Ionospheric ion response to the space weather event during 6-8 September 2017 M. Yamauchi1, A. Schillings1,2, T. Sergienko1, C.-F. Enell3, R. Slapak3, M.G. Johnsen4, A. Tjulin3, H. Nilsson1, P. Wintoft5, M. Wik5, I. Dandouras6 1. IRF, Kiruna, Sweden, 2. Lulea University of Technology (LTU), Kiruna, Sweden, 3. EISCAT Scientific Association, Kiruna, Sweden, 4. Tromsø Geophysical Observatory (TGO), Tromsø, Norway, 5. IRF, Lund, Sweden 6. IRAP, CNRS and University of Toulouse, Toulouse, France

Summary Effect of X-flares near local noon (§3.1) Density (Ne) spike @<200 km, at the time of X flare (Fig 2a, 3a, 4a, 5a) Temperature and Sq current increased directly after X flare (Fig 1j, 5b) No change in upflow after X flare (Fig 3d)  pre-condition for outflow? Effect of ICME, GOES proton event, or SEP-like event (§3.2+3.4)? Outflow was 8th>7th>6th in dayside (Fig 5c)  consistent with Cluster Cannot distinguish if this is due to ICME or SEP-like event (Fig 1b-1f) IMF direction is important for ICME-effect (1st: Bz>0, 2nd: Bz<0, Fig 1d,h,i) Substorm-like motion of auroral arc before 1st ICME (Fig 4)  SEP effect? Many turning to IMF Bz<0 in the late morning sector (§3.3) Horizontal flow is enhanced, but upflow is decreased (Fig 3d, 4d, 6b,c,e) Different timing between horizontal flow and vertical flow (Fig 6b,c) Sudden turning from Bz>0 to Bz-15 nT near local noon (§3.5) Outflow region becomes outside EISCAT field-if-view for Bz<0 (Fig 2-4)  Bz>0 might favor outflow if only dayside effect is considered.

Figure 1 Bz change 2ndCME Cluster pass Bz changes 1stCME X flares

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Figure 2 X flares 1stCME Bz change 2ndCME Bz change

Figure 3 X flares 1stCME Bz change 2ndCME Bz change

Figure 4

Figure 5 Figure 6