Alfvén waves as a possible source of long‐duration, large‐amplitude, and geoeffective southward IMF. Issue 5 (16th May 2014)

• Record Type: Journal Article
• Authors: Zhang, X.‐Y.; Moldwin, M. B.; Steinberg, J. T.; Skoug, R. M.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 5(2014:May)
• Page Start: 3259
• Page End: 3266
• Publication Date: 2014-05-16
• Subjects: Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2013JA019623
• Languages: English
• ISSNs: 2169-9380

Abstract

<abstract abstract-type="main" id="jgra50985-abs-0001"> <title>Abstract</title> <p id="jgra50985-para-0001">The southward component (<italic>B</italic>_{<italic>s</italic>}) of the interplanetary magnetic field (IMF) is a strong driver of geomagnetic activity. Well‐defined solar wind structures such as magnetic clouds and corotating interaction regions are the main sources of long‐duration, large‐amplitude IMF <italic>B</italic>_{<italic>s</italic>}. Here we analyze IMF <italic>B</italic>_{<italic>s</italic>}events (<italic>t</italic>&gt; 1 h, <italic>Bz</italic>&lt;−5nT) unrelated with any well‐defined solar wind structure at 1 AU using ACE spacecraft observations from 1998 to 2004. We find that about one third of these <italic>B</italic>_{<italic>s</italic>} events show Alfvénic wave features; therefore, those Alfvén waves in the solar wind are also an important source of long‐duration, large‐amplitude IMF southward component. We find that more than half of the Alfvén wave (AW)‐related <italic>B</italic>_{<italic>s</italic>} events occur in slow solar wind (<italic>V</italic>sw &lt; 400 km/s). One third of the AW‐type <italic>B</italic>_{<italic>s</italic>}events triggered geomagnetic storms, and half triggered substorms.</p> </abstract>