Results from the

Galileo

Energetic Particle Detector During the

Amalthea Encounter

of November 5^th, 2002

Dr. Thomas Armstrong

Lucas Miller

Scott Wadley

Dr. Richard McEntire

Dr. Donald Williams

9 December, 2003

American Geophysical Union

San Francisco, California, USA

Presentation Number SM22B-0255

Table of Contents

1 Preliminary............................................................................................................................................................ 1

1.1 Objectives:.................................................................................................................................................. 1

1.2 Background Information............................................................................................................... 2

2 The New Data.......................................................................................................................................................... 4

2.1 Orientation............................................................................................................................................... 4

2.2 Science.......................................................................................................................................................... 6

3 The Outlook......................................................................................................................................................... 18

3.1 Conclusions:........................................................................................................................................... 18

4 References............................................................................................................................................................ 20

A Appendix: Contact information for the Authors................................................................. A-1

List of Figures

Figure 1.1 EPD Low Energy Magnetospheric measurements System (LEMMS) Detector Head 3

Figure 2.1 (Galileo’s Trajectory Over the Amalthea Orbit)......................................................... 4

Figure 2.2 (Galileo’s Trajectory Over Amalthean Centered Coordinates)........................ 5

Figure 2.3 Galileo EPD Orbit A34 Distribution of 32 Sector Rates............................................... 6

Figure 2.4 (16 Sector EPD Energy Ion Data Collected Over Amalthea Swingby) Part II 7

Figure 2.5 ( High Energy Electrons as Measured by the EPD Instrument Over the Amalthea Swingby) 8

Figure 2.6 (Galileo EPD Orbit A34 Deadtime Corrected Ion Flux Spectra).............................. 9

Figure 2.7 (Uncorrected Ion Fluxes for Particles with Pitch Angles Between 80 and 100 Degrees Over the Amalthea Swingby..................................................................................................................................... 11

Figure 2.8 (Uncorrected Ion Fluxes for Particles with Pitch Angles Between 80 and 100 Degrees Between 3.8 and 5.3 Rj)............................................................................................................................................................ 12

Figure 2.9 Galileo EPD Ion Pitch Angle Distributions in the Inner Jovian Magnetosphere Part I 13

Figure 2.10 Galileo EPD Ion Pitch Angle Distributions in the Inner Jovian Magnetosphere Part II 14

Figure 2.11 Galileo EPD Ion Pitch Angle Distributions in the Inner Jovian Magnetosphere Part III 15

Figure 2.12 (Galileo EPD Orbit A34 Time Series of 64 Sector Rates: Examination of Possible Amalthean Moonlets).......................................................................................................................................................... 16

List of Tables

Table 1.I Important Facts about Jupiter, Amalthea, Galileo, the EPD, and Charged Particles 2

Table 1.II Amalthea Encounter Velocity Summary.......................................................................... 3

1 Preliminary

The purpose of this document is to reformat the poster presentation given at the American Geophysical Union on December 9^th 2003, in San Francisco CA by Dr. Thomas Armstrong and Lucas Miller with contributions by the other authors

1.1 Objectives:

There are four main objectives sought in this research:

1. Evaluate the performance of the Galileo Orbiter Energetic Particle Detector in the intense radiation environment of the inner (< 6 Rj) Jovian magnetosphere

2. Search for signatures of interaction between trapped radiation and natural satellites—especially Amalthea.

3. Calculate and check parameters essential to the interpretation of trapped radiation observations—especially pitch and phase angles.

4. Begin the analysis of the sources, losses, and transport of trapped radiation.

1.2 Background Information

Table 1.I provides some of the necessary facts about the environment of study.

Table 1.I Important Facts about Jupiter, Amalthea, Galileo, the EPD, and Charged Particles

Description	Symbol	Value	Units
Jupiter
Mass	MJ	1.9*10^27	kg
Equatorial Radius	RJEQ	71398	km
Roche Limit	RJRoche	134211	km
Magnetospheric Angular Velocity	wJ	1.76*10^-4	Rad/s
Amalthea
Mass	MA	7.17*10^18	kg
Idealized Radius	RA	86.2	km
Density	rA	1800	kg/m^3
Orbital Radius		181300	km
Orbital Period	PA	11.96	hours
Orbital Eccentricity		0.003	~
Galileo
Mass	MGal	2223	kg
Velocity at Amalthea	V	17.05	km/s
Beginning of Mission		10/18/89
End of Mission- RIP		09/21/03
EPD
Ion Energy Range	DEZ³1	0.022-100	MeV
Electron Energy Range	DEe-	.015-11	MeV
Charged Particles (At Amalthea)
Gyro-Radius for 1 MeV Proton	R+1 MEV	5.180	km
Gyro-Radius for 2 MeV Proton	R+2 MEV	7.327	km
Gyro-Radius for 1 MeV Electron	R-1 MEV	0.170	km
Gyro-Radius for 10 MeV Electron	R-10 MEV	1.255	km

Table 1.II Provides calculated values for the velocities of various components in the Jovian centered system.

Table 1.II Amalthea Encounter Velocity Summary

Description	Velocity
	Magnitude
	km/s
Amalthea's Orbit	26.47
Jovian Magnetic Field Rotation at Amalthea	31.88
Galileo	34.11
1 MeV Protons ÑB	3.49