Structure of the magnetopause at 6.6 R E in terms of 50- to 150-keV electrons

The shape and the structure of the magnetopause are examined during several passages of the magnetopause past ATS 5 and Explorer 45 on August 4, 1972. Determination of boundary normals and comparison of observations at the two satellites indicate that the magnetopause shape in the afternoon sector was close to the shape indicated by theory. Magnetopause normals for a series of closely spaced inward/outward magnetopause passages indicate that these passages were not caused by surface waves moving along the magnetopause. Hodograms of the magnetic field observed during the first two magnetopause passages indicate that the magnetopause was a tangential discontinuity. The magnetic field changes during these passages were used to derive the magnitude and the direction of electrical currents, principally eastward, flowing in the magnetopause. The third passage was very rapid, so a detailed evaluation of the structure was not possible, but it also indicated a tangential discontinuity. A rotational discontinuity was observed in the magnetosheath followed by several magnetopause crossings where the field changed from northeastward in the magnetosheath to northward in the magnetosphere. The magnetopause currents associated with these passages flow northeastward, parallel to the magnetic field. These last observations agree with either open or closed magnetosphere models.

Section: Magnetopause Normals and Distortionsmentioning

confidence: 99%

The magnetopause at 5.2R_Eon August 4, 1972: Magnetopause shape and structure

Kaufmann¹,

Cahill²

1977

“…Since the first spacecraft observations of the noon magnetopause near t0 RE, it has been clear that this solar windmagnetosphere boundary is frequently in motion under the fluctuating pressure of the solar wind [Sonnet et al, 1960;Cahill and Amazeen, 1963;Cahill and Patel, 1967;Kaufmann and Konradi, 1969;Aubry et al, 1971]. There have been occasional observations at distances much closer than t0 RE, usually associated with magnetic storms [Cummings and Coleman, 1968; Lezniak and Winckler, 1968;Skillman and Sugiura, 1971]. Most of such observations have been by geosynchronous (6.6 R E circular orbit) satellites, since such satellites spend half their time in the outer dayside magnetosphere at an ideal location to observe inward motion of the magnetopause [Russell, 1976;Rufenach et al, 1989].…”

Section: Introductionmentioning

confidence: 99%

Periodic magnetopause oscillations observed with the GOES satellites on March 24, 1991

Cahill¹,

Winckler²

1992

Self Cite

The GOES 6 and 7 satellites were in the dayside magnetosphere late on March 24, 1991, when the magnetopause moved in to geosynchronous orbit. Observations on GOES 6 near 1030 local time (LT) indicated six inward and outward periodic movements of the magnetopause past the satellite over a 30-rain interval. Later the magnetopause moved farther in, placing GOES 6 (1100 LT) in the magnetosheath and then moving in past GOES 7, near 1245 LT. The periodic oscillations of the magnetopause at GOES 6 suggest surface waves propagating toward the dawn flank of the magnetopause.

“…The day side magnetopause forms a boundary that both confines the geomagnetically trapped particles and prevents the penetration of the solar wind ions and electrons into the magnetosphere [Freeman et al, 1963;Freeman, 1964;Anderson et al, 1965;Frank, 1965;Lezniak and Winckler, 1968;Vasyliunas, 1968a, b;Singer and Bame, 1970]. Imp 3 particle measurements have shown the existence of a permanent layer of electrons having energy greater than 40 keV.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of the magnetopause energetic electron layer

Meng¹,

Anderson²

1975

Three years of Imp 5 data show that the magnetopause layer of energetic electrons was present during 227 of 230 orbits over this period and extends along the magnetopause from geomagnetic latitudes as low as 40° to latitudes corresponding to the polar cap. It also exists at the boundary between the magnetosheath and the polar cusp region. The data show that the integral energy spectrum of these electrons (Ee > 18 keV) varies greatly with the planetary Kp index and hardens with increasing Kp values. The average spectrum can be represented by a power law J(> E) ∝ E−α, where α = 1.94 ± 0.19. The intensity of the magnetopause layer electrons increases with increasing Kp values and also has a weak dependence on the magnitude of the north‐south component of the interplanetary magnetic field. The energy density of the energetic electrons in this layer is of the order of 10−14 erg/cm³.