GCS paramters and measurements are shown in Measurement File


This is the drag model fitting for my measurements of the May 27, 2013 CME. The fitting parameters are

Front	Gamma (/km)	V_0 (km/s)	V_SW (km/s) (Determined by ACE)	R_0 (R_S)
Compression	-1e-9	389.0	336.3	26.55
Ejecta	-1e-6	50	336.3	6.21

This is an extremely slow event, so there are a number of difficulties fitting it. This event is certainly not fast enough to generate a shock wave, so I made sure to specify that it is a compression front. It also isn't really visible until the HI-1 FOV. The ejecta starts out very slow before accelerating. Most of the work I have done has been with fast CMEs, so I modified my drag fitting to work with an accelerating event rather than a decelerating event. This CME is also propagating at a latitude of 35.2 degress N. This further complicates the drag model, as it is hard to compare CME leading edge positions to ACE on the Sun-Earth line, and it is also possible that the usptream solar wind speed at ACE is far different than what the main bulk of the CME encounters. All told, I am highly skeptical that this is actually a geoeffective event. Perhaps part of the compression region encounted a high speed solar wind stream, but that would likely be the extent of it. Looking at the ACE data, I think the low Dst at this time is associated with a CIR, given the dramatic change in solar wind speed, and the period of heightened Density followed immediately by a period of heightened temperature.



The particular CME I measured, which is the only front sided CME near the in-situ signature, is associated with a filament off the NW limb. Again, I am very skeptical that this CME could be Earth affecting, though part of the compression front could strike the Earth. I just think a CIR is the main driver of this event.
AIA 171 video>
AIA_304 video
And the event is well observed by both STEREO A and B, though given the CME propagating away from the Sun Earth line it is not observed very far off. Given the position of the STEREO spacecraft by May 2013, there may also be issues observering CMEs further from the Sun.