Data gaps due to missing telemetry: ~ 5.5 h.

Note, that the link to the catalogue page  is now: http://www.cbk.pan.wroc.pl/resik_catalogue.htm.

Bad Luck with Two Recent X-flares

Recent Solar Days, centered around 18 March 2003 (http://sohowww.nascom.nasa.gov/sunearth2003/events.html), have been greeted by the Sun with the two, very much unexpected X-ray class events. The events took place at the same near the limb active region. The first flare occurred on March 17 with the maximum around 19:05 UT (X1.5, S14W38) and the next flare on March 18 at 12:08 UT (X1.5, S14W46). We awaited very much any X-class events as they are expected to be strong enough in order to show-up potential Ni XXVII He-like triplet lines (cf. weekly 49, 2002) in third order reflection. The instrument is tuned for such measurements all the time provided the intensity of the event reaches the threshold. However, we have rather bad luck with these „celebrity” flares, as you may see on the Figures (enlargements of the catalogue pages). RESIK did not switch to 3^rd order mode in any of them.

Figure 1. Extracted portions of the RESIK Catalogue showing time coverage of recent X-class observations by our instrument.

Figure 2. Averaged first order spectra collected for the two recent X-flares. The location of the source relative to the dispersion plane allows to see substantial part of S XV 1s² – 1s3p line (the most prominent spectral feature seen).

Our bad luck with 3^rd order measurements has been due to rare coincidence of flare timing and the orbital position of the CORONAS-F satellite. For the first flare (March 17), just before the trigger for 3^rd order had to be issued, the HV was turned off. Later on, the flare signal was so strong that detectors were mostly saturated. On the decay phase, the trigger level was not met by few counts. However RESIK was most of the time doing spectral recording in the first order each 2 s. This lasted long enough that the memory quota allocated by SSNI telemetry had been filled up by 18 March ~10:30 UT, and telemetry flow has been stopped. The telemetry was made free again, after telemetry dump (around 13:00 UT), which was the reason that we missed the rise phase of the second event. Notwithstanding of this bad luck (every solar observer knows this well), we collected hundreds of spectra covering the rise and decay of the first flare, and thousands of spectra (in first order) during decay of the second event. Examples of the event-integrated spectra are shown in Figure 2.

Prepared by: Janusz Sylwester js@cbk.pan.wroc.pl and Barbara Sylwester bs@cbk.pan.wroc.pl.