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Stephen White

Radio and Hard X-ray Studies. Stephen White. Energy distributions. Still a discrepancy between the electron energy distribution derived from radio observations and from HXR spectra: radio data show flatter energy distributions. LOw Frequency ARray (LOFAR).

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Stephen White

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  1. Radio and Hard X-ray Studies Stephen White

  2. Energy distributions • Still a discrepancy between the electron energy distribution derived from radio observations and from HXR spectra: radio data show flatter energy distributions

  3. LOw Frequency ARray (LOFAR)

  4. low-energy brems. (solid yellow), high-energy brems. (solid orange), nuclear line and cont. (solid blue), pion-decay (solid purple), 2223 MeV (dotted purple), solar 511 keV (dashed purple), solar-scattered N-capture (solid light green), He line (dashed light blue).

  5. Energy distributions • Still a discrepancy between the electron energy distribution derived from radio observations and from HXR spectra: radio data show flatter energy distributions • Traditional explanation has been that the energy ranges are different: HXR below 100 keV depend on 200-300 keV electrons, radio depends on >500 keV electrons. • Easy, right: just compare in same energy range. But: HXR spectra above 500 keV are complicated. • Similarly, in big flares the radio spectra are difficult because the peak in the spectrum is at high frequencies and it is hard to get the spectral index • And when you do have high frequencies, there is a surprise waiting …

  6. High-frequency observations from the Solar Submillimeter Telescope show a rising component above 200 GHz – not a continuation of the microwave component.

  7. Morphology

  8. Low-frequency/decimeter radio telescopes • Nancay Radio Heliograph: continuing, may add 600 MHz • Brazilian Decimetric Array (BDA) • Chinese Spectral Radio Heliograph (CSRH) • LOFAR: spread across Europe, core in the Netherlands, high spatial resolution • Murchison Widefield Array (MWA): joint US-Australia project based in Western Australia at proposed location of SKA • Long Wavelength Array: US project in New Mexico

  9. Microwave/millimeter telescopes • Frequency Agile Solar Radio Telescope (FASR): still pending at NSF/AGS, “OVSA upgrade” should receive $5M this month • Siberian Solar Radio Telescope upgrade (SSRT) • Nobeyama Radio Heliograph: will cease operations • Solar Submillimeter Telescope: expanding frequencies • Expanded Very Large Array: broad frequency coverage, excellent resolution, little observing time • Allen Telescope Array: plan to do some solar work, F10.7 • Atacama Large Millimeter Array: limited flare observations, small field of view

  10. Future needs 1 • Better spatial resolution at both HXR and radio: in large eruptive flares there must be time-variable structure on small scales in HXR; want radio to test connectivity (below 10 GHz to see loops better; FASR) • In order to achieve better spatial resolution, (both) need both better sensitivity and dynamic range • Compare radio/HXR spectra from the footpoints with radio/HXR spectra in the loops separately • Better time resolution (both) to look for motion

  11. Future needs 2 • Coronal magnetic field strength measurements: where is the energy in the corona that is available for conversion? (compare with PF) (FASR) • Continuous spectral coverage in the radio in order to exploit information in gyrosynchtotron spectra, in particular measure magnetic fields on flaring loops (FASR) • Imaging of energy release sites: if indeed radio spikes are release sites, high-resolution decimeter images, previously unavailable, will show them (FASR) • Per Gordon Hurford: “every pixel in a dynamic spectrum is an image” (FASR) • … including shocks detected in regions of weak plasma emission (FASR)

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