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EGU2008-A-05100 / poster board XY0816 / 2008-4-16

Sudden formation of bi-directional ion beam, and associated large-scale configuration change, in the equatorial ring current at 19 MLT and L=4.

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EGU2008-A-05100 / poster board XY0816 / 2008-4-16

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  1. Sudden formation of bi-directional ion beam, and associated large-scale configuration change, in the equatorial ring current at 19 MLT and L=4. M. Yamauchi1, R. Lundin1, H. Nilsson1, I.Dandouras2, H. Reme2, G. Stenberg3, M. Andre3, P.-A. Lindquvist4, P.W. Daly5, H. Frey6, Y. Ebihara7, E. Kronberg5, and A. Balogh8 (1) IRF-Kiruna, (2) CESR, Toulouse, (3) IRF, Uppsala, (4) KTH, Stockholm, (5) MPS, Katlenburg-Lindau, (6) UCB/SSL, Berkeley, (7) Nagoya U, (8) ICL, London EGU2008-A-05100 / poster board XY0816 / 2008-4-16

  2. Observation (@19 MLT, L=4, equator) CLUSTER detected sudden changes in the ion flux at ~0643:00 UT (event #1) and at ~0648:30 UT (event #2)  Fig 1, Fig 5 unusual (#1) flux increase in H+ (0.1 MeV), He+ (0.2 MeV), CNO+ (0.5 MeV). (#1) flux decrease in e- (0.1 MeV), H+, He+, CNO+ (>MeV), unusual (#1) flux decrease in ring current O+ (<0.4 MeV). unique(#2) sudden appearance of bi-directional field-aligned beam (<keV). unusual (#2) flux decrease in ring current H+ and O+ (<40 keV). Simultaneously, CLUSTER detected strong DC field (>5 mV/m) and Pi2-like diamagnetic |B| depletion (20%, 0.01 Hz range).  Fig 1 unique (#1) Cold ion is detected: He+ rich, but no O+! IMAGE/FUV show unusual (#1) arrival of isolated auroral bulge  Fig 2 (mark) unusual (#2) filamentation of transpolar arc  Fig 2 (mark) Minor geomagnetic activity (AL~-200nT, Dst=-58 nT).  Fig 3 Both ion/field changes are detected simultaneously at all S/C.  Fig 4 The wave is detected only at event #2, and it is most likely generated by the bi-directional field-aligned beam Fig 4

  3. Figure 3: Geomag. Cluster Location (GSE) onset #1 #2 MCQ = Cluster conjugate

  4. Figure 5: > 5 keV

  5. Simultaneous with SC-3 leading, duskward convection of 20km/s, no wave, and 0.2 MLT/min motion in IMAGE  tailwardE-field was carried by the convection together with the auroral bulge at ground. 2. DC disturbance in B & flux decrease of >0.1 MeV  diamagnetic effect: large-scale configuration change 3. Rich in cold He+ but no O+ plasmaspheric He+ at 4 RE! 4. Flux increase of <0.1 MeV H+ , but no wave  No local acceleration. How can we supply? 5. Minor magnetospheric activity energy source? Indications: (a) plasmasphere-magnetosphere coupling in the equatorial inner magnetosphere, (b) filling of medium-energy ring current ions by auroral bulge, (c) propagation of DC E-field in the equatorial plane. Event #1 summary:

  6. 1. Simultaneous at SC-1, 4 and -3 within 1 sec sudden activation 2. Bi-directional along B, and DC E-field disturbancedoubleparallel potential is carried by convection? 3. Wave with randomly changing Pointing flux direction (not shown here) wave is caused by the bi-parallel beam 4. Change in >5 keV large-scale configuration change by E-field 5. Filamentation in the transpolar arcbut, the relation is not clear (?) 6. Only minor magnetospheric activityEnergy? Indications: (a) new-type of beam-formation (b) role of the transpolar arc Event #2 summary:

  7. Viking case No dispersion  not drifted  local energization Energy normally < 100 eV  observed all local time 8 MLT

  8. Mostly // direction 4s spin plots of ion Pitch angle: //  (spin)  //

  9. 90 min MeV 103 keV 0.01~40 keV 25 min H+ O+ H+ He+

  10. Agree with DC E-field ExB drift velocity = 25~50 km/s 4-15 eV for H+ => 15-60 eV for He+ 60-250 eV for O+

  11. Timing (12sec resolution) 06:43:00 06:48:30 leading 60s behind 25s behind

  12. ASY/SW

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