Yes, these are safe to delete.
Orion Improvement is a component that is collecting unexpected errors in the software (usually dealt with silently) and logging them to this directory. Normally once a week these get anonymized, summarized, sent to solarwinds.com, and deleted (unless you clicked "No do not send data" on the "Help SolarWinds Improve" dialog when you installed). Either something in your system is generating a ridiculous number of exceptions or the weekly summary/upload process has been failing for a long time. You could look at the range of timestamps on those files to understand which is the case.
The easiest way to stop this from happening in the future is to uninstall "SolarWinds Orion Improvement Program".