Major Ha flares (importance ~2) in plages with only small or no spots constitute a rare but well observed aspect of solar activity. Information relating to 83 such flares has been assembled and studied. In the years 1956-1968 these flares represented ~ 7~ of all confirmed flares of importance 2. In general, the flares were of unusually long duration and rose to maximum intensity slowly. A flash phase was often absent or poorly defined. In a number of cases, the flare emission included two bright filaments more or less parallel. The flares usually occurred during the late, flare-poor phase of a center of activity, and their outbreak did not presage a resurgence of activity in subsequent rotations. The flares were frequently associated with the position of dark filaments.Like major flares in general, the flares in regions with small or no spots usually were associated with long-enduring radiation (gradual rise and fall and/or postburst increase) at ~ 10 cm, and with X-ray enhancements (2-12/~) at least as great as 4 times the quiet Sun. They were deficient, in the associated occurrence of strong, impulsive, centimetfic bursts and of X-ray events > 20 times the quiet Sun. The absence of large spots apparently did not inhibit the occurrence of Type II bursts.Only 41% of the major flares here studied were accompanied by shortwave fades and of these ionospheric disturbances only a few were great events. In general the flares were not followed by the detection of high energy particles or the onset of geomagnetic storms. However, a few of the flares (including those of 1967 January 11 and February 13) apparently were associated with well observed particle emission and suggest that the presence of a large complex spot is not always necessary for the acceleration of energetic particles or the emission of solar plasma at the time of a large Hc~ flare.

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The proton flare of August 28, 1966 began on Ha records at 15h21m35 ~ UT. It presented an unusually complex development with flare emission occurring in two distinct plages. The brightest part of the flare attained maximum intensity, 152 % of the continuum, between 15h30 TM and 15h32 m UT. Photometric measurements show that a long-enduring part of the flare continued to decline in intensity until at least 21h20 TM UT.The flare developed first in parts of the plages that were near the extremities of a filament and a complex system of curvilinear absorption structures, possibly an eruptive prominence in projection. During the rise to maximum intensity a large expanding feature moved southward from the site of the flare with a velocity ~ 700 km/sec. Its appearance on monochromatic records of the chromosphere made in the center of Hc~ and 0.5 A on either side was consistent with the effect of an advancing phenomenon that induces a small shift of the Hc~ absorption line, first to longer, and then to shorter wavelengths.Two bright flare-filaments were obvious aspects of the event by 15~128m and dominated the main phase of the flare. Loop-type prominences were observed in absorption as early as 15h40 m. General Description of Outbreak and Development of the H~ FlareThe proton flare of August 28, 1966 (Imp. 2B or greater, N22 E05) occurred in two well-defined plages, each with separate spot groups, and presented an unusually complex development. The first evidence of flare-emission on the He patrol films of the McMath-Hulbert Observatory (0.5 A band pass) occurred at 15h21 m35 s UT ** when a small area, region 1 in Figure 1A, on the North side of filament F ( Figure 1B) suddenly increased in intensity. Thirty seconds later another small point, region 2, directly across the filament and on the South side was also the site of flare-emission. These two initial brightenings were in the plage surrounding the dying/3 spot group (Mt. Wilson No. 16111) that preceded by approximately 15 ~ the large/37 spot (Mt. Wilson No. 16114) near which the principal He emission of this proton flare would occur. By 15h22m35 S flare-emission had started at regions 3 and 4 within the large bright plage surrounding the/~7 spot. The flare then broke out in numerous small bright points, some of which are indicated in Figure 1. Intensity increased rapidly at 15h24 TM and 15h25 m UT and maximum intensity was reached between 15h3ff n and 15h32 m UT. (See Figure 2.)The regions of enhanced emission for this flare fall naturally into two parts, the

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