Dynamic Ly alpha jets

Abstract

The solar chromosphere and transition region are highly structured and complex regimes. A recent breakthrough has been the identification of dynamic fibrils observed in H alpha as caused by field-aligned magnetoacoustic shocks. We seek to find whether such dynamic fibrils are also observed in Ly alpha. We used a brief sequence of four high-resolution Ly alpha images of the solar limb taken by the Very high Angular resolution ULtraviolet Telescope (VAULT), which displays many extending and retracting Ly alpha jets. We measured their top trajectories and fitted parabolas to the 30 best-defined ones. Most jet tops move supersonically. Half of them decelerate, sometimes superballistically, the others accelerate. This bifurcation may arise from incomplete sampling of recurrent jets. The similarities between dynamic Ly alpha jets and H alpha fibrils suggest that the magnetoacoustic shocks causing dynamic H alpha fibrils also affect dynamic Ly alpha jets.

5 pages, 7 figures; changed title and content; accepted in Astronomy and Astrophysics; eps figures in full resolution are available at http://www.astro.sk/~koza/publications/vault/figs/

References in corpus (11)

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• High Resolution Observations and Modeling of Dynamic Fibrils
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• An explanation of the solar transition region
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Cited by in corpus (7)

• The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations
• Transverse Oscillations in Slender Ca II H Fibrils Observed with Sunrise/SuFI
• On the Active Region Bright Grains Observed in the Transition Region Imaging Channels of IRIS
• H-alpha features with hot onsets III. Fibrils in Lyman-alpha and with ALMA
• Chromospheric backradiation in ultraviolet continua and Halpha
• The Quiet-Sun Photosphere and Chromosphere
• Solar Spectroscopy and (Pseudo-)Diagnostics of the Solar Chromosphere