Blobs in recurring EUV jets
Qingmin Zhang Submitted: 2014-05-20 19:44
Coronal jets are one type of ubiquitous small-scale activities caused by
magnetic reconnection in the solar corona. They are often associated with
cool surges in the chromosphere.
In this paper, we report our discovery of blobs in the recurrent
and homologous jets that occurred at the western edge of NOAA active
region 11259 on 2011 July 22.
The jets were observed in the seven extreme-ultraviolet (EUV)
filters of the Atmospheric Imaging Assembly (AIA) instrument
aboard the Solar Dynamics Observatory (SDO). Using the base-difference
images of the six filters (94, 131, 171, 211, 193, and 335 Å), we
carried out the differential emission measure (DEM) analyses to explore
the thermodynamic evolutions of the jets. The jets were
accompanied by cool surges observed in the Hα line center of
the ground-based telescope in the Big Bear Solar Observatory.
The jets that had lifetimes of 20-30 min recurred at the same place
for three times with interval of 40-45 min. Interestingly,
each of the jets intermittently experienced several upward eruptions at the
speed of 120-450 km s-1. After reaching the maximum heights,
they returned back to the solar surface, showing near-parabolic trajectories.
The falling phases were more evident in the low-T filters than in
the high-T filters, indicating that the jets experienced cooling after the
onset of eruptions. We identified bright and compact blobs in the
jets during their rising phases. The simultaneous
presences of blobs in all the EUV filters were consistent with the broad
ranges of the DEM profiles of the blobs (5.5≤ log T≤7.5), indicating
their multi-thermal nature. The median temperatures of the blobs were
~2.3 MK. The blobs that were ~3 Mm in diameter had lifetimes
of 24-60 s.
To our knowledge, this is the first report of blobs in coronal jets. We
propose that these blobs are plasmoids created by the magnetic reconnection
as a result of tearing-mode instability and ejected out along the jets.
Authors: Q. M. Zhang and H. S. Ji
Publication Status: accepted for publication in A&A
Last Modified: 2014-05-21 13:36