The flare’s dark imprint is at the bottom left corner of the „bright” sunspot, on this continuum subtracted image

On 2026-06-24, I observed the flare that occurred and peaked at around 0710Z, in the neutral carbon lines C I 9095 and C I 9112. Both darken subtly when the flare is present, just like oxygen does. But unlike with oxygen, which has an obvious chromosphere, I failed so far to identify anything meaningful for these carbon lines.

Also much like the oxygen, sunspots show excess light, while plages show a deficit, the disk being overall rather dull in comparison to neighboring continuum lines.

An interesting factor when processing these pictures is that the reference lines land on tellurics, and hence the solar lines doppler visibly as we scan from solar west to east.

The flare is at the big „bright” sunspot, bottom left.

(tovább…)

I observed the Sun in multiple wavelengths, recording spectroheliograms in Sr II 4077, Fe I 4383, and spectra in the UV — no disks, because of the clouds. Always the mandatory clouds.

Fe I 4383

If I identified the lines correctly

Sr II 4077 delta1

Sr II 4077 division

Sr II 4077 delta2

Sr II 4077 continuum at 11 pixels distance

Sr II 4077 line reconstruction

O I 7772 ~ continuum, dark smudge at center-top-left

On 2026-04-05, I imaged the Sun across multiple wavelengths, and found that areas that are dark smudges in oxygen are:

• rather unassuming bright-ish plages in:
  • Hα
  • Ca II 8542
  • Na I D2
• nothing obvious, small sunspot aside, in:
  • continuum
  • Fe I 7781
• dark in:
  • (O I 7772, hence smudge)
  • He I D3
  • He I 10830
  • H Paschen gamma

The images presented below are from scans recorded across several hours, each wavelength is the result of several scans stacked together. During acquisition, no major flares were reported. More about oxygen smudges here, here and here.

(tovább…)

During my campaign to observe the neutral oxygen triplet in the infrared, through full disk spectroheliograms, I noticed a few things:

• flares darken in oxygen, sometimes accompanied by shifts, one I measured was around 25 km/s
• obvious doppler shifts (of at least 1 km/s) are rare, judging by a superficial inspection of my collected data
• a general loss of contrast on the disk, active regions, plages darken and spots don’t darken that much,
• dark smudges on the disk
• chromosphere, prominences, some with doppler shifts,
• a light blanket just beyond the limb, above the active regions, a feature I am familiar with from He I D3, He I 7065 and He I 10830
• and a filament maybe (more on that later)

Smudges are areas that stand out as darker than expected, after taking into account spots, flares, and active regions. After contrasting the oxygen against a nearby continuum, either by subtraction or by division, smudges are revealed to be darker in oxygen, when compared to nearby active regions (which are themselves darkened) and thus a bit surprising. Smudges are stable across several minutes/hours, or even a day or two, while the flares I recorded are often times darker and short lived, on the order of minutes mostly. These smudges seem related to active regions, but don’t stand out in GONG Hα, where they can be a mere brighter spot like many others that don’t show up as smudges, nor AIA 1700 where the underlying area usually looks like any other active area that doesn’t show a smudge in oxygen. Better correlation can be seen with say SUVI 0304 or SUVI 0094 as small bright features in EUV, but it isn’t one-to-one either. Smudges stand out when they are somewhat towards the disk center, inside say 2/3 solar radii.

Below I compiled some scans with a nearby SUVI and AIA disk for comparison. I included smudges (marked with S), small and bright flares (marked with F), for context.

Instruments: 62/400 doublet, EO 775/25 OD4 narrow band filter, OD 0.6 neutral density filter, modified Sol’Ex, with 1800 ln/mm grating, modified/cooled ASI 678MM, JSol’Ex. Variable to good skies.

(tovább…)