r/Astronomy • u/MrThePuppy • 1d ago

Astro Art (OC) Temperature of the X8.2 solar flare of September 10th, 2017

I made this video from public NASA Solar Dynamics Observatory data, using my own processing code. It shows the X8.2 flare of 10 September 2017 at the Sun's western edge (sunspot region 12673). This was the second largest flare of solar cycle 24, and it launched what Liu et al. (2018, ApJL 864, L24) called a "truly global" EUV wave.

Color shows temperature, from violet (0.4 million K) through green (about 2 million K) to red (16 million K). Brightness shows how much plasma is at that temperature. I scaled each temperature separately so that the faint hot plasma shows up next to the cooler corona. White marks pixels where the flare saturated the detectors. Earth is shown to scale at top left.

How I made it:

Data: I downloaded the six extreme-ultraviolet channels of SDO's Atmospheric Imaging Assembly (94, 131, 171, 193, 211 and 335 Å). That's one image per channel per minute from 15:25 to 17:00 UT, 576 images in all, from the Joint Science Operations Center: http://jsoc.stanford.edu (series aia.lev1_euv_12s).

Calibration: I corrected the pointing and aligned the images with aiapy, binned them 2x2 (1.2 arcseconds, about 870 km per pixel), and estimated the noise in every pixel.

Temperature: for every pixel of every frame (4 million pixels in each of 96 frames), I solved for the differential emission measure, which is the amount of plasma at each temperature. I used AIA's temperature response and the regularized inversion of Plowman & Caspi (2020), which I implemented in my open-source Python package utu: https://github.com/sun-data/utu

Color: I turned each temperature distribution into a color with my open-source package colorsynth, which spreads temperature across the visible spectrum like a prism: https://github.com/sun-data/colorsynth

Rendering: each video pixel is one data pixel. The whole run took several hours on my workstation.

Data: NASA/SDO and the AIA science team.

218 Upvotes

99% Upvoted

8 comments sorted by

8

u/TheXTrunner 1d ago

just a tiny bit of blooming there

5

u/PM_ME_YOUR_HAGGIS_ 1d ago

I thought surface temp was circa 5k C? Not 400,000?

2

u/teridon 19h ago

While SDO AIA does have an instrument capable of imaging the photosphere at around 4,500 angstroms (~6000K), these images are of the solar corona. The corona can be millions of degrees.

One of the reasons the SDO satellite was launched was to study the mechanisms by which the solar corona was heated. I'm no solar physicist but the way I understand it is that there are two primary mechanisms by which the corona is heated: 1) magnetic reconnection, and 2) Wave Heating (Alfvén Waves).

4

u/OschaRobey 17h ago

So the blue and green we see on the Sun's surface are not actually the surface, but hot gas just above it. Am I understanding this correctly?

3

u/teridon 17h ago

That's correct. In general, the "cooler" plasma is near the so-called surface, but it rapidly rises in a region called the transition zone, about 1,500km above the surface.

1

u/MrThePuppy 16h ago

The reason I didn't include the cooler plasma is that the differential emission measure technique demonstrated here only works for plasma where absorption is negligible. The cooler plasma tends to have much more absorption so we usually analyze that in a different way.

1

u/emzak 21h ago

Just you wait when you learn the sun's corona temperature.