Plasma Density Structures in the Inner Magnetosphere Derived From RPI

Measurements

B. Reinisch1, X. Huang1, P. Song1, J. Green2, S. Fung2

V. Vasyliunas3, and D. Gallagher4

1University of Massachusetts Lowell 2NASA Goddard Space Flight Center

3Max-Planck Institut für Aeronomie, Lindau4NASA Marshal Space Flight Center

 IMAGE Science Meeting

4 May 2003Lowell, Massachusetts

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Areas of Research

• Plasmaspheric density model.• 2-D plasmaspheric snapshots• Storm-time depletion and refilling• Polar region model• 2-D polar region snapshots• Magnetospheric field line distortion• Wave propagation theory and method

development

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Empirical Magnetospheric Density Distribution

Average2000-2001

L = 7

6

5

June 20010800 LT

March 20011200 LT

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PROPAGATION ALONG THE FIELD LINE

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Profile Inverted from the scaled Traces

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One pass of IMAGE on June 8, 2001

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

L=2.22

L=3.23

20:58:56UT

20:36:57UT

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Profile Fitting Function

-βe e0

inv

π αλN = N cos

2 λ

Ne0 equatorial density

flatness (~1)

steepness

inv invariant latitude

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Modeled two dimensional density distribution for MLT=8.0 on June 8, 2001

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During Storm LS = 2.84

Measured profile

Quiet-time model

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Refilling ratio (Ne0/Ne0,quiet) as function of t and L

Storm

FullFull

Full

Depleted

?

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Figure 2 (a) is a scaled X-mode frequency–virtual range trace and (b) is the derived Ne-true range profile from the trace using the inversion technique

described above.

X-Trace

(a)

(b)

0 200 400 600 800 10001.5

2.0

2.5

3.0

3.50 50 100 150 200 250

2000-07-18(23:37 UT)

Geo

cent

ric

Dis

tanc

e, R

(RE)

Electron Density, Ne (cm -3)

Plasma Frequency, fpe

(kHz)

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1 2 3 4 5 610-1

100

101

102

103

104

(A)

Ne R

= -4.70

Ele

ctro

n D

ensi

ty, N

e (cm

-3)

Geocentric Distance, R (RE)

Figure 4 (A) bin-averaged Ne vs. R. The error bars correspond to the Ne standard deviation of densities from each corresponding average, (B) bin-averaged Ne/R vs. Kp, .

0 1 2 3 4 5 6 7 8 9e6

e7

e8

e9

e10

e11

(B)

Ne/R eKp

= 0.232

Ne /R

Kp index

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Figure 6. Comparison of polar region Ne models [Persoon et al, 1983; Gallagher et al., 2000], DE 1 in-situ particle measurements and the RPI-derived model for Kp = 0, 3,and 5 (along a magnetic latitude of 88).

RPI

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15

16

17

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The Arc Length DES for a Dipole Field

2 2ESs s s s

s

D 3= sinλ 1+ 3sin λ + ln 3sinλ + 1+ 3sin λ

L 3

(Ls,

s)

DDESES

0 5 10 15 20 25 30 35 400.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

DE

S / L s

s (o)

2 April 2002 0.25 MLT --- LS=3.36, S= -17.1ºR = DR = DESES = 2.0 = 2.0

RR

9 March 2002 1.71 MLT --- LS=4.12, S= 3.87ºR = DR = DES ES = 0.5= 0.5

RR

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A Stretched Field Line02 Mar 2001 1.85 MLT --- LS=2.48, S=-23.5º

R = 2.5, DR = 2.5, DES ES = 2.1 = 2.1 = 0.4 Re = 0.4 Re

RR

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A Compressed Field Line23 Mar 2001 13.35 MLT --- LS=3.70, S=37.4º

R = 4.5, DR = 4.5, DES ES = 5.2 = 5.2 = 0.7 Re = 0.7 Re

RR

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Summary• Instantaneous measurement of plasma distribution along geomagnetic field

line (a validated method)

• Database for empirical plasmapheric models and algorithm exists (require more detailed analyses, L-shell, LT, Dst, SW, IMF dependences)

• Time series of plasmaspheric filling factor can be used to study storm-time depletion-refilling processes (tested in one case)

• 2-D plasmaspheric density snapshots are available (tested two cases, one with convection tail)

• Polar empirical model for Kp and R developed (Lat. LT, SW, IMF dependences)

• 2-D polar snapshots show structures (require more event studies, possibly with other instruments)

• Discrepancy between the observed and model predicted equatorial field line lengths are found (require systematic studies)

• Wave propagation theory (require further development)

• Density inversion for Z mode traces (not started yet)

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