Query, Sodales:
Does a magus posses an arcane connection to themselves at all times, for the purpose of spells which are ranges beyond personal which they may for some reason desire to cast upon themselves?
Ever seen a witch spit during a spell?
Yes, they would - arcane connections don't need to be fixed (ie, made permanent) in order to use. Therefore, you don't need to do anything special to the wide number of arcane connections that a magi has at hand for himself. (one's own hair is likely the easiest. blood would also be easy, albeit a bit painful - and as Pralix mentioned, while "spit" would only likely last for a few hours or days, the magi can get it fresh whenever they want!)
EDIT - I believe a target's breath also counts (although it doesn't act as a connection for very long) - so unless the magi is using silent casting, he's got what amounts to his own words acting as an AC.
Worst case senario:
Bite your nails or pull out a hair - instant AC.
It's so easy we ended up figuring the answer would always be that you do.
No. You aren't an AC to yourself. You are yourself.
You can create an AC rather quickly, nail, hair, blood are relatively easy to access and even do so quickly. You will also have to penetrate R:Arch and R: Personal are rather far apart in magnitude, and depending upon the casting total and penetration scores, it may not be easy or even possible.
Oh, and if an enemy is touching you do they have an AC to you? No. An AC is something that was a part of something else.
I don't think there's any requirement to use an arcane connection for penetration at arcane connection range - see page 84 of the main book for a counter example (Agony of the Beat is a Voice range spell).
You misunderstand.
There is a requirement to penetrate (or suppressing MR) for spells cast upon oneself at ranges greater than personal. Penetration is an issue here, in that the caster must lower his MR OR be able to penetrate his own MR.
casting on yourself at a range other than personal? How and why are you doing this?
How: Just like on anyone else at that range.
Why: Because I have a spell, and it's not R: Personal.
In Exempli
- I'm going into combat. I don't want to, but I have little choice, it must be done. Being a squeamish sort of fellow, I want to improve my odds of survival, so I cast Preternatural Growth and Shrinking and Gift of the Bear's Fortitude on myself. I know both spells, at R: Touch. Luckily I'm already touching myself but must technically penetrate my own MR. Good thing I can lower it while I cast my spells, eh?
- It's 3 AM and my neighbour's kids are screaming. You'd think stone walls would stop the noise, but no! I have important labwork to do! If only I could fall asleep, it would probably OK as I'm a heavy sleeper, but actually falling asleep? In that noise!? Good thing I know the Call to Slumber, eh. Can't cast it on the kiddies as I can't see them (though I can certainly percieve them!) and probably couldn't raise my voice enough to be heard through the walls anyway. But I can cast it on myself, at R: Voice. And that works.
Well, Tellus's response, and it was the original question in the opening post.
Sorry - my post didn't say what I meant it to. I thought you were saying that if you were using an arcane connection, you had to cast at arcane connection range, which isn't the case.
Yes. My curiousity on this issue stems from the idea that there may be hostile casters out there, and suppressing your MR for a combat round (6 seconds) is a vulnerability that can be offset by taking the penetration skill and pulling a hair from your head or biting a piece of your nail. Or, as pointed out, spitting into your hand.
Hm. don't see why not - using an arcane connection and Sympathetic bonuses doesn't require ceremonial casting, after all. Although, as Jonathan.Link mentioned, technically having access to the thing (ie yourself) is not QUITE the same thing as having access to something that is an arcane connection to the thing (a piece of hair or saliva) - although as others are pointing out, they're really easy to get ahold of. If you're holding your own talisman, for example - that's a +4 multiplier right there. With the following sympathetic bonuses:
Caster is blood relative of the target...I'd allow this one. You share the same parents, after all (+1)
Birth Name (+1)
Name used in secret rituals (+1)
Troupe-approved additions to the list... call it another +2 for "casting on yourself".
Although that does beg the question - if you know your own Secret Magic Name...do you have to shout it out loud in the casting process? Or is it enough to simply know it? Because if it's the former, there may be reasons why you wouldn't want to use it.
Given that to use the arcane connection, you must be touching it, and given the amount of hair I have that falls out and sticks to my hat, it goes towards explaining why Jerbiton's like the pointy hat 
It's containing a dozen or so arcane connections to them at any given time.