Survey
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AURORAE ON JOVIAN PLANETS An introduction to the aurora phenomenon: • What is it? • How does it happen? Mechanism. • Where and when does it happen? Keys to undestand auroras: -Solar wind -Magnetosphere -Interaction of trapped particles with atoms forming the atmosphere Mechanism: Emission: Extension to other planets: Any planet?? Conditions: 1.Solar Wind 2.Magnetosphere 3.Atmosphere Jupiter: Exceptional magnetosphere: •Size •Intensity •Interaction with Io (source of plasma for the magnetosphere of Jupiter) Bright and permanent aurorae around both poles HST HST + Chandra Aurora on Io, Galileo,1998 Saturn: •Conventional magnetosphere •Exposed to solar wind. •Has an atmosphere Cassini, 2008 Aurora in saturn. HST.90’s Uranus: Magnetosphere: -Medium sized -Twisting Structure -Almost “empty” Difficult deteccion! (weak aurorae) Curiosity: Uranus is a tilted planet and so is its magnetosphere Result is a distorted auroral oval which might be near the equator Neptune: Dense atmosphere Magnetic field (tilted) Is exposed to solar wind BUT… Weak auroras, and only visible at X-Ray and UV wavelenghs Reason: Neptune´s magnetosphere is almost empty. Only Spectrometry Observations On the outer planets, auroral emissions have been observed in: • • • • • • X-Rays EUV-UV ( H2 Lyman and Werner bands and also H Ly α) Visible n IR (H3+ emissions, also H2) f IR (hydrocarbon emissions) Radio Saturn and Uranus auroras: UV IR Radio From earth Neptune: information only avaible in UV and radio Wavelenghs regions from the Voyager II encounter. Ref. High Frequency Active Auroral Research Program Inducing artificial auroras 1st artificial aurora was created on 5 March1969, shotting a rocket with a beam of electrons against the magnetosphere 1972, other lattitudes.Hawaii, beam of e- came back to earth on the expected spot in the South pole, creating an aurora