67173
Magneto-acoustic waves are sound waves that have been modified by the presence of a magnetic field , and Alfvén waves are similar to ultra low frequency radio waves that have been modified by interaction with matter in the plasma .
 person: Alfvén
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Alfvén 
Answer:
 person: Alfvén