Escaping ions over polar cap

Inner magnetosphere,

Bow shock/Foreshock, and

Ancient magnetosphere

Why?(1) Why do we research escape(2) Why do we research heating/energization(3) Why do we research Inner magnetosphere (low energy ions)(4) Why do we research bow shock / foreshock(5) Why do we research aurora

(a) We are looking at phenomena that observations are not easily predicted by theories, and therefore are basic processes of plasma that needs to be understood(b) Inter-comparison between Earth-Venus-Mars = (1) and (4)(c) RBSP mission will intensify world-wide study = (2) and (3)(d) We are under aurora with ground-based facility = (2) and (5)

Inner magnetosphereInner magnetosphere (Cluster observation): * We found cold source in addition to hot source energy in the tail (finished) * We found ionosphere source in addition to tail source (need 0.5 man-year) * We found equatorially-confined ions (need 1 man-year, on-going) * We derived the velocity of the drift from (need 0.5 man-year) * We found mass-dependent drift of energetic ions that no theory has predicted (need 1 man-year) * We found that some aurora is related to solitary structure in the inner magnetosphere (need 1 man-year). * We plan to study north-south asymmetric cases (need 1 man-year, on-going) * We plan to study contamination effect of the radiation belt particles (need 1 man-year)

Sub-to several-keV ion patterns in the inner magnetosphere (near perigee of Cluster)

Viking

Cluster westward drift

eastward drift

eastward drift

Perigee, 11 MLT

14 MLT

poleward

6 MLT

9 MLT

12 MLT

15 MLT

18 MLT

Time-lag (hours)

Statistics: fossil of substorm

(1) Moves eastward

(2) Decrease in time for both probability and energy

(Yamauchi and Lundin, 2006)

Further classification by two populations

Peak AE during latest 6 hours vs Pattern in spectrogram

Peak AE (a) (b) (c) (d)

< 300 nT 0 4 26 10

300~500 nT 0 8 17 1

> 500 nT 5 33 3 4

Pattern in Spectrogram

Warm (1 keV, 0.5/cc)

Cold (0.2~0.6/cc)

Observation

Back-trace to 8 Re and Forward simulation

finding out source

+1° 0° -1° -2°

No

Yes

Yes

?

No

No

S/C-4

S/C-1

S/C-3

Relative S/C position: all at 9.0±0.1 MLT

23:40-24:00 UT

H+

O+

H+

O+

H+

O+

1000~2000 km

E

ions ≈ 3000 km/s

ions > 5000 km/s

keV

P/A

P/A

06:42 06:46 06:4806:44

IMAGE (FUV)

Equatorial trapped 100 eV H+

(1) Trapped (pitch angle ~ 90°) and confined to Equator

(2) nearly 50% in the noon and dusk sectors, and 35% in

night-dawn.

(3) Variable content of He+. (majority is less than 5%)

(4) Variable energy ratio between He+ and H+ (1 to 4),

contrasting to the previous report.

(5) Time scale of about an hour.

Modeling Ancient magnetosphere/ionosphere

Prognosis of O/H ratio of atmospheric escape from non-magnetized Ancient Earth

Increase in EUV/FUV SWDP IMF (IMF) SEP

Jeans & Photo-chemical (H, He)

++ same same same +

Hydrodynamic (all) ++ (regime change)

same same same +

Ion pick-up (H, He) (#1) + same + same

Wave and E// (all) ++

(cf. Earth)

+

(cf. Earth)

same + ++

Momentum transfer (all)

++ + same ++ same

O/H ratio of escape + (#2) + same + +

#1) depending on relative extent of ionosphere and exosphere#2) because non-thermal > thermal for Earth-sized planet

Mars-Venus-Earth difference 2: Bow shock and foreshock

* Planetary size matters, Earth ≈ Venus ≠ Mars (no foreshock) because of

(1) Gyroradius ≈ bow shock size for Mars

(2) Extended exosphere due to low gravity produces cold ions at bow shock

(3) This makes Mars an ideal laboratory to study micro-scale physics, i.e., ion

motion. For example, we need new classification of shock.

* Future plan (3-5 years)

(1) bow shock reflection statistics

(He++/H+ ratio etc)

(2) comparison with cold ion

Venus-Mars difference

For Mars: RS ~ 5000 km for Martian Subsolar

2 keV H+ under 6 nT rg = 1000 km

5/cm3 H+ c/pi = 100 km

(1) size: finite gyroradius effect

(2) cold ions: only Mars has cold ion at bow shock

SW parameter

RS (BS radius)

MA

(n1/2 V/B)

c/pi ( n-1/2)

& c/piRS

rg ( V/B)

& rg/RS

Venus 1 1 1 & 1 1 & 1

Earth ~ 5 ~ 1.2 ~ 1.7 & ~ 0.3 ~ 2 & ~ 0.4

Mars ~ 0.5 ~ 1.4 ~ 3 & ~ 5 ~ 4 & ~ 8

Foreshock (Venus/Earth=yes, Mars=no)

Martian specialty on Bow shock acceleration

QT QL FSQT

& //acceleration

accelerationoblique acceleration

// acceleration

escapeescape

on-going worksold works

Foreshock: He++ and H+ show different behavior

inbound-outbound asymmetry:Quick ExB drift

Heating event

Freja O+ injections

O+ = not well-studied

H+ = well-studied

in 1° x 1h bin.