How big can prominences be?

Quiescent prominences are perhaps the largest entities to occur on the sun in  H-alpha band. The 2010 April 12 example was already detached at its northern end, and would erupt into space some hours later.  In "Secrets of the Sun" Cambridge Uni Press 1984, p96 Ron Giovanelli gives an example, shown in mid-eruption, that may have been about the size of our 2010 prominence, when still attached to the sun.

Post Flare Loops at the west limb

AR11169 at the west limb

Cloudy skies prevented viewing of this region in the morning - but a curious GOES plot suggested a large flare behind the sun's west limb. Brief clear moments in the afternoon showed the remains of very large PFL.  The SDO satellite's AIA_304 detector (EUV) caught good views of the loops, active over hours. This glimpse showed few details - but material could be seen draining into the sunspot

Flares behind either limb seem to produce "flat-topped" flux peaks rather than the usual sharp spikes. This suggests the unseen flare was a GOES X-class.

Spotless Flare in an Old Active Region

M1.3 flare in the sun's east

While logging events in AR's in solar west and north, the GOES X-ray flux began to rise. At first the flare site could not be found - then the spotless eastern limb was viewed, showing this flare - which reached GOES M1.3, and was approaching its peak. Precursor events were missed.
       The flare site is that of old AR11158 - site of the first SC24 GOES X2.2 Feb 15.  The now spotless site hosted the strongest "spotless" flare that I've seen. It's assumed that a large filament ejected at the site - but searches in the H-alpha "wings" showed nothing. A strong CME from the site followed.

A Sudden Burst of Global Activity on the Sun

                               Three active sunspot groups 2011 March 7.

This composite shows the three main active regions in the northern hemisphere.  High-lite of the day was the M1.3 flare at 03:58UT.  All attention was on the various sunspot groups - when the rising GOES flux showed the onset of a flare.  At first the site could not be located - I had not expected a flare at the eastern limb, where there were no sunspots.  The M1.3 was large and bright - and located at the now spotless site of  earlier AR11158 - that hosted the GOES X2.2 flare in February (C24's strongest flare so far).
During the M1.3 flare small transients occurred in the three Active Regions shown, all within a two minute window- perhaps triggered by the flare. Was this an example of a global solar event?

Note: the three groups are drawn to the same scale. Their positions on the disc are shown as solar coordinates. (The groups are more widely spaced than the sketch suggests)