Abstract Explosive Events (EEs) observed by SUMER on SoHO at the 1393.8Å Si iv line are analyzed. We look for EEs to study their number distribution at low energies. Eight data sets taken in June 1996 in raster observations are used. In these observations a field on the solar disk is scanned several times during a period considerably longer than the typical timelife of an EE. To look for EE, we first identified the maxima and locations of spectral line increases. The maxima that took place at inner locations of the rastered fields were considered as possible EEs. From this sample, the cases where the spectral line underwent Doppler shifts at most ±3″ from the location of the maximum were considered EEs. After a selection, the region within 5″ of the event was ignored for 5min either side of the EE in order to conclusively select a different maxima. Based on the analysis of the locations of EEs, it was seen that the more intense EEs tend to take place at given regions while at the intermediate regions the observed EEs are less intense. Therefore we refer to them as Regions of Enhanced Emission (REE) and Quiet Regions (QR), respectively. The width of the REE regions, as seen in North–South direction is about 10–30″. In this work, a total of 487 EEs are analyzed, 266 at REE and 221 at QR. Also, Histograms are made of the maxima of the amplitude of the spectral line during EEs at both REE and QR. At the Histogram for EEs at QR the number grows as the flux decreases with a slope of −1.8. For EEs at REE the Histogram has a maximum about 1Wattsm−2 sr−1 Å−1 with a high energy slope of about −1.6. These numbers are both below the value required to give an important input of energy for coronal heating, as analyzed in the case of microflares (Hudson, 1991). The averages of the maxima of EEs at each set for the REE and QR are computed. The scatter plot of the average values indicates that there is a linear relation between them and the maximum amplitudes of EEs at REE are about two times larger than the amplitudes for EEs at QR.
The number distribution of weak Explosive Events observed by SUMER/SoHO
Advances in Space Research ; 58 , 10 ; 1997-2002
2016-07-26
6 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
The number distribution of weak Explosive Events observed by SUMER/SoHO
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