Equinox Sun

Autumn Arrives

Nearly a month has passed since my last solar observing session. Conditions finally improved on September 22nd, the day of the autumnal equinox. The sky cleared for only a few morning hours before clouds eventually returned in the afternoon. Temperature was in the 70's while breezes ruffled papers. Short episodes of steady atmosphere existed between mostly mediocre seeing. I observed for nearly an hour beginning at 11:55 am EDT, just 10.5 hours before the exact time of the equinox. At noon the Sun's center was only about 10 arc minutes north of the celestial equator!

A few decent sunspots and filaments were scattered about the solar disc, but none were truly spectacular. The first image below, a 24-image mosaic made with a 2X Barlow lens, shows the Earth-facing side of the Sun on September 22nd. An impressive dark filament on the Sun's left (east) side is the most striking feature. (Click on the image for a larger view.)

The southeastern portion of the Sun, shown in the next 3-image mosaic, had the majority of interesting features. The long dark filament was an enormous prominence on the Sun's limb a few days before September 22nd. Two days after September 22nd the long prominence to the lower left of the sunspots also became a large filament when it rotated onto the solar disc.

The next two images were made by stacking 100 of the best frames from a 1,000-frame video. These pictures show good detail because seeing was good during most of the time the video was recorded. The first image shows sunspots 2170 (above) and 2169 (below) split by a horizontal filament.

Notice the structure to the left of the horizontal dark filament. It looks very much like the shape of magnetic field lines around the north and south poles of a bar magnet!

Gases shaped by magnetic fields on the Sun

Iron filings reveal the shape of a bar magnet's magnetic field

The group of sunspots near the southeastern limb are shown next in good detail.

Finally, here's a nice prominence hanging below the Sun's southern limb.

October usually brought clear weather at my old home in Lynchburg. I wonder if this will be true in Williamsburg.