Reading a sentence "37岁秦岚登T台走秀气场全开秀迷人天鹅颈", I check online the meaning of the idiom 气场全开,which is given as 自己不说话，站在那里别人都怕自己 (you scare the other people with your silence), but that sounds ridiculous in this context.
I think it's not the traditional usage in Chinese (that means it's not appropriate to appear in the formal written language), but obviously, it's quite popular in young people's daily talks.
The phrase "气场全开 " can be divided into two parts, the first two words' meaning refers to the influences of the thinking, personalities, characters, and behaviors of a person; the last two words' meaning describes the degree, be full of or thoroughly.
So combined together, the meaning of 气场全开 can be apprehended to depict someone with great influences on the surroundings or public. People with the character of "气场全开" has notable characteristics (personal authority or charming or outstanding competence or good-looking etc.)of behavior, becoming the center of attention, other people cannot omit the sense of the presence of him/her, and what's more, they feel the energy from that person and become to appreciate and worship to him/her.
At last, the phrase is a commendatory term.
This term is a bit of a slang, so I think it has a lot of variation in the usage, and the multiple meanings are still changing, they are a little hard to pin down compared to a formal vocab term.
However these are some of the common applications of the term I've seen:
Most often, I see it used to represent confidence, in the way that you can stand tall and take control of a situation/group/conversation etc. Being able to be a natural leader (or at least so since a huge amount of seeing this vocab is overly shy people wanting to change)
If you think of the english phrase "fake it til you make it" it has a bit of the same energy. The difference being that the chinese slang can be used for those who don't need to fake it.
In your original sentence, it is saying that 秦嵐 walked the cat walk in a very confident way,a way the grabbed the attention of those present and took control of the energy of the room.
Imagining the confidence and apparent ease of controlling the situation successful model's display is actually a great example of the aura meant by 气场全开 overall. The person in the group that everyone else naturally congregates around etc.