#   Instability-Driven Limits on Ion Temperature Anisotropy in the Solar Wind: Observations and Linear Vlasov Theory, Ben Maruca, PhD Colloq. 

 



####  calendar\_today Date and Time 

 **April 13, 2012** 

 09:00AM - 10:00AM EDT 

 



 

The Ph.D. colloquium by Ben Maruca will be held on Friday, April 13, at  
9:00 AM in Phillips Auditorium.  
  
At 10:30 AM, Ben will defend his thesis in Room M-240, 160 Concord Ave.  
  
Talk Title: Instability-Driven Limits on Ion Temperature Anisotropy in  
the Solar Wind: Observations and Linear Vlasov Theory  
  
Abstract: Kinetic microinstabilities in the solar wind arise when its  
non-thermal properties become too extreme. This thesis project focused  
specifically on the four instabilities associated with ion temperature  
anisotropy: the cyclotron, mirror, and parallel and oblique firehose  
instabilities. Numerous studies have provided evidence that proton  
temperature anisotropy in the solar wind is limited by the actions of  
these instabilities. For this project, a fully revised analysis of data  
from the Wind spacecraft's Faraday cups and calculations from linear  
Vlasov theory were used to extend these findings in two respects.  
First, theoretical thresholds were derived for the alpha-particle  
temperature anisotropy instabilities, which were then found to be  
consistent with a statistical analysis of Wind alpha-particle data.  
This suggests that alpha-particles, which constitute only about 5% of  
ions in the solar wind, are nevertheless able to drive temperature  
anisotropy instabilities. Second, a statistical analysis of Wind proton  
data found that proton temperature was significantly enhanced in plasma  
unstable due to proton temperature anisotropy. This implies that  
extreme proton temperature anisotropies in solar wind at 1 AU arise from  
ongoing anisotropic heating (versus cooling from, e.g., CGL double  
adiabatic expansion). Together, these results provide further insight  
into the complex evolution of the solar wind's non-fluid properties.

 

 



 

 See also:- [ PhD Colloquium ](/filter_by/phd-colloquium)
 
 

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