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Ann. Geophys., 24, 3179-3184, 2006
www.ann-geophys.net/24/3179/2006/
© European Geosciences Union 2006
On the distribution of energy versus Alfvénic correlation for polar wind fluctuations
B. Bavassano and R. Bruno
Istituto di Fisica dello Spazio Interplanetario, Istituto Nazionale di Astrofisica, Rome, Italy
Abstract. Previous analyses have shown that polar wind fluctuations at MHD scales appear as a
mixture of Alfvénic fluctuations and variations with an energy imbalance in
favour of the magnetic term. In the present study, by separately examining the
behaviour of kinetic and magnetic energies versus the Alfvénic correlation
level, we unambiguously confirm that the second population is essentially
related to a large increase of the magnetic energy with respect to that of
the Alfvénic population. The relevant new result is that this magnetic
population, though of secondary importance in terms of occurrence frequency,
corresponds to a primary peak in the distribution of total energy. The fact
that this holds in the case of polar wind, which is the least structured type
of interplanetary plasma flow and with the slowest evolving Alfvénic turbulence,
strongly suggests the general conclusion that magnetic structures cannot be
neglected when modeling fluctuations for all kinds of wind regime.
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