Follow along I got "all astray" in this search. Even though I'm not a pilot, I have an interest in aircraft. "I think" this came about as a kid, as my Gramps had stacks of old mechanics/ science mags with all kinds of stuff about WWII aircraft. Also as a young "ham" (amateur radio) op in the mid 60's, there was still WWII "surplus" and much of that is aircraft "stuff"
I've always been interested in "weird" AC starting systems, such as the Coffman starter made famous in "the Flight of the Phenix"---a gunpowder operated starter
The old WWI stuff and some later had a thing I've always heard was called "shower of sparks" which is used to boost the magneto for starting. These are either hand cranked or generated by a battery operated buzzer / vibrator. JUST LIKE a Model T Ford spark coil (Which is incidently, really the very first "COP" (coil on plug) ignition system----a coil for each cylinder
So, looking for "shower of sparks" I found this GREAT video on a car Jay Leno had built--a Rolls Chassis with a Rolls Merlin engine, and a HAND BUILT body from the firewall back Look at about 14:00 for the Booth hand cranked starting magneto--which is a low voltage permanent magnet magneto that boosts one of the main mags
Also, "Mooney" aircraft use a Bendix built buzzer based system for starting..........same deal only a buzzer to generate AC instead of a hand cranked mag
https://www.donmaxwell.com/shower-of-sparks
From the above link:
"When starting our Mooneys the ignition switch is turned to the far right. The starter vibrator is activated in this position and can be heard as a buzzing sound. The ignition key is pushed inward to activate the starter. At the same time, the ignition switch internally grounds the right magneto so it will not operate. The right magneto is set at the same 25 degrees as the left for normal operation, so we do not want it to fire and cause the engine to “Kick Back”. So during the starting process, only the left magneto is used for starting. The ignition switch also selects the “retard points” and disables the normal points in the left magneto.
The vibrator switch is now supplying interrupted aircraft battery power to the left magneto coil thru the retard points. When the piston reaches TDC on the compression stroke, the retard points open allowing the magneto coil to charge and discharge as rapidly as the vibrator points can open and close. The result is a continuous spark that resembles a lightning bolt igniting the fuel/air mixture. This event continues for a few degrees of rotation on each cylinder until the engine starts and the switch is released to the both position. In the both position, the right magneto is enabled as well as the left magneto’s main set of points."