Michael Brown

Swarthmore College, NSF Center for Magnetic Self-Organization

Tim Gray, Ed Dewey ’10, Bevan Gerber-Siff ’10, Kevin Labe ‘11Vernon Chaplin ’07, Lake Bookman `08

M. J. Schaffer

E. V. Belova

Research supported by US DOE and NSF

Outflow jets, ion heating, and 3D structure in SSX

SSX parametersIon Density (protons) 1014 -1015 cm-3

Temperature (Te,Ti) 20 - 80 eV

Magnetic Field 0.1 Tesla

Ion gyroradius 0.5 cm

Alfvén speed 100 km/s

S (Lundquist number) >1000

Plasma 10-100%

Poloidal flux 3-4 mWb

Spheromak formation

2D MHD simulation

Tangled 3D magnetic lines (lab and solar)

one foot tall 5 earth diameters tall

Ele

ctro

n D

iffus

ion

Reg

ion

Reconnection geometry (2D model)

Sepa

ratr

ix

Inflow (slow)

Outflow (fast, Alfvenic)

Current flow (out)Electron flow (in)

3D hybrid simulation (Y. Lin)

Kinetic ions (5x108 ions), fluid electrons

Simulation results: 3D resistive MHD (E. Belova, PPPL)

SSX device (distributed probe array)

•Opposing magnetized plasma guns•Close fitting copper flux conserver•Midplane IDS access for flow studies

Local 3D probe measurements

Right-handedSpheromak

Left-handedspheromak Reconnected

poloidal flux

Merging studies in prolate geometry(2003-2007)

• 0.4 meter diameter, 0.6 meter length • reconnection at midplane

• formation of prolate FRC object • ultimately unstable with slow growth rate

Counter-helicity merging (prolate)

3D probe measurements in SSX

3D probe measurements in SSX

3D probe measurements in SSX

Bi-directional outflows in SSXHigh resolution ion Doppler spectroscopy

(Cothran, et al, PRL to be submittedJ. Fung thesis ‘06)

Ion Doppler Spectroscopy (1.33m)

Ion Doppler Spectroscopy (1.33m)

Ion Doppler spectrometer layout

IDS line shapes (high resolution)

Observation of bi-directional outflow

Data is effectively f(v_r)… one pixel is 10 km/s

Stills from IDS movie

Dynamics of the flow (bursts, turbulence) encoded in the lineshape

Bi-directional outflows on the sun

D. Innes (SOHO SUMER chromosphere)Innes, Nature, 1997

Innes, Solar Physics, 1997

Location of SUMER slit on solar disk

SiIV light dispersed along slit

Velocity resolution 10 km/s

Spatial resolution1000 km

Spatially localizedevents

Hot ions in SSX

Cothran, et al (SSX)

(low density discharges,after glow discharge conditioning, short gas delay)

Hot ions in SSX (merging)

IDS hot ion temperature measurement (one shot, 1014

density)

IDS hot ion flow measurement

IDS hot ion temperature measurement (average, 5x1014

density)

Scaling of Ti with density

Scaling of Ti with density (single sph)

Dipole-trapped, Gaussian fit, early in formation (30-40 s)

IDS ion temperature measurement HeII 468.57 nm (THe > TC)

Te from CIII (97.7 nm) to CIV (155 nm) ratio

Te from CIII (97.7 nm) to CIV (155 nm) ratio (single spheromak)

Te from SXR array fitting

Observe electron heating with SXR during 30-40 s reconnection period

Hot ions in the extended corona

Cranmer, Space Science Rev, 2002 (UVCS)

UVCS line of sight

Greater than mass ratio ion temperatures

Quadrupole measurement in SSX

Mattheaus, et al, GRL (2005)Landreman, (2003)

Cothran, et al, GRL (2003)

Driven magnetic reconnection experiments

Cothran et al GRL 30, 1213 (2003)Brown et al ApJL 577, 63 (2002)Brown et al Phys. Plasmas 9, 2077 (2002)Brown et al Phys. Plasmas 6, 1717 (1999)Kornack et al Phys. Rev. E 58, R36 (1998)

Magnetic probe array

RGEAs

Large slots cut into FC rear walls define the reconnection region

3D magnetic structureEnergetic particles

3D magnetic probe array

600 coils, 558 array

~2 cm spacing

25 three channel 8:1multiplexer/integratorboards

10 eight channel 8-bitCAMAC digitizers

Full probe readoutevery 0.8 s

Quadrupole out-of-plane field

Ion inertial scale 2 cm

Trajectory of Polar spacecraft

Path of tiny Polar

Trajectory of POLAR spacecraft

Polar trajectory

Mozer, et al, PRL (2002)

POLAR SUB-SOLAR OBSERVATION OF THE ION SCALE

Merging studies in oblate geometry(2007-2008+)

• 0.5 meter diameter, 0.4 meter length • turbulent merging process

• formation of oblate FRC object (sometimes)•Ti higher, Te lower than prolate

• often unstable with Alfvenic growth rate

Trapezoidal flux conserver in SSX

Trapezoidal flux conserver in SSX

Trapezoidal flux conserver in SSX

FRC equilibrium with trapezoidal FC

2D merging simulation (N. Murphy)

Stable Oblate FRC in SSX (sometimes)

Ti and Te in oblate merging in SSX

Ti higher, Te lower than prolate

Density at midplane with merging

Dynamic merging events in SSX

Unstable! Turbulent?

Summary (1)

Bi-directional sub-Alfvenic outflowmeasured with ion Doppler spectroscopy on SSX

Hot ions and warm electrons also observed in the laboratoryusing spectroscopy/soft x-rays

Summary (2)

Measurement of Ti for different ion mass(Carbon, Helium, Silicon)

Electron heating observed during mergingevents using soft x-ray array…

less heating for single spheromak

Summary (3)

3D structure measured at the ion inertial scale in SSX merging experiments

First laboratory measurement ofout of plane quadrupole field observed onlength scale similar to Polar observations

at the magnetopause

Summary (prolate)

Bi-directional sub-Alfvenic outflowmeasured with ion Doppler spectroscopy on SSX

Both ions/electrons heated by reconnection

Spheromak merging createsunstable prolate FRC object

with reconnection at midplane

Summary (oblate)

Merging in oblate geometry in SSX

Hot ions and warm electrons also observed in the laboratoryusing spectroscopy/soft x-rays

Future studies (fall 2008)

Measurement of Ti for different ion mass(Carbon, Helium, Xenon)

Continue search for stable mergingin oblate geometry

Future studies (fall 2008)

High resolution, high frequency mag probe(Tobin Munsat collaboration)

Mach and retarding grid ion probes