@article{Good:2022:10.5194/egusphere-egu22-11274,
author = {Good, S and Hatakka, L and Ala-Lahti, M and Soljento, J and Osmane, A and Kilpua, E},
doi = {10.5194/egusphere-egu22-11274},
title = {Cross helicity of interplanetary coronal mass ejections},
url = {http://dx.doi.org/10.5194/egusphere-egu22-11274},
year = {2022}
}

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TY  - JOUR
AB  - <jats:p>&lt;p&gt;Like the solar wind in general, interplanetary coronal mass ejections (ICMEs) display magnetic field and velocity fluctuations across a wide range of scales. These fluctuations may be interpreted as Alfv&amp;#233;nic wave packets propagating parallel or anti-parallel to the local magnetic field direction, with cross helicity, &amp;#963;&lt;sub&gt;c&lt;/sub&gt;, quantifying the difference in power between the counter-propagating fluxes. We have determined &amp;#963;&lt;sub&gt;c&lt;/sub&gt; at inertial range frequencies in a large sample of ICME flux ropes and sheaths observed by the Wind spacecraft at 1 au. The mean &amp;#963;&lt;sub&gt;c&lt;/sub&gt; value was low for both the flux ropes and sheaths, with the balance tipped towards the positive, anti-sunward direction. The low values indicate that Alfv&amp;#233;nic fluxes are more balanced in ICMEs than in the solar wind at 1 au, where &amp;#963;&lt;sub&gt;c&lt;/sub&gt; tends to be larger and anti-sunward fluctuations show a greater predominance. Superposed epoch profiles show &amp;#963;&lt;sub&gt;c&lt;/sub&gt; falling sharply in the upstream sheath and being typically close to balance inside the flux rope near the leading edge. More imbalanced, solar wind-like &amp;#963;&lt;sub&gt;c&lt;/sub&gt; values are found towards the trailing edge and further from the rope axis. The presence or absence of an upstream shock also has a significant effect on &amp;#963;&lt;sub&gt;c&lt;/sub&gt;. Coronal and interplanetary origins of low &amp;#963;&lt;sub&gt;c&lt;/sub&gt; in ICMEs are discussed.&lt;/p&gt;</jats:p>
AU  - Good,S
AU  - Hatakka,L
AU  - Ala-Lahti,M
AU  - Soljento,J
AU  - Osmane,A
AU  - Kilpua,E
DO  - 10.5194/egusphere-egu22-11274
PY  - 2022///
TI  - Cross helicity of interplanetary coronal mass ejections
UR  - http://dx.doi.org/10.5194/egusphere-egu22-11274
ER  - 

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