In this study we have been examining particle and wave data associated with the magnetopause/magnetosheath region of the terrestrial magnetoshere as observed by the Polar and Cluster spacecraft. The purpose is to better understand the nature of the reconnection process as pertains to particle energization and wave growth and dissipation.
Contributions within Discipline:
Reconnection in the dayside magnetopause is a fundamental way in which energy from the solar wind enters the Earth's magnetosphere. We have shown that the magnetopause boundary is a site of inverted-V electron structures, associated with parallel electric fields. We have shown that these structures may be a low-altitude signature of reconnection at higher altitudes along the magnetic field line.
Using eigenvalue analysis for the upper-hybrid/Langmuir waves trapped in cylindrical density structures, we have found that quasi field-aligned wave modes are associated with density cavities, while radial modes are excited within an enhanced density column. We thus show that density irregularities of various types can support a discrete wave spectrum featuring wide-ranging frequency gaps.
We have reported direct observations of plasma waves and banded fine structure within a density cavity in the terrestrial magnetosphere. These observations appear to be consistent with eigenmode trapping of partially electrostatic waves. We conclude that density cavities are an important source of plasma waves including continuum and kilometric continuum emission and the fine structure can be a remote diagnostic of density structures within the plasmapause/plasmasphere region.
As a direct result of our terrestrial analyses, we report observations of radio waves and banded fine structure observed by Cassini in the Saturn inner magnetosphere. A careful examination of the emission fine structure suggests that the emission bands may be due to eigenmode trapping from density enhancement source regions. The observations are similar to those made at both the Earth and Jupiter and suggest that radio emission fine structure is a remote diagnostic of density fluctuations in planetary magnetospheres.
Observations of whistler mode emission, including chorus, were made near the magnetopause and mid-altitude cusp. We detect at least two and possibly three distinct groups of narrow-banded chorus emission with a primary source region at the magnetic equator. The groups include emission propagating near the resonance cone angle, emission propagating along a density duct, and possibly emission reflected from the low-altitude cusp. The results indicate that the mid and low-altitude cusp, perhaps unlike the high-altitude cusp, is not a significant source of narrowband chorus emission.
Journal Publications:
Yoon, P. H. and J. D. Menietti, On fine structure emission associated with
plasmaspheric density irregularities,
Menietti, J. D. and P. H. Yoon, Plasma waves and fine structure emission bands
within a plasmapause density cavity source region,
Menietti, J. D., P. H. Yoon, and D. A. Gurnett, Possible eigenmode trapping
in density enhancements in Saturn's inner magnetosphere,
Menietti, J. D., R. A. Frahm, A. Korth, F. S. Mozer, and Y. Khotyaintsev,
Polar and Cluster observations of a dayside inverted-V during conjunction,
Menietti, J. D., O. Santolik, and P. Cetin Abaci,
Chorus observed by Polar near the mid-altitude cusp,
Submitted to
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