Injection Timing of Near-Relativistic Proton and Electrons: Context for the 20 January 2005 Solar Energetic Particle Event

The extraordinarily prompt and intense solar energetic particle (SEP) event of 20 January 2005 may offer an extreme example of the acceleration/injection process. This process could be examined from 1AU with ~1-minute time resolution because the Earth was magnetically well-connected to the injection region, so that the pitch-angle distributions of the SEPs were strongly collimated along the interplanetary magnetic field. We attempt to place this SEP event into the context of other magnetically well-connected high-energy events. We have identified 16 beam-like near-relativistic (175-315 keV) electron events in the 1.0-min-average ACE/EPAM data set that are accompanied by intense >100 MeV proton events in the 5.5-min-average GOES data set. We developed a 3-parameter analytic function that allows us to quantitatively describe the profile of the rise phase of the electron and proton events (Haggerty and Roelof, Proc. Solar Wind 11, 2005). We found no statistically significant relation between the electron and proton rise function parameters. We have now compared the timing of the electron and proton injections with the onset of radio emission signatures of electron synchrotron emission (8800 MHz microwaves from Solar Geophysical Data) and coronal escape of low-energy electrons (decametric 14 MHz type III from WIND/WAVES). Our preliminary results are that in most events the protons are injected within ~ +/-10 min of the electrons (which is about the time resolution of the GOES data), but there are several events with considerably longer differences (~+/-20 min). Most of the electron injections and some of the proton injections are delayed 10-20 min after the start of the 14 MHz type III burst, while some proton injections appear within ~+/-10 min of the burst (again within the GOES time resolution). Most electron and proton injections are delayed by 5-30 min after the start of the 8800 MHz microwave emission. The injection/emission delays in the 20 January 2005 SEP (Simnett and Roelof, this Session) appear to fall at the more prompt limits of the timing distributions for this class of magnetically well-connected SEP events.