@prefix ns0: . @prefix skos: . ns0:resource [ ] ; ns0:altLabel [ ] ; skos:definition """[Text from the NASA THEMIS home page, http://www.nasa.gov/mission_pages/themis/spacecraft/ESA.html ] The Electrostatic Analyzers (ESAs) (on THEMIS) measure how many electrons and ions they detect with a specified energy from a certain direction at a given time (the particle distribution function) over the energy range from ~3 eV to 30 keV. These thermal electrons and ions are the particles responsible for creating the aurora. The ESA measurements allow scientists to derive the density, velocity, and temperature of the ambient electrons and ions (plasma). Knowing these quantities at the five THEMIS probes will allow scientists for the first time to determine the time of substorm onset. More Information: http://www.nasa.gov/mission_pages/themis/spacecraft/ESA.html Group: Instrument_Details Entry_ID: THEMIS-ESA Group: Instrument_Identification Instrument_Category: Solar/Space Observing Instruments Instrument_Class: Magnetic Field/Electric Field Instruments Short_Name: ESA-THEMIS End_Group Group: Associated_Platforms Short_Name: THEMIS End_Group Online_Resource: http://www.nasa.gov/mission_pages/themis/spacecraft/ESA.html Online_Resource: http://themis.ssl.berkeley.edu/instrument_esa.shtml Sample_Image: http://www.nasa.gov/images/content/164126main_idpu_med2.jpg Creation_Date: 2008-08-12 Group: Instrument_Logistics Instrument_Owner: NASA End_Group End_Group"""@en ; skos:prefLabel "THEMIS-ESA"@en ; skos:inScheme ; skos:broader ; a skos:Concept . skos:prefLabel "Magnetic Field/Electric Field Instruments"@en ; a skos:Concept ; skos:narrower .