UKIRT Observations of the Impact and Consequences of Comet Shoemaker–Levy 9 on Jupiter☆

Ionospheric Effects of Comet Shoemaker–Levy 9 Impacts with Jupiter

“…From measurements taken some hours after the impacts at sites A and E, Kim et al (1996) reported "that the intensities of the H + 3 lines on the impact site are significantly reduced compared with those on the undisturbed areas, although the H + 3 emission on the undisturbed areas varies longitudinally at the same latitude." This is confirmed by Dinelli et al (1997), who submitted UKIRT observations of sites B and C to exhaustive analysis of spectra in the 3.2-4.1 µm range, but not by Encrenaz et al (1995) and Schulz et al (1995) who also detected enhanced H + 3 emission at, albeit different, sites G/D and F. Dinelli et al (1997) and Miller et al (1997b) were able to attribute H + 3 enhancements, in the case of site B, to the proximity of the southern auroral oval as well as to pointing difficulties in combination with the normal spatial variation of H + 3 and, in the case of site C, to ionospheric heating prior to impact. UKIRT also observed increased emission at site G/D which may be explained simply by limb brightening and H + 3 spatial variation rather than SL9-related increases in column density.…”

“…In the hours following impact, Orton et al (1995) and Carlson et al (1997) observed a significant increase in temperature across a 20,000-km diameter region at the E impact site, and Lagage et al (1995) detected a 30,000-km bright spot at 12 microns at the L impact site. UKIRT observations showed atmospheric heating extending up to 45,000 km around site C which may be attributed either to (1) extensive trains of cometary tail material impacting before the main fragment, (2) re-entry of ejected material after fragment impact, or simply (3) shock-heated gas traveling at very high velocities (∼100 km/s) and at very high altitudes beyond the visible plumes (Dinelli et al 1997). This is further corroborated by the 3-4 µm observations of McGregor et al (1996), who observed rings around the G and K impact sites attaining radii of some 20,000 km after about 2 1 2 h post impact.…”

“…19. Thus measurements of decreases in H + 3 emissions in the hours following the impacts (e.g., Dinelli et al 1997) are simply explained in terms of our current understanding of the non-auroral jovian ionosphere.…”

Latitudinal Profiles of the Jovian IR Emissions of H+3 at 4 μm with the NASA Infrared Telescope Facility: Energy Inputs and Thermal Balance

“…Meridional winds in the upper atmosphere are no more than 100 m/s (Clarke et al 1996, Dinelli et al 1997, so transport of H + 3 is not sufficiently rapid to transfer significant amounts from the aurorae to lower latitudes (see below). (We consider the fact that Waite et al (1997) do show X-ray emission due to heavy ion precipitation covering the dip equator is probably an artifact of the relatively large point-spread-function of ROSAT.…”

“…We have discussed these as if they were direct energy depositions, in the form of local particle precipitation linked to magnetospheric regions which extend from inside of the orbit of Io to the radiation belts. But the energy could be supplied indirectly, in the form of H (Clarke et al 1996, Dinelli et al 1997, this lifetime would give a half-life distance of 1,000 km.…”