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Sub-keV Phenomena of Dayside Ring Current

Sub-keV Phenomena of Dayside Ring Current. M. Yamauchi , R. Lundin, H. Nilsson (IRF-Kiruna), Dandouras, H. Reme (CESR, Toulouse), G. Stenberg, M. Andre (IRF, Uppsala), P.-A. Lindquvist (KTH, Stockholm), Y. Ebihara (Nagoya U.), C. Vallat (ESTEC, Nordwijk),

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Sub-keV Phenomena of Dayside Ring Current

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  1. Sub-keV Phenomena of Dayside Ring Current M. Yamauchi, R. Lundin, H. Nilsson (IRF-Kiruna), Dandouras, H. Reme (CESR, Toulouse), G. Stenberg, M. Andre (IRF, Uppsala), P.-A. Lindquvist (KTH, Stockholm), Y. Ebihara (Nagoya U.), C. Vallat (ESTEC, Nordwijk), P.W. Daly (MPS, Katlenburg-Lindau), A. Balogh (ICL, London)

  2. Sub-keV Ring Current? Traditional view of the ring current : > 5 keV only 2002-7-20 ions H+ He+ O+ Sub-keV Cavity Cluster (SC-1) CIS data over perigee traversal at noon

  3. However Example 1: wedge-like structure poleward eastward drift Viking 14 MLT westward drift eastward drift Cluster Perigee, 11 MLT

  4. Viking probability of event Motion and source 6 MLT 9 MLT 12 MLT 15 MLT 18 MLT Cluster Time-lag (hours) Backward Superposed Epoch Analyses using 700 traversals.

  5. Case study : 2001-10-21 event Substorm onset H+ O+ South North

  6. H+ O+ +0.1° 0° -0.1° Inter-SC time-of-flight (at 9.0 MLT) V(10 keV) = VE-VB << VE SC-4 10 keV 0.1 keV 23:40 UT 23:40 UT SC-4 @ 23:50 UT: Yes 23:50 UT SC-3 @ 23:40 UT: No H+ O+ V(0.1 keV) ~ VE 23:50 UT SC-3 ∆t < 13 min (100 eV/C-3 & 10 keV/C-4)  t < 30 min  drift distance = VE * t < 20000 km started at 7~9 MLT.

  7. Wedge-summary Wedge-like dispersed sub-keV ring current is a fossil of substorm activity (model is right!) by VExB ≥ VB-drift. It's source extends from midnight to morning (both statistics and case study) O+ source is different from H+ source

  8. Example 2: heating Viking , 8 MLT Cluster , 19 MLT ions H+ He+ O+ e- i+ heating? heating? No dispersion  not drifted  local energization Energy normally < 100 eV  observed all local time Only one extremely intense event over 5 years Cluster obs.

  9. Unusual heating on 2002-5-19 Energy range: >900 eV & 5-900 eV ion+ (C1) ion+ (C3) 0645 0650 0655 0700 H+ (C4)

  10. 06:48:30 Feature-1: Timing simultaneous at all SC in 12sec resolution SC-1: leading ion+ (C1) SC-3: 60s behind SC-1 ion+ (C3) 0642 0646 0650 SC-4: 25s behind SC-1 H+ (C4)

  11. cf. SC-location

  12. Mostly // direction 4s spin plots of ion Feature-2: Pitch angle: //  (spin)  //

  13. Feature-3: Wave simultaneous! 4s spin plots of ion SC-1: 06:48:30 UT V n dB dE B0 ion

  14. more wave: broadband + stagnant 150 nT  ΩP = 4 Hz ion dE dB S// E/B ΩHe? dBZ BB-EM spin effects stagnant dBX

  15. Substorm-level disturbance simultaneous with heating Feature-4: DC field 06:48:30 UT = heating EY potential B SC separation up to 1 min:  temporal structure 0640 0645 0650 0655 already from 0643 UT

  16. Feature-5: >5 keV component ion+ ion+ ion+ E = 0.005~40 keV P/A (> 5 keV) P/A (< 0.2 keV) 06:43 precursor 06:48:30: heating H+ He++~O+ sudden decrease

  17. for > 100 keV component ion+ e- H+ He+ & He+ + C +, N + & O+

  18. strong ExB drift Feature-6: Precursor  (spin)

  19. // direction of drift: rotate  drift direction Y (duskward) X (sunward) - UxB (estimated E) direction

  20. and agree with DC E-field EX<0 0600 0620 0640 0700 EY>0 EY<0 ExB drift velocity = 25~35 km/s 3-6 eV for H+, 13-25 eV for He+, 50-100 eV for O+ 40 42 44 46 48 50

  21. Feature-7: Composition (1) From energy peak: plasmaspheric He+ rich //  Precursor (06:44 UT) Heating (06:49 UT) • = 0° • = 180° • = 360°  // H+ He+ O+ 18 eV 70 eV He+ O+ ratio=4: O+/He+ or He+/H+ 10 100 [eV] 10 100 [eV]

  22. Composition: Precursor part O+ He+ He+ becomes detection range only when |E| is strong.

  23. (2) TOF mass analyser: He+ rich Composition precursor heating H+ He++ He+ O+ contamination 0643 0644 0645 0646 0647 0648 0649

  24. (3) >100 keV: plasmaspheric He+ Composition precursor heating

  25. Feature-8: magnetospheric condition Not special (just a minor storm/substorm)

  26. Nothing special Feature-9 : ground conj. only 50 nT activity precursor heating

  27. Indications from data (heating): 1. Simultaneous at SC-1, 4 and -3 sudden activation 2. Bi-directional along B local hearing (not propagated) 3. Simultaneous wave with randomly changing Pointing flux direction even the wave is locally generated? 4. DC disturbance in B and E substorm-level activity? 5. Change in >5 keV large-scale configuration change 6. Precursor with cold ExB drift, no energization related ??? 7. Rich in He+ for cold, sub-keV and 100 keV component  plasmaspheric He+ is supplied well before the event? 8. Only minor magnetospheric activity Mystery !

  28. Summary Sub-keV part of dayside ring current is not empty! Wedge-like dispersed sub-keV ions (statistics + case study) Fossil of substorm with eastward by VExB > VB-drift Some are originated from morning sector O+ source is different from H+ source Heating (case study, unusual event, not well understood) Local heating at equatorial plane by sudden onset He+ rich Precursor with strong DC E-field (and E-B drift) Not clear ground signature, before substorm onset

  29. Thank you

  30. all at 06:48:30 UT (12s resolution) SC-1: leading All info 25~150 eV 5-25 eV ET PA 25~150 eV 5-25 eV SC-3: 60s behind SC-1 25~150 eV 5-25 eV ET PA 25~150 eV 5-25 eV SC-4: 25s behind SC-1 ET PA O+ 30~500 eV 0642 0644 0646 0648 0650 0652 0654 0656

  31. Particle vs. wave 4s spin plots of ion

  32. Feature-# **: **

  33. Feature-# **: **

  34. Yes, of course more: wave 0645 0700 dE dB S// E/B 0630 0700 0730

  35. Cluster Examples Westward (magnetic) drift Eastward (electric) drift Noon Early morning Late morning only < 1 keV also > 1 keV also > 1 keV

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