I'm trying to find some type of space weather or other natural occurrences that would result in the intensity of Earth's magnetic field dropping for a few hours to maybe a week or two at most. Polarity reversal doesn't work and I don't think I'm getting anywhere with solar flares. Any ideas? I'm starting to get annoyed with how safe this planet is!
There is no good answer according to modern Earth's magnetism theory - but then we don't know too much about Earth's magnetism.
According to the dynamo theory, Earth's magnetosphere is created by convection processes in the Earth's outer core. Those processes get disrupted from time to time, which results in Geomagnetic excursion or even Geomagnetic reversal, but those disruptions take years, often hundreds of years to play out. There is no indication that convection can just stop for a few hours or even a few weeks.
But "no indication" does not mean that this is impossible. Maybe there is a way for the dynamo to get stopped that quickly. Either way, it should be caused by a process in Earth's interior. Any changes in cosmic weather just can't have any impact on the interior.
Blame it on Magnetic Reconnection.
- It's natural. You are not inventing anything.
- It's not well understood, so you can fudge the specifics.
- It's the trigger for solar flares, so you can still use them.
- You can probably tailor a disaster for your narrative, as hinted here.
It is at present not known whether reconnection can happen in a continuous fashion or whether it is always intermittent. Solar flares and magnetospheric substorms — two phenomena believed to be initiated by reconnection — are highly burst-like occurrences, raising the possibility that the reconnection process is intrinsically intermittent, storing and releasing magnetic energy in an explosive and uncontrolled manner.
In layman's terms, it's where two or more magnetic fields push together and start sharing and rearranging their ion loops. What was once a magnetic "barrier" layer between them is suddenly gone, like a rubberband snaps and the whole system has to rebalance.
Your disaster might go something like:
- Unusual sun activity leads to a magnetic "storm": a series of reconnection ripples.
- The Earth's magnetopause is compromised as they hit faster than the magnetopause can recover.
- Extra fireworks caused by solar plasma far deeper into the Earth's atmosphere and the turbulence from the reconnections themselves bring the magnetic storm to our front door.
- "Aftershocks" as the system balances, ripple and dissipate through the magnetosphere, but also cause compression waves that can channel plasma in unpredictable ways.