Forcefield-inside-brain would likely not work against Thor anyways. .
As far as the fight goes, Thor's shown ridiculous resistance against Telepathy, so Jean isn't as powerful as she should be. He also is kind of a weather GOD, so the weather witch might as well not even exist. Polaris? Well....Thor drained Magneto's magnetic energy, I'm sure he could do similarly to Polaris. Sue storm throws up a shield which either falters after a few Mjolnir swings, or gets phased through by the hammer anyways.
I thought IW's shield can snatch Thor's Hammer in mid flight when thrown. I think i saw a scan where she almost did that. Although im not sure if it would help them if she could.
That's a triple reinforced forcefield right there. Nothing is getting through that. 'Member, Sue's forcefield is already strong, added with jean's and polaris's...that's practically impenetrable. It's a stalemate, really. The girls will be too protected by the field as storms pelts thor with everything she's got while inside the field. Thor's endurance is his saving grace.
The sun won't be a problem with Storm there. She can control stars.
Thor loses this fight. Jean may not be able to beat him via TP, but she can definately distract him with it and take up some of his concentration.
Polaris is the useless one here. Storm can counter Thor's weather powers. Honestly, it is difficult to tell which of the two would have greater control over the weather. Storm has the ability to become one with Thor's mother. She is a mortal with the power of a goddess. Thor is a god with the power of a god. He has a godly life-force, but Storm can match him in elemental power. She has even greater fine-tune control, etc. With Jean distracting him via telepathic assaults, Sue assaulting him with her powers as well (remember how Sue once impaled Galactus with her field...it did not hurt Galactus, but it will hurt Thor) and Storm doing her thing with the elements, he will be overwhelmed.
Invisible Woman and Jean can combine their powers to create a super strong field. Storm is in the force-field with them and controlling the elements from behind the protection of their force-fields. I am not sure if Polaris can control magnetism through other people's force-field so whe may have to be by herself behind her own force-field (which is not too impressive). She may be able to manipulate the iron in his blood if she doesn't get taken out right off the bat and the opther women are keeping him busy.