Shoemaker-Levy Research Articles

Search for Jovian Hectometric and Kilometric Radiation by GEOTAIL Spacecraft during the Impact of Comet Shoemaker-Levy 9.

We made a survey for Jovian hectometric and kilometric radiation by GEOTAIL spacecraft before, during, and after the impacts of Comet Shoemaker-Levy 9 (SL-9). We attempted to identify the radiation from Jupiter based on a k vector determination. However, we did not find clear enhancement of the Jovian radiation activity in the whole period nor around each impact time. With regard to the Jovian magnetospheric activity, the enhancement of synchrotron and X-ray radiation in association with the SL-9 event has been already reported. Synchrotron radiation increased during the week of the impacts, and X-rays was clearly detected just around K impact time at the magnetic conjugate footprints of the impact sites. This suggests that a strong perturbation at the impact sites has given non negligible change in the inner magnetosphere directly or indirectly. Our results suggest that such activities were limited in the inner magnetosphere only on low L shells, and there were few amount of direct coupling between the cometary fragments and the Jovian outer magnetosphere. This is consistent with the ground-based observation of the decametric radiation that no significant change was detected during the SL-9 event.

Possible nature of the explosion of the Tunguska meteorite and the breakup of the Comet Shoemaker-Levy

We consider the process of fracture of a solid celestial body with a certain strength entering a planetary atmosphere. Using an integral approach in fracture mechanics, we show that the process of fragmentation of a meteorite occurs in several stages and is completed when the maximum value of the aerodynamic drag is reached. The characteristic size of the fragments formed depends on the properties of the meteorite material. At the end of fragmentation, the stage of rapid deceleration of the fragments begins: “pumping” the energy of the meteorite into a shock wave. The proposed technique is illustrated using the examples of the interaction of the Tunguska meteorite with the Earth's atmosphere and the interaction of Comet Shoemaker—Levy with Jupiter's atmosphere.

Comet Shoemaker‐Levy 9: Fragment and progenitor impact energy

Initial observational data from the impact of fragments of Comet Shoemaker‐Levy 9 (SL9) are compared with smoothed particle hydrodynamic (SPH) calculations to determine their pre‐impact diameters and the equivalent diameter of the SL9 progenitor. Diameters (solid ice) of 2.0±0.1, 2.0±0.05, 2.1±0.04 and 1.9±0.05 km for fragments A, E, G1, and W are obtained from impact‐induced plume heights from the Hubble Space Telescope (HST) data. Applying these values to scale apparent diameters for the balance of 18 SL fragments in Weaver et al.'s [1995] catalog of 22 objects yields a SL9 progenitor diameter of 5.0±1.8 km. This corresponds to total impact energy of 1.2 (+1.8−0.8) × 1030 erg. Such an energetic event occurs on Jupiter and Earth at least every 4,900 +4,700, −2,700, and ∼0.5 × 108 years, respectively.

Changes in Jupiter's Synchrotron Radiation due to the Impact of Comet Shoemaker-Levy 9

view Abstract Citations (11) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Changes in Jupiter's Synchrotron Radiation due to the Impact of Comet Shoemaker-Levy 9 Sukumar, S. Abstract Synchrotron radiation from Jupiter at λ20 cm (1420 MHz) and λ74 cm (408 MHz) was monitored using the DRAO synthesis radio telescope during the infall of the cometary fragments of Shoemaker-Levy 9 (Comet l993e) between 1994 July 16 and July 22. Follow-up observations were also conducted later in 1994 August and September. Although no abrupt changes were detected in the integrated flux density of Jupiter during the impact period, slow enhancements of ≍1 Jy over a time scale of few days were observed at both wavelengths Subsequently, a steady decline in Jupiter's integrated flux density has been observed at λ20, while the decline at λ74 is more rapid and the flux density has even dropped below the preimpact level during 1994 September. These observations imply significant changes to the Jovian magnetosphere during and after the impact of the cometary fragments. Models suggesting energy-dependent energization of relativistic electrons as well as hardening of the electron energy spectrum by cometary dust in Jupiter's magnetosphere are found to be broadly consistent with the radio observations. Publication: The Astronomical Journal Pub Date: September 1995 DOI: 10.1086/117613 Bibcode: 1995AJ....110.1397S Keywords: PLANETS AND SATELLITES: JUPITER; COMETS: INDIVIDUAL: SHOEMAKER-LEVY 9; RADIATION MECHANISMS: CYCLOTRON AND SYNCHROTRON full text sources ADS | data products SIMBAD (1)

An explanation of synchrotron radiation enhancement following the impact of Shoemaker‐Levy 9 with Jupiter

The impact of comet Shoemaker‐Levy 9 (SL‐9) with Jupiter generated a marked increase in synchrotron radiation levels, contrary to predictions that cometary dust would reduce the observed level of synchrotron radiation. The observed increase can be explained by the acceleration of magnetospheric electrons by shock waves emanating from fragment impact points and propagating upward into the Jovian magnetosphere.

Nitrogen and oxygen photochemistry following SL9

The collision of SL9 with Jupiter caused many new molecular species to be deposited in the Jovian stratosphere. We use a photochemical model to follow the evolution of the impact‐derived species. Our results regarding the nitrogen and oxygen compounds are presented here. NH3 photolysis initiates the nitrogen photochemistry. Much of the nitrogen ends up in N2, nitrogen‐sulfur compounds, and HCN, but NH3 and nitriles such as C2H3CN may also exist in observable quantities a year or so after the impacts. Oxygen species survive for a long time in the Jovian stratosphere. The only major oxygen‐containing compounds that exhibit dramatic changes in the lower stratosphere in the first year following the impacts are SO, SO2, and OCS — H2O, CO2, and CO are comparatively stable. We discuss the important photochemical processes operating on the nitrogen and oxygen species in the Jovian stratosphere, make predictions concerning the temporal variation of the major species, and identify molecules that might act as good tracers for atmospheric dynamics.

The effect of the impact of comet Shoemaker Levy‐9 on Jupiter's aurorae

We present infrared spectra and images of the jovian aurorae taken at wavelengths sensitive to the H3+ molecular ion during the period around the impact of Comet Shoemaker Levy‐9. The spectra were obtained using CGS4 on the United Kingdom Infrared Telescope and the images using NSFcam on NASA's Infrared Telescope Facility. Comparison with spectra obtained in May, 1993, shows that while the relative intensities of the northern and southern auroral zones prior to and during impact week (July 16–22, 1994) were broadly comparable with those of 1993, a few days after the last collision the northern aurora was considerably enhanced and its southern counterpart somewhat depressed. The north/south auroral ratio was returning to more normal values a week later. The effect of material drifting from the impact sites to the southern auroral zone is discussed in relation to these results.

Comet Shoemaker‐Levy 9 at Jupiter

From the 16th to the 22nd of July, 1994, the world was privileged to witness an event that probably recurs less often than once a century. Collision of the brightest nuclei of Periodic Comet Shoemaker‐Levy 9 produced enormous dark clouds that were the most dramatic and easily observed features on Jupiter recorded by human visual observation. They were seen by tens of thousands of people through hundreds or thousands of telescopes ranging in aperture from 5 to more than 100 cm. Tens of millions of people participated vicariously in the impact event through viewing on television the magnificent images from the Hubble Space Telescope (HST) and from numerous ground‐based telescopes.

Galileo infrared observations of the Shoemaker‐Levy 9 G Impact Fireball: A Preliminary report

The Galileo spacecraft was fortuitously situated for a direct view of the impacts of the fragments of comet Shoemaker‐Levy 9 in Jupiter's atmosphere. The Galileo Near Infrared Mapping Spectrometer (NIMS) instrument observed several of the impact events in several discrete bands and with a temporal resolution of roughly five seconds. Data have been received for the G impact showing two phases of strong infrared emission. The first phase is approximately one minute in duration and corresponds to the initial fireball and early plume development. This is followed six minutes later by the onset of heating by plume ejecta falling back on the upper atmosphere. This report provides a preliminary description of the fireball phase. The first detection of the G fireball occurred at 07:33:37 UT on July 18, 1994, approximately five seconds after the initial signal recorded by the Galileo Photopolarimeter‐Radiometer (PPR) instrument. The preceding NIMS measurement, occurring approximately one second before the initial PPR signal, showed no evidence of fireball emission. The detected duration of the fireball at 4.38 µm was 70 seconds. Spectra in the first half of this period show blackbody‐like emission, with absorption features from overlying methane and molecular hydrogen. The strengths of these features place the fireball in the upper troposphere and lower stratosphere, above the ammonia cloud layer. The emitting surface rises and accelerates, achieving a velocity of 2–3 km/sec after 25 seconds, in qualitative agreement with that expected for an explosion in an inhomogeneous atmosphere.The Galileo spacecraft, en route to Jupiter, was in a position to obtain a direct view of the impacts of Comet Shoemaker‐Levy 9 fragments on the nightside of Jupiter, providing an opportunity to investigate the early temporal evolution of the impact events. It was predicted that the comet fragments would produce high temperature bolides as they entered the atmosphere and then explode, producing hot fireballs which would rise, expand, and cool (Sekanina, 1993; Zahnle and Mac Low, 1994; Chevalier and Sarazin, 1994; Ahrens et al., 1994; Boslough et al., 1994). Much of the predicted radiation occurs in the infrared region, and time‐resolved infrared spectral observations, obtained over a broad wavelength range, are ideal for studying these phenomena.

The Fragment R Collision: W. M. Keck Telescope Observations of SL9

The W. M. Keck telescope was used to observe the impact of comet Shoemaker-Levy 9 (SL9) fragment R at a wavelength of 2.3 micrometers on 21 July 1994. The data showed three outbursts. The first flash lasted about 40 seconds and was followed 1 minute after its peak by a second flash that lasted about 3 minutes. A third, longer lasting flare began 6 minutes after the first flash and lasted for 10 minutes. At its maximum brightness, the flare outshone Jupiter. The two short flashes are probably associated with the initial meteor trail and the subsequent fireball, respectively. The bright flare occurred when the impact site rotated into view. These data show that the explosion ejected material at least 1300 kilometers above the visible cloud tops. The luminosity of the impact site during the long bright flare was probably maintained by the release of gravitational potential energy, as this material fell back onto the lower atmosphere.

Potential solar influences at Jupiter within a period spanning the impact of comet Shoemaker-Levy 9 with the planet (SOLTIP World Interval IV)

The impact of comet Shoemaker-Levy 9 (SL-9) with Jupiter occurred within a period marking the change over from solar maximum to solar minimum activity in solar cycle 22. In consequence, co-rotating interaction regions, flare-related disturbances, and coronal mass ejections potentially perturbed the Jovian magnetosphere during the period of cometary impact. SOLTIP (Solar Connection with Transient Interplanetary Processes) has called a World Interval, SOLTIP Interval IV, suitably bridging the predicted period of arrival of dust and significant cometary fragments at the planet and, within this time span, 9 May – 9 October, 1994, multi-disciplinary space-based and ground-based solar observations are in process of being formally coordinated, analyzed and made available to observers of the SL-9/Jupiter encounter. In this way, diverse aspects of the circumstances and consequences of the impact of comet Shoemaker-Levy 9 with the Jovian magnetosphere can be interpreted against the background of whatever solar-related interplanetary activity concomitantly occurred.

AAT Observations of Comet Shoemaker Levy-9 Collisions with Jupiter

AAT Observations of Comet Shoemaker Levy-9 Collisions with Jupiter

Optical Imaging and Spectroscopy of the Interaction With Jupiter of Comet Shoemaker-Levy 9

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An Early Report on Iue Observations of the Impact of Comet Shoemaker-Levy With Jupiter

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The Collision of the Comet Shoemaker-Levy 9 with Jupiter: Detection and Evolution of HCN in the Stratosphere of the Planet

The Collision of the Comet Shoemaker-Levy 9 with Jupiter: Detection and Evolution of HCN in the Stratosphere of the Planet

Possible radio wave precursors associated with the comet Shoemaker‐Levy 9/Jupiter impacts

We suggest that prior to its impact with Jupiter, comet Shoemaker‐Levy 9 will behave as an electrical generator in the Jovian magnetosphere, converting planetary rotational energy to electrical energy via a dust/plasma interaction. This electrical energy will then be deposited in the dayside auroral region where it may drive various auroral phenomena including cyclotron radio emission. Such emission could be detected by spacecraft like Ulysses and Galileo many hours prior to the actual comet impact with the upper atmosphere. We apply the theory originally developed to explain the spokes in Saturn's rings. This theory allows us to quantify the driving potential associated with the comet and, consequently, to determine the radio power created in the auroral region. We conclude that if enough fine dust is present in the cometary system, comet‐induced auroral radio emissions will reach detectable levels. This emission should be observable in the dayside hemisphere about 12–24 hours prior to each fragment impact.

New Jovian ring?

We follow the orbital evolution of small dust particles generated from the break up of comet Shoemaker‐Levy 9. In addition to the usual perturbations, we also consider electrostatic charging and the consequent magnetospheric effects. We show, that in about ten years following the break up, a small fraction of the dust will settle into orbits well inside the magnetosphere. The forming ring will be comprised of dust particles with radii in the range of 1.5 < a < 2.5 µm that follow retrograde orbits in the radial range of 4.5 < r < 6 RJ. We estimate the peak optical depth of this new ring in the range of 10−8 < τmax < 2 × 10−6.

Optical imaging of impact sites of Comet Shoemaker-Levy 9 at Bisei Astronomical Observatory

The impact sites of the Comet Shoemaker-Levy 9 are observed with the 101-cm telescope at Bisei Astronomical Observatory until the end of August with B, V, R, I, and methane-band (0.89em) filters. The outline of the observation is briefly described.

An estimate of the Comet Shoemaker-Levy 9 fragment sizes from the debris fields

The impacts of Comet Shoemaker-Levy 9 left spots on Jupiter with diameters on the order of tens of thousands of kilometers, which have the appearance of debris fields strewn upon the Jovian cloud tops. In this note we employ a measurement of the optical depth of the debris at the impact site of fragment G to estimate mass in the debris field and lower limits to the G fragment mass of 4×1012 – 4×1013 g and diameter of 0.1 – 0.3 km.

Comet Shoemaker‐Levy to Hit Jupiter in 1994 July

MeteoriticsVolume 29, Issue 1 p. 4-5 Comet Shoemaker-Levy to Hit Jupiter in 1994 July Paul Weissman, Paul Weissman Associate EditorSearch for more papers by this author Paul Weissman, Paul Weissman Associate EditorSearch for more papers by this author First published: January 1994 https://doi.org/10.1111/j.1945-5100.1994.tb00647.xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume29, Issue1January 1994Pages 4-5 RelatedInformation