An ionospheric heater is an array of antenna

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

s which are used for heating the ionosphere

Ionosphere

The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

, and which can create artificial aurora

Aurora (astronomy)

An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...

.

Current facilities

• The European Incoherent Scatter Scientific Association (EISCAT
  EISCAT
  EISCAT is an acronym for the European Incoherent Scatter Scientific Association. It operates three incoherent scatter radar systems, at 224 MHz, 931 MHz in Northern Scandinavia and one at 500 MHz on Svalbard, used to study the interaction between the Sun and the Earth as revealed by disturbances in...
  
  ) operates an ionospheric heating facility, capable of transmitting over 1 GW http://e7.eiscat.se/groups/Documentation/BasicInfo/ http://www.kurasc.kyoto-u.ac.jp/s-ramp/abstract/s19.txt effective radiated power
  Effective radiated power
  In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...
  
   (ERP), near Tromsø
  Tromsø
  Tromsø is a city and municipality in Troms county, Norway. The administrative centre of the municipality is the city of Tromsø.Tromsø city is the ninth largest urban area in Norway by population, and the seventh largest city in Norway by population...
  
   in Norway
  Norway
  Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
  
  .

• Russia
  Russia
  Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
  
   has the Sura ionospheric heating facility
  Sura Ionospheric Heating Facility
  The Sura Ionospheric Heating Facility, located near the small town of Vasilsursk about 100 km eastward from Nizhniy Novgorod in Russia, is a laboratory for ionosphere research. Sura is capable of radiating about 190 MW, effective radiated power on short waves. This facility is operated by the...
  
  , in Vasilsursk
  Vasilsursk
  Vasilsursk is an urban locality in Vorotynsky District of Nizhny Novgorod Oblast, Russia, located on the Sura River, not far from its fall into the Volga. Population:...
  
   near Nizhniy Novgorod, capable of transmitting 190 MW ERP.

• The United States has three ionospheric heating facilities:
  • HAARP
    High Frequency Active Auroral Research Program
    The High Frequency Active Auroral Research Program is an ionospheric research program jointly funded by the U.S. Air Force, the U.S. Navy, the University of Alaska, and the Defense Advanced Research Projects Agency ....
    
     - 4 GW ERP (north of Gakona, Alaska
    Gakona, Alaska
    Gakona is a census-designated place in the Valdez-Cordova Census Area in the U.S. state of Alaska. As of the 2000 census, the population of the CDP was 215.-Geography and climate:...
    
    )
  • HIPAS Observatory
    HIPAS Observatory
    The HIPAS Observatory is an ionospheric heater, which can radiate 70 MW ERP at either 2.85 MHz or 4.53 MHz. located 30 miles Northeast of Fairbanks, Alaska, in the small community of Two Rivers. It is located at: 64° 52’ 19" N latitude and 146° 50’ 33" W longitude and operates year-round...
    
     - 70 MW ERP (northeast of Fairbanks, Alaska)
  • Arecibo Observatory
    Arecibo Observatory
    The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
    
     (in Puerto Rico
    Puerto Rico
    Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
    
    )

Ionosphere modification

According to researchers noted in USAF research paper "Weather as a Force Multiplier: Owning the Weather in 2025", ionosphere heating was among techniques investigated by the former Soviet Union to either enhance friendly or disrupt enemy communications by modifying the natural ionosphere.