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.     

On the production and interaction of planetary solitary waves: Applications to the Jovian atmosphere

We present further evidence that strengthens the case for our interpretation of many features in the Jovian atmosphere as solitary Rossby waves (solitons). These include: a mechanism whereby such waves can evolve from the instability of the basic shear flows; further interpretation of the interaction between observed features, and comparison with calculations of the interaction between planetary solitons of a restricted class; and calculations of the morphology for a type of shear flow other than the type considered originally by Maxworthy and Redekopp.     

Solar-planetary cycles in Jupiter's great red spot darkness

The change in the darkness of the Great Red Spot (GRS) of Jupiter (1894–1974) has been analysed with Fourier (FFT), Maximum Entropy and Power spectrum (Blackman-Tukey window) (PSA) methods of spectrum analysis. Significance, non-randomness and stationarity tests assigned high variance to periodicities of 33 ± 4, 13–15, about 11, 9 and 3 yrs. The highest correlation between solar activity and GRS darkness was found for the 14th and 16th solar cycle. The periodicities obtained are interpreted as the combined eftects of solar activity, planetary resonances and internal jovian mechanisms.     

Physical parameters of the Jovian atmosphere

The following physical parameters have been computed for the Jovian atmosphere between 270 and ?300 km: (1) Pressure, (2) Density, (3) Speed and sound, (4) Number density, (5) Density scale. It has considered that the top of the clouds is at 0 km. For the calculations of these parameters we have used:

1. for the altitudes 270-0 km data from Voyager I and II.
2. for the altitudes ?300–0 km data from Voyager II and spectroscopic observations.

     

A theory of the Jovian hydrogen torus

The Jovian hydrogen torus associated with Io, that was observed by Judge and Carlson, has been found by them to be a third of a torus rather than a complete torus. It is shown that the energetic particles observed by Pioneer 10 do not ionize atomic hydrogen sufficiently fast to erode the torus as observed. It is proposed that the reason an incomplete torus exists is the presence of a corotating cold magnetospheric plasma. If this explanation is correct, the angular extent of the fractional torus is a measure of the density of the magnetospheric plasma near Io's orbit, which is found to be ～10²cm^?3. It is shown that such a plasma may provide an adequate input to Io, where it can recombine and escape, to form enough hydrogen atoms to explain the number of observed torus atoms. Thus the magnetospheric plasma may serve as both the source and the sink of the torus. However, while it is not difficult to make the plasma be the sink of the toroidal hydrogen, it is difficult (although perhaps possible) to self-consistently make it the source. It may be necessary to invoke some other mechanism to generate the hydrogen.     

Interpretation of spatial and temporal variations of hydrogen quadropole absorptions in the Jovian atmosphere observed during the 1972 apparition

During the 1972 apparition of Jupiter, we carried out a patrol of the (3,0) S(1) and (4,0) S(1) quadrupole lines of molecular hydrogen in the equatorial region and in bands bounded by ±15 and ±49° zenographic latitude from the McDonald and Table Mountain Observatories. At the center of the Jovian disk, we found evidence of temporal variability of both lines over the duration of our observing period. We employ a technique which takes into account all radiative transfer processes in an inhomogeneous model of Jupiter's atmosphere, and use it to derive the effective level of formation of the spectral lines and the relative abundance of hydrogen. In this way, we are able to correlate measured changes in the equivalent widths of the hydrogen lines with variations in cloud structure. The effective pressure level at which the (4,0) S(1) line is formed varies in the range 2 ± 0.5 to 1.3 ± 0.2 atm, while for the (3,0) S(1) line, the pressure varies between 1.6 ± 0.5 and 1 ± 0.4 atm. If these variations are interpreted in terms of changes in elevation of the top of a dense lower cloud deck, the elevation apparently varied with an amplitude of 25 km during the observational period.Spatial variations in the strengths of both lines were also found. Both lines are weaker at the east limb than at the center of the disk (15–19%) while the variations toward the west limb are less pronounced (5%). Similar center-to-limb variations were found in the latitude bands bounded by ±15 and ±49°, although the lines were stronger in the northern component at the time of the observations.     

A theory of Jovian dekametric emission

Many Jovian dekametric storms, like terrestrial magnetic storms, commence suddenly, not just as seen from the Earth, but in real time. ‘Main Rotation phase’ storm commencements rarely occur before Jupiter's Northern Hemisphere magnetic pole crosses the central meridian, but occur abundantly immediately thereafter. ‘Early Io phase’ storm commencements occur increasingly abundantly as Io approaches phase 100°, but only rarely thereafter.In explanation of Main Rotation storms, this paper proposes that, as Jupiter's eccentric northern hemisphere magnetic pole crosses the heliocentric central meridian, Jupiter's magnetic tail swings abruptly from Jupiter's morning to afternoon side. It ascribes Early and Late Io storms respectively to the emergence and re-entry of Io through the sunward boundary of the Jovian magnetosphere.     

A theory of Jovian shadow bursts

The shadow events in the dynamic spectra of Jovian decametric emission are explained as the result of interaction between electron bunches responsible for S and L emissions. The relevant dispersion relation is derived for the fast extraordinary mode in the cold magnetospheric plasma in the presence of S and L electron bunches. The growth rate of the synchrotron maser instability is studied in the presence and absence of S-electrons. It is shown that the synchrotron maser instability responsible for L-emission can be temporarily quenched by the invasion of S-electrons, thereby stopping the L-emission. The theory accounts for various observed features of the shadow events.     

Cosmic ray ionization of the Jovian atmosphere

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic ray-induced cascade may be especially importannt in ionizing the atmosphere at levels where the total number density exceeds 10¹⁹ cm^?3 (well below the ionospheric layers produced by solar euv). A model containing both positive and negative ion reactions has been employed to compute equilibrium electron and ion number densities. Peak electron number densities on the order of 10³ cm^?3 may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH₄⁺ and C_nH_m⁺ cluster ions, with n ? 2; it is suggested that the absorption of galactic cosmic ray energy at such relatively high pressures in the Jovian atmosphere $\text{(M ? 10}{}^{18}\text{to}\text{10}{}^{20}\text{cm}{}^{\mathrm{?3}}\text{)}$ and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.     

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.     

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.     

A wave driven model of the Jovian equatorial jet

We explore the consequences of assuming that the equatorial jet, which is the most prominent feature of the atmospheric motions on Jupiter, is driven by vertically propagating Kelvin and mixed Rossby-gravity waves that are absorbed during their passage through the stratosphere to produce a mean zonal flow. Since even the basic atmospheric parameters on Jupiter are still largely a matter of conjecture, we are not able to produce a unique model but one that can span a whole range of possible conditions and which can be refined (or rejected) as more information becomes available.     

Dynamo region and the equatorial electrojet in the Jovian atmosphere

The existence of the dynamo region is identified in the atmosphere of Jupiter. It is found that the dynamo region extends from an altitude of 130 km (0.153 mbar) to 330 km (0.027 μbar) reckoned from zero altitude corresponding to 43.8 mbar pressure level. Physical features of the equatorial electrojet in the ionosphere of Jupiter are modelled in detail. The Jovian equatorial electrojet has a maximum eastward current density of about 1.5 Akm^?2 at an altitude of 270km (0.33 μbar) with a latitudinal half width of about ±11°. The thickness of the equatorial half width is 100 km in altitude range. The type I instability in the electrojet can exist only if the electron streaming velocity exceeds the value of about 250 m s^?1.     

Thermodynamics of selected trace elements in the Jovian atmosphere

The thermochemistry of several hundred compounds of twelve selected trace elements (Ge, Se, Ga, As, Te, Pb, Sn, Cd, Sb, Tl, In, and Bi) has been investigated for solar composition material along a Jupiter adiabat. The results indicate that AsF₃, InBr, TlI, and SbS, in addition to CO, PH₃, GeH₄, AsH₃, H₂Se, HCl, HF, and H₃BO₃ proposed by Barshay and Lewis (1978), may be potential chemical tracers of atmospheric dynamics. The reported observations of GeH₄ is interpreted on the basis of new calculations as implying rapid vertical transport from levels where T ? 800°K. Upper limits are also set on the abundances of many gaseous compounds of the elements investigated.     

The zonal distribution of hydrogen in the Jovian atmosphere

The Voyager ultraviolet spectrometer disclosed strong longitude variation in the midlatitude Lyman alpha brightness of Jupiter. Minimum brightness of 16 and 14.4 kR were observed from Voyagers 1 and 2, respectively, with the intensity rising to peaks of 21 and 19.6 kR at a longitude near 110°. Observations of Jovian Lyman alpha, made with the International Ultraviolet Explorer (IUE) beginning in December 1978, and continuing through January 1982, also show a region of persistently enhanced but variable flux near a longitude, λ, of 100°; however, IUE measured brightnesses are consistently lower than those of Voyager. Although the Lyman alpha flux from the “normal” region of the plant between λ 200 and 300° remained nearly constant during the period of the IUE observations, that from the “perturbed” region centered on λ 110° varied by ±25% from the mean. The sources of Lyman alpha flux include resonance scattering of solar and interplanetary Lyman alpha, and excitation by charged particle precipitation. That portion of the dayside flux due to charged particle excitation has been variously estimated at between 2.3 and 7 kR. About 1 kR of the dayside flux is due to resonance scattering of the sky background. It is assumed that H and an absorber (CH₄) are distributed above the homopause according to the local height distribution of temperature. The daytime equation of radiative transfer is solved to determine the longitudinal distribution of freely scattering atomic hydrogen that would account for the observed flux. This daytime solution shows that if the hydrogen bulge is the result of localized heating and a consequent increase in scale height, the temperature in the perturbed region must be about 100°K warmer than that in the normal region. The nightside Lyman alpha brightness exhibits a longitude variation very similar to that on the dayside. The H distribution derived from the dayside solution is used with the nightside flux to estimate the longitude variation of particle precipitation on the nightside.     

Five micron limb-darkening and the structure of the Jovian atmosphere

By observing the transit of various cloud features across the Jovian disk, Terrile and Westphal (1977) have constructed limb-darkening curves for three regions in the 4.6 to 5.1 μm band. Several models currently employed in describing the radiative or dynamical properties of planetary atmospheres are here examined to understand their implications for limb-darkening. The statistical problem of fitting these models to the observed data is reviewed and methods for applying multiple regression analysis are discussed. Analysis of variance techniques are introduced to test the viability of a given physical process as a cause of the observed limb-darkening. The intermediate flux region of the North Equatorial Belt appears to be in only modest departure from radiative equilibrium. The limb-darkening curve for the South Temperate Belt is rich in structure and cannot be satisfactorily ascribed to any single physical mechanism; a combination of several, as yet unidentified, processes is likely involved. The hottest areas of the North and South Equatorial Belts exhibit limb-darkening curves that are typical of atmospheres in convective equilibrium. In this case, we derive a measure of the departure of the lapse rate from the dry adiabatic value (η?1.68), which furnishes strong evidence for a phase transition at unit optical depth in the NEB and SEB. Although the system NH₃H₂S cannot be entirely ruled out, the freezing of an aqueous ammonia solution is shown to be consistent with the parameter fit and solar abundance data, while being in close agreement with Lewis' (1969a) cloud models.     

Conjecture about a hurricane system in the Jovian atmosphere

Kuiper (1972) had suggested that the Great Red Spot (GRS) of Jupiter is a giant hurricane. We present further arguments in support of this idea and propose that it may also apply to the smaller vortices such as the white and brown ovals (barges). Our estimates indicate that the spin-down time-constants for these Jovian vortices are significantly shorter than the observed lifetimes. Thus, the motions must be sustained through the continued release of internal energy. In analogy with the CISK mechanism for the terrestrial hurricane, transport of water vapor, which is observed on Jupiter, may provide the latent energy to fuel the motions. The energy the planet emits must be transported upwards; therefore its troposphere should be convectively unstable. In such an atmosphere, the proposed solar driven meridional circulation is multicellular, of the Ferrel-Thomson type. If the energy transport from the planetary interior is accelerated by the upward motions in the circulation, eastward zonal jets develop such as observed in the equatorial region. But if the upward flow of energy is impeded by the prevailing downward motions in the meridional circulation (which occur, for example, near 20 latitude), we propose that the convective instability is amplified. The conditions then are more favorable for the development of hurricanes which may appear in the form of the GRS and the white and brown ovals. The GRS with its large size and long life time (indicating that it is very deep) is unique, and we suggest that it may have been induced by meteor impact.     

Penetration of solar uv radiation and photodissociation in the Jovian atmosphere

We present computations of the photodissociation coefficients for NH₃, N₂H₄, PH₃, and H₂S in the Jupiter atmosphere. The calculations take into account multiple scattering and absorption using the radiative-transfer method known as δ-Eddington approximation. The atmospheric models include two cloud layers of variable thickness and haze layers above the upper cloud and between the clouds. One of the results of the radiative computations deal with the reflectivity of the Jovian atmosphere as a function of wavelength. A comparison with available data on the albedo of the planet gives some important indications about mixing ratios and distributions of gases and aerosols. The results for the photolysis rates are compared with similar rates obtained by considering either the direct flux or the flux determined by the molecular gas absorption alone. The latter is usually the approximation used in aeronomic models. The results of this comparison show that a considerable difference exists with direct flux photodissociation but significant differences with molecular absorption flux exist only in atmospheric regions where photodissociation is relatively small.     

Low order effect of crand input in the Jovian atmosphere

Modeling of the Jovian atmosphere shows that cosmic ray induced albedo neutron decay is inadequate to account for Pioneer 10 and 11 projected electron levels on Jupiter. High energy solar protons must also be excluded as an important neutron decay source. Analysis of neutron flux data near the top of the Jovian atmosphere can lead to the determination of He/H₂ and³He/⁴He ratios for the Jovian atmosphere.     

On the nature of the blue and ultraviolet absorption in the Jovian atmosphere

Spatially resolved reflectivities from 3000 to 6600 Å of three positions from the center to the limb of the Jovian Equator, North Equatorial Belt, and North Tropical Zone are analyzed to determine the vertical distribution and wavelength dependence of various sources of blue and uv absorption. Six different models of the distribution of absorbing dust particles are examined. In each model, the variation of dust optical depth and cloud single-scattering albedo are determined. Only those models having dust above the upper NH₃ cloud layer will fit the data. The high altitude dust distribution is approximately uniform over the three regions examined. The contrast in reflectivity of the belts and zones may be modeled by a different cloud single-scattering albedo in the different regions.