Simultaneous Interferometer and

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Simultaneous Interferometer and Multi-frequency
survey of Jupiters synchrotron radiation
Anil Bhardwaj 1, Hiroaki Misawa 2, Kota Imai
2, Fuminori Tsuchiya 2, Testuro Kondo
3,4 and Akira Morioka 2
1 SPL, Vikram Sarabhai Space Centre, ISRO,
Trivandrum, India 2 Planetary Plasma Atmos.
Research Centre, Tohoku Univ., Japan 3 Kashima
Space Research Centre, NICT, Japan 4 Ahyou
University, Korea
Acknowledges collaboration with C.H.
Ishwara-Chandra (NCRA) and N. Udaya Shankar (RRI)
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Outline

• Review Jupiters synchrotron radiation (JSR)
• What is JSR?
• Purpose of this study Investigations of dynamics
  of low energy relativistic electrons in Jupiters
  radiation belt.
• Introduction of the JSR observation
• Interferometer observation in Feb. 24 to Mar. 3,
  2003 and May to June, 2008.
• Simultaneous spectrum (3252300 MHz) and
  interferometer observations in May to June,
  2007.
• Results
• Characteristics of JSR variations and their
  frequency dependence / solar activity dependence.
• Expected processes of the JSR variations inferred
  from radio image analyses.

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Relativistic Electron Intensity for Jupiter
L3
L21
L6
EarthL3
(Pioneer 10 data Baker and Van Allen, 1976)
Electron intensity of Jupiter is 2-3 orders
larger than that of the Earth comparing at the
same L-shell.
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Jupiters Synchrotron Radiation (JSR)
Auroral regions
Radiation belts
Atmospheric
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Recent Topics of JSR study

• Short term variation
• (time scale days to weeks)

Jupiters Radiation belt has long been thought
as a stable region protected by the strong
magnetic field
Recent Observations of JSR reveal evidences
of short term variations Miyoshi et al.,
1999, GRL Bolton et al., 2002, Nature etc.
Presence of some dynamic processes within the
radiation belt.
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An expected scenario of short-term JSR variation
Solar UV/EUV variation (F10.7)
(Sun)
JSR obs. _at_ 2.3GHz in Nov. 1996
JSR
(Miyoshi et al., 1999)
JSR flux enhancement (Brice and McDonough,
1973)
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Expected variations in the radio image
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Investigation of dynamics of Jupiters inner
magnetosphere by precise survey of short-term
variations of JSR at lower frequenciesf 300
800 MHz ( E 5 10 MeV)
Purpose of this study Low Freq. Observation
Previous JSR observation mainly at 1.52.3 GHz
(E 1520 MeV electrons) --- Dynamics of lower
energy electrons have not been known well ---
Investigation of time-scale of short-term
variations and their frequency (energy)
dependence. Investigating the causes of Source
(transportation/acceleration) and Loss
processes.
Expectation Source Little E-dependence,
correlation with solar UV/EUV? Loss
E-dependence, large at high freq.? (synchrotron
loss)
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GMRT observations for Jupiter

• Observations
• 1. Feb. 24 Mar. 3, 2003 (80 hours, 8 days) ?
  opposition
• 2. May 23 June 27, 2007 (24 hours, 12 days) ?
  opposition Multi-freq. observation with the
  Japanese telescopes
• 3. May 7 June 23, 2008 (30 hours, 14 days)
  pre-opposition for avoiding back-ground
  confusion
• Frequency 610 MHz (main)
• 2003 observation each days observation lasted
  for about 10 hours (Jupiters rotation period).
• 2007, 2008 observations each days
  observation lasted for about 2 hours when
  Jupiters magnetic longitudes to the Earth (CML)
  were about 100 or 280 degrees. In these CMLs,
  JSR total flux is almost equal, and both
  equatorial and polar JSR regions (major JSR
  sources) are observable more clearly than other
  CMLs.

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Observation Systems
325 MHz / 785 MHz Tohoku Univ., Japan
2.3 GHz NiCT, Japan
610 MHz Interferometer GMRT

• 34 m parabola
• Tsys70 K

• 31 m by 33 m parabola
• Tsys150/100 K

• 45 m parabola 30 sets
• Tsys92 K

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GMRT observation in 2003

• Observation period Feb. 24 Mar. 3, 2003

Feb.28
Feb.24

• Total flux increased from 5.3 Jy to 6.5 Jy.
• Solar F10.7 increased simultaneously.

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Fe XII 195 Å
Feb. 23 Feb. 24 Feb. 25 Feb. 26
Feb. 27 Feb. 28 March 1 March 2
March 3 March 4 March 6 March 8
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Comparison of model simulation (red, blue) with
Observed flux (pink)
the variation of radial diffusion coefficients
(DLL) used for the calculated flux variations.
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GMRT observation in 2003

• Variation of source regions during flux enhance
  period (Feb. 24 ? 28)

• Flux increased 5.3 Jy (Feb.24) ? 6.5 Jy
  (Feb.28).
• Flux peaks moved inward and the flux level
• increased simultaneously. Furthermore the
• flux increase occurred around the equator.
• ? Inferring enhanced radial diffusion
• initiated by solar variation.

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Back-ground for the 2003 observation
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Multi-frequency observation in 2007
JSR flux standardized at 4.04AU

• The JSR variations seem to be larger at lower
  frequencies.
• Low frequency JSR variations do not correlate
  well with the solar flux variations ?
  points to some processes independent of solar
  activity.

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GMRT observation in 2007

• Variation of source regions during flux enhance
  period (June 2 ? 6)

• Flux increased 4.4 Jy (June 2) ? 4.7 Jy (June 6)
• Flux peaks moved outward and the flux
• increase occurred outside of the peak region.
• ? Not homogeneous (solar induced)
• diffusion.
• Inferring partial diffusion (Jupiter
  origin) or Earth-like injection?

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GMRT observation in 2008

• Observation period May 7 June 23, 2008

May 22
June 23
May 7
May 21

• Total JSR flux at 610 MHz varied by almost 20 in
  spite of quite low solar activity. It suggests
  that some other factors (may be of Jupiter
  origin) affect dynamics of low MeV electrons in
  Jupiters inner magnetosphere.

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GMRT observation in 2008

• Variation of source regions during flux enhance
  period (May 21 ? 22)

• Flux increased 5.0 Jy (May 21) ? 5.4 Jy (May 22)
• Flux peaks moved outward and the flux
• increase occurred almost all region.
• ? Not homogeneous (solar induced)
• diffusion.
• Inferring partial diffusion (Jupiter
  origin)
• Earth-like injection?

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Summary

• Purpose Investigation of low MeV electron
  dynamics in Jupiters inner
• magnetosphere
• Method Lower frequency observations for JSR
• 1. Radio imaging observation
  mainly at 610 MHz using GMRT
• 2. Multi-frequency observation
  at 325 2300MHz (?? 5-20MeV)
• Observations 1. Feb. 24 Mar. 3, 2003
• 2. May June, 2007 (core time
  May 23 June 27, 2007)
• 3. May June, 2008 (core time May 7 June
  24, 2008)
• Results
• 1. Detection of variability with the time
  scale of days to weeks.
• 2. Larger variations at lower frequencies.
• 3. Solar UV/EUV flux affects low MeV electron
  variations during the
• high solar flux. Some other additional
  controlling factors (may be of
• Jupiter origin) are also required,
  particularly at lower solar activity (?of
  new ideas !!)
• Future works

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THANKS !!
Contact Anil_Bhardwaj_at_vssc.gov.in
Inform inspire innovate