A statistical study of the upstream wave boundary outside the Earth's bow shock

Abstract

The forward boundary of the upstream wave region ahead of the earth's bow shock is located statistically by using combined field and plasma data from a single spacecraft, Heos 1. Interpreting the wave as arising from reflected protons traveling upstream with effective velocity V∥ = pV along the interplanetary field, where V is the solar wind bulk speed, we find that the overall average boundary corresponds to a velocity V∥ ≈ 2V for protons reflected from the daylight sector of the bow shock. More refined partitions of the data give p ≈ 1.6 around the subsolar point and p > 2 along the daylight flanks of the shock.

The ULF wave foreshock boundary: Cluster observations

“…The onset of waves in coincidence with large IMF rotations would be in conflict with the quasi‐steadiness condition and therefore might lead to an incorrect identification of the boundary. An early study on the UWFB by Diodato et al [] using magnetic field data from Heos‐1 shows that the boundary is strongly dependent upon the cone angle θ B x , the angle between the IMF direction and the axis. However, the low‐resolution magnetic data (48 s) used in this work‐induced significant uncertainties on the boundary crossings.…”

A Study of the Association of Pc 3, 4 Micropulsations with Interplanetary Magnetic Field Orientation & Other Solar Wind Parameters.

“…according to Diodato et al (1976). This implies that the paths of particles a little below I keV were coincident with the boundary of the wave foreshock.…”

“…The linking of diffuse ions, quasi-parallel structure, and upstream waves is supported by a simple calculation which at the same time relates the waves to the low, rather than the high, end of the backstreaming ion spectrum. T'e parameter p used in former studies to characterize the foreshock boundary Diodato et al, 1976) can be found in terms of the guiding center energy of an observed return proton: Table 1. In that case, the 1 keV foreshock boundary was tangent close to the subsolar point of curve C, where p z1.6…”

“…For an account of the pre-ISEE status of upstream wave and particle observations, the reader is referred to Greenstadt (1976) and Diodato et al (1976). It was no surprise, therefore, that preliminary calculations indicated that the classes of ions were themselves associated with distinguishable local field-to-shock orientations, as represented by cone angle eBn between BSW and the local normal ( Paschmann et al, 1979;Gosling et al, 1979), and by the more sophisticated representations of Bonifazi et al (1979).…”

Preliminary results from the solar wind experiment on the ISEE-2 satellite

“…Using the method sketched by Diodato et al (1976), we have checked whether the presence or absence of backstreaming ions was consistent with the observed direction of the interplanetary magnetic field. As shown in Figure 10, the agreement turned out to be very satisfactory.…”