Search for forerunner activity associated with coronal mass ejections
The possible existence of energetic disturbances in the corona significantly before the associated surface events has profound implications for the location and mechanisms of prevent coronal energy storage. Precursor activity associated with coronal mass ejections (CMEs), if it exists, would reflect the evolution and magnitude of the energy release for failure of magnetic equilibrium characterizing the interval before and during the events. Jackson and Hildner (JH) studied 21 CMEs observed with the Skylab white-light coronagraph, and found a low-density plateau rimming each event for which good coverage was available. They concluded that this ''forerunner'' material could not be explained by mere translation of the overlying coronal plasma. Jackson further inferred from the Skylab data that the forerunner must start moving significantly before the onset of the associated CME, thus identifying this phenomenon as a form of precursor activity. We have performed a systematic search for forerunners using the white-light coronagraph observations obtained with the Solwind instrument on board the P78-1 satellite. Forty-four bright, well-observed events were selected and analyzed, employing selection criteria and analysis methods similar to those used by JH. Approximately half of these events either do not exhibit low-density plateaus in front or are questionable (e.g., a frontal plateau only appears intermittently). Based on our analysis of the remaining CMEs, we conclude that identification of the forerunner as a distinct entity probably is not warranted, and that the low-density plasma is an integral part of the CME itself. copyright American Geophysical Union 1987
- Research Organization:
- E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, D.C.
- OSTI ID:
- 6148614
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 92:A7
- Country of Publication:
- United States
- Language:
- English
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