Magnetars with Low Magnetospheric Twist

Summary Table

Category	Progenitor	Type	Energy Mechanism	Emission Mechanism	Counterparts									References	Brief Comments
					LF Radio	HF Radio	Microwave	Terahertz	Optical/IR	X-rays	Gamma-rays	Gravitational Waves	Neutrinos
Other	Magnetars with Low Magnetospheric Twist	Repeat	Mag. reconnection	Pulsar-like	Yes	---	Maybe	Maybe	Maybe	Maybe	Unlikely detectable	---	---	https://arxiv.org/pdf/1904.12036.pdf, https://arxiv.org/abs/1910.06979	Unlikely to form in Galactic magnetars.

Definitions: LF Radio (3 MHz to 3 GHz); HF Radio (3 GHz to 30 GHz); Microwave (30 to 300 GHz)

Model Description

FRBs may be created in the closed field line regions of magnetar magnetospheres. Crustal slippage on the surface of the magnetar causes magnetic reconnection and thus particle acceleration, producing coherent emission. To allow emission to escape, the magnetars must have a low-density plasma in the closed field line regions, and hence must have low magnetospheric twist.

Observational Constraints

Unlikely to form in Galactic magnetars, which have a relatively high magnetospheric twist. Signals above a few MeV are expected to be suppressed by photon splitting and magnetic pair production in the magnetosphere.