Note on tracking Sun-Earth connection event

ICME Event: 2011/09/18

Observer: Eleni Nikou on 2019/06

1. ICME
  1.1. Catalog
     # Identified in ICME catalogs: Richardson & Can List
      RC catalog:
      Disturbance start time: 2011/09/18 10:00 UT
      Ejecta      Start time: 2011/09/18 12:00 UT
      Ejecta      End   time: 2011/09/18 21:00 UT
      dv = 40 km/s, v = 440 km/s, vmax= 480 km/s
      MC index:     1
      Dst:        -30 nT
      Suggested source CME: -
      V_transit: -
      
  1.2. Comments
      Overall ICME quality index: 2
      ICME signatures: Bmax: 5.7 nT
               ICME signatures: u decreases smoothly, low beta, Tp<Texp
      
      Disturbance time 440 km/s  -> search window 4 days -> 2011/09/14

2. CME

    2.1, A, Candidate A
     A.1. LASCO  
       #CME 2011/09/14 20:12:05 UT, partial halo CME (CDAW)
           

     A.2. STEREO
         front-side CME, (first frame at COR2-A 20:54 UT)

     A.3. AIA & GOES 
          #GOES flare C9.2,  14-Sep-2011 20:42 UT from AR11297, S18W48

	      The active region is on the southern western hemisphere and it is constistent with the observations. It is detected by STA first.

     A.3. Comment
          Could be the source: The timing and orientation is in agreement with the observations

     2.1, B, Candidate B
     B.1. LASCO  
       #CME 2011/09/15 00:00:06 UT, partial halo CME (CDAW)
           

     B.2. STEREO
         front-side CME, (first frame at COR2-A 00:24 UT)

     B.3. AIA & GOES 
          #GOES flare C4.6, 15-Sep-2011 00:24 UT, AR11297, S18W50

	      The active region is on the southern western hemisphere and it is constistent with the observations. It is detected by STA first.

     B.3. Comment
          The orientation is in agreement with the observations, but it is unlike that this is the source because of the timing. Based on the transit velocity the CME needs more that 2 days to arrive to Earth.


3. Other Comments

   The source is difficult to be identified because the two events have only 4 hours difference and they are both Earth directed. They come from the same active region and it is likely that there is an interaction between the two and we have multiple ejecta. We could maybe say that Candidate B is the source because of the velocity data. It is faster than Candidate A, but still it is risky to reach a conclusion. What we can say though is that the source region is AR11297.
    
 
4. Summary
    SW index 2
    Source index 2
    Overall index 2