Evidence for a distant /greater than 8,700 R sub J/ Jovian magnetotail - Voyager 2 observations
(Previously announced in STAR as N82-18106)
Lepping, R. P.↗
Engineering topics
Klein, L. W.
Publications and source records attributed to Klein, L. W..
Large-scale variations of the interplanetary magnetic field - Voyager 1 and 2 observations between 1-5 AU
(Previously announced in STAR as N82-13594)
Burlaga, L. F.↗
Interplanetary magnetic clouds at 1 AU
Statistical characteristics of magnetic clouds observed in the interplanetary medium near earth are investigated. Forty-five magnetic clouds are identified in which one component of B changes direction by rotating parallel to a plane, while the component of B normal to that plane is either constant or zero. Three classes of clouds are identified: clouds preceded by a shock, clouds followed by a stream interface, and clouds associated with a CME. In superposed epoch plots, the maximum field strength is found to be approximately the same for each class of clouds. Temperatures are all low, densities are somewhat high, and the pressure is higher that the ambient pressure in all three types of clouds. The physical characteristics of the magnetic clouds and their rate of occurrence suggests that many or all of the clouds may be related to coronal mass eject elements observed in white light data.
Klein, L. W.↗
Evidence for a distant ( 8700 R sub J) Jovian magnetotail: Voyager 2 observations
A correlative survey of magnetometer (MAG) and Planetary Radio Astronomy (PRA) 1.2 kHz continuum radiation measurements from Voyager 2 provide evidence for at least eight distant Jovian magnetotail sightings occurring about once a month over the first 2/3 of 1981 at distances of approximately 5,000 to 9,000 R sub J. The occurrences of these events are in good agreement with prior Plasma Wave Science and Plasma Science identifications. Observations of these distant magnetotail, or tail filament, encounters appear most prevalent in both MAC and PRA data sets when the spacecraft was closest to the Jupiter-Sun axis at approximately 6,500 R sub J from the planet; the PRA events are also most intense during those times. A specific tail encounter occurring in mid-February 1981 is analyzed and shown to possess a remarkably symmetric magnetic field signature and to have a bipolar field structure in the central region. The bipolarity is characteristic of most of the eight events.
Lepping, R. P.↗
Large-scale variations of the interplanetary magnetic field: Voyager 1 and 2 observations between 1-5 AU
Observations by the Voyager 1 and 2 spacecraft of the interplanetary magnetic field between 1 and 5 AU were used to investigate the large scale structure of the IMF in a period of increasing solar activity. The Voyager spacecraft found notable deviations from the Parker axial model. These deviations are attributed both to temporal variations associated with increasing solar activity, and to the effects of fluctuations of the field in the radial direction. The amplitude of the latter fluctuations were found to be large relative to the magnitude of the radial field component itself beyond approximately 3 AU. Both Voyager 1 and Voyager 2 observed decreases with increasing heliocentric distance in the amplitude of transverse fluctuations in the averaged field strength (B) which are consistent with the presence of predominantly undamped Alfven waves in the solar wind, although and necessarily implying the presence of them. Fluctuations in the strength of B (relative to mean field strength) were found to be small in amplitude, with a RMS which is approximately one third of that for the transverse fluctuations and they are essentially independent of distance from the Sun.
Burlaga, L. F.↗
Observations of the magnetic field and plasma flow in Jupiter's magnetosheath
A comprehensive description is given of the Jovian MS magnetic fields, and explanations of these phenomena are proposed. While emphasizing Voyager 1 and 2 magnetic field observations and their relations to the plasma observations, it is also shown that the same phenomena are present in the Pioneer 10 magnetic field data. An unusually high occurrence of nearly north or south fields is observed in the outbound MS, especially in the vicinity of the MP. It is noted that the outbound MS fields and their variations tend to occur in a plane parallel to the local MP, according to large scale MP models.
Lepping, R. P.↗
Surface waves on Saturn's magnetopause
Voyager 1 magnetometer data have shown that small-amplitude surface waves occurred on Saturn's dayside magnetopause, causing multiple inbound crossings of this boundary. These waves were travelling approximately parallel to Saturn's equatorial plane along the magnetopause ('tailward'), suggesting that they were driven by the rotation of Saturn's magnetosphere. Hydromagnetic waves (possibly slow mode) were observed in the adjacent magnetosheath.
Lepping, R. P.↗
Interplanetary magnetic clouds at 1 AU
Magnetic clouds are defined as regions with a radial dimension approximately 0.25 AU (at 1 AU) in which the magnetic field strength is high and the magnetic field direction changes appreciably by means of rotation of one component of B nearly parallel to a plane. The magnetic field geometry in such a magnetic cloud is consistent with that of a magnetic loop, but it cannot be determined uniquely. Forty-five clouds were identified in interplanetary data obtained near Earth between 1967 and 1978; at least one cloud passed the Earth every three months. Three classes of clouds were identified, corresponding to the association of a cloud with a shock, a stream interface, or a CME. There are approximately equal numbers of clouds in each class, and the three types of clouds might be different manifestations of a coronal transient. The magnetic pressure inside the clouds is higher than the ion pressure and the sum is higher than the pressure of the material outside of the cloud.
Klein, L. W.↗
Jupiter's magnetopause, bow shock, and 10-hour modulated magnetosheath Voyagers 1 and 2
This summary report discusses Jupiter's magnetopause, bow shock and magnetosheath, based on fine scale magnetic field data from the Voyager 1 and 2 encounters. Explicit models of the dawnside magnetopause and bow shock in Jupiter's orbital plane employ an axisymmetric parabola and hyperbola, respectively, and satisfy average boundary crossing positions, inbound and outbound; these models are determined separately for the two encounters. A new phenomenon has been discovered in Jupiter's magnetosheath. It is manifested as (5 or) 10 hour quasi-periodic modulation of the direction of the magnetic field in the outbound magnetosheath, predominantly in the northward (N) and southward (S) directions. It was seen to occur during both encounters and appears most evident in Voyager 2 outbound observations.
Lepping, R. P.↗
Observations of the magnetic field and plasma flow in Jupiter's magnetosheath
Large scale (many minutes to 10 hours) magnetic field structures consisting predominantly of nearly north-south field direction were discovered in Jupiter's magnetosheath from the data of Voyagers 1 and 2 and Pioneer 10 during their outbound encounter trajectories. The Voyager 2 data, and that of Voyager 1 to a lesser extent, show evidence of a quasi-period of 10 hours (and occasionally 5 hours) for these structures. The north-south components of the field and plasma velocity were strongly correlated in the outbound magnetosheath as observed by Voyagers 1 and 2, and the components orthogonal to the north-south direction showed weak correlations. For both Voyager encounters the sense (positive and negative) of the north-south correlations were directly related to the direction of the ecliptic plane component of the interplanetary magnetic field using the field and plasma measurements of the non-encountering spacecraft.
Lepping, R. P.↗
Jupiter's magnetopause, bow shock, and 10-hour modulated magnetosheath: Voyagers 1 and 2
Fine scale magnetic field data from the Voyager 1 and 2 magnetopause and bow shock crossings at Jupiter were analyzed. Explicit models of the dawnside magnetopause and bow shock in Jupiter's orbital plane employ an axisymmetric parabola and hyperbola, respectively, and are determined separately for the encounters. A new phenomenon was discovered in the magnetosheath. It is manifested as (5 or) 10 hour quasi-periodic modulation of the direction of the magnetic field in the outbound magnetosheath, predominantly in the northward (N) and southward (S) directions. It was seen to occur during both encounters and appears most evident in Voyager 2 outbound observations, probably due to the extreme tailward extent of the Voyager 2 trajectory through the magnetosheath. The durations of the N to and from S transitions range from tens of minutes to approximately 3 hours. The directional variation of the field during these transitions is fairly well restricted to a plane parallel to the local model magnetopause location. These signatures may be due to magnetosheath field line draping modulated by the large scale motion of the magnetospheric plasma disk.
Lepping, R. P.↗