Transcript JOVIAN MAGNETOSPHERE MAGNETOSPHERIC MAGNETIC …

A subalfvenic plasma flow past
the magnetized obstacle:
Ganymede magnetosphere
Igor I. Alexeev and Elena S. Belenkaya
Scobeltsyn Institute of Nuclear Physics,
Lomonosov Moscow State University,
Leninskie Gory, 119992, Moscow, Russia
[email protected]
Content
 Jupiter magnetosphere global structure
and magnetic field at Ganymede’s orbit
Ganymede aurora spot at Jupiter and aurora
at Ganymede
Ganymede orbit placed near to
(1) Jupiter magnetosphere Alfenic radius,
(2) inner edge of the Jovian current disk,
(3) equatorial projection of the main oval
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2013 February 15
Astronomy Picture of the Day
Shadows Across Jupiter Image Credit & Copyright: Damian Peach
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Paraboloid model full size
Near Ganymede magnetosphere
Alexeev, Belenkaya, AG, [2005]
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Paraboloid model of the Jovian magnetosphere
Model components
Time-dependent model parameters
In a Jovian solar-magnetospheric
coordinate system: Bm(t) =
Bd(Ψ) - planetary field vector
+ BMD(Ψ,BDc,RD1,RD2) - field from
Ψ magnetic dipole tilt angle
R1 subsolar MP distance
RD2 and RD1 radial distances of the
equatorial current disc
+ Bsd (Ψ,R1) - from currents
shielding planetary field
+ BMD(Ψ,BDc, R1,RD1,RD2) - field from
currents shielding current disc field
+ BTS(Ψ,,R2,Bt) - from cross-tail +
closure magnetopause currents
+ b(kJ,BIMF) - fraction of the IMF
penetrating the magnetosphere
inner and outer edges of the current
disc
R2 radial distance of the inner edge of
the tail current sheet
Bt/(1+2 R2/ R1)1/2 tail field strength at
the inner edge of the tail current sheet
BDC current disc field strength at the
outer edge of the current disc
BIMF IMF vector
kJ coefficient of the IMF penetration
Alexeev, Belenkaya, AG[2005]
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The transition from dipole like to stretched
tail-like field lines in Jupiter magnetosphere.
R2
R1
RD1
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RD2
RD1
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Ψ =0
Bt=3 nT
BDC=3 nT
R1 =92.8 RJ
R2 =85.4 RJ
RD1 =84.4 RJ
RD2 =16.4 RJ
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The transition from dipole like to
stretched tail-like field lines.
Nearest Earth tail edge (e.g. Lui et al.,
1992). The carton is based on data by
AMPTE CCE Magnetic Field Experiment
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Ulysses the jovian magnetospheric magnetic
field
Measured by Ulysses the
magnetic field dependent
on the radial distance r
(Cowley et al., 1996) is
marked by solid curve.
For comparison there are
also shown magnetic field
strength calculated by
present model (heavy
curve).
Equatorial current disk
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Alexeev and Belenkaya, AG, [2005]
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Relative intensity versus pitch angle versus time and
position for 15- to 29-keV electron data as
generated and reported by Toma´s et al. [2004a,
2004b] using data from the Galileo EPD instrument
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Energetic ion spectra and plasma
beta=1 at Ganymede orbit
Mauk et al. [2002]
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Satellite Footprints Seen in Jupiter
Aurora
Ganymede's
auroral footprint.
near the center,
This ultraviolet image of Jupiter was taken with the Hubble
Space Telescope Imaging Spectrograph (STIS) on November
26, 1998. John Clarke, BU, USA.
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Unipolar jovian generator
Mauk et al. [2002].
Landay and Lifshitz, 1959
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Schematic of the relationship
between observed equatorial
electron field-aligned
enhancements reported by Toma´s
et al. [2004a, 2004b] and the
circuit of electric currents that
connects Jupiter’s middle
magnetosphere to the auroral
ionosphere. The auroral circuit
figure is based on concepts of Hill
[1979] and Vasyliunas [1983] as
replotted by Mauk et al. [2002]. It
is understood that the shape of the
field lines in the actual Jovian
system are substantially stretched
away from the dipolar configuration.
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Ganymede/plasma parameters
Kivelson, et al. (2004), Magnetospheric interactions with satellites, in Jupiter: The Planet, Satellites
and Magnetosphere, Cambridge Univ. Press, Cambridge, U. K.
Bo, jovian magnetic field,
ne,
< Z >, eq. av. (lobe) ion charge
< A >, eq. av. (lobe) ion mass in mp
ni, ion no. density
m, ion mass density
kTi, equator ion temperature
kTe, electron temperature
pi,th, pressure thermal
pi,en (20 keV – 100 MeV ions)
pe (both “cold” and “hot” electrons)
p(nPa), eq. (max) total pressure
vcr, local corotation velocity
vs, satellite orbit velocity
v, plasma azimuthal vel.
u, relative velocity (range),
vA, eq. Alfven speed
cs, eq. sound speed
B2o/2μo, eq. (lobe) magnetic pressure
u2, eq. av. ram pressure
u2, lobe ram pressure
Ganymede Lander,
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64 nT
5 elns cm −3
1.3
14
4 ions/cm3
54 amu/cm3
60 eV
300 eV
0.04 nPa
3.6 nPa
0.2 nPa
3.8 nPa
187 km/s
11 km/s
150 km/s
139 km/s
190 km/s
280 km/s
1.6 nPa
1.7 nPa
0.08 nPa
Bs, maximum Ganymede surface field
ΣA= (μovA)−1, Alfven cond. eq.
ΣP, av. ionosph. Pedersen cond
ΣH, av. ionosph. Hall cond
M/mi, ions per s added locally to flow
fpe, av. electron plasma freq.
fpi, av. plasma freq. mass mi ion
fce, eq. (lobe) electron cyclotron freq.
fci, eq. (lobe) cyclotron freq. mass mi ion
ρg,th thermal ions gyroradii eq. (lobe)
ρg,pu pickup ions gyroradii eq. (lobe)
MA = u/vA equator (range)
Ms = u/cs(range) Mf = u/( v2A + c2s)1/2 (range)
vφ /vcr
θA (degrees) =tan−1(u/vA)
β = p / (B2/2μo) (lobe)
ΣP (av)g/ΣA (eq)
M ̇ /ρiur2s(range)
Bsurf / Bbg(range)
ρ,pgu/rs(range)
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1500 nT
4.2 S
2S
0.1 S
6x1026 s−1
20 kHz
140 Hz
1.8 kHz
0.09 Hz
36 km
200 km
0.73
0.5
0.8
36
2.4
0.5
5-500
13-23
0.01-0.08
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Inductive interaction of conducting bodies with a
magnetized plasma, A. V. Gurevich, A. L. Krylov, and E. N.
Fedorov, Zh. Eksp. Teor. Fi., 75, 2132-2140 (1978)
VA<<V0<<Vdif=(μoΣP)-1 ΣP<<ΣA
Kivelson, et al. (2004),
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Jia et al., JGR, 2009
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Jia et al., JGR, 2008
I║=ΣA· 6RG·V flow BJ
Imp=2· Rss·Bmp/µ0=1 MA
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I = DVB/µ0VA, Belcher [1987]
I║= MA· 6RG· BJ/µ0=1.14 MA
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Figure 1. Raw HST image (zoom) of Jupiter’s northern auroral region displaying the ultraviolet
footprint of Ganymede in the anomaly region. The image was obtained with HST/ACS/SBC with the
F125LP filter on 2 March 2007 during the GO-10862 HST campaign. The central meridian longitude is
145 (S3), and the exposure time is 100 s.
Controversy Grodent, D., B. Bonfond, A. Radioti, J.-C. Gerard, X. Jia, J. D. Nichols, and J. T. Clarke (2009),
Auroral footprint of Ganymede, J. Geophys. Res., 114, A07212, doi:10.1029/2009JA014289
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Hubble Space Telescope images shown auroral
emission from electron excited atomic
oxygen.
Line at 1356 Å
Open-closed field line boundary
The thermal Jovian plasma at Ganymede
can produce a maximum of only ~10-40 R,
Max brightness are 200 R – 400 R
300 R intensity can produce by 75-300 eV
Controversy Mellisa A McGrat et al, JGR, in press 2013 doi: 10.1002/jgra.50122
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Ganymede’s auroral footprint
The emitted power of
Ganymede’s auroral footprint as a function of
Ganymede’s orbital longitude and, consistently, as
a function of Ganymede’s
latitude in Jupiter’s
plasma sheet.
400 kV2 М A = 800 GW
Emitted power 2 GW ~0.25%
Controversy Grodent et al, JGR, 2009
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Conclusions
• Ganymede’s orbit is mostly interesting
region of the Jupiter’s magnetosphere.
• Magnetometer and energetic particle
detector with energy 1 keV – 1 Mev data
will bring a high scientific output.
• Steady magnetic reconnection and
particle acceleration can be studied
• Aurora phenomena can be studied by UV
imager
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Thank you!!!
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