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

North-south symmetry of trapped particle motion for fixed MLT ⇒ inbound-outbound asymmetry = temporal change of 1-2 hour

a zoo of various patterns

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Decay in time partly came from rapid degradation of the sensor

Clu

ster

Sta

tistic

s

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(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.

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Comparison of observation and ion drift simulation.

0.1 keV

t ≈ 6 hr

t ≈ 4 hr

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.

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Next: O+/H+ and He+/H+ differences

(a) Vertical stripes

Appearances of H+, He+, and O+ are not correlated

types (a)-(c)

2001-2006 (~300 relatively clean data out of ~760 traversals)

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(b) Wedge-like energy-latitude dispersed ionsTiming & energy are quite different among H+, He+, and O+ (drift theory predicts same energy-time diagram for all species).

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(c) Short bursts of low-energy 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+).

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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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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.

3-spacecraft mission (high inclination)

NorthIn-situ (spinning)Cold ion mass spectrometerHot ion (3~4 different types)Energetic ionsPhotoelectronMagnetometer+Waves (ΩN)Langmuir Probe(plus alpha)

UV/visible (narrow FOV)IR (narrow FOV)Cold ion mass spectrometerHot ion mass analyserPhotolectron MagnetometerLangmuir Probe(plus alpha)South

FOV

Imaging (3-axis) & monitoring

Daughter (gradient)

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In-situ #1 mother (spinning)* Mass spectrometer (cold) (Bern)* Ion analyzers (0.03 – 30 keV): (1) Narrow mass range (Kiruna) (2) Wide mass range (Toulouse) (3) No mass (LPP) (4) low G-factor mass (Japan)* Ion mass analyzer (> 30 keV) (UNH)* Electron (photoelectron) (London)* Magnetometer (Graz)* Waves (ΩN≠ΩO) (Prague)

* Langmuir Probe (Brussels)* ENA monitoring substorm (Berkeley)

* (Potential Control=SC subsystem)

PayloadsRemote sensing & monitoring (3-axis)* Optical (emission) (LATMOS & Japan) (1) N+: 91 nm, 108 nm (2) N2

+: 391 nm, 428 nm (3) NO+: 123-190 nm, 4.3 µm (4) O+: 83 nm, 732/733 nm* Mass spectrometer (cold) (Goddard)* Ion analyzer (< 0.1 keV) (Kirina)* Electron (photoelectron) (London)* Langmuir Probe (Brussels)* Ionospheric sounder (Iowa)* Magnetometer (Graz/UCLA)* Waves (ΩN≠ΩO) (Prague)* Ionospheric optical emission (???)

Optical imager needs a scanner keep in-situ spacecraft within FOV.

* underline: core, * colored: important,* black: optionalPossible methods for ion analyzers:

Magnet, Magnet-TOF, reflection-TOF,MCP-MCP TOF, shutter-TOF 11

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.

End

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Next: O+/H+ and He+/H+ differences

(a) Vertical stripes

Appearances of H+, He+, and O+ are not correlated

types (a)-(c)

2001-2006 (~300 relatively clean data out of ~760 traversals)

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(b) Wedge-like energy-latitude dispersed ions

p/a < 45°

p/a ≈ 90°

cf. drift theory predicts same energy-time diagram for all species14

(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. 15

(d) Warm trapped ions confined near equator

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)

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