摘要:

A possible source of free energy available for accelerating charged particles is conversion of magnetic energy to particle energy in reconnecting magnetic fields. Recent simulations using test particles suggests that reconnection may efficiently accelerate particles to the maximum energies that are observed in several astrophysical contexts. A simple analytic formula is used in conjunction with the simulation results to predict the maximum energy achievable in a particular plasma environment with the result that in solar flares reconnection is capable of accelerating particles to several GeV. In magnetospheric substorms the predicted maximum can reach several hundred keV, and near magnetic sector crossings in the solar wind the maximum energy can approach 100 keV.

ISSN:0094-8276    

DOI:10.1029/GL013i003p00205

年代:1986

数据来源: WILEY

摘要:

A simple but effective mechanism is proposed to account for the increase of ion kinetic temperature across an oblique or perpendicular shock. This mechanism is based on the nonadiabatic motion of the transmitted ions across the shock ramp, which can lead to an ion gyrophase‐bunching behind the shoc

ISSN:0094-8276    

DOI:10.1029/GL013i003p00209

年代:1986

数据来源: WILEY

摘要:

Based on the formation of a stagnation line at the magnetopause the electromagnetic energy transport from the solar wind into the dayside magnetosphere is analyzed. The resulting energy flux is proportional to v∞B∞² sin² (θ∞‐ ϕ∞), where v∞and B∞are the solar wind speed and magnetic field and θ∞‐ ϕ∞is the angle between the IMF and the stagnation line projected into the interplanetary space. A stagnation line parallel to the separator gives approximately the sin4(θ∞/2) energy flux dep

ISSN:0094-8276    

DOI:10.1029/GL013i003p00213

年代:1986

数据来源: WILEY

摘要:

Recent analyses of ion measurements obtained from the Differential Ion Flux Probe (DIFP) on the deployed Plasma Diagnostics Package (PDP) during the OSS‐1/STS‐3 mission have provided an additional insight into the plasma‐electrodynamics of the Space Shuttle Orbiter: (1) Measured ion flow directions and energies suggest that the disturbance created in the ionospheric plasma by the Shuttle Orbiter may be confined to an interaction region that extends on the order of 10 m in the forward direction and has a boundary thickness of about 2 m. (2) A correlation between the DIFP and pressure gauge measurements indicates a direct, local proportionality between the neutral gas and ion densities. (3) Preliminary results from a theoretical model of the possible interaction between measured secondary, high inclination ion streams and the ambient plasma indicate the generation of broad‐band electrostatic noise such as that observed by wave instruments on

ISSN:0094-8276    

DOI:10.1029/GL013i003p00217

年代:1986

数据来源: WILEY

摘要:

Observations of the electric field at frequencies from 2‐128 Hz, using the burst mode of the spherical double probe on ISEE‐1, have been examined for a time period previously identified as containing the passage of a near‐earth neutral line past the satellite. Most of the power occurred at frequencies less than 20 to 50 Hz. Intense waves (3‐>30 mV/m) at approximately half the lower hybrid frequency, were observed throughout the plasma sheet from the neutral sheet to the high latitude boundary, but only during the period of the large dc electric field andE×Bvelocity associated with the substorm neutral line. The wavenumber obtained by including a Doppler shift term in linear fits of the frequency of the peaks of the power spectra was comparable to the inverse electron gyroradius (k ρe<1). These results are consistent with the lower hybrid drift instability and inconsistent with ion beam driven instabilities (which may explain the much weaker waves observed at higher frequencies). The largest amplitude waves occurred at the neutral sheet when the southward component of the magnetic field was 6 gammas, in contrast to theoretical work which has suggested that the instability would be suppressed there. The observed waves could provide an anomalous resistivity of ∼3×10−7to 1×10−4s (compared to the classical v

ISSN:0094-8276    

DOI:10.1029/GL013i003p00221

年代:1986

数据来源: WILEY

摘要:

During the Spacelab 2 mission the Plasma Diagnostics Package (PDP) performed a fly‐around of the shuttle at distances of up to 300 meters while an electron beam was being ejected from the shuttle. We discuss a magnetic conjunction of the shuttle and the PDP while the electron gun was operating in a steady (DC) mode. During this conjunction, the PDP detected a clear funnel‐shaped emission that is believed to be caused by whistler‐mode emission from the beam. Ray‐path calculations show that the shape of the funnel can be accounted for by whistler‐mode waves propagating near the resonance cone. Because the beam and waves are propagating in the same direction, the radiation must be produced by a Landau, ω/k∥= vb, interaction with the beam. Other types of waves generated by the beam are al

ISSN:0094-8276    

DOI:10.1029/GL013i003p00225

年代:1986

数据来源: WILEY

摘要:

The Pioneer Venus Orbiter Ultraviolet Spectrometer (PVOUVS) measured the OI 1304 Å intensity over a range of spacecraft altitudes (150 to 300 km at periapsis). The atomic oxygen density is determined from the dayglow by comparing the data to the intensities predicted in a Monte Carlo model which correctly simulates the partial frequency redistribution of photons in a non‐isothermal, absorbing atmosphere. The analysis yields atomic oxygen densities consistent with the in situ determinations of the PV Bus Neutral Mass Spectrometer and PVO Neutral Mass Spectrometer and supports recent laboratory measurements of the electron impact excitation cross section of atomic oxygen. Furthermore, the potential inherent in ultraviolet remote sensing for determining the global distribution of atomic oxygen is demonstrat

ISSN:0094-8276    

DOI:10.1029/GL013i003p00229

年代:1986

数据来源: WILEY

摘要:

Mozer [1984] has published some ISEE‐1 data on the electric field in the magnetospheric equatorial plane which show a polarization of the low latitude boundary layer, consistent with tailward plasma flow. A reinterpretation of these data suggests that the potential difference may be typically 30 kV for the combined dawn and dusk layers, out of a total of 50‐60 kV across the polar cap. Therefore, the LLBL is at least as important as the competing process of magnetic reconnect

ISSN:0094-8276    

DOI:10.1029/GL013i003p00233

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i003p00235

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i003p00237

年代:1986

数据来源: WILEY