Monitoring of the l=-44 deg. and the l=+44 deg. regions in the H2 and H3+ lines: detection of emissions in the Northern hemisphere
We have monitored the impact region (l=-44deg) using IRSPEC at NTT between July 22 UT 20:40 and July 23 UT 4:00, in the H2 (2.12 microns) and H3+ (3.53 microns) emission lines. The slit, aligned with the impacts parallel, has a width of 4.4 arcsec.
On July 22 (UT 20:40 - 23:00) the H3+ line was detected in sites C, (W,K,U) and L. A continuum, approximately equal to the H3+ line intensity, was observed on (W,K,U) and L, but was not present on C. The H3+ emission appeared more extended over the longitude range while the 3.5 microns continuum was more localized over the impact sites. Later, on July 23 UT 3:30, the (V,T,E,F) group and the H site were also detected in the H3+ line.
The H2 S(1) line (2.12 micron) has been monitored on July 22 UT 23:00 - 0:00. Two emissions were recorded, in the L site and at the position of the (R,S,G,Q) group. In the L site, the continuum was stronger but the H2 line was weaker than in the other groups.
Following the suggestion made by B.Mosser that near-IR emission might appear in the northern hemisphere at the same longitude as the impact sites, as a result of particle transfer along the magnetic field lines, we have also observed the l=+44 deg. region on July 23 between UT 0:25 and 1:45. We have detected emissions, both in H2 and H3+ lines, which seem to be associated to impacts located at the same longitude. The point located at the same longitude as the (R,S,G,Q) group showed an emission at 2.12 micron, with a continuum about 3 times weaker than at l=-44 deg., and a H2 line of comparable intensity. It also corresponded to a maximum of H3+ emission, although this emission was much more extended over the longitude range than the H2 one. At UT 0:45, we have observed the adjacent northern region at lower latitude (l~ +30 deg.) in the H3+ line. A very weak H3+ emission was detected near the longitude of the (R,S,G,Q) group (indicating some extension of its northern counterpart), but no continuum was detectable.
On July 23 UT 04:00, two other H3+ emission maxima were observed at l=+44 deg., at the same longitude as the A site and the (V,T,E,F) group.
T. Encrenaz, R. Schulz, J. A. Stuewe, G. Wiedemann