Evolution of Alfvénic fluctuations inside an interplanetary coronal mass ejection and their contributions to local plasma heating: Joint observations from 1.0 AU to 5.4 AU

Kavli Affiliate: John D. Richardson

| First 5 Authors: Hui Li, Chi Wang, John D. Richardson, Cui Tu,

| Summary:

Directly tracking an interplanetary coronal mass ejection (ICME) by widely
separated spacecrafts is a great challenge. However, such an event could
provide us a good opportunity to study the evolution of embedded Alfv’enic
fluctuations (AFs) inside ICME and their contributions to local plasma heating
directly. In this study, an ICME observed by Wind at 1.0 au on March 4-6 1998
is tracked to the location of Ulysess at 5.4 au. AFs are commonly found inside
the ICME at 1.0 au, with an occurrence rate of 21.7% and at broadband
frequencies from 4$times 10^{-4}$ to 5$times 10^{-2}$ Hz. When the ICME
propagates to 5.4 au, the Aflv’enicity decreases significantly, and AFs are
rare and only found at few localized frequencies with the occurrence rate
decreasing to 3.0%. At the same time, the magnetic field intensity at the
AF-rich region has an extra magnetic dissipation except ICME expansion effect.
The energetics of the ICME at different radial distance is also investigated
here. Under similar magnetic field intensity situations at 1.0 au, the
turbulence cascade rate at the AF-rich region is much larger than the value at
the AF-lack region. Moreover, it can maintain as the decrease of magnetic field
intensity if there is lack of AFs. However, when there exists many AFs, it
reduces significantly as the AFs disappear. The turbulence cascade dissipation
rate within the ICME is inferred to be 1622.3 $Jcdot kg^{-1}cdot s^{-1}$,
which satisfies the requirement of local ICME plasma heating rate, 1653.2
$Jcdot kg^{-1}cdot s^{-1}$. We suggest that AF dissipation is responsible for
extra magnetic dissipation and local plasma heating inside ICME.

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