摘要:

The Fokker‐Planck equation for the transport of solar cosmic rays in interplanetary space, including the convection and energy‐change terms as well as an absorbing boundary at finite distance from the sun, is solved for the exponential decay phase of solar particle events. The solution is applied to the case of low‐energy (≈10 Mev) particles for which convection is important. Convective effects, particularly the relative constancy and energy‐independency of the exponential decay time, previously noted in connection with the equilibrium anisotropy, appear explicitly in this

ISSN:0148-0227    

DOI:10.1029/JA076i004p00759

年代:1971

数据来源: WILEY

摘要:

A realistic inclusive model for the post‐acceleration propagation of solar flare particles is presented that is suitable for numerical solution. The model assumes diffusion and energy loss in the solar atmosphere, gradual escape into the interplanetary medium, anisotropic energy‐dependent diffusion in a stochastic interplanetary magnetic field whose average configuration is the Archimedian spiral pattern, convection and adiabatic deceleration produced by the solar wind, and an absorbing boundary for the particles at a finite heliocentric radius. By using parameter values that are supported by or at least do not contradict experimental data concerning the particle environment, sets of curves are obtained from detailed computer calculations. The predictions of the model are in qualitative accord with existing experimental observations of the intensity versus time behavior of solar flare particles as a function of particle species, energy, flare longitude, and heliocentric radius of observation. Furthermore, the model is able to account reasonably well for observed features of the proton anisotropy versus time behavior as a function of energy and flare longit

ISSN:0148-0227    

DOI:10.1029/JA076i004p00768

年代:1971

数据来源: WILEY

摘要:

Observations of the differential energy spectrum of solar protons in the range 0.3 to 25 Mev obtained with the Injun 5 polar‐orbiting satellite for the solar particle event that began on January 24, 1969, are presented. The data show that (a) the differential energy spectrum exhibits a peak for the first few hours after the event, with the maximum intensity moving from ∼1.1 Mev at ∼6 hours after the flare onset to 0.54 Mev at ∼12 hours after the flare, and (b) the differential intensity is a monotonically decreasing function of energy ∼30 hours and ∼56 hours after the flare. Spectrums observed in (a) are consistent with diffusive velocity dispersion during propagation in the interplanetary medium. The spectrums observed in (b) can be described by a power law in kinetic energyEof the formdj/dE=KE−γ. It has been suggested in the past that low‐energy solar‐flare particles are stored for periods of a few days in the immediate vicinity of the sun. By using the shape of the spectrums in (b) we derive upper limits to the electron (or ion) density in the (presumed) storage region in the vicinity of the sun of 4×105to 3×104cm−3. These electron densities correspond to solar radial distances of 3 to 6Rs(solar radii). If adiabatic deceleration is taken into account, the densities are ∼105cm−3corresponding to ∼4Rs. It is concluded that for the event of January 24, 1969, storage of low‐energy protons did not take place in the immediate (3 to 6Rs) vicinity of the sun. The implications of the results are discussed in the context of current models of low‐e

ISSN:0148-0227    

DOI:10.1029/JA076i004p00792

年代:1971

数据来源: WILEY

摘要:

During the latter stages of cycle 19, a characteristic series ofMregion magnetic storms were observed from 1962–1964. Energetic particle events were associated with many of these storms. The relation between the corotating particle stream and magnetic disturbances is examined. These particle increases appear to be similar to those that sometimes appear on the next solar rotation after a large flare‐associated particle event. Both sets of data strongly suggest that the volume above some active centers is magnetically closed. This provides the trapping region with particles preferentially escaping from the base of the preceding portion of the bipolar region. Many of the statistical studies ofMregions, which established that there is a geomagnetic minumum some 3 days after the central meridian passage of an active center, support this view. A simple model for these particle events is propo

ISSN:0148-0227    

DOI:10.1029/JA076i004p00808

年代:1971

数据来源: WILEY

摘要:

We present Pioneer 8 observations of magnetosheath and interplanetary VLF electric fields, consisting of hourly ranges of the potential amplitude in a broadband channel (0.1 to 100 kHz) and in a 15% bandpass channel centered on 400 Hz. Significant signals are correlated with position with respect to earth, and with solar wind plasma parameters obtained from the lunar orbiting Explorer 35 spacecraft. We detect two principal features: noise bursts or spikes with duration less than approximately 10 sec, and persistent signals with durations typically 1 day or more. The noise bursts coincide with plasma and magnetic field discontinuities where these data are available for comparison. The persistent signals correlate loosely with solar wind density, and this correlation holds whether the density increases are due to interplanetary shocks, the ‘snow plow’ effect, or other processes. Although the experiment is too limited to provide unambiguous determination of the wave modes, at present it appears most likely that ion acoustic waves have been detec

ISSN:0148-0227    

DOI:10.1029/JA076i004p00828

年代:1971

数据来源: WILEY

摘要:

One class of waves observed in the interplanetary medium within several earth radii of the earth's bow shock consists of discrete wave packets with amplitudes that are a significant fraction of the background magnetic field. In the spacecraft frame, these wave packets have periods of about 2.5 sec, grow rapidly in time and decay more slowly, and are left‐handed with respect to the magnetic field. By using the measured solar wind density and cold plasma dispersion theory, however, we show that these wave packets must be right‐handed in the plasma frame at frequencies from about 2 to 4 times the proton gyrofrequency. The propagation vector of these waves is found to point away from the earth's bow shock and to lie between the solar wind flow direction and the average spiral field. The waves are being carried away from the sun by the solar wind, since their velocity is less than the solar wind speed, but they appear to be associated with the intersection of the field line with the earth's bow shock. Since they must be generated in the solar wind plasma, this generation may be caused by the presence of particles streaming upstream from the sh

ISSN:0148-0227    

DOI:10.1029/JA076i004p00845

年代:1971

数据来源: WILEY

摘要:

Energetic electron (Ee>22 kev andEe>45 kev) observations of the lunar orbiting Explorer 35 satellite from 15 magnetotail crossings at geocentric distances of about 60REare presented. The longitudinal and latitudinal distributions are shown at two different flux intensities (low fluxes and high fluxes (cutoffJ(Ee>22kev)>345 electrons/cm2sec ster)). At low fluxes with the counting rate threshold above the cosmic ray background, the occurrence frequency of energetic electrons is almost the same from the dawn side to the dusk side of the tail. The latitudinal distribution shows the occurrence frequency of energetic electrons to be highest near the solar magnetospheric equator and gradual falling off away from the equatorial plane. At high flux levels (J(Ee>22kev)>345 electrons/cm2sec ster andJ(Ee>45kev)>278 electrons/cm2sec ster), the distributions are strongly dependent on longitude and latitude. The occurrence frequency is much higher in the dawn side and near the equator. The region where fluxes were found least frequently is in the northern part of the tail on the dusk side. This dawn to dusk asymmetry appears to increase with increasing flux threshold levels.

ISSN:0148-0227    

DOI:10.1029/JA076i004p00862

年代:1971

数据来源: WILEY

摘要:

The flux time profiles and correlation with the local magnetic fields of energetic electrons (<40 kev) in the magnetospheric tail have been studied using four months of Imp 3 data. The following results were obtained: Fluxes of 102to 8×105cm−2sec−1have been measured beyondXse=−20RE. The energetic electrons have been confined to the plasma sheet and this general characteristic is almost the same as at the Vela orbit (∼18RE). The electrons are almost always present throughout the entire plasma sheet, including the evening side of the magnetospheric tail. There is evidence that the energetic electrons are magnetically confined in much the same way as electron fluxes nearer the earth in the skirt and cusp regions. These regions are recognized to be part of the plasma sheet. Electron island fluxes are recognized as results of the expansion of the plasma sheet beyond its normal

ISSN:0148-0227    

DOI:10.1029/JA076i004p00873

年代:1971

数据来源: WILEY

摘要:

Daytime high‐latitude fluxes of low‐energy (107cm−2ster−1sec−1with typical energy fluxes in the range 0.01 to 0.1 ergs cm−2ster−1sec−1. It is concluded that solar wind plasma can penetrate to low altitudes through the high‐latitude cusp in the magnetopause, which is often referred to as the neutral point. This flux is related to a number of geophysical phenomena, including magnetospheric surface currents, daytime auroras, VLF and LF emissions, ionospheric irregular

ISSN:0148-0227    

DOI:10.1029/JA076i004p00883

年代:1971

数据来源: WILEY

摘要:

Energetic (>30 kev) proton and electron flux measurements were made at 6.6REon ATS 5 during magnetopause crossings on September 29, 1969, and March 8, 1970. In each event an order of magnitude decrease in the electron flux was observed more than 200 electron gyroradii before the boundary was reached, while the proton flux remained unchanged until after the boundary crossing. To explain these data, an outward‐directed electric field is assumed to have existed in a region 800 to 1000 km wide on the earthward side of the magnetopause, creating anE×Bdrift oppositely directed to and greater than the electron ∇Bdrift, thereby excluding electrons but not protons from this region. The required electric field is about 65 mv/meter, producing a potential of about 50 kv across the boundary layer. These data are consistent with models of a closed magnetosphere and are inconsistent with a completely open magnetosphere, but they apply only during periods of extreme magnetic acti

ISSN:0148-0227    

DOI:10.1029/JA076i004p00892

年代:1971

数据来源: WILEY