Jupiter's White Oval turns red

Jupiter's remaining White Oval changed color in late 2005 and became noticeably red in early 2006, as reported by amateur observers. We present wind and color analyses from high spatial resolution images taken with the Hubble Space Telescope Advanced Camera for Surveys in April 2006. These images suggest that the recent color change was tied to a strengthening of this storm, as implied by increased vorticity, causing it to become more like the Great Red Spot. From a historical perspective, the current activity may be consistent with the generation of new anticyclones at this latitude in the coming months and years.     

Constraints on the NH3 and PH3 distributions in the great red spot

Spatially resolved IUE observations of the Great Red Spot and the South Tropical Zone in the wavelength region of the NH₃ predissociation bands between 1900 and 2200 Å show slightly stronger absorption in the Great Red Spot than in the South Tropical Zone. Neglecting stratopheric haze, vertically inhomogeneous Rayleigh scattering radiative transfer models find an enhanced [NH₃]/[H₂] mixing ratio at the 80- to 125-mbar pressure level in the Great Red Spot of a factor of 3 to 10 with respect to the South Tropical Zone. Upper limits on the mixing ratio of PH₃ and the eddy diffusion coefficient above the Great Red Spot are considerably lower than earlier predictions.     

A solitary wave theory of the great red spot and other observed features in the Jovian atmosphere

We show that solitary waves in a planetary, zonal shear have a shape and flow field that are virtually identical to those observed around the Red Spot and numerous other features that have seen in the Jovian atmosphere. We also suggest that the theoretically calculated interaction between solitary waves has many characteristics in common with the observed interactions between these same Jovian features, and show that available atmosphere models are consistent with the very restrictive requirements of the theory.     

L-bursts in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's L-bursts are observed with high-resolution radio spectrographs. The L-bursts are characterized by their emission envelopes. The duration of envelopes varies from one to a few seconds increasing towards the opposition of Jupiter to reach a maximum in the vicinity of 10 to 20 d after opposition. Modulation lanes appear within the emission envelopes. The magnitude of thef-t slopes of lanes is determined by the central meridian longitude (CML) of Jupiter, and partly by the longitude of Io. The sign of the slopes depends on the CML only. The yearly averages for thef-t slopes do not seem to be related to the Jovicentric declination of the Earth. Most lanes are relatively faint. A summary of the properties of modulation lanes is given. A peculiar case of polarization of an L-burst is shown. Certain shadow events are interpreted as occultation effects caused by overdense meteor trails drifting in the upper atmosphere winds.     

Jupiter: Its red spot and disturbances in 1970–1971

Photographic observations of Jupiter and its Red Spot between 11 December 1970 and 12 October 1971 are reported. The Red Spot had a mean rotation period of 9^h55^m38^s.5, the shortest to be observed since the apparition of 1931–1932. The outstanding event of the apparition was an outburst of activity in the South Equatorial Belt which was similar in many ways to the great disturbance of 1928.     

S-bursts in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's S-bursts are observed with sweep-frequency and multi-channel receivers operating at frequency ranges 21–30 and 20.85–23.20 MHz, respectively. Spectra obtained with time resolutions of 0.2, 0.02, and 0.004 s are compared, the frequency resolution being 50 kHz. The most normal appearance of S-bursts is in trains with a frequency range of the order of 1 MHz. Narrow-band Strains also occur. Narrow-band L-emissions in region B are often associated with S-bursts, obviously in the manner described by Flagget al. (1976). Synoptic spectral observations indicate that region B for S-bursts exhibits a drift in longitude similar to that for L-bursts. The Io phase profile for S-bursts has a maximum in the vicinity of 80° in region B and 230° in region C. S-bursts observed in 1976 have higher drift rates than those compiled by Krauscheet al. (1976). Region C bursts have simpler spectra and lower drift rates than region B bursts.     

Jupiter: Its red spot and other features in 1969–1970

Photographic observations of Jupiter and its Red Spot between 13 November 1969 and 21 September 1970 are reported. The Red Spot continues its 90-day oscillation in longitude with considerable regularity. An outstanding event of the apparition was the appearance of a new disturbance in the South Tropical Zone. A bright spot at zenographic latitude 23°.8 N displayed the shortest rotation period ever recorded on Jupiter, 9^h47^m3^s.     

Models for Polar Haze Formation in Jupiter's Stratosphere

We present coupled chemical-microphysical models for the formation, growth, and physical properties of the jovian polar haze based on a gas-phase photochemical model for the auroral regions developed by A. S. Wong et al. (2000, Astrophys. J.534, L215-217). In this model, auroral particle precipitation provides an important energy source for enhanced decomposition of methane and production of benzene and polycyclic aromatic hydrocarbons (PAHs). We find that at high altitude, A₄ (pyrene, a hydrocarbon consisting of four fused aromatic rings) should homogeneously nucleate to form tiny primary particles. At lower altitudes, A₃ (phenanthrene) and A₂ (naphthalene) heterogeneously nucleate on the A₄ nuclei. These particles subsequently grow by additional condensation of A₂ on the nucleated particles and by coagulation and eventually sediment out to the troposphere. We run different cases of the aerosol microphysical model for different assumptions regarding the fractal dimension of aggregate particles formed by the coagulation process. If coagulation is assumed to produce spherical particles (of dimensionality 3), then their mean radius at altitudes below the 20-mbar pressure level is computed to be approximately 0.1 μm. If coagulation produces fractal aggregates of dimension 2.1, then their equivalent mean radius below the 20-mbar level is much larger, of order 0.7 μm. Aggregates with fractal dimensions between 2.1 and 3 form with equivalent mean radii between 0.1 and 0.7 μm. In every case, mean particle radius is found to decrease with increasing altitude, as expected for a system approximately in sedimentation-coagulation equilibrium. The predicted range of altitudes where aerosol formation occurs and the mean size to which particles grow are found to be generally consistent with observations. However, our calculations cannot presently account for the large amount of total aerosol loading inferred by M. G. Tomasko et al. (1986, Icarus65, 218-243). We suggest that the primarily neutral chemical pathway to heavy hydrocarbon and PAH formation proposed by Wong et al. (2000) may proceed too slowly to produce a sufficient amount of condensible material. Inclusion of ion and ion-neutral reactions in the chemical scheme could potentially lead to the prediction of higher PAH production rates, higher nucleation rates, and greater aerosol loading, producing better agreement with the observations.     

Hydrogen from Jupiter's atmosphere in the Jovian magnetosphere

The passage of Ulysses through Jupiter's magnetosphere presents a new opportunity to investigate the contribution to the Jovian magnetosphere of ions of atmospheric origin. A determination of the magnetospheric H⁺/He²⁺ flux ratio allows an estimate of the relative abundance of ionospheric material in the Jovian magnetosphere. We find that the H⁺/He²⁺ flux ratio, measured in the energy/charge range between 0.65 and 60 keV/e, steadily increases from a solar wind level of 25 at the magnetopause to a value of 700 at the point of closest approach, and then steadily decreases whilst approaching the magnetopause on the outbound path. We conclude from this that: (1) there is a significant solar wind component throughout the outer and middle magnetosphere; and (2) a significant fraction of the protons in the middle magnetosphere are of nonsolar origin.     

Activity in Jupiter's atmospheric belts between 1904 and 1963

Microphotmeter tracings of Lowell Observatory photographs of Jupiter from 1904 to 1963 reveal periodic variations in the amount of dark material present in the atmospheric belts. These variations do not appear to be correlated with solar activity.     

Some particularities affecting the movements of Jupiter's red spot

The fluctuations in longitude of Jupiter's Red Spot are discussed. The long term fluctuations show behaviour similar to the fluctuations of zonal circulations on the Earth from 1830–1950. The three-monthly fluctuations have a temporal connection with the inferior conjunction of Mercury 1963–1971. Solar activity may be the key to both phenomena.     

Variants of tilted-V events in Jupiter's decametric radio spectra

Spectra of complex Jovian S-storms can be interpreted as groups of tilted-V variants. In such an approach the basic components (wide-range S-bursts, narrow-range S-trains, emissions of type N, and shadow events) are arranged in a predictable sequence. It seems that the application of tilted-V variants offers some order for the chaos evident in many S-storm spectra.     

Long-term cyclic variations of prominences, green and red coronae over solar cycles

Long-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.     

Cassini CIRS retrievals of ammonia in Jupiter's upper troposphere

The zonal mean ammonia abundance on Jupiter between the 400- and 500-mbar pressure levels is inferred as a function of latitude from Cassini Composite Infrared Spectrometer data. Near the Great Red Spot, the ammonia abundance is mapped as a function of latitude and longitude. The Equatorial Zone is rich in ammonia, with a relative humidity near unity. The North and South Equatorial Belts are depleted relative to the Equatorial Zone by an order of magnitude. The Great Red Spot shows a local maximum in the ammonia abundance. Ammonia abundance is highly correlated with temperature perturbations at the same altitude. Under the assumption that anomalies in ammonia and temperature are both perturbed from equilibrium by vertical motion, we find that the adjustment time constant for ammonia equilibration is about one third of the radiative time constant.     

Bursts of type N in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's decametric emission often display narrow-band features, referred to as events of type N (Carr et al., 1983). The average bandwidth of these emissions is in the vicinity of 200 kHz, their durations are typically in the decasecond range, and their f-t slopes are small and random. Although the N-bursts can be described as narrow-band L-bursts, it seems that they are realted to S-bursts in their area of occurrence in the Io-B region, the durations of the emission envelopes, and their bandwidths. Possible implications are discussed.     

On the difference in darkness between sunspots

The effects of the magnetic field as well as the velocity field on sunspot equilibrium are discussed. The gas pressure difference, P, between a spot and the environments in the same horizontal layer is primarily determined by the magnetic field. Using recent model atmospheres we find that P shows a maximum value, P _max, at a depth of 650 ± 150 km below the photosphere. The value of P _max suggests that the curvature of the field lines is important for the equilibrium.It appears that, at an optical depth of unity in the umbra, the density has a value close to that of the environment at the same geometric depth (see Figure 4). If such is the case the expression for the umbra temperature (Equation (15)) may be considerably simplified (Equations (17) and (18)) and compared with observations.     

Very low frequency (VLF) hiss in Jupiter's magnetosphere

The particle energy required to generate the observed VLF hiss in the Jovian magnetosphere has been computed under longitudinal and transverse resonance condition. It is shown that the minimum energy required by electrons to generate VLF hiss under the longitudinal resonance condition lies in the range of 100eV–1keV for the wave frequencies of 2–10 kHz, while the corresponding energy range for the transverse resonance condition for the same frequency range comes out to be 8 keV–40 keV. Further, the average radiated power by the erenkov process in the Jupiter's magnetosphere atL=5.6 Rj by electrons of energy 10 eV, 100 eV, and 1 keV for the wave frequency of 5 kHz has also been computed.     

Interaction of S- and L-bursts in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's decametric emission are observed with a high-resolution radio spectrograph. Certain events observed in region Io-B display interaction effects between the S- and L-emissions. The effect appears as a gap in the L-emission after a passage of an S-burst. In a typical case the L-emission has a relatively narrow bandwidth, the S-burst appears as a sloping line crossing it, and the duration of the emission gap is a substantial fraction of a second. The gap has sharp, sloped edges; its leading edge has anf-t slope which is the same as that of the S-burst while the slope of the trailing edge is lower. A kind of tilted V-pattern is thus formed. It is suggested that some more complicated spectral patterns may also be produced this way. It seems that an emission model consisting of S-bursts from bunches of gyrofrequency-emitting electrons ascending a flux tube and interacting with L-emitting bunches of electrons having more stationary guiding centers is inadequate to explain the complex S-L interactions.Contribution of No. 36 of the Department of Astronomy, University of Florida, U.S.A.     

The Origin of Water Vapor and Carbon Dioxide in Jupiter's Stratosphere

Observations of H₂O rotational lines from the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite (SWAS) and of the CO₂ ν₂ band by ISO are analyzed jointly to determine the origin of water vapor and carbon dioxide in Jupiter's stratosphere. Simultaneous modelling of ISO/LWS and ISO/SWS observations acquired in 1997 indicates that most of the stratospheric jovian water is restricted to pressures less than 0.5±0.2 mbar, with a disk-averaged column density of (2.0±0.5)×10¹⁵ cm⁻². Disk-resolved observations of CO₂ by ISO/SWS reveal latitudinal variations of the CO₂ abundance, with a decrease of at least a factor of 7 from mid-southern to mid-northern latitudes, and a disk-center column density of (3.4±0.7)×10¹⁴ cm⁻². These results strongly suggest that the observed H₂O and CO₂ primarily result from the production, at midsouthern latitudes, of oxygenated material in the form of CO and H₂O by the Shoemaker-Levy 9 (SL9) impacts in July 1994 and subsequent chemical and transport evolution, rather than from a permanent interplanetary dust particle or satellite source. This conclusion is supported by quantitative evolution model calculations. Given the characteristic vertical mixing times in Jupiter's stratosphere, material deposited at ∼0.1 mbar by the SL9 impacts is indeed expected to diffuse down to the ∼0.5 mbar level after 3 years. A coupled chemical-horizontal transport model indicates that the stability of water vapor against photolysis and conversion to CO₂ is maintained over typically ∼50 years by the decrease of the local CO mixing ratio associated with horizontal spreading. A model with an initial (i.e., SL9-produced) H₂O/CO mass mixing ratio of 0.07, not inconsistent with immediate post-impact observations, matches the observed H₂O abunda nce and CO₂ horizontal distribution 3 years after the impacts. In contrast, the production of CO₂ from SL9-produced CO and a water component deriving from an interplanetary dust component is insufficient to account for the observed CO₂ amounts. The observations can further be used to place a stringent upper limit (8×10⁴ cm⁻² s⁻¹) on the permanent water influx into Jupiter. This may indicate that the much larger flux observed at Saturn derives dominantly from a ring source, or that the ablation of micrometeoroids leads dominantly to different species at Saturn (H₂O) and Jupiter (CO). Finally, the SWAS H₂O spectra do not appear fully consistent with the ISO data and should be confirmed by future ODIN and Herschel observations.