Abstract


  CHROMOSPHERIC ANEMONE JETS AS EVIDENCE OF SMALL-SCALE, INTERMITTENT MAGNETIC RECONNECTION IN SOLAR CHROMOSPHERE

  A. Singh., Amity University, alkendra@gmail.com
  H. Isobe, Graduate School of Advanced Integrated Studies in Human Survivability, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8501, Japan,
  A. Hillier, Deptt. of Applied Mathematics and Theoretical Physics (DAMTP), University of Cambridge , Wilberforce Road, Cambridge CB3 0WA,UK,
  K. Shibata, Kwasan and Hida Observatories, Kyoto University, 17-1 Kitakazan-ohmine-cho, Yamashina-ku, Kyoto 607-8471, Japan,

The Solar Optical Telescope (SOT) onboard Hinode discovered numerous, small-scale jets in the chromosphere outside sunspots with Ca II H broad band filter (Shibata et al. 2007). Statistical studies show that the chromospheric anemone jets have: (1) a typical length ~1.0 Mm–4.0 Mm, (2) a width ~100 km – 400 km, (3) a lifetime ~100 s –500 s, and (4) a velocity ~5 km/s – 20 km/s (Nishizuka et al. 2011). The chromospheric anemone jets are supposed to be formed as a result of the magnetic reconnection between small bipole and the overlying existing field (also see Singh et al. (2011) for variety of reconnection features observed in chromospheric anemone jets). The high-resolution observations of chromospheric anemone jets have shown multiple plasma ejections and the intermittent nature of magnetic reconnection in the solar chromosphere, highlighting the need for fast reconnection to occur in a highly collisional plasma (Singh et al. 2012). However, the reconnection process through which fast magnetic reconnection would occur in the solar chromosphere is not yet understood. According to Singh et al. (2015), it is due to the tearing mode instability occurring in a Sweet-Parker current sheet in a partially ionized plasma and the subsequent non-linear instability due to the plasmoid-dominated reconnection, the Sweet–Parker current sheet tends to have a fractal-like structure, and when the magnetic field in the chromosphere is sufficiently strong the tearing mode instability can reach down to the kinetic scales, which are hypothesized to be necessary for fast reconnection.

References:

1. Shibata, K. et al. 2007, Science, 318, 1591
2. Nishizuka, N. et al. 2011, ApJ, 731, 43
3. Singh, K.A.P. et al. 2011, Phys. of Plasmas, 18, 111210
4. Singh, K.A.P. et al. 2012, ApJ, 759, 33
5. Singh, K.A.P. et al. 2015, PASJ, 67, 96