ena generation mechnism
DESCRIPTION
ENA generation mechnism. Krimigis et al, 2004. Some Questions about the Interaction between Trapped Particles and Neutrals. What is the source of trapped particles? How are they accelerated to high energies? What is the principal loss mechanism? - PowerPoint PPT PresentationTRANSCRIPT
Dynamics of Energetic Particles and Neutrals in Saturn’s Variable Magnetosphere
by S.M. Krimigis (1), D.G. Mitchell (1), D.C. Hamilton (2), N. Krupp (3), S. Livi (1), E. C. Roelof (1), Dandouras (4), B. H. Mauk (1), J. P. Brandt (1), C. Paranicas (1) , J. Saur (1), T. P. A rmstrong (5), S. Bolton (6), A. F. Cheng (1), G. Gloeckler (2), K. C. Hsieh ( 7), W. -H. Ip (8), A. Lagg (3), L. J. Lanzerotti (9), R. W . McEntire (1), D. J. Williams (1), W. Kurth (10), and M. Dougherty (11) (1) Applied Physics Laboratory, Johns Hopkins Uni versity, Laurel, Maryland, (2) University of Maryland, College Park, Maryland, (3) Max-Planck-Institut für Sonnensystemforschung, Lindau, Germany (4) Centre D'Etude Spatiale Des Rayonnements, Toulouse, France, (5) Fundamental Technologies, Inc., Lawrence, Kansas, (6) Jet Propulsion Laboratory, Pasadena, CA, (7) Univer sity of Arizona, Tucson, Arizona, (8) National Central University, Taiwan, R.O.C., (9) Bell Laboratories, Murray Hill, New Jersey, (10) Univers ity of Iowa, Iowa City IA (11) Imperial College, London, UK
Some Questions about the Interaction between Trapped
Particles and Neutrals
What is the source of trapped particles?
How are they accelerated to high energies?
What is the principal loss mechanism?
How do particles respond in the rotating magnetic field of Saturn?
Are particle collisions with ring and icy moon surfaces important?
1
10
100
1 10 100
Aug. 18, 1999
H+
He+
O++
O+
He++
N+
High ChargeC,N,O
1 10 100
July 1, 2004
H+
He+
O++
O+ & water group
He++
H2
+
O2
+
C+
1 10 100
H+
He++
He+
S+
O+
O++O
3+
S++
S3+
S4+
Jan. 10, 2001
ma
ss (
am
u)
Earth Jupiter Saturn
Charge Energy Mass Spectrometer (CHEMS) on Cassini records “fingerprints” of ion composition at Earth, Jupiter, and Saturn
Plotted: 2/25/05
mass per charge (amu/e)
Some Questions about the Interaction between Trapped
Particles and Neutrals
What is the source of trapped particles?
How are they accelerated to high energies?
What is the principal loss mechanism?
How do particles respond in the rotating magnetic field of Saturn?
Are particle collisions with ring and icy moon surfaces important?
Highest ENA production
The density of OH in the 6-10 Rs region is comparable to H density in the Geocorona. O is probably about the same as OH. O+ lifetime in the Earth’s ring current is ~ 8h. O+ lifetime in the inner Saturn magnetosphere could be much shorter, depending on its radial placement (O, OH charge-exchange cross-section is larger than H)
Hydrogen Geocorona Rairden et al. (1986)
Earth RingCurrent
Devoid of energetic ions
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
(Mauk et al, GRL, June 2005)
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
Modulation persistence and phase lock suggest an “active” longitude (could be a quadrant) coupled with a preferred local time for ion injection
Neutral Gas?
Ion Dispersion
Event Gas
HotH+, O+
Saturn
Cassini
•Brightest ENA emission from interface between dense gas cloud in vicinity of E-Ring, and energetic ions just outside that region.
•Large scale ion injections are commonly seen as corotating brightenings in ENA.
•Ion injections are well correlated with SKR, including when they are seen repeating at Saturn’s rotational period.
•Oxygen ENA emission shows more pronounced, and more regular, rotation modulation than hydrogen.
•Energetic oxygen lifetime in the inner magnetosphere should be no longer than hours, given the density of the water-product cloud in the vicinity of the E-ring. The repeated, un-damped rotational modulation therefore requires nearly continual replenishment of the energetic oxygen ions.
•The synchronicity of the modulated ENA emission, as well as the unchanging energy dispersion, requires repeated injections preferentially at the same Saturn IAU longitude --possibly the same ‘clock’ that drives the SKR.
Summary of Observations on Periodicities