"bathe all life on Earth unabated with massive doses"

Hmm... Are you absolutely sure you are quoting that Nova episode correctly?

The reason I ask is because essentially the magnetic field protects Earth's atmosphere. And Earth's atmosphere protects us!

Earth's atmosphere is quite thick, and will continue to offer a LARGE and significant amount of protection from solar radiation, as it has always done, while the magnetic-poles go through their flip process.

Essentially... during the flip process, the upper atmosphere will get whisked away by the solar wind radiation at a faster rate...

But it would take hundreds of thousands of years (if not millions) for the atmosphere to noticeably start thinning to the point where Earth life comes under serious threat.

That's the problem we have with Mars today: there is no ATMOSPHERE to help protect us from solar and cosmic radiation.

And there's no atmosphere because there's no magnetic field.

Also interestingly, as a side note:

some say Earth also has a secondary (weaker) magnetic field, and that this second magnetic field might actually play a role in causing the primary field to flip.

So that secondary magnetic field might offer some limited additional protection to our upper atmosphere during the flip.

So ya...

if Nova is projecting a dooms day like scenario, by saying that everything is going to get blasted, in an "unabated" fashion... then I think the Nova writers were really overdoing it in that episode!

If that was true, then as other people pointed out here in these comments, we would see mass extinctions with each polar flip---especially with plants--but we do not.

HOWEVER...

having said that, I personally probably wouldn't spend a lot of extra time sunbathing during a polar flip phase!

Although even then... if someone spends a lot of time sunbathing now... I'm not sure the lack of a magnetic field would be all that significant to their already elevated cancer risk!