Bastille Day throughout history

Science Nugget: July 13, 2001


Yes, you've seen through our motives here - this is nothing more than a transparent ruse by which we get to show you more pretty pictures of solar events that took place on July 14, 2000. The first anniversary of this wonderful event is to be tomorrow, and although the calendar doesn't dictate solar phenomena (it's more the other way around), we can hope... If, incidentally, you are a history buff and found this page under the mistaken hope of seeing a medieval castle in Paris, sorry; we're talking about solar history here, and recent history at that.

But, in the interest of sincerity, let's look for remarkable things on the Bastille Days during the Yohkoh era, from 1992 on. First we just survey the GOES events from the archive, finding a short but interesting list of major flares. Then, looking at the ADS archive (NASA's Astrophysical Data Service), one already has half-a-dozen published papers in the literature on the event from the year 2000 alone!

Year by year... 1996, 1998, 2000

The Sun Celebrates Bastille Day! Flare eruption in H-alpha from region BBSO 3722 at 15:00 UT on July 14th, 1996 after limb transit. The flare registered C9 but probably was M-class. This image is clipped from a 2000 x 2000 pixel full-disk image from Big Bear Solar Observatory. The activity it depicts reflects the passage, over the solar west limb, of the "last best active region" of the previous solar cycle. This was the subject of an analysis of Yohkoh data by Sterling et al. in 1997.
The Sun Celebrates Bastille Day Again! In 1998 a nice M-class flare observed by TRACE demonstrates the ideas of the "breakout" model of 3D magnetic reconnection in the corona. Click on the image to get a views of the magnetic field in this model, and its cartoonification. See here for the analysis of Aulanier et al, published in 2000, mainly of TRACE data.
The Sun Celebrates Bastille Day Yet Again! In 2000 it was an X-class flare with most amazing properties, the subject of any number of scientific papers published and in the works. Clicking on the icon here gets you to the most recent Yohkoh science nugget but one on this topic and points to the others. All but the first paper in the reference list relates to this flare. It featured a sigmoid, an arcade, hard X-ray ribbons, filament eruption, coronal mass ejection, gamma radiation, interplanetary particles, geoeffectiveness, you name it - its size, duration, and energy made everything nicely observable.

Predictions for 2001

Solar activity is rather low at the time of writing, giving us a breather for something retrospective like this. But an astute reader will note that the memorable Bastille Day events occur only in even-numbered years, so we will probably have to wait until 2002 for more fireworks. But if something does happen tomorrow, we'll do a hasty postscript here.

July 13, 2001
H. Hudson <>.