Oxygen Injection Events observed by Freja Satellite M. Yamauchi 1, L. Eliasson 1, H. Nilsson 1, R. Lundin 1, and O. Norberg 2 1.Swedish Institute of Space Physics,S Kiruna, Sweden 2. Swedish Space Corporation - Esrange, S Kiruna, Sweden We surveyed heavy ion injections at 1700 km altitude. *They are mostly found in nightside subauroral region *Only few % are found in dayside They seem to have different generation mechanisms.  We show three of them during magnetic storm. (1) Mono-energetic O+ injection near local noon with O+ first and H+ later. (2) Heavy ion injection adjacent to cusp at lower energy than H+. (3) A multiple heavy ion dispersion event which can be traced back to one localized energization of dense oxygen with strong pitch-angle anisotropy within 1000 km distance from the spacecraft.

Oxygen is important Space-level circulation of oxygen/heavy ions has an obvious cross-disciplinary importance on subjects such as: * Evolution of Earth, planets, satellites * Modeling of ancient Earth (astrobiology) * Atmospheric environment * Chemistry of reservoir (CO 2, SiO 2, SO) * Basic plasma physics * Solar-terrestrial physics / energy and mass transfer * Plasma and neutral circulation in the exosphere Phobos-2 observation of oxygen escape from Mars [Lundin et al., 1990]. Top: energy-time spectrogram. Bottom: energy-mass matrix Cluster observation of oxygen escape from the Earth [Nilsson et al., 2004] H+ O+ AND O+ escapes a lot (1~10 kg/s from Earth/Mars) AND O+ behaves differently from H+ O+ H+ e- O +,O 2 + O+O+ H+H+

Freja observation / general ion injections in night/morning sectors O+ H+ e- O+ H+ e- Commonly-found ion injections near or equatorward of the nightside auroral zone. O+ = not well-studied H+ = well- studied Freja examples Clear nightside preference Some in dayside Not artifact of 63°inclination The total number of traversals with clear injection events in each bin is scaled by the size of the square. The numbers with # are the orbit number. in 1° x 1h bin. * Search all heavy ion injection events ( keV) from Freja * Obtain distribution/statistics & Examine exceptional cases

#1 + #2 : ~1330 UT cusp O+ H+ e- " SPI " event #1 event #2 11 MLT 12 MLT13 MLT 14 MLT energy ratio = 15~20 Kp=7+, IMF ≈ 50 nT (dawnward) Freja energy-time spectrogram and geomagnetic activity. 1. Heavy ion (labeled O+ but could include N+): keV 2. Proton (H+): keV 3. Filed-aligned electron (e-): keV O+ H+ 68°CGLat66°CGLat63°CGLat

#1. Midday Mon Heavy Ion Injection Event ∆T = H TOF / V //2 - H TOF / V //1 note: pitch-angle dependent H VF / V //2 - H VF / V //1 = ∆T * V sat / V C or H VF = H TOF * V sat / V C Time-of-Flight (TOF) Velocity Filter (VF) (A) morning or (B) evening  difficult (C1) dayside same hemisphere  difficult (C2) opposite hemisphere = cusp (IMF B Y effect)  possible Mono-energetic heavy ion injection (0.3-1 keV range) at L=7 The O + /H + energy ratio = 15~20  O + (0.3 keV= 60km/s) Narrow band  only O +, not N + despite storm condition O+ before H+  ??? (mass filtering mechanism) Only this event in 2.5 years  due to strong IMF B Y (≈ 50nT)? Source Distance? 0.32 UT to :32:06 UT (6 spin) * Time-of-flight (TOF) distance ≈ 1 Re  unrealistic * Velocity filter (VF) distance > 10 Re  possible Source? Route?

#2. Heavy Ion Injection Adjacent to the Cusp Only this event in > 100 cusps  different from FAST result Lower energy than H+  different from FAST result Why Freja (h=1700km) - FAST (h= km) discrepancy? * Upper energy threshold of Freja is too low  probably no * O+ (not H+) loss process right above Freja  surprising * Thermalization right above Freja & contamination  surprising * Only during special magnetic storms  need investigation

#3 : ~1850 UT "wedge" event #3 (1) (2) (3) 9 MLT 10 MLT O+ H+ e- 60°CGLat66°CGLat P/A=0~90° P/A=90~180° P/A=40~140° Kp=6- O+ Freja energy-time spectrogram and geomagnetic activity. 1. Heavy ion (labeled O+ but could include N+): keV 2. Proton (H+): keV 3. Energetic electron (e-) keV 4. Field-aligned electron (e-): keV radiation belt? 63°CGLat

#3. Multiple Heavy Ion Dispersion Event If they are really injection events... * They have different dispersion curves (1) 18:50:10 UT (0.56 keV to 0.13 keV in 12s)  TOF=10s (2) 18:50:25 UT (1.0 keV to 0.24 keV in 24s)  TOF=25s (3) 18:50:40 UT (2.4 keV to 0.32 keV in 75s)  TOF=45s  simultaneous start times (within 5 second) * Time-of-flight (TOF) distance < 1000 km Non-gyrotropic distribution + downgoing flux  Anisotropic source distribution (1) Anisotropy of the source distribution was maintained ~ 1min.  Single source & source distribution = 3 peaks (2) Very close source (~ 10 Ω O+, i.e., <100km)  Can be multiple sources & source distribution = 1 peak In any interpretation, the generation mechanism is a mystery Multiple heavy ion injection (0.1-3 keV) at 60°-65° at 9 MLT Downgoing >> Upgoing  Injection (Not heating by wave) Without H+  Only heavy ions (O+ or N+) Oblique rather than perpendicular  Source distribution Non-gyrotropic  ? (Ω O+ ≥ 100 Hz ~ phase-mixing within 1s) note: no signature of strong (~ 100 km/s) convection. Only this event in 2.5 years  ?

Summary of Heavy Ion Injection Events We examined all heavy ion data of Freja satellite ( ) * Most injection events occur in the nightside * Some unusual events in the dayside (1) Mono-energetic injection with O+ faster than H+ (13 LT) VF source > 10 Re (TOF distance ~ 1 Re).  From the southern dayside ionosphere (cusp) Mass-filtering mechanism is unknown (2) O + injection (lower energy than H + ) adjacent to the cusp Freja-FAST discrepancy Generation mechanism is unknown (3) Multiple dispersive O+ injections from a nearby source In oblique direction with non-gyrotropic distribution Sudden localized anisotropic energization at < 1000 km. Generation mechanism is a mistery