus on the transmission of the magnetic fluctuations across the shock and we analyze the characteristic wave modes of solar wind turbulence in the vicinity of the shock observed by both spacecraft. Methods. The observed ICME event is characterized by a magnetic helicity-based technique. The ICME-driven shock normal was determined by magnetic coplanarity method for the Solar Orbiter and using a mixed plasma and field approach for Wind. The power spectra of magnetic field fluctuations were generated by applying both a fast Fourier transform and Morlet wavelet analysis. To understand the nature of waves observed near the shock, we used the normalized magnetic helicity as a diagnostic parameter. The wavelet-reconstructed magnetic field fluctuation hodograms were used to further study the polarization properties of waves. Results. We find that the ICME-driven shock observed by Solar Orbiter and Wind is a fast, forward oblique shock with a more perpendicular shock angle at the Wind position. After the shock crossing, the magnetic field fluctuation power increases. Most of the magnetic field fluctuation power resides in the transverse fluctuations. In the vicinity of the shock, both spacecraft observe right-hand polarized waves in the spacecraft frame. The upstream wave signatures fall within a relatively broad and low frequency band, which might be attributed to low frequency MHD waves excited by the streaming particles. For the downstream magnetic wave activity, we find oblique kinetic Alfvén waves with frequencies near the proton cyclotron frequency in the spacecraft frame. The frequency of the downstream waves increases by a factor of ∼7–10 due to the shock compression and the Doppler effect.

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Section: Summary and Discussionsupporting

confidence: 90%

Section: Observation Of the Icme And Its Driven Shockmentioning

confidence: 96%

Turbulence and wave transmission at an ICME-driven shock observed by the Solar Orbiter and Wind

Zhao

Zank

et al. 2021

A&A

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“…Another possibility is that turbulent cascade is anisotropic giving the ∼ −5/3 slope in perpendicular direction as suggested by Goldreich and Sridhar (1995). In sheath regions perpendicular to turbulence dominates (e.g., Moissard et al, 2019;Good et al, 2020b) as is typical in general in the solar wind.…”

Section: Summary and Discussionmentioning

confidence: 96%

“…Now, we covered only the upper end of the kinetic range that likely affects the results. Solar Orbiter (Müller et al, 2013) and Parker Solar Probe (Fox et al, 2016) can also shed new insight into CME sheaths (e.g., Good et al, 2020b) and allow investigation on how fluctuation properties in CME sheaths evolve in the inner heliosphere.…”

Section: Summary and Discussionmentioning

confidence: 99%

Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions

Kilpua

Good

Ala‐Lahti

et al. 2021

Front. Astron. Space Sci.

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We report a statistical analysis of magnetic field fluctuations in 79 coronal mass ejection- (CME-) driven sheath regions that were observed in the near-Earth solar wind. Wind high-resolution magnetic field data were used to investigate 2 h regions adjacent to the shock and ejecta leading edge (Near-Shock and Near-LE regions, respectively), and the results were compared with a 2 h region upstream of the shock. The inertial-range spectral indices in the sheaths are found to be mostly steeper than the Kolmogorov −5/3 index and steeper than in the solar wind ahead. We did not find indications of an f−1 spectrum, implying that magnetic fluctuation properties in CME sheaths differ significantly from planetary magnetosheaths and that CME-driven shocks do not reset the solar wind turbulence, as appears to happen downstream of planetary bow shocks. However, our study suggests that new compressible fluctuations are generated in the sheath for a wide variety of shock/upstream conditions. Fluctuation properties particularly differed between the Near-Shock region and the solar wind ahead. A strong positive correlation in the mean magnetic compressibility was found between the upstream and downstream regions, but the compressibility values in the sheaths were similar to those in the slow solar wind (<0.2), regardless of the value in the preceding wind. However, we did not find clear correlations between the inertial-range spectral indices in the sheaths and shock/preceding solar wind properties, nor with the mean normalized fluctuation amplitudes. Correlations were also considerably lower in the Near-LE region than in the Near-Shock region. Intermittency was also considerably higher in the sheath than in the upstream wind according to several proxies, particularly so in the Near-Shock region. Fluctuations in the sheath exhibit larger rotations than upstream, implying the presence of strong current sheets in the sheath that can add to intermittency.

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“…While this noise model is expected to be a large improvement over the model employed in W21 it is still important to note one of its deficiencies. The fluctuations in the magnetic field strength, which represent compressive fluctuations, are generally weaker than those of its components that describe incompressible fluctuations (e.g., Good et al 2020). This is a strong hint that the underlying fluctuations would be better described using rotations, rather than the additions that we use in our noise model.…”

Section: Noise Modelmentioning

confidence: 91%

Multi-point analysis of coronal mass ejection flux ropes using combined data from Solar Orbiter, BepiColombo, and Wind

Weiss¹,

Möstl²,

Davies³

et al. 2021

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Context. The recent launch of Solar Orbiter and the flyby of BepiColombo opened a brief window during which these two spacecraft, along with the existing spacecraft at L1, were positioned in a constellation that allowed for the detailed sampling of any Earth-directed coronal mass ejection (CME). Fortunately, two such events occurred during this time period with in situ detections of an interplanetary coronal mass ejection (ICME) by Solar Orbiter on the 2020 April 19 and 2020 May 28. These two events were subsequently observed in situ by BepiColombo and Wind as well around a day later. Aims. We attempt to reconstruct the observed in situ magnetic field measurements for all three spacecraft simultaneously using an empirical magnetic flux rope model. This allows us to test the validity of our flux rope model on a larger and more global scale. It additionally allows for cross-validation of the analysis with different spacecraft combinations. Finally, we can also compare the results from the in situ modeling to remote observations obtained from the STEREO-A heliospheric imagers, which were able to capture the interplanetary evolution of the coronal mass ejections. Methods. We made use of the 3D coronal rope ejection model (3DCORE) in order to simulate the ICME evolution and reconstruct the measured flux rope signatures at the spacecraft positions. For this purpose, we adapted a previously developed approximate Bayesian Computation sequential Monte-Carlo (ABC-SMC) fitting algorithm for the application to multi-point scenarios. This approach not only allows us to find global solutions, within the limits of our model, but to also naturally generate error estimates on the model parameters and detect potential ambiguities. Results. We show that we are able to generally reconstruct the flux rope signatures at three different spacecraft positions simultaneously by using our model in combination with the flux rope fitting algorithm. For the well-behaved April 19 ICME, our approach works very well and displays only minor deficiencies. The May 28 ICME, on the other hand, shows the limitations of our approach for less clear ICME measurements or strongly deformed shapes. Unfortunately, the usage of multi-point observations for these events does not appear to solve inherent issues, such as the estimation of the magnetic field twist or flux rope aspect-ratios due to the specific constellation of the spacecraft positions, which all lie near the ecliptic plane. As our general approach can be used for any fast-forward simulation based model, we give a blueprint for future studies using more advanced ICME models.

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Cross Helicity of the 2018 November Magnetic Cloud Observed by the Parker Solar Probe

Cited by 18 publications

References 47 publications

Turbulence and wave transmission at an ICME-driven shock observed by the Solar Orbiter and Wind

Turbulence and wave transmission at an ICME-driven shock observed by the Solar Orbiter and Wind

Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions

Multi-point analysis of coronal mass ejection flux ropes using combined data from Solar Orbiter, BepiColombo, and Wind

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