There is an extended article on this in the May issue of Analog Science Fiction Science Fact.
It would seem to be a very significant risk, especially to power grids and communications. Consider how your life would be affected if major sections of the electricity grid, telephone and communications satellites were to become inoperative, not only over all Australia, but worldwide. It is likely that repairs could take months in some cases, due to a shortage of replacement parts (transformers and communications equipment, not to mention replacement satellites). Not to mention skilled people to install them. 
How would you go with no power or frequent blackouts (and all the follow-ons from this), maybe for months, no or limited telephone, no internet, no GPS?
John
				
			 
			
		 
			
				
			
			
				John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
			
			
		 
	
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