Because we all love talking about AGU’s data policy, you should know that when you go to the JGR Space Physics GEMS manuscript submission site, in fact the GEMS site for any AGU journal, you will see this notice above the login fields:
I don’t actually know how long it has been there. I go to this login page a lot but often fail to spend any time on it, quickly zipping to the login fields and moving on to my editorial tasks. I posted last summer about this change that “data available from authors” is not allowed, with a list of available generic data repositories that will mint a digital object identifier for your data files. I keep getting comments and some pushback from the community about this, and now I just noticed and carefully read this “Important” statement on the GEMS login page! So it is a convenient time to have a blog post about it.
This has been slowly changing throughout my time as EiC. When I had just started, AGU was in the process of fully implementing its stated data policy. I then had a couple of other posts in 2014 about how the editorial board for JGR Space Physics this policy, and then another in 2015 on supporting information. That one actually stated that it was okay to have the digital values stored as supporting information along with the paper but this is no longer allowed. Well, please upload it as supporting information for review purposes, with a note to the editor that this is what you are doing, but upon acceptance, upload those files to a DOI-minting data repository for permanent archiving.
Authors: please plan accordingly with your digital data, both observational and numerical. AGU wants all of the numbers behind the figures available to reviewers and readers. Please include data sets as supporting info during submission but have a statement about the repository to which it will be uploaded in the Acknowledgments section, and include all weblinks to existing data repositories.
Reviewers: please check data availability for the manuscripts that you review. This should now be part of your checklist. AGU HQ staff and the editor should also be checking this, but you are critical to this process too.
Note that this supersedes the posted Data Policy at the AGU Author Resources pages, which still describe the policy enacted in 2014. I hope that this webpage is updated soon.
More about FAIR data policies can be found at the COPDESS website.
Notes from the JGR-Space Physics Editor-in-Chief 
Ironic, given AGU’s history ignorance of implementing data privacy.
More practically… they have a data repository finder. All I could find on it that was relevant to JGR-Space Physics was the PDS. PDS is great for planetary (non-Earth) things – but which of their listed repositories are the Earth orbiting datasets supposed to go to. E.g. MMS papers put there data where?
If you obtain your data from some publicly accessible archive, then you would presumably give the URL for that archive. Data analysis tools (e.g., SPEDAS) are also somewhat standardized, so you would also need to specify which package you used, if it is separate from the data. I am mostly a data analysis guy, so this has been sufficient for me.
This is more of an issue for papers involving massive simulations (global MHD, 3-D PIC, etc.) because they would be generating data. Those who run their simulations on CCMC could presumably point there, but others would have to submit to some repository.
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