摘要:

Recent measurements from the plasma wave instrument on the Galileo spacecraft have shown that Langmuir waves observed in conjunction with a type III solar radio burst contain many beat‐type waveforms, with beat frequencies ranging from about 150 to 650 Hz. Strong evidence exists that the beat pattern is produced by two closely spaced narrowband components. The most likely candidates for these two waves are a beam‐generated Langmuir wave and an oppositely propagating Langmuir wave produced by parametric decay. In the parametric decay process, nonlinear interactions cause the beam‐driven Langmuir wave to decay into a Langmuir wave and a low‐frequency ion sound wave. Comparisons of the observed beat frequency are in good agreement with theoretical predictions for a three‐wave parametric decay process. Weak low‐frequency emissions are also sometimes observed at the predicted frequency of the ion

ISSN:0094-8276    

DOI:10.1029/95GL00303

年代:1995

数据来源: WILEY

摘要:

Solar wind measurements from the Pioneer 10, Pioneer 11, Voyager 2, IMP 8, and Pioneer Venus Orbiter (PVO) spacecraft were examined to search for long‐term periodicities during the last three solar cycles. For the time of the last solar maximum, these measurements confirm the existence of the periodic 1.3‐year enhancements in solar wind velocity reported byRichardson et al.[1994]. For most of the preceding two solar cycles, long‐term velocity enhancements occurred that were similar in structure but lacked the 1.3‐year periodicity. It appears that long‐term enhancements in solar wind velocity, with durations on the order of a few months to a year, are a common feature throughout the he

ISSN:0094-8276    

DOI:10.1029/95GL01017

年代:1995

数据来源: WILEY

摘要:

We present the first observations of a CME by two spacecraft separated substantially in heliographic latitude. Ulysses and Geotail both see similar features in the plasma and magnetic field parameters during an interval in which Geotail is located in the deep magnetosheath (>150 RE) and Ulysses is located in the solar wind at 5 AU, ∼20° S of Geotail, and ∼51° W (in the direction of solar rotation) of Geotail. Based on the similarity in plasma and magnetic field parameters and similar inferred ejection times from the Sun for both features we argue that the same CME is observed by both spacecraft. The portion of the CME observed by Ulysses is traveling much faster than the portion observed by Geotail. Thus the CME has significant latitudinal structure since at any given time the high latitude portion of the CME extends much further out in radial distance. Furthermore, this implies that a simple calculation of the arrival time of a CME at the Earth may not be done if the observing spacecraft is located substantially away from the ecliptic

ISSN:0094-8276    

DOI:10.1029/95GL01016

年代:1995

数据来源: WILEY

摘要:

Ulysses measurements of energetic and solar wind particles taken near 5 AU between 20 and 30 degrees south latitude during a well‐developed recurring corotating interaction region (CIR) show that the CIR's corotating energetic ion population (CEIP) associated with the trailing reverse shock starts within the CIR at the stream interface. This is consistent with an earlier result obtained by Pioneers 10 and 11 in the ecliptic plane between 4 and 6 AU. The Ulysses/Pioneer finding is noteworthy since the stream interface is not magnetically connected to the reverse shock, but lies 12–17 corotation hours from it. Thus, the finding seems to be inconsistent with the basic model that generates CEIP particles at the reverse shock and propagates them along field lines. Eliminating the inconsistency probably entails an extension of the standard model such as cross‐field diffusion or a non‐shock energization process operating near the stream interface closer to

ISSN:0094-8276    

DOI:10.1029/95GL00951

年代:1995

数据来源: WILEY

摘要:

The Saturn magnetosphere model of Richardson and Sittler [1990] is extended to include the outer magnetosphere. The inner magnetospheric portion of this model is updated based on a recent reanalysis of the plasma data near the Voyager 2 ring plane crossing. The result is an axially symmetric model of the plasma parameters which is designed to provide accurate input for models needing either in situ or line‐of‐sight data and to be a useful tool for Cassini plann

ISSN:0094-8276    

DOI:10.1029/95GL01018

年代:1995

数据来源: WILEY

摘要:

It has been suggested byVerigin et al.[1993] that the response of the Martian magnetotail to changes in the solar wind ram pressure indicates the presence of an intrinsic dipole magnetic field. 3‐D hybrid particle simulations of Mars were performed including the magnetotail regions. The simulations are in agreement with published Phobos 2 data from the 3 elliptical orbits and reproduce the magnetopause diameter dependence on the solar wind ram pressure reported byVerigin et al.[1993]. However, the simulations were performed with no intrinsic field present, indicating that the dependence of the magnetotail width on ram pressure, is not a discriminator for the presence of the intrinsic fiel

ISSN:0094-8276    

DOI:10.1029/95GL01185

年代:1995

数据来源: WILEY

摘要:

It is shown from flux transfer event (FTE) occurrence statistics, observed as a function of MLT by the ISEE satellites, that recent 2‐dimensional analytic theories of the effects of pulsed Petschek reconnection predict FTEs to contribute between 50 and 200 kV to the total reconnection voltage when the magnetosheath field points southward. The upper limit (200 kV) allows the possibility that FTEs provide all the antisunward transport of open field lines into the tail lobe. This range is compared with the voltages associated with series of FTEs signatures, as inferred from ground‐based observations, which are in the range 10–60 kV. We conclude that the contribution could sometimes be made by a series of single, large events; however, the voltage is often likely to be contributed by several FTEs at differen

ISSN:0094-8276    

DOI:10.1029/95GL01008

年代:1995

数据来源: WILEY

摘要:

We examine the consequences of magnetic reconnection at the high‐latitude magnetopause using a three‐dimensional global magnetohydrodynamic simulation of the solar wind interaction with the Earth's magneto sphere. Magnetic field lines from the simulation reveal the formation of magnetic flux ropes during periods with northward interplanetary magnetic field. These flux ropes result from multiple reconnection processes between the lobes field lines and draped magnetosheath field lines that are convected around the flank of the magnetosphere. The flux ropes identified in the simulation are consistent with features observed in the magnetic field measured by Hawkeye‐1 during some high‐latitude magnetopause cr

ISSN:0094-8276    

DOI:10.1029/95GL01014

年代:1995

数据来源: WILEY

摘要:

Ten transient magnetic structures in Earth's magnetotail, as observed in GEOTAIL measurements, selected for early 1993 [at (−) XGSM= 90 ‐ 130 RE], are shown to have helical magnetic field configurations similar to those of interplanetary magnetic clouds at 1 AU but smaller in size by a factor of ≈ 700. Such structures are shown to be well approximated by a comprehensive magnetic force‐free flux‐rope model. For this limited set of 10 events the rope axes are seen to be typically aligned with the YGSMaxis and the average diameter of these structures i

ISSN:0094-8276    

DOI:10.1029/94GL01114

年代:1995

数据来源: WILEY

摘要:

We analyze the temporal relationship between PMSE (polar mesosphere summer echoes) and long‐period vertical motions using the Poker Flat, Alaska radar data. The results show that the vertical velocity leads PMSE by 90° to 180° with a possible upward trend in phase with increasing frequency. We show that this is consistent with the current PMSE theories which depend primarily upon the presence of charged ice aerosols for the enhancement of radar scat

ISSN:0094-8276    

DOI:10.1029/95GL01010

年代:1995

数据来源: WILEY