The Solar Plexus is a major area of nerve meeting points near the stomach area.

You can literally think of it as the Sun of the body.

Take a look at the famous Leonardo Da Vinci drawing below and notice how the body seems to have a central point around the Solar Plexus.

The Solar Plexus has some significant influences on the body's aura but I think you are probably alluding to another major aspect of it which is that it acts as your vibrational sense...your true sixth sense. It is the seat of emotion.

If you think about where you feel, say, strong negative emotion, you'll probably find that it is in your stomach area...the Solar Plexus.

How this relates to manifesting is that if you feel good about something you wish to manifest (i.e. your Solar Plexus is radiating positive emotion), you will eventually manifest that thing.

And I think this is the reason that alot of books written around 1900 gave such prominence and attention to that region of the body. I believe that people in that New Thought movement realized that there was some relationship between this part of the body and getting what you want in life.

With the current spate of reality creation teachers like Abraham, we can now fine-tune our understanding and say it isn't the Solar Plexus itself that is doing the manifesting but the strength and pureness of our energy flow towards our intended manifestation subject, which is indicated by our emotional feeling about it.

So "activating" your Solar Plexus would really mean just feeling good about what you want.

I think you may be touching on what we call Chakras. Chakras are energy centers located along the spine from head to groin. There are seven major centers of energy, and many minor chakras as well. The main ones are:

1. Crown Chakra located one the top of the head, energy color purple;

3. Throat Chakra located at the Adam;s apple, energy color blue-green;

4. Heart Chakra located at the Heart, energy color green or pink;

5. Solar Plexus Chakra located at the base of the breastbone, energy color yellow;

6. Belly Chakra, located just below the belly button at uterine level (for women)

7. Root Chakra, located at the juncture of the legs, energy color red.

So when you speak of "manifesting" your solar plexus, I think you need to look into the chakras. There is much info on the Internet about Chakras and how to energize each one. A Reiki Healer can re-align and re-energize these Chakras. This is a whole 'nother world in and of itself! I hope this info starts you researching this energy and helps you along. Blessings, Jai, RM/T, CRT, CCH.