Solar Physics

, Volume 279, Issue 2, pp 497-515

First online:

Heliospheric Observations of STEREO-Directed Coronal Mass Ejections in 2008 – 2010: Lessons for Future Observations of Earth-Directed CMEs

  • N. LugazAffiliated withSpace Science Center, University of New HampshireInstitute for Astronomy, University of Hawaii Email author 
  • , P. KintnerAffiliated withInstitute for Astronomy, University of HawaiiUniversity of Rochester
  • , C. MöstlAffiliated withSpace Science Laboratory, University of CaliforniaKanzelhöhe Observatory – IGAM, Institute of Physics, University of GrazSpace Research Institute, Austrian Academy of Sciences
  • , L. K. JianAffiliated withDepartment of Astronomy, University of MarylandHeliophysics Science Division, NASA Goddard Space Flight Center
  • , C. J. DavisAffiliated withDepartment of Meteorology, University of ReadingSFTC Rutherford Appleton Laboratory
  • , C. J. FarrugiaAffiliated withSpace Science Center, University of New Hampshire

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We present a study of coronal mass ejections (CMEs) which impacted one of the STEREO spacecraft between January 2008 and early 2010. We focus our study on 20 CMEs which were observed remotely by the Heliospheric Imagers (HIs) onboard the other STEREO spacecraft up to large heliocentric distances. We compare the predictions of the Fixed-Φ and Harmonic Mean (HM) fitting methods, which only differ by the assumed geometry of the CME. It is possible to use these techniques to determine from remote-sensing observations the CME direction of propagation, arrival time and final speed which are compared to in-situ measurements. We find evidence that for large viewing angles, the HM fitting method predicts the CME direction better. However, this may be due to the fact that only wide CMEs can be successfully observed when the CME propagates more than 100 from the observing spacecraft. Overall eight CMEs, originating from behind the limb as seen by one of the STEREO spacecraft can be tracked and their arrival time at the other STEREO spacecraft can be successfully predicted. This includes CMEs, such as the events on 4 December 2009 and 9 April 2010, which were viewed 130 away from their direction of propagation. Therefore, we predict that some Earth-directed CMEs will be observed by the HIs until early 2013, when the separation between Earth and one of the STEREO spacecraft will be similar to the separation of the two STEREO spacecraft in 2009 – 2010.


Coronal mass ejections STEREO Heliospheric imagers Methods