Up: Analysis of evolution of
On 19 October 1995, during the coordinated international observing
campaign, we obtained a long time series of observations of the NOAA 7912
active region with the French Multichannel Subtractive Double Pass
spectrograph (MSDP) mounted at the German Vacuum Tower Telescope
(VTT) on Tenerife. We also used images taken with Yohkoh Soft X-ray
Telescope (SXT). In the investigated active region two X-ray jets were
observed with the Yohkoh/SXT at 10:29 UT and 16:59 UT which had
major response at radio wavelengths (type III bursts)
[15, (van Driel-Gesztelyi et al. 1998a;]
[12, Schmieder et al. 1998).] The jets were related to two small
flares (GOES levels B3.2 and B1.3 and 1B and 1N importance in H
,
respectively).
![\begin{figure}
\resizebox {12cm}{!}{\includegraphics{ds1686f1.eps}}
\hfill
\parbox[b]{55mm}{}\end{figure}](/articles/aas/full/1999/16/ds1686/Timg2.gif) |
Figure 1:
Yohkoh/SXT observation and magnetic fields of NOAA 7912 active
region co-aligned with MSDP H image on 19 October 1995. Upper
left panel: X-ray image taken at 10:07 UT; upper right panel: Kitt Peak
magnetogram taken at 14:59 UT; lower left panel: H image at 10:58
UT with the X-ray contour; lower right panel: H image at 10:58 UT
with the 50 Gauss magnetic field contours |
Jets are normally related to relatively small chromospheric flare events,
while their impact in the corona and the interplanetary space may be much
more important than that of confined flares of much higher chromospheric
importance. Normally, jets occur in regions with high shear and certain
magnetic complexity: at one of their footpoints there is frequently found
an included, or parasitic polarity.
Spectral observations being at our disposal allow us to investigate the
kinematics of material motions in the specified active phenomena. We
analyze what kind of magnetic and chromospheric features correspond to
footpoints of X-ray bright loops and how the chromospheric structures
evolve due to the flare and jet activity.
Most of the formerly published papers on complex analysis of active
regions' evolution concerned the regions displaying high flare activity. The
main aim of this paper is to analyze the activity evolution in a region of
medium activity in order to investigate the influence of rather low energy
release on filaments, fibrils and chromospheric brightenings.
Up: Analysis of evolution of
Copyright The European Southern Observatory (ESO)