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

Key Point (1) Slapak et al. (2017): O+ Loss Rate from the Earth for Kp < 7 : Floss µ exp(0.45*Kp)  ∫Floss ≈ 1018 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

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

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: 2001 – 2005 (Slapak et al., 2017) ~ 2x1025 s-1 Kp # samples X

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

(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 ≈ 109-10 W to J// through B

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

(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)

(3) Non-linearity for Kp>7 example: Halloween event (2003-10-29) O+ energy H+ O+ (>0.3 keV) pitch angle O+ (<0.3 keV)

(3) Non-linearity for Kp>7 example: Halloween event (2003-10-29) entire 2003 Flux after scaling to the ionosphere Reference: 1-year data in the same region 2003-10-29  higher than extrapolation

(3) Non-linearity for Kp>7 Examined 6 “extreme” events Dates VSW(km/s) NSW (cm-3) Dst [nT] Kp 2001-3-31 ~ 720 38 -387 9- 2001-4-12 4.4 -271 7+ 2003-5-30 ~ 810 52 -144 2003-10-29 (2000 ?) -350 9 2004-11-7 ~ 700 90 -117 8 2004-11.10 ~ 790 18 -259

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

(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

(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

Summary and Conclusion (1) Slapak et al. (2017): Ion Loss Rate from the Earth for Kp < 7 : Floss µ exp(0.45*Kp)  ∫Floss ≈ 1018 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 >> 1018 kg (atmospheric O2 and N2)  O+ escape can no longer be ignored in the evolution of the atmosphere

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

End / extra slides

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

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

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

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

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