ON THE NATURE OF THE SOLAR WIND FROM CORONAL PSEUDOSTREAMERS

Journal Article · Fri Apr 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/749/2/182· OSTI ID:22020364

Wang, Y -M; Grappin, R ^[1]; Robbrecht, E ^[2]

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1. LUTH, Observatoire de Paris, CNRS, Universite Paris-Diderot, 92195 Meudon (France)
2. Royal Observatory of Belgium, 1180 Brussels (Belgium)

Coronal pseudostreamers, which separate like-polarity coronal holes, do not have current sheet extensions, unlike the familiar helmet streamers that separate opposite-polarity holes. Both types of streamers taper into narrow plasma sheets that are maintained by continual interchange reconnection with the adjacent open magnetic field lines. White-light observations show that pseudostreamers do not emit plasma blobs; this important difference from helmet streamers is due to the convergence of like-polarity field lines above the X-point, which prevents the underlying loops from expanding outward and pinching off. The main component of the pseudostreamer wind has the form of steady outflow along the open field lines rooted just inside the boundaries of the adjacent coronal holes. These flux tubes are characterized by very rapid expansion below the X-point, followed by reconvergence at greater heights. Analysis of an idealized pseudostreamer configuration shows that, as the separation between the underlying holes increases, the X-point rises and the expansion factor f{sub ss} at the source surface increases. In situ observations of pseudostreamer crossings indicate wind speeds v ranging from {approx}350 to {approx}550 km s{sup -1}, with O{sup 7+}/O{sup 6+} ratios that are enhanced compared with those in high-speed streams but substantially lower than in the slow solar wind. Hydrodynamic energy-balance models show that the empirical v-f{sub ss} relation overestimates the wind speeds from nonmonotonically expanding flux tubes, particularly when the X-point is located at low heights and f{sub ss} is small. We conclude that pseudostreamers produce a 'hybrid' type of outflow that is intermediate between classical slow and fast solar wind.

• OSTI ID: 22020364
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 749; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CURRENTS
EXPANSION
HELIOSPHERE
PLASMA
PLASMA SHEET
SOLAR WIND
SUN