Types of AT Fields

There are four types of AT Fields. The first is the basic latent field inherent in all living beings. The next two are derived from the first and take either a passive or aggressive stance. The final type is a collection of specialized versions - only one of which will be discussed here.

Latent
All sentient life forms possess an AT Field - according to Kaoru. This includes Angels, EVAs, and even Humans. This latent AT Field can go unnoticed for an individual's whole life. The AT Field is what holds the bodies of humans together and ties their consciousness to that same body. By this, the components of any physical being in the EVA universe can be described by the formula:

AT Field + LCL quantity = Physical Entity (with soul)

The latent field is the basis for all other AT Field types. When manifested, the AT Field can serve as a defensive barrier, an offensive weapon, or a tool to effect other AT Fields in the area. AT Fields do not become visible unless they are actively engaged in something - such as collision with matter, energy, or other AT Field.

Defensive
The most often used form, the defensive AT Field is seen several times during the course of the series. When activated, the defensive field will distort the space around it, creating a barrier. The field doesn't become visible until it is hit with by an attack, at which point the standard octagonal fluctuations in the field can be seen.

Offensive
Not seen too many times in the series, the offensive AT Field is the extension of a latent field in an aggressive manner. The offensive field can take on a couple of forms - either as a projection of the latent AT Field, or as a warping of the defensive AT Field. One of the more memorable offensive AT Fields is the one produced by Unit 01 during the battle with the Fourteenth Angel. After reactivating and regenerating its left arm, Unit 01 creates an offensive field that deflects the Angel's ribbon attack, shatters the Angel's AT Field, and causes massive damage to the Angel's body. Another instance of the offensive AT Field is seen during Asuka's battle against the JSSDF . Although not a projection like Unit 01's, Unit 02's offensive field still does the necessary damage - taking out several tilt-engine air craft in one blow. Unit 02 offensive field seems to be produced by a warping of the defensive field so that it makes contact with nearby targets only.

Anti-AT Field
Seen only during the Third Impact, the Anti-AT Field plays an important role in the Instrumentality. These specialized fields can only be created with the aid of an S2 unit. The mass produced models' S2 engines go critical and their intertwined AT Fields merge with Lillith's into a singular Anti-AT Field. The purpose of this field is to counteract the AT Fields of the human race and reduce their bodies to LCL - from which their individual souls can be extracted.
   It should also be noted that the Anti-AT Field's effects are seen earlier in the series - although it is not identified by name. After Unit 01's acquisition of an S2 organ, Shinji's body is turned into LCL inside the entry plug and his soul is absorbed into the EVA itself. This event is caused by the influence of the newly acquired organ which gives the EVA the ability to control its AT Field in ways previously impossible (such as offensively).