When Coronal Holes are Smiling.... - October 26, 2022

  • Released Thursday, May 11, 2023
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Solar Dynamics Observatory (SDO) operates in a geosynchronous orbit around Earth to obtain a continuous view of the Sun. The particular instrument in this visualization records imagery in the ultraviolet portion of the spectrum at wavelengths normally absorbed by Earth's atmosphere - so we need to observe them from space.

In another example of pareidolia (Wikipedia) we have what appears to be a smiling face in the SDO/AIA 193 Angstrom filters formed by the arrangement of the darker coronal holes.

Coronal holes form at the footpoints of open magnetic field lines which form a 'fast track' for the outflowing solar wind. These 'open' field lines do not connect back to the Sun but instead reach out to the heliopause and interstellar medium. The fast solar wind has an average speed of about 750 kilometers per second, compared to the slow solar wind with speeds from 300 to 500 kilometers per second.

For comparison, we include the same time frame from the AIA 171 Angstrom filter where the 'face' is much less pronounced.

Several solar coronal holes are visible in an entertaining configuration in this SDO imagery taken from the AIA camera with the 193 Angstrom filter.

The solar coronal holes prominent in the 193 Angstrom filter above are almost invisible in the 171 Angstrom filter.




What is the PSF (Point Spread-Function)?

Many telescopes, especially reflecting telescopes such as the ones used on SDO (Wikipedia), have internal structures that support various optical components. These components can result in incoming light being scattered to other parts of the image. This can appear in the image as a faint haze, brightening dark areas and dimming bright areas. The point-spread function (Wikipedia) is a measure of how light that would normally be received by a single camera pixel, gets scattered onto other pixels. This is often seen as the "spikes" seen in images of bright stars. For SDO, it manifests as a double-X shape centered over a bright flare (see Sun Emits Third Solar Flare in Two Days). The effect of this scattered light can be computed, and removed, by a process called deconvolution (Wikipedia). This is often a very compute-intensive process which can be sped up by using a computers graphics-processing unit (GPU) for the computation.
Time slates for the multiple movies above, for custom compositing. Make sure to match the event and frame tag for the SDO frames you are using.

Time slates for the multiple movies above, for custom compositing. Make sure to match the event and frame tag for the SDO frames you are using.

Credits

Please give credit for this item to:
NASA's Scientific Visualization Studio

This page was originally published on Thursday, May 11, 2023.
This page was last updated on Saturday, July 27, 2024 at 12:57 AM EDT.

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