FASR Flare Science: Lessons from the Nobeyama Radioheliograph

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FASR Flare Science Lessons from the Nobeyama
Radioheliograph

• Dale E. Gary
• New Jersey Institute of Technology

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Outline

• The FASR concept
• The NoRH specifications that are important for
  flare research
• What we have learned about flares from Nobeyama
• How FASR will use these lessons

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FASR Instrument (Antennas)

• Three arrays, 6 km baselines (lt1 at 20 GHz)

Array Designation Number of Antennas Frequency Range Antenna Size
FASR-A High Frequency Array 100 2-24 GHz 2 m
FASR-B Low Frequency Array 60 0.2-3 GHz 6 m
FASR-C Log-Periodic Dipole Array 40 20-300 MHz Log-dipole
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FASR Instrument (Receivers)

• Broadband RF transmission, Digital FX Correlator

Quantity Spec
Frequency Resolution 0.1 (FASR-C) 1 (FASR-A,B)
Time Resolution 10 ms (FASR-B,C) 100 ms (FASR-A)
Polarization Stokes IV (QU)
Instantaneous Bandwidth 1 GHz
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FASR Signal Path
Element
RF Converter Room
IF Processor Room
LO distribution
Analog fiber- optic cable
Front-end
Polyphase Filter Bank
RF-IF converter
12-bit Digitizer
1-bit Sampler

Correlator and DSP
Back-end
From other antennas
LAN

Internet
On-line Calibration
Data Storage
Control Room
Burst monitor(s)
RFI monitor(s)
Computing System
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FASR-A
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FASR-B,C
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FASR Calibration

• Must calibrate for
• Instrumental/environmental changes (e.g.
  temperature)
• Troposphere (weather)
• Ionosphere
• Design will emphasize instrumental stability (no
  rapid secular changes)
• Use satellite signals for initial instrument
  calibrations
• Use cosmic sources for antenna (amp/phase)
  calibration before sunrise and after sunset
• Use self-cal (plus noise cal source) during the
  day (FASR-A,B)
• Use GPS measurements of TEC tip-tilt (FASR-B,C)

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FASR Science Community Input

• International Science Workshop, 2002 May, Green
  Bank, WV
• Special session, 2002 American Astronomical
  Society meeting
• Kluwer/Springer Astrophysics and Space Science
  Library Book Solar Space-Weather Radiophysics
  (17 chapters on all aspects of radiophysics of
  the Sun and inner heliosphere)

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FASR Science Goals

• Designed to be the worlds premier solar radio
  facility for at least two decades after
  completion.
• Full capability to address a broad range of solar
  science
• Directly measure coronal magnetic fields
• Image Coronal Mass Ejections (CMEs)
• Obtain radio spectral diagnostics of particle
  acceleration / energy release, with excellent
  spatial and temporal resolution
• Image radio emission from shocks (type II),
  electron beams (type III), and other bursts over
  heights 1-2.5 Rs
• Construct 3D solar atmospheric structure (T, B,
  ne) over a wide range of heights

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NoRH Legacy for Flare Science

• Instrument parameters relevant to flare research
• Key flare results based on selection of 28 papers
• Morphology
• Dual-frequency studies
• Timing
• Correlation with X-rays

Stephen White
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NoRH Instrument Parameters(Relevant to Flare
Studies)

• Two frequencies (17 34 GHz)
• usually both optically thin in flares
• good for both thermal and nonthermal emission
• Full Sun field of view
• Solar-dedicated, solar-optimized
• Dual circular polarization
• Spatial resolution 15 (17 GHz), 8 (34 GHz)
• Redundant baseline calibration scheme using Sun
  as calibration source
• 84 antennas (1500 ? independent baselines)
• Pipeline processing scheme
• 50 ms time resolution, with 1 s resolution for
  non-flare data

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Source Morphology

• Using dual polarization to deduce double source
  structure

Hanaoka (1997)
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Source Morphology

• Interacting Loops

Hanaoka (1997)
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Source Morphology

• Interacting Loops

Nishio et al. (1997)
Nishio et al. (2000)
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Source Morphology

• Conclusions
• Impulsive flares usually show asymmetry (see also
  Kundu et al. 1995).
• 17 GHz microwaves may be from loop-top or
  footpoints, or both
• Missing from this list are events showing almost
  no structure (even with 5 restored beam using
  super-resolution), e.g. 5 events in Kundu, et al.
  (2001c)

FASRs 1 resolution is neededwill it be enough?
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Dual-Frequency Loops
Yokoyama et al. (2002)
White et al. (2002)
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Dual-Frequency Loops
Kundu et al. (2001c)
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Dual-Frequency Loops
White et al. (2002)
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Additional Model of Dual-f Loops
Melnikov et al. (2002)
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Loops and Loop Models Conclusion

• About half of the large loop events observed at
  17/34 GHz are brighter near the footpoints (as
  expected).
• A significant number have looptop sources, which
  appears to require anisotropic pitch angles for
  the injected electrons.
• We must be more sophisticated in our models to
  account for even the grossest of characteristics
  for some events.
• FASRs imaging spectroscopy will give more
  complete loop diagnostics.

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Electron Dynamics (spectral changes)

• Use morphology to identify magnetic topology
• Identify mirror points
• Model spectral changes (seen with OVSA) to
  determine electron diffusion parameters
• Model pitch-angle diffusion as needed to account
  for obs.

17 GHz 10.6 GHz 5.0 GHz
Lee et al. (2000)
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Electron Dynamics (TOF)

• Requires high time resolution observations (lt1 s)
• Do timing at spatially distinct source locations

Bastian (1999)
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Electron Dynamics (TOF)

• Hard X-ray and main 17 GHz source are
  simultaneous
• Remote 17 GHz source is delayed by 500 ms
• Acceleration is near main source
• Speed is 120,000 km/s

Hanaoka (1999)
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Particle Trajectories
and Electron Dynamics
Type U bursts observed by Phoenix/ETH and the VLA.
from Aschwanden et al. (1992)
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LDE Source Morphology
Altyntsev et al. (1999)
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LDE Source Morphology
Kundu et al. (2004)
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Imaging Spectroscopy

• Lots of related activity was occurring at the
  same time, at dm l.
• FASR will image sources throughout the entire
  spectral range.
• Timing and spatial relationships should allow a
  detailed understanding of associations if not
  causal connections.

Kundu et al. (2004)
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Energy Release and Particle Acceleration
This cartoon shows the general spatial
relationships expected for loop sources.FASR
will image this entire structure for the first
time.Electrons can run, but they cannot hide
(G. W. Bush).
from Aschwanden et al. 1996
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Flare Productivity/Space Weather

• Long-term observations (Kundu et al. 2001b)
• Coronal Heating (White et al. 1995)
• Eruptive events (Hori et al. 2000)
• Relation to type II, type III (Nakajima
  Yokohama 2002 Aurass et al. 2002)

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Flare Productivity/Space Weather

• Solar-dedicated instrument can look at long-term
  flare productivity.
• Small events (lt 10 sfu) in typical active
  region show relaxation of energy buildup,
  avoiding major flares.

Kundu et al. (2001b)
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Flare Productivity/Space Weather

• Contours show active region, and gray-scale shows
  location of tiny radio events.
• FASR will provide magnetic field and temperature
  maps of the active region, along with full
  spectroscopic imaging of the events (and at 10
  times higher spatial resolution).
• Radio diagnostics should allow us to track energy
  release and conversion to heating.

Kundu et al. (2001b)
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Flare Productivity/Space Weather

• Active region transient brightenings (ARTBs) with
  17 GHz flux densities lt 1 sfu appeared to be
  consistent with thermal emission.
• However, Gary et al. (1997) showed that there is
  plenty of non-thermal microwave emission at lower
  frequencies.

White et al. (1995)
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Flare Productivity/Space Weather

• Even fainter events are seen outside of active
  regions, in numbers that may implicate them for
  heating the corona.
• FASR will provide counts of such events over the
  entire disk, and provide additional spectroscopic
  imaging diagnostics.
• The sensitivity of FASR to such events is likely
  to be confusion limited, and it remains to be
  determined what the flux density limit will be.

Krucker et al. (1997)
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Flare Productivity/Space Weather

• Erupting prominences and other moving features
  associated with flares.
• FASRs higher resolution and multifrequency
  imaging will allow excellent radio diagnostics.

Hori et al. (2000)
Gopalswamy
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Flare Productivity/Space Weather

• Collimated jet associated with type II burst.

Nakajima Yokoyama (2002)
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Flare Productivity/Space Weather

• Moving 17 GHz feature (531-533 UT) associated
  with type II burst.

Aurass et al. (2002)
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Nancay CME Movies
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Observed CME Spectrum
from Bastian et al. 2001
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How FASR Will Use These Lessons

• Full Sun (to 17 GHz)
• Solar-dedicated, solar-optimized
• 1 resolution (at 20 GHz)
• Excellent imaging/dynamic range (5000 baselines)
• High time resolution (100 ms)
• Wide, densely sampled frequency range

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Conclusion

• FASR is being designed to address an extremely
  rich range of solar science, utilizing
  state-of-the-art technology.
• Some aspects of the instrument have yet to be
  defined, and help is sought in the design,
  simulations, and software effort.
• Please help to make FASR an international effort.
  By working together we can make FASR a truly
  remarkable facility.

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FASR Contacts

• FASR web page
• http/www.ovsa.njit.edu/fasr/
• FASR U.S. Tim Bastian, Dale Gary, Stephen White,
  Gordon Hurford
• FASR France Monique Pick, Alain Kerdraon

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FASR Endorsements

• 2001 Astronomy Astrophysics Survey Committee
• Ranked as one of 17 priority projects for this
  decade
• one of 3 solar projects, with ATST and SDO
• 2003 Solar and Space Physics Survey Committee
• Ranked as top priority in small (lt150 M)
  projects
• 2002-2004 Design Study (NSF/ATI)
• 3 workshops for community input
• Science consensus, hardware and software design
  options, and development of management plan.
• 2004-2006 FASR Long-Lead Prototyping Proposal
  (NSF/ATI)

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Magnetic Field Spectral Diagnostics

• Model spectra along 2 lines of sight
  a) negative polarity sunspot, b) positive
  polarity sunspot.
• The coronal temperature and the magnetic field
  strength can be read directly from the spectra.

Model from Mok et al., 2004 Simulation from Gary
et al. 2004
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2D Magnetogram

• B map deduced from 124 GHz spectra (b) match the
  model (a) very well, everywhere in the region.
  (c) is a comparison along a line through the
  center of the region.
• The fit only works down to 119 G (corresponding
  to f 3 fB 1 GHz)

from Gary et al. 2004
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Coronal Magnetograms

• Accurate simulation of FASR coronal
  magnetograms of potential and non-potential
  active region, and difference compared with
  current-density map from the model.

from Gary et al. 2004
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Bl from Free-Free Emission

• This capability remains speculative, but with
  sufficient polarization sensitivity, Bl can be
  deduced everywhere down to 20 G using
• where n is the spectral index

from Gelfreikh, 2004Ch. 6
from Gary Hurford, 2004Chapter 4
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Magnetic Topology from QT Layer

• Upper panels show radio depolarization line
  (DL) at a single frequency due to mode-conversion
  at a quasi-transverse (QT) layer, vs.
  photospheric neutral line (NL).
• Using FASRs many frequencies, a QT surface can
  be mapped in projection. The surface changes
  greatly with viewing angle.

from Ryabov, 2004Chapter 7
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FASR Science Goals (2)

• Image CMEs both on the disk and off the limb
• Observe non-thermal electrons in CMEs easily
• Possibly detect free-free emission in some CMEs
• Relate other forms of activity (both thermal and
  nonthermal) that take place simultaneously, with
  perfect co-registration
• Observe analog of EIT/Moreton waves/coronal
  dimmings, filaments, type II bursts, and CMEs all
  in one panoramic view!
• No occulting disk!

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Observed CME Spectrum
from Bastian et al. 2001
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Imaging the CME Density Enhancement via Free-Free

• Early FASR simulation
• New simulations are underway by Vourlidas and
  Marque
• see Vourlidas, 2004Chapter 11

Image simulated with Image simulated
with 73-element array 37 element
array
from Bastian Gary 1997
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FASR Science Goals (3)

• Radio spectral diagnostics of particle
  acceleration energy release, with excellent
  spatial and temporal resolution
• Directly image energy release region
• Follow evolution of electrons from acceleration,
  through transport, and escape or thermalization
• Obtain spectral diagnostics of energy/pitch angle
  distributions
• see tomorrows poster by
  Lee et al.

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Energy Release and Particle Acceleration
Subsecond timescales, with rapid frequency drift
over 100s of MHz.The decimetric part of the
spectrum has never been imaged.
from Aschwanden et al. 1996
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Panoramic View Proffered by Radio Emission
from Benz, 2004Chapter 10
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Solar Flare Diagnostics
Multifrequency imaging allows spatially resolved
spectral diagnostics
More complete simulations are now underway, see
poster by Lee et al.
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FASR Science Goals (4)

• Image radio emission from shocks (type II),
  electron beams (type III), and other bursts over
  heights 1-2.5 Rs
• Global view of type II emission (multi-frequency
  gives multiple plasma layers)
• Relate type II to CME, waves, accelerated
  particles
• Follow type III (and U-burst) trajectories
  throughout frequency, and hence height

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EIT Waves and Shocks
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High Spectral and Temporal Resolution
Complete imaging over a wide frequency range that
connects solar and IP events.Integrated view of
thermal, nonthermal, flare, CME, shocks, electron
beams.
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Particle Trajectories
Type U bursts observed by Phoenix/ETH and the VLA.
from Aschwanden et al. (1992)
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Particle Trajectories
from Raulin et al. (1996)
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FASR Science Goals (5)

• Construct 3D solar atmospheric structure (T, B,
  ne) over a wide range of heights
• Image individual heated loops
• Image filaments, filament channels, eruptions,
  with spectral diagnostics
• Combine radio, EUV, X-ray diagnostics for
  complete model of 3D structure

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Diagnostics of Loop Heating

• FASR spectra of individually imaged hot loops
  yield detailed diagnostics

from Achwanden et al., 2004Chapter 12
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3D Model Using VLA/SERTS/EIT

• Model simultaneously fits radio brightness, EUV
  DEM, temperature and density parameters

from Brosius 2004Chapter 13