High BLE activity for 15 seconds after connection

[jumpingfool]

I am developing a BLE peripheral application on nRF52832 and SDK 14.3.

I have been power profiling my application and quite happy with the results, except for when the peripheral first connects. Power usage goes crazy for about 15 seconds before calming down again - see below screenshot of the output from the power profiler:

What is the device doing when this happens? The peripheral is connecting to an iPhone and is bonded.

This is clearly BLE activity but I'm pretty sure it has nothing to do with my application!

[jumpingfool]

I am profiling a custom design with on-board Power Amplifier, so the 60mA peaks during radio activity are not a concern. The graph makes it look worse than it is - even during the "crazy" period the average current over the 15 sec is only around 500uA so not catastrophic. I'm still keen to know if it's necessary though as my application will require relatively frequent connect/disconnect cycles.

The screenshots above are showing a connection from nRF Connect on iOS - I did try to run nRF Connect on the desktop to see if it changed anything but wasn't able to get it to run at the same time as the power profiler.

I also spun up a sniffer today to see if that gave any clues - I can see a few scan/responses going back and forth while this activity is happening but I wouldn't have thought that service discovery would have taken this long to complete?