1 / 17

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).

geona
Télécharger la présentation

Stephen White

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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)

More Related