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Astron. Astrophys. 360, 729-741 (2000)

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5. Conclusions

The particularly quiet conditions of particle propagation in interplanetary space make the 1996 July 9 event well suited to study the relationship between coronal energy release and the acceleration of energetic and mildly relativistic particles and their injection into interplanetary space. Comparison of in situ measurements of these particles and remote sensing diagnostics of coronal processes shows the following:

  1. The acceleration of protons and electrons during the impulsive phase of the flare has no interplanetary counterpart observable at the SoHO site. The radio spectra provide evidence that this is because particles are mainly injected into closed structures in the low corona during this early phase of the event.

  2. Mildly relativistic electrons ([FORMULA] keV) and energetic protons ([FORMULA] MeV) observed at 1 AU have distinctly different injection profiles. The proton injection proceeds through two successive, gradually evolving phases with different spectra, while the electron injection is mainly impulsive and accompanies only the rise of the first (p-component) proton injection. However, a minor ([FORMULA]25%) contribution of continual electron injection during the first proton rise is still possible. Electron production during the second proton rise is less than 5%.

  3. The main electron injection can be traced back to a simultaneous period of electron acceleration in the corona which shows up as a broadband enhancement of radio emission from a few GHz to some tens of MHz. This occurs in and above the flaring active region. Escaping electron streams are traced by the second hectometric to kilometric type [FORMULA] burst group.

  4. A coronal shock wave traced by its decimetric-to-metric type [FORMULA] radio emission accelerates the electrons that emit the radio burst, as well as electrons producing the first hectometric type [FORMULA] group. They have no significant counterpart in near-Earth electrons.

  5. The p-component proton injection, which proceeds during about 1.5 hours after the flare onset, has a globally similar time profile as the metric-decametric (type [FORMULA]) radio continuum which is related to the large scale reconfiguration of the corona in the course of the CME lift-off.

  6. The subsequent softer, but more energetic d-component proton injection evolves without a signature of correlated changes in the middle corona. We suggest that the delayed acceleration is driven by the CME. The shock acceleration cannot be ruled out, but there is no positive evidence for the interplanetary shock in the event.

  7. Studies of SEP genesis should not be reduced to resolving an alternative "impulsive flare acceleration vs. interplanetary CME-driven shock acceleration", but should also comprise coronal acceleration at a global scale between the flare and the interplanetary CME, especially an acceleration related to reconfiguration of the solar corona during the CME development.

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© European Southern Observatory (ESO) 2000

Online publication: August 17, 2000