|Note: The pictures shown below were imaged at a different orientation. This accounts for the features to appear at different locations on the Solar disc.|
On September 9th, 2017 I captured several images of the Sun which showed a very interesting feature. Above, on the top image if you look down just inside the 5:00 position you will see a circular feature. The image just below shows a closer look. Inside that apparent circle was a very active area including two active regions (AR 2674 and AR 2679). Sunspots and plages are clearly visible. Plage is a French word meaning "beaches". It always appears around a sunspot or an "active region" as a bright dense area in the chromosphere. You can also see the effects of the magnetic fields on the chromosphere in that area.
There were many opinions as to what this circular feature could have been. With the help of HAL member and retired NASA engineer Bub Dutilly, I was connected with Dr. Joe Gurman at NASA Goddard Space Flight Center. Joe did a considerable amount of research reviewing many images of the Sun as well as data that was gathered from the Solar happenings on September 29th. Using data and images from Big Bear Solar Observatory in San Bernadino County, California. Dr. Gurman was looking for like information to compare against. He also used data recorded at SDO (Solar Dynamics Observatory at NASA Goddard). One of the theories is that this could have been a "Moerton Wave" (A wave-like disturbance in the chromosphere initiated by a solar flare). The following video recorded at SDO was viewed to see if it indeed was a "Moerton Wave". (The area we are observing is just inside the edge at the 3:00 position). https://umbra.nascom.nasa.gov/aia/aia_20170909_193_diff.mov As a result of that research we were able to eliminate a "Moerton Wave" as a possibility. Dr. Gurman concluded; "I believe it is a filament channel in the form of (more or less) a circle. They happnen."
For additional opinions Dr. Gurman referred me to two other NASA researchers at Goddard, Dr. Holly Gilbert and Dr. Therese Kucera.
Dr. Gilbert observed that the circle is not really a circle. She said; "It might be "two filaments (one very curved on the right, and the other on the left slightly curved). Although they looked connected, I don't think they are".
Dr. Kucera compared my images to those on the NSO GONG site (National Solar Observatory - Global Oscillation Network Group). Dr. Kucera said; I think what we are looking at is a curved shape in the fibrils, thin dark threads on the chromosphere that can trace the magnetic field direction." Immediately below is the image from the NSO GONG site. The area we are talking about is shown just inside the edge at the 3:00 position.
In closer review of the "circular feature" it is apparent that it is not a circle at all. It is the conclusion of the experts that I imaged filaments (probably 2) in such a way that they formed almost a circle. In all of the September 29, 2017 Hydrogen-alpha solar images I have been able to find, it appears that I have the only pictures that show such a clearly defined filament structure.
(Filaments are masses of relatively cool and dense material suspended above the photosphere in the low corona by magnetic fields, generally along a magnetic inversion, or neutral, line separating regions of opposite magnetic polarity in the underlying photosphere. They appear as dark, elongated features.)
Thanks very much for all of the time and expertise that Dr.'s Gurman, Gilbert, and Kucera of NASA Goddard dedicated to this research.
Note: Definitions source: The Cambridge Encyclopedia of the Sun