Case study of multi-temperature coronal jets for emerging flux MHD models^⋆

¹ Observatoire de Paris, LESIA, UMR8109 (CNRS), 92195 Meudon Principal Cedex, France
e-mail: reetikajoshi.ntl@gmail.com, reetika.joshi@obspm.fr
² Department of Physics, DSB Campus, Kumaun University, Nainital 263 001, India
³ Centre for Mathematical Plasma Astrophysics, Dept. of Mathematics, KU Leuven, 3001 Leuven, Belgium
⁴ SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
⁵ Instituto de Astrofisica de Canarias, Via Lactea, s/n, 38205 La Laguna, Tenerife, Spain
⁶ Department of Astrophysics, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain
⁷ Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029, Blindern 0315, Oslo, Norway
⁸ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern 0315, Oslo, Norway

Received: 24 February 2020
Accepted: 11 May 2020

Abstract

Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated.

Aims. We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit–jaw high spatial and temporal resolution images.

Methods. The AIA filters allow us to study the temperature and the emission measure of the jets using the filter ratio method. We studied the pre-jet phases by analysing the intensity oscillations at the base of the jets with the wavelet technique.

Results. A fine co-alignment of the AIA and IRIS data shows that the jets are initiated at the top of a canopy-like double-chambered structure with cool emission on one and hot emission on the other side. The hot jets are collimated in the hot temperature filters, have high velocities (around 250 km s⁻¹) and are accompanied by cool surges and ejected kernels that both move at about 45 km s⁻¹. In the pre-phase of the jets, we find quasi-periodic intensity oscillations at their base that are in phase with small ejections; they have a period of between 2 and 6 min, and are reminiscent of acoustic or magnetohydrodynamic waves.

Conclusions. This series of jets and surges provides a good case study for testing the 2D and 3D magnetohydrodynamic emerging flux models. The double-chambered structure that is found in the observations corresponds to the regions with cold and hot loops that are in the models below the current sheet that contains the reconnection site. The cool surge with kernels is comparable with the cool ejection and plasmoids that naturally appears in the models.