Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Abstract. The plasma and magnetic-field instruments on the Helios 2 spacecraft, which was on 3 April 1979 located at 0.68 AU, detected an interplanetary coronal mass ejection (ICME) that revealed itself by the typical signature of magnetic field rotation. The solar wind flow speed ranged between 400 and 500 km/s. We present here some detailed proton velocity distributions measured within the ICME. These cold distributions are characterized by an isotropic core part with a low temperature, T≤105 K, but sometimes reveal a broad and extended hot proton tail or beam propagating along the local magnetic field direction. These beams lasted only for about an hour and were unusual as compared with the normal ICME protons distribution which were comparatively isotropic. Furthermore, we looked into the velocity and field fluctuations in this ICME and found signatures of Alfvén waves, which might be related to the occurrence of the hot proton beams. However, it cannot be excluded that the beam originated from the Sun.

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Photospheric magnetic field of an eroded-by-solar-wind coronal mass ejection

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317001077 ◽

2016 ◽

Vol 12 (S327) ◽

pp. 67-70

Author(s):

J. Palacios ◽

C. Cid ◽

E. Saiz ◽

A. Guerrero

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Coronal Mass Ejection ◽

Coronal Hole ◽

Interplanetary Medium ◽

Flux Rope ◽

Magnetic Characteristics ◽

Interplanetary Coronal Mass Ejection ◽

Fast Wind ◽

Mass Ejection

AbstractWe have investigated the case of a coronal mass ejection that was eroded by the fast wind of a coronal hole in the interplanetary medium. When a solar ejection takes place close to a coronal hole, the flux rope magnetic topology of the coronal mass ejection (CME) may become misshapen at 1 AU as a result of the interaction. Detailed analysis of this event reveals erosion of the interplanetary coronal mass ejection (ICME) magnetic field. In this communication, we study the photospheric magnetic roots of the coronal hole and the coronal mass ejection area with HMI/SDO magnetograms to define their magnetic characteristics.

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Geomagnetic effects of high-density plasma with southward magnetic field in the interplanetary coronal mass ejection observed on May 2–3, 1998

Earth Planets and Space ◽

10.1186/bf03351927 ◽

2006 ◽

Vol 58 (3) ◽

pp. 315-322 ◽

Cited By ~ 1

Author(s):

Haruka Adachi ◽

Tohru Sakurai ◽

Katsuhide Marubashi

Keyword(s):

Magnetic Field ◽

Coronal Mass Ejection ◽

High Density ◽

Interplanetary Coronal Mass Ejection ◽

Mass Ejection ◽

Density Plasma

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

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2020.610278 ◽

2021 ◽

Vol 7 ◽

Author(s):

E. K. J. Kilpua ◽

S. W. Good ◽

M. Ala-Lahti ◽

A. Osmane ◽

D. Fontaine ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Statistical Analysis ◽

Coronal Mass Ejection ◽

Inertial Range ◽

Spectral Indices ◽

Shock Region ◽

Field Fluctuations ◽

The Mean ◽

Mass Ejection

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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Multi-point observations of a reconnection outflow associated with interacting flux ropes in the solar wind

10.5194/egusphere-egu2020-8621 ◽

2020 ◽

Author(s):

Zoltan Vörös ◽

Emiliya Yordanova ◽

Owen Roberts ◽

Yasuhito Narita

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Flow Shear ◽

Magnetic Flux Ropes ◽

Interplanetary Coronal Mass Ejection ◽

Flux Ropes ◽

Magnetic Field Magnitude ◽

Field Fluctuations ◽

Mass Ejection ◽

The Magnetic Field

Twisted magnetic flux ropes embedded in an interplanetary coronal mass ejection (ICME) often contain oppositely oriented magnetic fields and potentially reconnecting current sheets. Reconnection outflows in the solar wind can be identified through magnetic field and plasma signatures, for example, through decreasing magnetic field magnitude, enhanced bulk velocity, temperature and (anti)correlated rotations of the magnetic field and plasma velocity. We investigate a reconnection outflow observed by ACE, WIND and Geotail spacecraft within the interaction region of two flux ropes embedded into an ICME. The SOHO spacecraft, located 15 RE upstream, 120 RE in GSE Y and 5 RE in GSE Z direction from the ACE spacecraft, does not see any plasma signatures of the reconnection outflow. At the same time the other spacecraft, also separated by more than 200 RE in X and Y GSE directions, observe strong plasma and magnetic field fluctuations at the border of the exhaust. &#160;The fluctuations could be associated with Kelvin-Helmholtz (KH) instability at the border of the reconnection outflow with strong flow shear.&#160; It is speculated that the KH instability driven fluctuations and dissipation is responsible for stopping the reconnection outflow which is therefore not seen by SOHO.

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Spatial coherence of interplanetary coronal mass ejection-driven sheaths at 1 AU

10.5194/egusphere-egu2020-13474 ◽

2020 ◽

Author(s):

Matti Ala-Lahti ◽

Julia Ruohotie ◽

Simon Good ◽

Emilia Kilpua ◽

Noé Lugaz

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Spatial Coherence ◽

Field Measurements ◽

Interplanetary Coronal Mass Ejections ◽

Magnetic Structures ◽

Interplanetary Coronal Mass Ejection ◽

Field Fluctuations ◽

Mass Ejection ◽

The Magnetic Field

We report on the longitudinal coherence of sheath regions driven by interplanetary coronal mass ejections (ICMEs). ICME sheaths are significant drivers of geomagnetic activity at the Earth, with a considerable fraction of ICME-driven storms being either entirely or primarily induced by the sheath. Similarly to Lugaz et al. (2018; doi:10.3847/2041-8213/aad9f4), we have analyzed two-point magnetic field measurements made by the ACE and Wind spacecraft in 29 ICME sheaths to estimate the coherence scale lengths, defined as the spatial scale at which correlation between measurements falls to zero, of the field magnitude and components. Scale lengths for the sheath are found to be mostly smaller than the corresponding values in the ICME driver, an expected result given that ICME sheaths are characterized by highly fluctuating, variable magnetic fields, in contrast to the often more coherent ejecta. A relatively large scale length for the magnetic field component in the GSE y-direction was found. We discuss how magnetic field line draping around the ejecta and the alignment of pre-existing magnetic structures by the preceding shock may explain the observed results. In addition, we consider the existence of longitudinally extended and possibly geoeffective magnetic field fluctuations within ICME sheaths, the full understanding of which requires further multi-spacecraft analysis.

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