Dawn-Dusk Oscillation of the Io Plasma Torus and the Vasyliunas E-V Theorem

Dawn-Dusk Oscillation of the Io Plasma Torus and the Vasyliunas E-V Theorem

A. J. DesslerDept. of Atmospheric Science

Texas A&M UniversityCollege Station, Texas

and

B. R. SandelLunar and Planetary Laboratory

University of ArizonaTucson, Arizona

Boston MOP Meeting 15 July 2011

IO TORUS DAWN-DUSK OFFSET

Approaching Ansa

Dawn Ansa Dusk Ansa

Receding Ansa

Viewed from Voyager

Viewed from Earth

Torus w/ Ribbon on inner (i.e., Jupiter) side

OSCILLATION OF IO TORUS

A

Voyager Earth

A is Magnetic Anomaly at λIII ~110°

Approaching

Dawn A

Approaching

Dawn

Dusk Ansa

Receding Ansa

Dusk Ansa

Receding Ansa

Magnetic Anomaly – Announced (John Clarke et al. 2002 Birmingham DPS meeting).Quantitatively defined (Denis Grodent et al. 2008 JGR and Hess et al. 2011 JGR).

Weak B

Dessler & Sandel, 1979 data from Voyager Schneider & Trauger, 1991 data from Earth 12 years apart

Areas A and B are equalAnomaly magnetic field

maps to equator

No Anomaly change in B-field at Equator

Flux tube Big-Foot resistant to interchange

EFFECT OF MAGNETIC ANOMALY

A Dusk

Magnetic-Anomaly flux tubes map to equator to form impoundment region

LimitedOutflow

LimitedOutflowDawn A

Central Meridian Longitude (System III)CML provides snapshots of Ribbon Distances

Dawn minus Dusk Distance

Anomaly between Dawn and NoonMaximum outflow – Max Offset

Anomaly between Dusk and MidnightMinimum outflow – Minimum Offset

Dawn

min

us D

usk

Ribb

on D

istan

ce

Outflow from torus toward tail causes Torus Offset

Maximum Outflowfrom torus toward Tail

Max Offset

Dawn Dusk

Noon

Local-Time range of Anomalyat given CML viewed from Earth

Anomaly out of the way. Maximum

Outflow – Max Offset

Noon to Dawn

Anomaly ~110°

Dawn

min

us D

usk

Ribb

on D

istan

ce

Minimum Outflowfrom torus toward Tail

Dawn Dusk

Noon

Midnight

Midnight to Dusk

Local-Time positions of Anomalyat given CML viewed from Earth

Anomaly Impedes Outflow

Anomaly out of the way. Maximum

Outflow

Noon to Dawn

Dawn

min

us D

usk

Ribb

on D

istan

ce

CONCLUDING THOUGHTS• The Improved Magnetic-Anomaly Model explains the torus

oscillation.• Other Jovian spin-periodic phenomena can be explained by

this Magnetic-Anomaly Model.

• The Vasyliunas E-V Theorem is important. E is a result of V, E cannot cause V.

Please contact me for more information, wild ideas, or discussion.

e-mail: [email protected]

• Extra slides follow

TIME-VARYING ELECTRIC-FIELD HYPOTHESISThis idea suffers two flaws:

(a) Where is the E-field created so it knows Jupiter’s rotational phase?

Problem: As plasma flows down tail, a varyingV X B field is created at different distances — all longitude phases are mapped back to torus. Therefore, E-field will not work.

(b) Inconsistent with the Vasyliunas E-V Theorem. GRL 2001.

Problem: V X B can create E, but E cannot cause magnetospheric plasma to move. No E-fieldwill work.

CONCLUSIONS1. The Magnetic Anomaly vital to the Magnetic-Anomaly Model

has been discovered, and the Vasyliunas E-V Theorem provided needed guidance.

2. The torus oscillation is explained by an improved Magnetic-Anomaly Model.

The Magnetic-Anomaly Model is open for exploitation. Examples of Jovian spin-periodic phenomena that could be

explained by the Magnetic-Anomaly Model: a. How Active Sector works. It contains many Jovian spin-

periodic phenomena. See Sect. 10.7 in "PJM". b. The 10-hour Plasmoid "bubbles" travelling down the Jovian tail reported by McComas et al. Science 2007. c. The Simpson Clock – highest energy and flux of relativistic

electrons released from Jupiter when Magnetic Anomaly faces sunward.

d. The Lyman-alpha bulge. e. Extension to Saturn spin-periodic phenomena?

Longitudinal Extent of AnomalyA A

A No

on

A Da

wn

A M

idni

te

A Du

sk

A Mid

nite

A Du

sk

A No

on

A Dawn

Position of Anomaly for given CML Observed from Earth