Short Duration Active Region Brightenings Observed in the EUV and Ha by SOHO/CDS and HIDA/DST

Details Short Duration Active Region Brightenings Observed in the EUV and Ha by SOHO/CDS and HIDA/DST Short Duration Active Region Brightenings Observed in the EUV and Ha by SOHO/CDS and HIDA/DST

Jan 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004esasp.547..273b&link_type=abstract

Proceedings of 'SOHO 13 - Waves, Oscillations and Small-Scale Transient Events in the Solar Atmosphere: A Joint View from SOHO a

Computer Science

1

Sun: Chromosphere, Sun: Transition Region, Sun: Activity

Scientific paper

We present the 1st detection of an H counterpart to the EUV blinker, using observations from a coordinated campaign between the SOHO Coronal Diagnostic Spectrometer and the Kyoto University Hida Observatory, Domeless Solar Telescope (DST). The observations were performed during July and August 2002. By designing the CDS observing sequences for high cadence and long duration observations, we were able to identify many short duration (<3 mins.) brightenings simultaneously in the He I 584.334A and O V 629.732A spectral lines. These brightenings show similar characteristics (intensity increases, sizes) to longer duration EUV blinkers previously reported in active regions and the 'quiet' Sun. Focusing on two events which show pronounced emission in the upper chromosphere (He I), we have been able to identify cospatial bright points in the lower chromosphere (H line centre, 60.5A) which show enhanced emission during the EUV blinkers. These bright features have similar lifetimes to their EUV counterparts and their peak intensities occur close to simultaneously with the peak blinker intensities in the He I and O V lines. In both cases the He I and O V lines show excess line broadening at the peak of the event (>15 km s01) and in one event evidence of downward (red-shifted) motion is observed. A statistical study is being performed to provide a complete picture of the line width and velocity characteristics of these events and to determine whether the H counterparts are common, or confined to specific blinkers with pronounced He I emission. The high cadence of our observations also allowed us to examine the eects of spatial and temporal averaging on the determination of the properties of blinkers. We find that both short and long duration blinkers are composed of elementary brightening events and that such events can be undetectable in observations with low temporal cadence. Finally, the H brightenings appear to correlate well with the elementary EUV brightening events.

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