Fate of cold ions in the inner
magnetosphere: energization and
drift inferred from morphology and
mass dependence
M. Yamauchi1, I. Dandouras2, H. Reme2, Y. Ebihara3
(1) Swedish Institute of Space Physics
(IRF), Kiruna, Sweden
(2) CNRS and U. Toulouse, IRAP,
Toulouse, France
(3) Kyoto University, Uji, Japan
Geospace2014@Rhodos, 2014-9-17
1
a zoo of various patterns
North-south symmetry of trapped particle motion for fixed MLT
⇒ inbound-outbound asymmetry = temporal change of 1-2 hour
2
Cluster Statistics
Decay in time partly came
from rapid degradation of
the sensor
3
(a) Vertical stripes: Nearly vertical in the spectrogram, extending from
the about 10 keV to sub-keV (dispersion is very weak). Only found near
midnight during substorms. Mostly inbound-outbound asymmetric (life
time~1h), indicating substorm injection.
(b) Wedge-like energy-latitude dispersed sub-keV ions: Stronger
dispersion than (a), at slightly lower energy (up to few keV). Often
found in the morning to noon sectors some hours after a substorm.
Often inbound-outbound asymmetric, but can yet be explained by ion
drift (next figure) of <0.1 keV ion source.
(c) Short bursts of low-energy ions: a peak energy flux less than 100
eV but not thermal. Found all local time without clear relation to
geomagnetic activities. Often inbound-outbound asymmetric (life
time~1h), indicating a local phenomena.
(d) Warm trapped ions confined near equator: tens eV to a few
hundred eV without dispersion. Found all local time without clear
relation to geomagnetic activities. Comparison to different SC indicates
life time~1h, indicating a local phenomena.
4
0.1 keV
t ≈ 6 hr
t ≈ 4 hr
Comparison of observation and ion drift simulation.
Cool source (<0.1 keV, but not cold) can cause wedge-like dispersed sub-keV
ions with its inbound-outbound asymmetry even at noon, and hot source can
cause ion band (keV). Due to different drift velocity, two population has
different O/H ratio.
5
Next: O+/H+ and He+/H+
differences
(a) Vertical stripes
2001-2006 (~300 relatively
clean data out of ~760
traversals)
types (a)-(c)
Appearances of H+, He+, and O+
are not correlated
6
(b) Wedge-like energy-latitude dispersed ions
Timing & energy are quite different among H+, He+, and O+ (drift
theory predicts same energy-time diagram for all species).
7
(c) Short bursts of lowenergy ions:
Unlike most H+ bursts, He+ bursts
(time scale~1h) are in
perpendicular direction. It is also
independent from O+, indicating
local heating of He+ only.
(d) Warm trapped ions
confined near equator
Equatorially-confined hot ions
sometime show E(H+) < E(He+)
while majority is E(H+) = E(He+).
8
Conclusions & Future Observations
• There must be filtering mechanisms that select only cold
He+ and separates them from H+ and O+ for both
energization and transportation.
• We need more investigation on Mass dependency

Nitrogen Ion TRacing Observatory (NITRO)
for next ESA's M-class call
Sprinter meeting:
Saturday 11:30-16:00 (after coffee break)
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3-spacecraft mission (high inclination)
North
South
Imaging (3-axis)
& monitoring
FOV
Daughter (gradient)
In-situ (spinning)
UV/visible (narrow FOV)
IR (narrow FOV)
Cold ion mass spectrometer
Hot ion mass analyser
Photolectron
Magnetometer
Langmuir Probe
(plus alpha)
Cold ion mass spectrometer
Hot ion (3~4 different types)
Energetic ions
Photoelectron
Magnetometer+Waves (ΩN)
Langmuir Probe
(plus alpha)
In-situ spacecraft start with 6-7 Re apogee outside the radiation belts
during the first 2 years, and then gradually decrease the apogee
altitude to explorer the “dangerous” region. Monitoring satellite flies
just above the polar ionosphere at altitude ~2000 km.
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Payloads
In-situ #1 mother (spinning)
Remote sensing & monitoring (3-axis)
* Mass spectrometer (cold) (Bern)
* Optical (emission) (LATMOS & Japan)
(1) N+: 91 nm, 108 nm
* Ion analyzers (0.03 – 30 keV):
(2) N2+: 391 nm, 428 nm
(1) Narrow mass range (Kiruna)
(3) NO+: 123-190 nm, 4.3 µm
(2) Wide mass range (Toulouse)
(4) O+: 83 nm, 732/733 nm
(3) No mass (LPP)
* Mass spectrometer (cold) (Goddard)
(4) low G-factor mass (Japan)
* Ion mass analyzer (> 30 keV) (UNH) * Ion analyzer (< 0.1 keV) (Kirina)
* Electron (photoelectron) (London) * Electron (photoelectron) (London)
* Langmuir Probe (Brussels)
* Magnetometer (Graz)
* Ionospheric sounder (Iowa)
* Waves (ΩN≠ΩO) (Prague)
* Magnetometer (Graz/UCLA)
* Langmuir Probe (Brussels)
* Waves (ΩN≠ΩO) (Prague)
* ENA monitoring substorm (Berkeley)
* Ionospheric optical emission (???)
* (Potential Control=SC subsystem)
Possible methods for ion analyzers:
Magnet, Magnet-TOF, reflection-TOF,
MCP-MCP TOF, shutter-TOF
* underline: core,
* colored: important,
* black: optional
Optical imager needs a scanner keep insitu spacecraft within FOV.
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End
Yamauchi, et al. (2012), GRL, doi:10.1029/2012GL052366.
Yamauchi, et al. (2013), AnnGeo, doi:10.5194/angeo-31-1569-2013.
Yamauchi, et al. (2014), AnnGeo, doi:10.5194/angeo-32-83-2014.
Yamauchi, et al. (2014), JGR, doi:10.1002/2013JA019724.
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Next: O+/H+ and He+/H+
differences
(a) Vertical stripes
2001-2006 (~300 relatively
clean data out of ~760
traversals)
types (a)-(c)
Appearances of H+, He+, and O+
are not correlated
13
(b) Wedge-like energy-latitude dispersed ions
p/a < 45°
p/a ≈ 90°
cf. drift theory predicts same energy-time diagram for all species
14
(c) Short bursts of low-energy ions:
Unlike majority of H+ bursts, He+
bursts are mostly in perpendicular
direction and time scale ~ 1h.
Even independent from O+,
indicating local heating of He+
only.
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(d) Warm trapped ions confined near equator
Equatorially-confined hot ions
sometime show E(H+) < E(He+)
while majority is E(H+) = E(He+).
He+ is certainly heated e.g. by
He cyclotron waves (1980’s)
equator
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