JB2008 Dst + Ap Indices

[charlesc]

Hi All,

The JB2008 model requires an instance of JB2008SpaceEnvironmentData. However, as best I can tell, the current implementation can only read in two data sources: SOLFSMY.txt and DTCFILE.txt which have to be passed as DataSource instances.
Usually the model also requires the use of DSTFILE.txt and SOLRESAP.txt data. Does anyone know of any way to also pass these in? Are these values automatically being passed by some other mechanism? And if not, does anyone what values are used instead?
I think it would be something nice to add because Dst is used during more “interesting” storm conditions (I think for Dst<-75nT), and without it JB2008 misses some very cool detail! Would be happy to contribute to this if not already exisiting.

Thanks in advance for any info
Charles

[MaximeJ]

Hi @charlesc,

@charlesc

Usually the model also requires the use of DSTFILE.txt and SOLRESAP.txt data. Does anyone know of any way to also pass these in?

I don’t think so, I’ve found nothing in the tests related to these files and the Javadoc header of JB2008SpaceEnvironmentData clearly states that they are not used.

@charlesc

Are these values automatically being passed by some other mechanism? And if not, does anyone what values are used instead?

I don’t know… I hope someone more knowledgeable about JB2008 can answer you

@charlesc

I think it would be something nice to add because Dst is used during more “interesting” storm conditions (I think for Dst<-75nT), and without it JB2008 misses some very cool detail! Would be happy to contribute to this if not already exisiting.

That would be great !!

Cheers,
Maxime

[charlesc]

Hi @MaximeJ ,

Thanks for your answer.

I read the original Bowman 2008 paper (attached) and the documentation which led me to this question. I’m not sure how it could work without (although the output it gives seems reasonable which makes me think I am probably missing a trick…).

bowman2008.pdf (396.0 KB)

Thanks again.
Charles

[dgondelach]

Hi @charlesc,

According to Bowman’s paper, the JB2008 model uses the exospheric temperature change (dTc in the paper) as geomagnetic storm index. The Dst and ap values are needed to compute the dTc. For more information see the paper:

The geomagnetic storm temperature index used by JB2008 reflects the change in the exospheric temperature. This temperature change is computed from the change in the Dst index during a storm. Outside of storm periods this index is computed from Jacchia’s 1970 equation using the 3-hour ap value.

So the data in DSTFILE and SOLRESAP are not required by model itself, but only used to compute the dTc values in the DTCFILE.

Best regards,
David

[charlesc]

Hi @dgondelach,

Thank you for the clarification. This makes a lot of sense!

Thanks again.

Best,
Charles