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AGU: Geophysical Research Letters

 

Keywords

  • narrow-band
  • ultra-low

Index Terms

  • Planetary Sciences: Solar System Objects: Mercury
  • Radio Science: Waves in plasma
  • Space Plasma Physics: Kinetic waves and instabilities
  • Space Plasma Physics: MHD waves and instabilities

Abstract

Narrow-band ultra-low-frequency wave observations by MESSENGER during its January 2008 flyby through Mercury's magnetosphere

Scott A. Boardsen

Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, Maryland, USA

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

Brian J. Anderson

Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA

Mario H. Acuña

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

James A. Slavin

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

Haje Korth

Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA

Sean C. Solomon

Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, D. C., USA

During MESSENGER's first flyby of Mercury, numerous narrow-band ultra-low-frequency (ULF) waves and their harmonics were detected between closest approach (CA) and the outbound magnetopause (MP) crossing. The fundamental mode was at frequencies between the He+ (f cHe+) and the H+ (f cH+) cyclotron frequencies. A boundary layer (BL) was detected before the MP crossing. The ULF frequency and amplitude increased from CA to the edge of the BL. In the BL the frequency dropped by a factor of 2, and the amplitude increased by an order of magnitude. There was a large variation in the wave-normal angle (Ψ), with a slight tendency for Ψ to be perpendicular to the ambient magnetic field near CA and parallel away from CA. Near CA the parallel power tended to be larger than the perpendicular power, while away from CA the perpendicular power dominated. Large variations in wave polarization properties were observed.

Received 16 September 2008; accepted 5 November 2008; published 3 January 2009.

Citation: Boardsen, S. A., B. J. Anderson, M. H. Acuña, J. A. Slavin, H. Korth, and S. C. Solomon (2009), Narrow-band ultra-low-frequency wave observations by MESSENGER during its January 2008 flyby through Mercury's magnetosphere, Geophys. Res. Lett., 36, L01104, doi:10.1029/2008GL036034.

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