February 14, 2023

Speaker: William H. Matthaeus (University of Delaware)

Contact Information: whm@udel.edu

Title:  Turbulence in collisionless space plasma: the Big Picture 

Abstract: Turbulence is a near ubiquitous feature of fluids and plasmas in geospace, the heliosphere and in astrophysics and well as in laboratory plasma and in the terrestrial environment. Turbulence links large scale energy reservoirs with small scale dissipation processes. Consequently, it is responsible for many features of space plasmas including heating, charged particle scattering and energy transport across wide ranges of spatial scale and location.  This account of the Big Picture of space turbulence starts with the likely energy sources that powers the heating and acceleration of the solar wind.  What follows is a progression of cross scale couplings that are described in adaptations of classical turbulence theory.  At energy containing scales, von Karman similarity provides a top-down description of energy decay.   The von Karman picture is demonstrated using solar wind spacecraft data near earth.  At smaller scales a several decade inertial range is present the solar wind. Energy transfer through this cross scale conduit is described using three methods: phenomenology, Yaglom-Kolmogorov third order law, and scale filtering. Transfer through the inertial range generates small scale structures, or intermittency, in which kinetic processes are concentrated.   Finally, the kinetic dissipation itself, defined as conversion of fluid scale energy into internal energy, is accomplished though the pressure-work and the pressure strain interaction. These are quantified in some detail due to recent advances in both kinetic plasma simulation, and capable multispacecraft measurements.   The cross scale couplings discussed here span scales from the large energy reservoirs to kinetic scale dissipation and are illustrated using spacecraft missions including STEREO, ACE, Helios, Voyager, Parker Solar Probe, Cluster and Magnetosphere Multiscale. The presentation concludes with outstanding questions will be addressed by new missions such as Helioswarm and PUNCH.

Visitor's room: Room 111A

Visit Schedule:

Tuesday (14 Feb. 2023):

• 9:30 a.m.: 

• 10:00 a.m:  

• 10:30 a.m.: Hantao Ji

• 11:00 a.m.: Colloquium 

• 11:30 a.m.: Colloquium 

• 12:00 p.m.: Bahcall lunch

• 12:30 p.m.: Bahcall lunch

• 1:00 p.m.: Bahcall lunch

• 1:30 p.m.: 

• 2:00 p.m.: Tea Time with Grad Students in Grand Central

• 2:30 p.m.: Tea Time with Grad Students in Grand Central

• 3:00 p.m.:

• 3:30 p.m.:

• 4:00 p.m.: 

• 4:30 p.m.:

• 5:00 p.m.: Anatoly Spitkovsky (123 Peyton)

Dinner Sign-up - add your name here:

Tuesday (14 Feb. 2023) 6:30 pm at Chennai Chimney

1. Postdoc Host: Riddhi Bandyopadhyay

2. William H. Matthaeus

3. Shaunak Modak

4. Ankan Sur

5. Rajsekhar Mohapatra

6. David Hosking

7. Lengying Khoo

8. Jamie Rankin

STUDENTS HAVE PRIORITY.

PLEASE NO MORE THAN 8 PEOPLE (it is more difficult to properly interact with the speaker in larger groups).