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1 Introduction


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$\alpha$, respectively).
  
\begin{figure}
\resizebox {12cm}{!}{\includegraphics{ds1686f1.eps}}

 \hfill
 \parbox[b]{55mm}{}\end{figure} Figure 1: Yohkoh/SXT observation and magnetic fields of NOAA 7912 active region co-aligned with MSDP H$\alpha$ 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$\alpha$ image at 10:58 UT with the X-ray contour; lower right panel: H$\alpha$ 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.



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