Randy Gladstone

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PLANETARY X-RAY AURORAS
Randy Gladstone Southwest Research Institute San
Antonio, TX USA
European Planetary Science Congress 21 September
2006 Berlin
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• Saturn
• No clear auroral signature seen
• Jupiter
• Chandra HRC-I x-ray observations of Jupiter in
  Dec. 2000 and Feb. 2003 reveal an erratically
  pulsating hot spot with a luminosity of 1 GW,
  located near the region expected for the cusp
• The Jovian x-ray emissions result from heavy ion
  (O S) precipitation from just within the
  magnetosphere (with a possible contribution from
  ions originating in the solar wind)
• XMM-Newton observations show specific emission
  lines and indicate an electron bremsstrahlung
  component at energies gt2 keV
• Earth
• Energetic auroral x-rays due to electron
  bremsstrahlung
• To investigate the possibility of ion emissions
  at Earth, Chandra HRC observations were made of
  Earths cusp region in 2003 and 2004

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SATURN
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Saturn Observations Initial Chandra XMM
observations showed no aurora Ness et al.
2004ab. A hint of aurora appears on Jan. 20,
2004, but is not statistically significant.
Instead of correlating with FUV emissions
observed by HST, the x-rays match the variability
of a fortuitous solar flare Bhardwaj et al.
2005 Clarke et al. 2005.
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JUPITER
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Polar brightness maps in latitude system III
longitude, from Dec. 2000. The north hot spot is
near 67ºN, ?III170º the south hot spot drifts
like the 7.8 ?m hot spots seen by Caldwell et al.
1988.
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2000 North
2003 North
2003 South
The distinct 45-minute pulsation period observed
in Dec. 2000 (above) was not seen in Feb. 2003
(right), or in XMM data from Apr. and Nov. 2003.
The pulsations are still there, but they arent
nearly as regular as when first detected Elsner
et al. 2005
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Simultaneous Chandra ACIS x-ray pulse HST-STIS
FUV flare
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Bunce et al. 2004 High IMF, fast
flow simulation of pulsed reconnection at
magnetopause produces good agreement with
Chandra/STIS flare observations
5000 km
ion precipitation
electron precipitation
5000 km
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Smoothed XMM EPIC images of Jupiter in narrow
spectral bands Auroral emissions due to
precipitating O ions are easily distinguished
from reflected solar x-ray lines at higher
energies Branduardi-Raymont et al. 2006
OVII (0.55-0.60 keV)
OVIII (0.63-0.68 keV)




FeXVII (0.70-0.75 0.80-0.85 keV)
MgXI (1.30-1.40 keV)
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White North aurora Blue South aurora Purple
Disk
XMM-Newton EPIC spectra from Nov. 2003
observations of Jupiter. Data points for the
North and South aurorae are in white and blue,
respectively purple is for non-auroal disk
emissions. At gt2 keV, bremsstrahlung dominates.
Branduardi-Raymont et al. 2006
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EARTH
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PIXIE Earth Observations 2-12 keV, low spatial
resolution
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Chandra Earth Observations 0.1-10 keV, with very
high spatial resolution (0.5", 0.3 km from
apogee) Observation Plan Point at fixed RA
DEC, let Earth drift through FOV (30' 30') aim
for cusp at various LTs
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Chandra Earth Observations
2/7/03
12/16/03
1/6/04
1/24/04
1/30/04
2/15/04
2/28/04
3/4/04
3/7/04
4/10/04
4/13/04
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Chandra Earth Observations
2/7/03
12/16/03
1/6/04
1/24/04
1/30/04
2/15/04
2/28/04
3/4/04
3/7/04
4/10/04
4/13/04
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smoothed by 40 PSF for better SNR
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• Estimated X-ray Brightness
• from Chandra Observation
• 1273 counts in 20 minutes,
• from 500500 pixel area on bright arc (pixels are
  0.132" across) use Aeff 100 cm2
• ? Ex 1273/(2060)/100/
• (5000.132/2.06e5)2
• 1.0e5 photons/cm2/s/sr
• Observed emissions are
• completely consistent with
• electron bremsstrahlung

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• Summary
• Jupiter hot spot x-ray emissions are consistent
  with MeV oxygen precipitation associated with
  pulsed reconnection of near-magnetopause plasma
  into the cusp, as suggested by Bunce et al.
  2004 and Cravens et al. 2003
• Upcoming Jupiter observations in support of New
  Horizons flyby in Feb. 2007 108 ks Chandra time,
  72 ks XMM time ?
• Earth x-ray emissions show a variety of forms,
  from bright arcs to diffuse blobs
• The only Earth x-ray data for which nearly
  coincident particle exist (January 24, 2004)
  indicate that electron bremsstrahlung can explain
  the observed x-ray brightness (no need for heavy
  ions)
• Future Earth observations unlikely ?