Comments on Related Flares.
Abstract
On 18 September 1957 between 12h45rn and 21h00rn UT there took place on the solar disk near N 200 B 050 four major chromospheric brightenings that were reported by the various observers as either two, three, or four major flares. Examination of both hydrogen and calcium spectroheliograms showed that events 1 and 3 were in apparently identical locations within the plage, and that events 2 and 4 formed another set of homologous flares, to use the term currently applied to flares that repeat in the same region. The events can be interpreted either as four separate flares or, as two flares each with two phases and two maxima. If the first interpretation is correct, the events indicate that at least two families of homologous flares occurred within the same center of activity. Questions regarding possible physical differences between such families of flares immediately arise. The concomitant radio frequency emission and the detailed development of the flares seem to favor the second interpretation, and the events appear in our Working List of IGY Flares as two flares, each with two maxima. Imp or- F Beginning End Maximum tance Position <1303 >1425 1325 3 N23 E10 <1425 >1600 1530 N20 E04 <1722 >1818 1740 N 23 E08 1818 2110 1840 3+ N20 E03 This latter organization of the events means that the second phase of each flare is considered to be in some sense a consequence or development of phenomena initiated during the first phase. The observations thus suggest that events reported as major flares in the same center of activity with maxima separated by as much as two or more hours may refer, in some cases, to two phases of a complex solar event rather than to independent phenomena. Either interpretation of the four events on 1957 September 18 indicates that major homologous flares can repeat in less than 5 h and suggests that more information on recurrent flares is desirable.
- Publication:
-
The Astronomical Journal
- Pub Date:
- 1965
- DOI:
- 10.1086/109657
- Bibcode:
- 1965AJ.....70S.673D