On Sun-to-Earth Propagation of Coronal Mass Ejections
Abstract
We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs, each of which has wide-angle imaging coverage from both STEREO A and B, a long-duration interplanetary type II burst and in situ signatures near the Earth. Key results are obtained concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the maximum heating and radiation have elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs within a relatively short time scale following the acceleration phase; (4) CME-CME interactions seem a common phenomenon close to solar maximum. Comparison between different techniques (and data sets) gives important implications for CME observations and interpretations: (1) for the current cases triangulation with the fixed β approximation is more reliable than triangulation with the harmonic mean approximation below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the harmonic mean triangulation more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the observer; (3) our approach in comparing wide-angle heliospheric imaging observations with interplanetary radio type II bursts provides a novel tool in investigating CME propagation characteristics. Future CME observations and space weather forecasting are discussed based on the results.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2013
- Bibcode:
- 2013AGUSMSH32A..04L
- Keywords:
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- 7513 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Coronal mass ejections;
- 2111 INTERPLANETARY PHYSICS / Ejecta;
- driver gases;
- and magnetic clouds;
- 2139 INTERPLANETARY PHYSICS / Interplanetary shocks;
- 7534 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Radio emissions