Responding to post #9804:
500 ton TNT equivalent may not have much of a bang compared with Tzar Bombs, but it will still lead to a rapid and severe response from the USA and from NATO. That response may not be nuclear in the first instance, but the use of the TNW or WMD of any sort is open to all comers who object to the criminal actions of Russia. Every signatory to the UN Charter has an epiphany at that point; either support a criminal terrorist using WMD and be treated as a co-conspirator, with the economic and diplomatic consequences, or to object to the actions of Pukin'. Simple, stark choices, prior to any boots on ground, and there will almost certainly be both boots on ground and unfettered conventional arms supply to Ukraine to end Russian aggression and criminal actions..
We are well past the time.of calling Russia under Pukin' what it is, a criminal, terrorist state, and a sponsor of international terrorism. They have no compunction to kill their own people, they certainly have no objection to killing their neighbours.
On a military aviation theme, the use of TNW would drop all necessity to not upset Pukin', there are available assets to provide the Ukrainian airforce and army, would be thinking that a few hundred Oh6/OH58s would be a starting point, for interdiction,along with gallons of UH1s, to give mobility behind the FEBA, C130's to give an air bridge to the east, and (yaay) A-10's to prove that they can do what they were designed to do, and swarms of F16's, to save them from being turned into targets down at Tyndall.
In meantime, warm clothes, and ammo... And sufficient PGM to remove the rail links to Russia for the next couple of years.
To have an EMP effect the explosion has to take place in the upper atmosphere. The effect wasn't discovered until an American high altitude burst 'Starfish Prime' took place, knocking out some power in Hawaii, 900 miles from the detonation center. The altitude of the shot was about 250 miles. A tactical low altitude burst wouldn't cause a major EMP event. It certainly would cause other effects.....
From Wikipedia (other sources available)....
A high-altitude nuclear detonation produces an immediate
flux of gamma rays from the nuclear reactions within the device. These
photons in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the Earth's magnetic field, giving rise to an
oscillating electric current. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates
coherently.The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. ... A large device detonated at 400–500 km (250 to 312 miles) over
Kansas would affect all of the continental U.S. The signal from such an event extends to the visual horizon as seen from the burst point.