MySQL warm up time after restart because of lost connection MySQL 5.6.10 on Windows 7. 

I'm cleaning up and paring down a large INNODB table. Its .ibd file is originally 22 gigs. While I was in the middle of an ALTER, dropping some columns, the mysqld.exe process died.

Upon restarting and starting up mysqld, I noticed a lot of disk activity (~10mb/s) from mysqld, that has been going on for around 15 minutes so far. Also, in my data folder, there are files with names like "#sql-7b8_3.frm". 

Could someone shed light on what's going on?
After a bit or research, it looks like the '#sql-xxxx.frm' files are just temp files created during ALTER statements, and possibly other MySQL behavior such as OPTIMIZE. If the mysqld service crashes, those files tend to get stranded. There's a few other stack exchange threads asking how to get rid of them, and to be honest, none of them worked for me. There's one rather clunky one suggested by the error logs, but instead I just deleted the temp files and dropped the original table I was working on. Then I reimported the table from an earlier dump. 

During the course of an ALTER, '#sql-xxxx.frm' files are created. If the alter runs smoothly and completes, the '#sql-xxxx.frm' file will be deleted on its own.