Abstract
The interaction between a fast-speed and a low-speed stream causes
large-amplitude Alfvénic fluctuations; consequently, the intermittency
and the brief intervals of southward magnetic field associated with Alfvén
waves may cause high levels of AE activity, the so-called high-intensity,
long-duration, continuous AE activity (HILDCAA). In this article, the 4 h
windowed Pearson cross-correlation (4WPCC) between the solar wind velocity
and the interplanetary magnetic field (IMF) components is performed in order
to confirm that the less strict HILDCAA (HILDCAAs*) events include a larger
number of Alfvén waves than the HILDCAA events, once HILDCAAs disregard
part of the phenomenon. Actually, a HILDCAA event is entirely contained within
a HILDCAA* event. However, the opposite is not necessarily true. This article
provides a new insight, since the increase of Alfvén waves results in an
increase of auroral electrojet activity; consequently, it can cause
HILDCAAs* events. Another important aspect of this article is that the
superposed epoch analysis (SEA) results reaffirm that the HILDCAAs* are
associated with high-speed solar streams (HSSs), and also the HILDCAAs*
present the same physical characteristics of the traditional HILDCAA events.
Citation
ID:
132679
Ref Key:
prestes2017annaleshigh-intensity,