Dispersionless and Weakly Dispersed Injections in the Dayside Magnetosphere with Evidence of Mirror Wave Signatures

<p>We present observational evidence of mirror waves in the dayside inner magnetosphere as measured with instrumentation on the dual NASA Van Allen Probes spacecraft.  While mirror waves near the dayside bow shock have been reported from several spacecraft missions (e.g. Cluster, THEMIS, MMS), their presence in the dayside inner magnetosphere has not been reported.  We speculate that the mirror modes are associated with direct dayside injections under negative Bz conditions, and drift to lower L-shells.  The analyzed event coincides with the main phase of a CME shock-induced space weather storm, with high solar wind speeds in excess of 700 km/s and a sudden drop in Dst occurring approximately eight hours prior to the event.  The highest plasma beta values were measured by spacecraft B at 12:24 at magnetic noon at L ~ 4.5-5.5.  Spacecraft A later measured a similar feature at 13:00 local magnetic time.  The potential presence of such mirror waves would indicate dayside sources of anisotropy inside the magnetopause, or the penetration of bow shock particles into the dayside inner L-shells.  To our knowledge, this is the first time such waves have been reported in the inner magnetosphere.</p>

Local time asymmetries in the high-latitude boundary of the outer radiation zone for the different electron energies

Data obtained from the Alouette II satellite are used to examine various high-latitude boundaries of the outer radiation zone as a function of local magnetic time. Four different boundaries are defined and these are referred to as the 35-keV "background" boundary, the 35-keV "smooth" boundary, the 35-keV "sharp" boundary, and the 3.9-MeV "background" boundary. All of the boundaries show a marked dependence on local magnetic time. The 35-keV "smooth" and the 3.9-MeV "background" boundaries are identified with the stable trapping region and show a 1100–2300-hour asymmetry of about 3°. The 35-keV "background" boundary falls at higher latitudes than the other boundaries at all local times; a noon–midnight asymmetry of about 6° is observed as well as a marked dawn–dusk asymmetry. The 35-keV "background" boundary is tentatively associated with the boundary of closed geomagnetic field lines and it is suggested that there is a dawn–dusk asymmetry in the field configuration. The 35-keV "sharp" boundary is identified with the inner edge of the "cusp" region and its relation to the other boundaries is examined.