Their star becomes unstable, and gives off a continual coronal discharge. The planet is highly magnetic. The two qualities combine to produce an almost continuous ionic storm on the planet.
Seventeen major flares erupted on the Sun between 19 October and 5
November 2003, including perhaps the most intense flare ever measured
on the GOES XRS sensor—a huge X28 flare, resulting in an extreme
radio blackout, on 4 November. These flares were associated with CME
events that caused three geomagnetic storms between 29 October and 2
November, during which the second and third storms were initiated
before the previous storm period had fully recovered. The minimum Dst
values were −151, −353 and −383 nT. Another storm in this sequence
occurred on 4–5 November with a minimum Dst of −69 nT. The last
geomagnetic storm was weaker than the preceding storms, because the
active region on the Sun had rotated beyond the meridian where the
central portion CME created during the flare event passed to the side
of the Earth. The whole sequence became known as the Halloween Solar
Storm. The Wide Area Augmentation System (WAAS) operated by the
Federal Aviation Administration (FAA) was offline for approximately 30
hours due to the storm. The Japanese ADEOS-2 satellite was
severely damaged and the operation of many other satellites were
interrupted due to the storm.
The storm affected over half of the Earth-orbiting spacecraft,
intermittently disrupting satellite TV and radio services and damaging
a Japanese scientific satellite beyond repair. The solar activity also
sent several deep-space missions into safe mode or complete shutdown
and destroyed the Martian Radiation Environment Experiment aboard
NASA's Mars Odyssey mission. At the height of the storm, astronauts
aboard the International Space Station had to take cover from the high
radiation levels, which had only happened twice before in the
Remembering the Great Halloween Solar Storm
This would render all except low-frequency communication impossible, and it would fry electronic circuits that were not thoroughly hardened and isolated. It would not effect solar panels that were fused, but it would travel along any conductive transmission lines.
If it were continuous, or almost continuous, for a prolonged period it would damage or destroy any electronic device that was not completely shielded. With no access or ability to repair widespread electronic damage, and those systems that WERE repaired, hit again by another storm, this would have the desired consequences. Any devices that WERE left intact would be used very carefully, under very limited circumstances, under very well shielded conditions.
I would be like repetitive lightning strikes on every grid.