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Solar dynamic spectra C. Vocks and G. Mann 1. Spectrum of the quiet Sun: First results 2. How to obtain spectra: Beamformed data 3. Single station spectra 4. Summary and outlook 4 th Solar KSP Workshop, 08.-09. November 2010
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First solar spectrum: LBA Quiet Sun: 11 September 2009 Thermal emission Rayleigh-Jeans: I f 2 Broad maximum, not as expected… Reason: No calibration Antenna sensitivities 4 th Solar KSP Workshop, 08.-09. November 2010
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Antenna sensitivity: LBA
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4 th Solar KSP Workshop, 08.-09. November 2010 Normalized spectrum Plot: Dashed line: Itensity Solid line: I / f 2 Evidence for thermal emission above 60 MHz Lower f: Noise-dominated (synchroton radiation) Above 60 MHz: Dotted line increases Solid line is flat!
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4 th Solar KSP Workshop, 08.-09. November 2010 First solar spectrum: HBA Quiet Sun: 11 September 2009 Thermal emission Rayleigh-Jeans: I f 2 Again broad max., lot of RFI…
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4 th Solar KSP Workshop, 08.-09. November 2010 Antenna sensitivity: HBA
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4 th Solar KSP Workshop, 08.-09. November 2010 Normalized spectrum Plot: Dashed line: Itensity Solid line: I / f 2 Clear evidence for thermal emission
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4 th Solar KSP Workshop, 08.-09. November 2010 Normalized spectrum Plot: Dashed line: Itensity Solid line: I / f 2 Clear evidence for thermal emission
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4 th Solar KSP Workshop, 08.-09. November 2010 How to get dynamic spectra Necessary: Beamformed data → Station beam points to the source Beamformer: 1 sample per 5 µs On station level: Auto- and cross-correlation spectra Integration over time Each subrack sends 64 subbands to IP address No time integration at station 12.8 Mbit/s per subband
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4 th Solar KSP Workshop, 08.-09. November 2010 Spectra via Groningen Processed by Blue Gene / P Channels within subbands: Frequency resolution Data written to postprocessing cluster: Raw beamformed Dynamic spectra pipeline: Desired time and frequency resolution Data output as HDF5 or FITS Synergies with Pulsar KSP
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4 th Solar KSP Workshop, 08.-09. November 2010 Recent dynamic spectra Solar observations: 29 and 30 October 2010 Data processing: Pulsar pipeline Work in progress: Read data (python) Store spectrum, e.g. FITS Scintillation
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4 th Solar KSP Workshop, 08.-09. November 2010 Single-station spectra Beamformed data: Data streams from subracks Needs to be stored: local PCs, one per subrack For full bandwidth: 4 PCs Data handling: Previous estimates: Time integration and few channels Computational load manageable PELIKAN software
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4 th Solar KSP Workshop, 08.-09. November 2010 Summary and future work Summary: Single LOFAR stations: Used as spectrometer Thermal emission of the quiet Sun detected Dynamic spectra: Beamformed data Future work: Solar observations end of October, analyze data BF pipeline from pulsar group, scintillation Dynamic spectrum data format Station sends high data rate, pipeline in Groningen Local storage: PC receives data, PELIKAN
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