A unique pass of the DMSP F11 satellite, longitudinally cutting through the cusp and mantle, combined with simultaneous optical measurements of the dayside cusp from Svalbard has been used to ...determine the width in local time of the cusp. We have shown from this event study that the cusp was at least 3.7 hours wide in magnetic local time. These measurements provide a lower limit for the cusp width. The observed cusp optical emissions are relatively constant, considering the processes which lead to the 630.0 nm emissions, and require precipitating electron flux to be added each minute during the DMSP pass throughout the local time extent observed by the imaging photometer and probably over the whole extent of the cusp defined by DMSP data. We conclude that the electron fluxes which produce the cusp aurora are from a process which must have been operable sometime during each minute but could have had both temporal and spatial variations. The measured width along with models of cusp precipitation provide the rationale to conclude that the region of flux tube opening in the dayside merging process involves the whole frontside magnetopause and can extend beyond the dawn‐dusk terminator. The merging process for this event was found to be continuous, although spatially and temporally variable.
Two central issues in magnetospheric research are understanding the mapping of the low-altitude ionosphere to the distant regions of the magnetsphere, and understanding the relationship between the ...small-scale features detected in the various regions of the ionosphere and the global properties of the magnetosphere. The high-latitude ionosphere, through its magnetic connection to the outer magnetosphere, provides an important view of magnetospheric boundaries and the physical processes occurring there. All physical manifestations of this magnetic connectivity (waves, particle precipitation, etc.), however, have non-zero propagation times during which they are convected by the large-scale magnetospheric electric field, with phenomena undergoing different convection distances depending on their propagation times. Identification of the ionospheric signatures of magnetospheric regions and phenomena, therefore, can be difficult. Considerable progress has recently been made in identifying these convection signatures in data from low- and high-altitude satellites. This work has allowed us to learn much about issues such as: the rates of magnetic reconnection, both at the dayside magnetopause and in the magnetotail; particle transport across the open magnetopause; and particle acceleration at the magnetopause and the magnetotail current sheets.PUBLICATION ABSTRACT
On November 15, 1996, NASA FAST and POLAR satellites obtained data in the cusp/cleft region for extended intervals. POLAR sampled a narrow range of local times. FAST observed cusp/cleft plasma for ...more than 5 hours in local time. At 07:51 UT the satellites were in near magnetic conjunction, and the interplanetary magnetic field was steady for an extended interval before this time. We confirm prior observations that show solar wind plasma often enters the magnetosphere over extended regions of local time. For the one hour interval of steady solar wind conditions when POLAR encountered cusp/cleft plasma, irregularly spaced ion injections interspersed with intervals of nearly constant cusp/cleft ion fluxes were observed. The data are consistent with temporal variations in the reconnection rate. At the time of the near conjugate observations the data suggest that solar wind plasma entered the magnetosphere over an extended region of the magnetopause, i.e. not in small discontinuous patches.
It is often the case that the flux of the relativistic electrons in the outer radiation belt decreases substantially once the major magnetic storm takes place. After the disappearance of the ...relativistic electrons which can last as much as one day, an increase in the flux occurs, often to levels that exceed the pre-storm level. We have investigated a correlation of the increment of the relativistic electron flux at geosynchronous orbit with the interplanetary magnetic field (IMF) properties as well as the magnetic disturbance signature during the magnetic storms. Results demonstrate that a large flux enhancement occurs when the IMF is southward during the storm recovery phase.
One of the Brussels Radiation Belt Workshop recommendation was the establishment of a near-real-time data driven model of the inner magnetospheric energetic particle population (
L<8). Although the ...“ideal” missions and data sets for such a model do not exist at present, more spacecraft than ever before are currently sampling the inner magnetosphere. We attempt here in a case study of the 10 January, 1997 magnetic cloud event to construct such a model with the energetic electron data available from 5 geosynchronous and 6 elliptically orbiting satellites. We examine the constraints and difficulties of putting together a large number of datasets which are measured near-simultaneously at very different locations in the inner magnetosphere. First results indicate that we can achieve a time resolution of about 3 h for a given “snapshot” of the inner magnetosphere, and that large azimuthal asymmetries of the energetic electron population can be observed during large storms.
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