Transcript AURORAS IN JOVIAN PLANETS

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:
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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