  Solar active region (AR) 12192 of October 2014 hosts the largest sunspot
group in 24 years. It is the most prolific flaring site of Cycle 24, but
surprisingly produced no coronal mass ejection (CME) from the core region
during its disk passage. Here, we study the magnetic conditions that prevented
eruption and the consequences that ensued. We find AR 12192 to be "big but
mild"; its core region exhibits weaker non-potentiality, stronger overlying
field, and smaller flare-related field changes compared to two other major
flare-CME-productive ARs (11429 and 11158). These differences are present in
the intensive-type indices (e.g., means) but generally not the extensive ones
(e.g., totals). AR 12192's large amount of magnetic free energy does not
translate into CME productivity. The unexpected behavior suggests that AR
eruptiveness is limited by some relative measure of magnetic non-potentiality
over the restriction of background field, and that confined flares may leave
weaker photospheric and coronal imprints compared to their eruptive
counterparts.
