1. M. Yamauchi1, A. Schillings1,2, R. Slapak3, H. Nilsson1, I. Dandouras3
Erosion of Earth's atmosphere by ion escape: observations, a consistent model, and implications to the atmospheric evolution
M. Yamauchi1, A. Schillings1,2, R. Slapak3, H. Nilsson1, I. Dandouras3
1. IRF, Kiruna, Sweden
2. LTU, Kiruna, Sweden
3. EISCAT HQ, Kiruna, Sweden
4. IRAP, U. Toulouse/CNRS, Toulouse, France

2. Key Point
(1) Slapak et al. (2017): O+ Loss Rate from the Earth for Kp < 7 :
Floss µ exp(0.45*Kp)  ∫Floss ≈ kg ≈ atmospheric O2
(2) Yamauchi and Slapak (2018):
(a) Mass loading of these O+ extracts solar wind kinetic energy:
∆E µ (mO/mH)·(nO/nH) ~ substantial
µ Floss·vSW2
where Floss is the total O+ flux into the solar wind.
(b) Positive feedback between ∆E into the ionosphere and O+ energization by ∆E  non-linear Kp dependence
(3) Schillings et al. (2017): For large Kp ≥ 7+ (ancient condition) :
Floss (and ∆E) >> prediction by exp(0.45*Kp)
 O+ escape can no longer be ignored in the evolution of the atmosphere

3. (1) O+ escape vs. Kp: Cluster/CIS
Cluster could distinguish
(a) loss to the space
(b) flowing into the magnetotail

4. Cluster/CIS hot O+ obs. of direct escape
???
Kp≥8
1026
1025
~ 0.7x1025 s-1
1024
O+ Loss Rate :
Floss µ exp(0.45*Kp) R
Cluster/CIS: – 2005 (Slapak et al., 2017)
~ 2x1025 s-1 Kp
# samples X

5. (2) Feedback from escaping ions
VO+ increases while VH+ decreases
 Mass loading
 inelastic momentum conservation
 Extraction of kinetic energy

6. (2a) Energy extraction by O+ mass-loading ≠ 0
(1) Momentum conservation in the –x direction:
∆P = (ρ+dρ)·(v+dv)2 – ρu2 = 0
and dFloss (O+ supply from –z) plays as dρ
 dρ/ρ ≈ (dFloss/dx)·dx/ρv·S
(2) "inelastic" mixing means
∆E = (ρ+dρ)·(v+dv)3/2 - ρu3/2 < 0
 ∆E (extracted energy) ≈ Floss·vSW2/4
total O+ mass flux: Floss
(3) Amount is substantial:
nO+/nSW~0.01  rO+/rSW~0.16
 extract 7% of kinetic energy E
 ∆E ≈ W to J// through B

7. If "ionosphere" is connected to mass-loading region
finite s⊥ (∑P)
If ∑P = ∞, charges are canceled & E = 0
If ∑P = 0, charges cause E = -UxB
If ∑P = finite, E = finite & IP·∑P = finite µ ∆E

8. (2b) Combine with feedback to ion escape
Energy to ionosphere by mass-load:
∆E µ Floss·vSW2
Assume escape µ energy loss in the ionosphere: Floss µ ∆E
 Positive feedback !
Add two empirical relations
(1) Ion Loss Rate (Cluster):
Floss µ exp(0.45*Kp)
(2) Kp and VSW :
VSW µ 135·(Kp+1.2)
 ∆E µ Kp2 · exp(0.45*Kp)

9. (3) Non-linearity for Kp>7
example: Halloween event ( ) O+
energy H+
O+ (>0.3 keV)
pitch angle
O+ (<0.3 keV)

10. (3) Non-linearity for Kp>7
example: Halloween event ( )
entire 2003
Flux after scaling to the ionosphere
Reference: 1-year data in the same region
 higher than
extrapolation

11. (3) Non-linearity for Kp>7
Examined 6 “extreme” events
Dates
VSW(km/s)
NSW (cm-3)
Dst [nT] Kp
~ 720 38
-387 9-
4.4
-271 7+
~ 810 52
-144
(2000 ?)
-350 9
~ 700 90
-117 8
~ 790 18
-259

12. (3) Non-linearity for Kp>7
Shift of median flux
(a) Southern hemisphere
x 47
x 50
x 10
x 18

13. (3) Non-linearity for Kp>7
Shift of median flux
(b) Northern hemisphere
x 20
x 6
x 9
x 60
x 83
x 18

14. (3) Non-linearity for Kp>7
The O+ outflow during major storms is 1 to 2 orders of magnitude higher than during less disturbed time

15. Summary and Conclusion
(1) Slapak et al. (2017): Ion Loss Rate from the Earth for Kp < 7 :
Floss µ exp(0.45*Kp)  ∫Floss ≈ kg ≈ atmospheric O2
(2) Yamauchi and Slapak (2017): Extraction of Solar Wind kinetic energy by mass loading :
∆E µ Floss·vSW2  ∆E µ Kp2·exp(0.45*Kp) , for Kp < 7
(3) Schillings et al. (2017): However, for large Kp ≥ 7+ (condition of ancient time)
Floss (and ∆E) >> prediction by exp(0.45*Kp)
 ∫F >> kg (atmospheric O2 and N2)
 O+ escape can no longer be ignored in the evolution of the atmosphere

16. Future direction
Need to understand expansion and escape of neutral atmosphere too.
 ESCAPE mission (oral later)

17. End / extra slides

18. EISCAT (VHF) observation of September 2017 event.Vi
X-flare
CME = outflow
CME = aurora

19. ne 2017-9-07 CME = aurora Magnetometer Bx Riometer
2000 nT
Riometer
pulsating magnetometer < 5 Hz ne
EISCAT VHF (Tromsø)

20. Feedback from escaping ions
Extraction of kinetic energy: ∆E
Simple conservation laws:
 ∆E µ F · vSW2, but nothing else
Since F µ ionospheric current µ ∆E
 Positive feedback between
∆E µ F · vSW2 & F µ exp(0.45*Kp)
 ∆E µ Kp2 · exp(0.45*Kp) , for Kp<6
&
IMF BY effect can be explained

21. 2nd step: Plot the boxes and look at the plasma beta
Method
2nd step: Plot the boxes and look at the plasma beta
29 Oct 2003
Halloween event

22. Method
Year 2003
3rd step: Check the plasma beta parameter for the O+ outflow during the year
Scaled O+ flux log10 m-2s-1
Number of data points
Log10 plasma beta