Solar Xray Jets observe with YohkohSXT and TRACE

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Solar X-ray Jets observe with Yohkoh/SXT and TRACE

• Masumi Shimojo
• The Institute of Space and Astronautical Science,
  Japan
• Nariaki Nitta
• Lockheed Martin Solar Astrophysics Laboratory,
  U.S.A
• Kazunari Shibata
• Kwasan Observatory, Kyoto University, Japan

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Introduction
The soft X-ray telescope aboard Yohkoh has
discovered X-ray jets in the solar corona. These
X-ray jets are transitory X-ray enhancements with
an apparent collimated motion (Figure 1).
According to a more recent study that involved
1-D hydrodynamic simulations (Shimojo 1999), the
observed properties can be reproduced if we
consider an X-ray jet to be an evaporation flow
as a result of magnetic reconnection. However,
the fact that untwisting motions are seen in some
jets suggest that acceleration may at least
partly be of magnetic origin. Since 1998, TRACE
has revealed fine structure and dynamic motions
of corona and transition region. Chae et al.
(1999) found several EUV jets from TRACE data and
revealed that some properties of these EUV jets
are similar to those of X-ray jets observed with
Yohkoh. The result suggests that EUV and X-ray
jets may have the same physical origin. In this
poster, we present observational results based on
TRACE EUV and Yohkoh/SXT Soft X-ray data to
further study to fine structure of X-ray jets.
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An Example of Solar X-ray Jets

• Length 104 - 4x105 km
• Width 5x103 - 105 km
• Apparent Velocity 10 - 104 km/s
  (Ave. 200km/s )

Yohkoh/Soft X-ray Telescope

• Most jets are associated brightenings (small
  flares) at their footpoint.
• The X-ray intensity distribution along an X-ray
  jet often shows an exponential decrease with
  distance from the footpoint.

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Observation

• Yohkoh/Soft X-ray Telescope PFI Data
  Spatial Resolution 2.5 arcsec Temperature
  gt 2MK (Filter Al.1 AlMg)
• TRACE (Transition Region And Coronal
  Explorer) Spatial Resolution 1 arcsec
  Wave Length 171Å ( 1 MK) 195Å (
  1.6 MK)
• Event List
• 7 August 1998 0038 UT
• 20 May 1999 1110 UT

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Results
Helical Structure in X-ray Jets
7 August, 1998 Event
TRACE/195Å Images There is many fine structures
and some helical structures in the EUV-Jet.
Jet
Yohkoh/SXT Image There is no helical structure in
the X-ray jet.
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Spinning Motion in X-ray Jets
20 May 1999 1110 UT Event
In Trace 171Å images, we can find that the
spinning motion of some blob features.
Jet
I have movies in my laptop PC. Please contact
with me, I will show you the movie of this event
in this place.
TRACE 171Å EUV-Jet Spinning Motion
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Motion of Footpoint brightening Loops
The brightest parts (loops) move from East-South
region to East-North region of the footpoint
region. And the root of jets also move along the
brightest parts of the footpoint.
20 May 1999 1110 UT Event
This motion suggests that the region of energy
release move in the X-ray Bright Point during the
lifetime of the X-ray jet.
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The Difference of the Peak Time of Jets and
Footpoint flares
Although the peak time of X-ray intensity (SXT)
of the footpoint brightening is same as that of
X-ray jet, the peak time of EUV intensity (171Å)
of the footpoint brightening is earlier than
that of EUV-Jet.
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Discussion Conclusion

• Since the higher spatial resolution of TRACE
  data, we found the fine structures in X-ray jets
  and following properties
• Helical Structure and Spinning Motion
  ? The acceleration is of pressure gradient
  magnetic force ?
• Motion of Brightest Flare Loops at the Footpoint
  ? (Horizontal ?) movement of the energy release
  site ?
• The Difference of Peak Time between Jets and
  Flares ? The 1MK loops produced at the early
  phase of jets. ? In the early phase, the energy
  release rate is small ? or The flare
  loops at the early phase are smaller than the
  flare loops at peak phase ?