cold plasma: a previously hidden solar system particle population mats andré and chris cully...
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Cold plasma: a previously hidden solar system particle population
Mats André and Chris Cully
Swedish Institute of Space Physics, Uppsala
Cold plasma
• Cold: thermal energy, and drift energy,
less than a few eV.• From the Terrestrial ionosphere, planets or moons.• Cold ions hard to detect on SC charged to
a few Volts• The more we look for cold plasmas,
the more we find…
Cold plasma: The ionosphere
Atmosphere + sunlight/precipitating particles
Observations:• Groundbased: magnetometers (currents),
radio/ionosonds (density),
radars/incoherent scatter radars…• Low altitude SC (not much charged,
but instr. threshold, SC velocity…)
Cold flowing plasma: Wake behind a charged SC
Tail lobes
Density from
SC potential (calibrated)
Cluster
Engwall et al., (2009)
Cold plasma: Particle instrument vs wake detection
Cluster SC 4
SC potential control
(60 V => 7 V) -50 50vX
50
-50
vZ
km/sH+
Particles (black) SC 4
Wake E (red) SC 307:40 08:20 UT
-20
+20
km/s
Engwall et al., (2006)
Outflowing cold plasma
H+ outflow about 1026 ions/s Cluster
Engwall et al. (2009)
High altitude, high energy – likely to escape (ion detector)2×1025 /s (0.5 kg/s) 0+ (Nilsson et al., 2010)
Path to the lobes, where cold ion outflow has been detected (E-field instr.)1026 /s H+ (Engwall et al., 2009)
Oxygen ion heating and outflow (Cluster)
Cold plasma: Total vs hot density
Just inside the magnetopause
Total density from plasma frequency (WHISPER instrument)
Cluster
Sauvaud et al., 2001
2001-01-31
1000eV
10
cm-3
10
0.105:50 06:00 UT
Magnetic
reconnection,
Cluster
(magnetopause)
20 min
10s
6000km2 min
Reconnection jet
Magnetic reconnection,
Cluster (magnetopause)
Cold (eV) ions at the magnetopause
Important for EN at edge of recon. jet (acceleration)EN
30 s (1500 km)
4 s (200 km)
André et al. (2010)
Cold plasma: Recent results from the magnetopause
Cluster SC 4, 2008
Total about
150 MP crossings
Percent of crossings
Status report, to be continued…
10
30
1 4Time from MP (hours)
Cold ions, from
wake E, within
certain time inside MP
Red: high lat
Blue: low lat
Black: total
Cold plasma: Titan
0.1
cm-31000.1
Te (eV)0.1
10.0
18:00 19:00 UT 2009-06-22
Cassini Langmuir probe
Edberg et al., 2011
Cold plasma• How much cold plasma is there?• Cold plasma missing in estimates of ion outflow? Cold plasma changes dynamics. How can cold plasma stay cold?Always stay tuned to find cold plasma when
anywhere near a planet, moon or comet!