Twisting solar coronal jet launched at the boundary of an active region
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris
5 place Jules Janssen,
2 School of Astronomy and Space Science, Nanjing University, 210093 Nanjing, PR China
3 Instituto de Astrofisica de Canarias, via Lactea, s/n, 38205 La Laguna ( Tenerife), Spain
4 Dept. of Astrophysics, Universidad de La Laguna, 38200 La Laguna ( Tenerife), Spain
5 National Astronomical Observatory of Japan, Mitaka, 181-8588 Tokyo, Japan
6 UCL-Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
7 Max-Plank-Institut für Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
8 Departamento de Física, Universidad de Los Andes, A.A., 4976, Bogotá, Colombia
9 W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
Received: 1 July 2013
Accepted: 10 September 2013
Aims. A broad jet was observed in a weak magnetic field area at the edge of active region NOAA 11106 that also produced other nearby recurring and narrow jets. The peculiar shape and magnetic environment of the broad jet raised the question of whether it was created by the same physical processes of previously studied jets with reconnection occurring high in the corona.
Methods. We carried out a multi-wavelength analysis using the EUV images from the Atmospheric Imaging Assembly (AIA) and magnetic fields from the Helioseismic and Magnetic Imager (HMI) both on-board the Solar Dynamics Observatory, which we coupled to a high-resolution, nonlinear force-free field extrapolation. Local correlation tracking was used to identify the photospheric motions that triggered the jet, and time-slices were extracted along and across the jet to unveil its complex nature. A topological analysis of the extrapolated field was performed and was related to the observed features.
Results. The jet consisted of many different threads that expanded in around 10 minutes to about 100 Mm in length, with the bright features in later threads moving faster than in the early ones, reaching a maximum speed of about 200 km s-1. Time-slice analysis revealed a striped pattern of dark and bright strands propagating along the jet, along with apparent damped oscillations across the jet. This is suggestive of a (un)twisting motion in the jet, possibly an Alfvén wave. Bald patches in field lines, low-altitude flux ropes, diverging flow patterns, and a null point were identified at the basis of the jet.
Conclusions. Unlike classical λ or Eiffel-tower-shaped jets that appear to be caused by reconnection in current sheets containing null points, reconnection in regions containing bald patches seems to be crucial in triggering the present jet. There is no observational evidence that the flux ropes detected in the topological analysis were actually being ejected themselves, as occurs in the violent phase of blowout jets; instead, the jet itself may have gained the twist of the flux rope(s) through reconnection. This event may represent a class of jets different from the classical quiescent or blowout jets, but to reach that conclusion, more observational and theoretical work is necessary.
Key words: Sun: magnetic topology / Sun: UV radiation / Sun: corona / Sun: surface magnetism
© ESO, 2013