Magnetic Fluctuation Power Near Proton Temperature Anisotropy Instability Thresholds in the Solar Wind

Journal Article · Fri Nov 20 00:00:00 EST 2009 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.103.211101· OSTI ID:21370845

Bale, S D ^[1]; Kasper, J C ^[2]; Howes, G G ^[3]; Quataert, E ^[4]; Salem, C; Sundkvist, D ^[5]

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1. Physics Department and Space Sciences Laboratory, University of California, Berkeley, California (United States)
2. Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts (United States)
3. Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa (United States)
4. Physics Department and Astronomy Department, University of California, Berkeley, California (United States)
5. Space Sciences Laboratory, University of California, Berkeley, California (United States)

The proton temperature anisotropy in the solar wind is known to be constrained by the theoretical thresholds for pressure-anisotropy-driven instabilities. Here, we use approximately 1x10{sup 6} independent measurements of gyroscale magnetic fluctuations in the solar wind to show for the first time that these fluctuations are enhanced along the temperature anisotropy thresholds of the mirror, proton oblique firehose, and ion cyclotron instabilities. In addition, the measured magnetic compressibility is enhanced at high plasma beta (beta{sub ||} > or approx. 1) along the mirror instability threshold but small elsewhere, consistent with expectations of the mirror mode. We also show that the short wavelength magnetic fluctuation power is a strong function of collisionality, which relaxes the temperature anisotropy away from the instability conditions and reduces correspondingly the fluctuation power.

• OSTI ID: 21370845
• Journal Information: Physical Review Letters, Vol. 103, Issue 21; Other Information: DOI: 10.1103/PhysRevLett.103.211101; (c) 2009 The American Physical Society; ISSN 0031-9007
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANISOTROPY
COMPRESSIBILITY
CYCLOTRON INSTABILITY
FLUCTUATIONS
PLASMA
PROTON TEMPERATURE
PROTONS
SOLAR WIND
WAVELENGTHS
BARYONS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
INSTABILITY
MECHANICAL PROPERTIES
NUCLEONS
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
SOLAR ACTIVITY
STELLAR ACTIVITY
STELLAR WINDS
VARIATIONS