Incorrect Values in Magnetogram Imagery

[Jesterface23]

With solar cycle 25 ramping up, we have seen our first occurrence of odd pixels in SDO's HMI magnetogram imagery within a sunspot umbra.

SDO NASA official Dean Pesnell answered what was going on in the imagery. The imagery we look at on SDO's website is not science data. The near-realtime imagery uses a simplified algorithm delivering incorrect values for some strong fields.

To anyone new to this, here is an example of when the incorrect values occur. This happens to be within a red negative polarity spot,

 

Then there is one more note to share from Dean, "Please use the science data FITS files if your work is sensitive to this phenomenon.".

[Parabolic]

Bump

Edited August 13 by Parabolic

[Philalethes]

On 1/22/2023 at 11:44 PM, Jesterface23 said:

With solar cycle 25 ramping up, we have seen our first occurrence of odd pixels in SDO's HMI magnetogram imagery within a sunspot umbra.

SDO NASA official Dean Pesnell answered what was going on in the imagery. The imagery we look at on SDO's website is not science data. The near-realtime imagery uses a simplified algorithm delivering incorrect values for some strong fields.

To anyone new to this, here is an example of when the incorrect values occur. This happens to be within a red negative polarity spot,

 

Then there is one more note to share from Dean, "Please use the science data FITS files if your work is sensitive to this phenomenon.".

42 minutes ago, Parabolic said:

Bump

Right, this reference was exactly what I was referring to. Was pretty sure I'd read it somewhere, heh.

I suppose that's sufficient to conclude that it's not something inherent to the HMI measurements themselves. Would be interested to know in what exactly the simplified algorithm does to cause it though. Perhaps I'll send an email to inquire about it at some point if my curiosity overtakes me.