摘要:

Simultaneous observations of solar‐particle events at low (0.1 AU) spacecraft. (c) Several flare‐associated and nonflare intensity peaks are found to corotate with the sun. (d) Anisotropies are large during the onset phase of flare‐associated events with the maximum intensity coming from the solar quandrant (±45° to the sun‐spacecraft line) and still larger for corotating events. (e) The proton spectrum hardens during event onsets and becomes softer as the event progresses at both spacecraft. (f) Thejp/jαtime profile generally follows the proton profile and varies considerably during events; alsojp/jαdecreases as the proton spectrum hardens in accordance with Schatzman's (1963) model. (g) Thejα/jMratio is relatively less variable than thejp/jαratio. (h) Few intensity increases can be reliably associated with specific flares on the sun. It is concluded that, in view of the observations, multi‐spacecraft studies should allow the development of more sophisticated models for the understanding of l

ISSN:0148-0227    

DOI:10.1029/JA076i025p05921

年代:1971

数据来源: WILEY

摘要:

The response of the moon to magnetic‐field step transients in the solar wind has been investigated for over 100 events, by using simultaneous data from the Apollo‐12 lunar surface magnetometer and the lunar‐orbiting Explorer‐35 magnetometer. These transient events were all selected at times when the moon was in the free‐streaming solar wind and the Apollo‐12 magnetometer was on the lunar dark side. The lunar‐nighttime Apollo‐12 magnetometer data consistently show a distinct difference between radial and tangential surface magnetic‐field components for all step transients; this property strongly implies that the surface magnetometer is measuring a global rather than a local effect. The simplest model, although not unique, which qualitatively explains all the general aspects of the dark‐side transient‐response data is a spherically symmetric three‐layer model having a thin outer crust of very low electrical conductivity. The intermediate layer, of radial thicknessR1–R2, where 0.95RM≤R1

ISSN:0148-0227    

DOI:10.1029/JA076i025p05947

年代:1971

数据来源: WILEY

摘要:

A series of very distant crossings of the earth's bow shock has been identified by the magnetic field experiment on board Pioneer 8 at geocentric distances between 120 and 200RE, during the period December 19 to 25, 1967. The normal to the shock is generally found lying in or very near the ecliptic plane, at an average angle of 68° with respect to the earth‐sun line. The average ratio of field magnitudes on the interplanetary and the magnetosheath sides of the bow shock is nearly 2. The location of these crossings is consistent with that expected from the Dryer and Heckman computations of the distant bow‐shock configuration, when the aberration of the solar wind is taken into account. The shock is also aligned with the configuration extrapolated from the Explorer 33 observations that extend only to 75RE. Our conclusion is that a well‐developed bow shock is still observed at these very large distances. The intermittent observations are interpreted as an effect of the sweeping back and forth of the shock across the spacecraft orbit, due to time variations of the sola

ISSN:0148-0227    

DOI:10.1029/JA076i025p05970

年代:1971

数据来源: WILEY

摘要:

The auroral display appearing over Alaska on the night of February 13–14, 1958 (LT), was characterized by a relatively uniform level of auroral and magnetic activity. Synoptic maps of auroral orientations and motions and of magnetic disturbance from this night are used to infer the steady state magnetospheric convection during the display. The auroral motions imply an inward component to the convective motion during much of the display, westward motion at distances to 9REin evening and eastward motion beyond 9REin the evening hours and at radial distances 4 to 10REduring the morning hour

ISSN:0148-0227    

DOI:10.1029/JA076i025p05978

年代:1971

数据来源: WILEY

摘要:

The behavior of the plasma sheet in the distant magnetotail (r∼18RE) during auroral substorms is examined. In particular, the plasma sheet variations associated with major features of auroral displays during auroral substorms are identified, when Vela satellites were approximately ‘in the field of view (along geomagnetic field lines)’ of all‐sky cameras at Fort Yukon and College (Alaska). Data used in this study were taken during a 1‐week period in March 1968 when conjugate auroral flights were made by two airplanes. All‐sky camera pictures taken from these airplanes are used to supplement those from the two ground stations. The results are summarized in Figure 12, in which the variations of the cross section of the plasma sheet atr∼18REat four different epochs of an auroral substorm are schematicall

ISSN:0148-0227    

DOI:10.1029/JA076i025p05985

年代:1971

数据来源: WILEY

摘要:

The flux‐versus‐L profiles of trapped protons measured on board a sounding rocket near the equator in 1967 are compared with calculations based on a neutron albedo source and atmospheric losses. The observed fluxes at two different energy channels (20–50 Mev,>100 Mev) exceed the fluxes calculated by assuming Lingenfelter's neutron spectrum by factors ranging from 15 to 40. The shapes of the profiles suggest that time variations in the atmospheric density with durations of 150 days preceding these measurements affect the fluxes of those protons with sufficiently short life

ISSN:0148-0227    

DOI:10.1029/JA076i025p06004

年代:1971

数据来源: WILEY

摘要:

This paper reports on the initial results of the double‐probe direct‐current electric‐field experiment on the low‐altitude polar‐orbiting Injun‐5 satellite. With this experiment magnitudes of naturally occurring magnetospheric electric fields can be measured to an accuracy of ±30 mv/m, and under favorable conditions, to ±10 mv/m. At high latitudes, convection electric fields greater than 30 and sometimes greater than 100 mv/m are frequently observed in the auroral zone. A common feature of these high‐latitude convection fields is the occurrence of abrupt reversals or discontinuities in the east‐west convection velocity at auroral‐zone latitudes. The reversals have been observed at both dawn and dusk local times and at magnetically conjugate points in both hemispheres. For dusk‐dawn local times, these reversals correspond to an east‐west flow away from the sun on the high‐latitude side of the reversal and toward the sun on the low‐latitude side. Over the polar region above the auroral zone the convection fields are usually not greater than ±30 mv/m, in contrast to the larger field magnitudes observed at the auroral zone. At the boundary of the plasmapause and the light ion trough small 10‐ to 20‐mv/m electric‐field perturbations are sometimes observed, corresponding to generally westward convection outside the plasmasphere. At high altitudes, above about 1500 km, over the auroral‐zone and polar‐cap regions, irregular electric‐field ‘noise’ with amplitudes from 10 to 30 mv/m is often observed. Among the possible explanations of the high‐altitude electric‐field noise is the presence of significant (>0.5 mv/m) electric fields parallel to the geomagnetic field. The results presented are consistent with measurements made by using the barium cloud drift technique. The observed convection is also compared with models of magnetospheric st

ISSN:0148-0227    

DOI:10.1029/JA076i025p06014

年代:1971

数据来源: WILEY

摘要:

Twelve Ba+clouds were released at invariant latitudes 76° to 78° from three rockets launched from Cape Parry, Northwest Territories, Canada, for the study of polar‐cap electric fields and their relationship to polar‐cap magnetic‐field disturbances. All flights occurred under conditions characterized byKp≈3.Ewas typically between 20 and 40 volts/km, directed roughly from dawn toward dusk, and was more uniform in space and time thanEfields observed in the auroral belt. The measurements showed a large angular difference between the directions ofEandΔH, the horizontal polar‐cap magnetic disturbance. This meant thatΔHcould not be caused solely by ionospheric Hall currents in the form of a sheet across the polar cap; also the sign of the difference was opposite to that expected from other elements of the conductivity tensor. Various factors lead to the conclusion thatΔHis caused almost entirely by a source other than overhead ionospheric currents. This conclusion has the consequence that continuity for Hall current auroral electrojets cannot be achieved by way of the polar‐cap and midlatitude ionospheres as assumed in the past. A mutual solution for both theΔHproblem and the continuity problem was found in terms of a new model for continutity of the Hall current auroral electrojets. Continuity by way of field‐aligned currents is primarily a consequence of (gradN)/Nbeing greater than (gradE)/E.N= electron density at 100–130 km. The large‐scale properties of gradN/gradEappear to be compatible with the net distribution of field‐aligned currents required to explain both the polar capΔHand the simultaneous disturbance observed on the low‐latitude side of the auroral belt. The net field‐aligned currents are equivalent to two sheet currents flowing ‘out of’ and ‘into’ the auroral‐belt ionosphere, respectively, in the magnetic local time sectors 20–24h and 8–12h. Cause and effect between field‐aligned currents and precipitating particles is implied, in that the distribution of gradNat 100–130 km

ISSN:0148-0227    

DOI:10.1029/JA076i025p06028

年代:1971

数据来源: WILEY

摘要:

Two rockets have been launched into the auroral‐zone ionosphere to measure the vector electric field by the double Langmuir probe technique. During part of a flight near magnetic midnight into an active auroral display, an electric‐field component of about 20 mv/m was detected parallel to the magnetic‐field direction, in agreement with results from a previous nighttime flight. The second flight, near local noon, detected no such parallel field. The parallel field measured at night is consistent with that which might be expected from laboratory measurements and theory. The nighttime electric‐field component perpendicular to the magnetic‐field direction was generally southerly with an amplitude in the range of 5 to 40 mv/m. The perpendicular electric field measured near local noon was generally northerly in the range of 0.5

ISSN:0148-0227    

DOI:10.1029/JA076i025p06054

年代:1971

数据来源: WILEY

摘要:

An electron accelerator was flown on an Aerobee 350 rocket from Wallops Island, Virginia, in January 1969. At altitude the accelerator put out a series of electron‐beam pulses up to 1 sec long aimed downward along the magnetic‐field line. Several electron energies up to a maximum of 9.5 kev were used. The beam current was also varied up to a maximum of 490 ma. The highest power pulses were detected on the ground by sensitive optical systems. The vehicle neutralization was accomplished by collecting an ionospheric current equal to the beam current on a large aluminized mylar foil deployed perpendicular to the magnetic field. Attempts were made to measure electromagnetic waves that might be produced by the beam and also to measure with radar the ionization trail resulting from the beam interacting with the atmosphere. The artificial auroral rays produced by the electron beams appeared at the right place and time with about the right shape and intensity. This experiment demonstrates the feasibility of propagating electron beams long distances in space with relatively small alterations resulting from plasma instabilities or beam propagation probl

ISSN:0148-0227    

DOI:10.1029/JA076i025p06067

年代:1971

数据来源: WILEY