Report on the seminar (H. Hudson) Here are some personal comments about the ISEPs one-day seminar we held at SSL last Friday (Nov. 3 2006). Many of the world's experts in "solar sources of impulsive SEPs" were present, not counting a few, but of course we missed a lot of expertise in some key areas. Prior to the seminar I had been thinking that there were really three communities involved: SEPs, coronal magnetism, and solar activity. We probably did not have good enough representation from the coronal magnetic side. The presentations are all on line as .ppt (and mostly also as .pdf) but the movies may be confused. See Presentations (and Literature) at http://sprg.ssl.berkeley.edu:80/RHESSI/iseps/. The recent spate of nice papers on this subject seem to concur on a strong association of ISEPs with jets/narrow CMEs, arguably phenomena that are closely identifiable with one another. But the bottom line has to have been that there are still huge unsolved problems (could also probably be read as "great opportunities for understanding"). I'm attaching some comments that mostly reflect my ignorance and biases. Hugh 1. I think that the SEP and magnetic communities have not properly been aware of the "X-ray jet" phenomenon. This is a flare-like morphology first really recognized with the Yohkoh SXT images. Essentially one sees plasma spurting out from the deepest layers in well-collimated structures, usually originating in the leading polarity of a newborn active region. The jets often have a "three footpoint" morphology and invariably involve a soft X-ray loop system (microflare) connecting two of the footpoints. These are not flares and usually do not make it into anybody's listings (e.g., SGD's) but they are closely associated with SEPs. The morphology strongly reminds one of the original cartoon of Heyvaerts, Priest & Rust (1977). Early results from the SXT images included strong evidence (spatial as well as temporal) for an association with type III bursts (Aurass et al. 1994, Raulin et al., Kundu et al.) and the natural inference from this was that the jets provided a high-density channel from which the radio waves could escape. The further implication of this, namely that the dense structures (as well as the open field) had to be there _prior_ to the electron acceleration, has not been explored yet theoretically as far as I know. The jets can be quite minor in their low-coronal manifestations, but are unmistakeable in UV, EUV, or soft X-ray movies. There does not seem to be much evidence that electron events, 3He events, or ISEPs in general are _not_ associated with this jet physics. Powerful flares may also have impulsive SEP properties, but the jets are not so visible in major events. This might be entirely due to detectability issues, or it might be a basic difference between jets and flares. The coronal manifestations of the jets (narrow CMEs) probably require the injection of chromospheric material. Typically X-ray jets start from an empty corona. They are however repetitive. 2. Space vs time It seems to me that there is a confusion between time series, as seen at 1 AU, and spatial developments (as seen in the corona). In general the particle Larmor radii are small compared to the 1 AU integration times (as converted to a spatial coordinate rather than time). Thus a 1 AU time series should not be thought of as a time series at all, but as a spatial development in the acceleration region. The clear and obvious example of this is the shock acceleration in gradual SEPs - the wave disturbance crosses different field lines and the acceleration is distributed. This sort of distribution probably happens in impulsive SEPs too, except that the nature of the spatial restructuring, especially as it relates to the open field regions, is not so clear. If there is a spatially distributed exciter, what plasma motion can be identified with it? The problem is exacerbated by the large magnetic flux that needs to be involved in an ISEP in order to explain the spatial breadth of the phenomenon at 1 AU. 3. PFSS The "potential field source surface" (PFSS) models seem to be astonishingly good at establishing the connection of a lower-coronal event with an SEP. The connections are established not only via event coincidences, but also via direct radio imaging. Why is it so good?? We _know_ that the corona must be significantly non-potential if we are to have flares or CMEs at all. I think the answer must be that the non-potentiality does not extend strongly to large scales, with the corollary that CMEs don't appreciably add to the non-potentiality no matter how spectacular they seem. It would be nice to use the SEP/solar comparisons to learn about how PFSS gets it wrong systematically. We know from the construction that there are large systematic latitude errors in the mapping. Can we also identify systematic problems related to the morphology of emerging flux? 4. The chromosphere Although we did not have detailed presentations of the models, the distribution of charge states of the SEP ions seems like a crucial diagnostic. Droge et al. (2006) argue that the observations require the product of density and acceleration time be in the range 1-6 x 10^11. Since we see sub-second time scales in the acceleration of electrons, at least, this implicates the chromosphere rather than the corona. There simply is insufficient density above the transition region (see the comment above about a chromospheric origin for narrow CMEs).