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DOES A POLAR CORONAL HOLE'S FLUX EMERGENCE FOLLOW A HALE-LIKE LAW?

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A. Savcheva1, J. W. Cirtain2, E. E. DeLuca1 and L. Golub1

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Recent increases in spatial and temporal resolution for solar telescopes sensitive to EUV and X-ray radiation have revealed the prevalence of transient jet events in polar coronal holes. Using data collected by the X-Ray Telescope on Hinode, Savcheva et al. confirmed the observation, made first by the Soft X-ray Telescope on Yohkoh, that some jets exhibit a motion transverse to the jet outflow direction. The velocity of this transverse motion is, on average, 10 km s–1. The direction of the transverse motion, in combination with the standard reconnection model for jet production (e.g., Shibata et al.), reflects the magnetic polarity orientation of the ephemeral active region at the base of the jet. From this signature, we find that during the present minimum phase of the solar cycle the jet-base ephemeral active regions in the polar coronal holes had a preferred east-west direction, and that this direction reversed during the cycle's progression through minimum. In late 2006 and early 2007, the preferred direction was that of the active regions of the coming sunspot cycle (cycle 24), but in late 2008 and early 2009 the preferred direction has been that of the active regions of sunspot cycle 25. These findings are consistent with the observations of Wilson et al. suggesting that each cycle of solar activity begins at polar latitudes soon after the onset of the previous cycle.


Keywords

Sun: corona; Sun: magnetic fields; Sun: X-rays, gamma rays


PACS

96.60.pc Coronal holes

96.60.qd Sun spots, Solar cycles

95.55.Ka X- and &ggr;-ray telescopes and instrumentation

95.85.Nv X-ray

96.60.qe Flares

95.55.Ev Solar instruments

Subjects

Instrumentation and measurement

Astrophysics and astroparticles

Dates

Issue 1 (2009 September 1)

Received 2009 April 6, accepted for publication 2009 July 24

Published 2009 August 13



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