511th WE-Heraeus-Seminar

From the Heliosphere into the Sun– Sailing against the Wind –

Collection of presentationsEdited by Hardi Peter (peter@mps.mpg.de)

Physikzentrum Bad Honnef, GermanyJanuary 31 – February 3, 2012

http://www.mps.mpg.de/meetings/heliocorona/

Explosive Events – swirling transition region jets

W. Curdt (1), H. Tian (2), S. Kamio (1)(1) Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany(2) High Altitide Observatory, National Center for Atmospheric Research, Boulder, Co, USA

Synthetical spectra

Spinning spicules / macrospicules

Synopsis

Abstract. We present an alternative model for the nature of explosive events that is based on the lack of apparent motiondespite of high Doppler motion, the bifurcation in jets/spicules, the spectral tilt, and a rapidly growing number of directobservations. We argue that the observed helical motion in macrospicules - if scaled down to a radius comparable to the slit sizeof a spectrometer - should have a spectroscopic signature similar to what it observed in explosive events.

Synthetical spectra of a spicule rotating at 60 km/s with afaint (5%) upflow of 100 km/s for various LOS orientations.The spectrum of the į=45° case is very similar to thosepresented here and can reproduce our observations.

We arrive at a concept that supports the idea that EE andspicules may be different manifestations of the same helicitydriven scenario, and that can solve the old contradiction ofhigh (spectroscopic) velocity lacking apparent motion. Wesuggest that at least in some cases EEs / spicules are to becompared to the unwinding of torsional springs.

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Bibl.: Curdt & Tian, 2011, A&A 532, L9Curdt, Tian, & Kamio, 2012, Sol Phys, in pressDere et al.,1989, Sol.Phys. 123,41Madjarska et al., 2006, A&A 452, L11Rompolt, 1975, Sol Phys 41, 329Suematsu et al., 2008, PASP 397, 27, Wilhelm 2000, A&A 360, 351

Wilhelm (2000), Madjarska et al. (2006), and others con-clude: “From an observational point of view there seems to be noobvious distinction between macrospicules and other spicules“.With this proposition we assume that also in small-sizespicules helicity is quite common, although not easilydetectable.

Spectral line duringan EE (right). Theevent reaches Dopp-ler flows from -40 to+40 km/s. The incli-nation angle be-tween the Dopplerflow and the disper-sion direction isexplained by the

The spectral tilt

Sit-and-stare study in the Si III/120.6 nm line shown as O-tplot together with profiles at rest and through an EE. Theline splits symmetrically, upflow and downflow stay over fourminutes within the 0.3" wide slit. The classical interpretationof this EE as bi-directional jet would require that the jets staywithin cones with an opening angle of less than a degreethat, in addition, are aligned with the LOS. This is veryunlikely. Dere et al. mentioned already in 1989: “It is hard toexplain the lack of apparent motion of such high-velocity events“.The problem is still unsolved.

Lack of apparent motion in EEs

bifurcated structure ofspicules. Suematsu etal. (2008) interpret thebifurcation as theedges of a cylindricalstructure that are brightdue to the longer path-lengths in the peri-phery of the cylinder.

rotation of a narrow, size feature that – if projected into theimage plane – is tilted (left): the upflow (blue) is observedfurther up compared to the downflow (red). The spectral tiltprovides evidence of rotation (Rompolt 1975). In analogywith distant stars that are spectroscopic binaries,spectroscopes are able to detect rotation even for sub-resolution features.

SUMER raster ofa macrospicule inO V (62.9 nm).The Doppler flowis not visible in theradiance image.

SOT images (sharpened) reveal the

(5s cadence)

adopted from Suematsu et al. 2008