solar dynamic spectra c. vocks and g. mann 1. spectrum of the quiet sun: first results 2. how to...
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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
4th Solar KSP Workshop, 08.-09. November 2010
4th Solar KSP Workshop, 08.-09. November 2010
First solar spectrum: LBA
Quiet Sun: 11 September 2009
• Thermal emission
• Rayleigh-Jeans: I f2
Broad maximum,not as expected…
Reason:
• No calibration
• Antenna sensitivities
4th Solar KSP Workshop, 08.-09. November 2010
4th Solar KSP Workshop, 08.-09. November 2010
Antenna sensitivity: LBA
4th Solar KSP Workshop, 08.-09. November 2010
Normalized spectrum
Plot:
• Dashed line: Itensity
• Solid line: I / f2
Evidence for thermal emission above 60 MHz
Lower f: Noise-dominated (synchroton radiation)
Above 60 MHz:
• Dotted line increases
• Solid line is flat!
4th Solar KSP Workshop, 08.-09. November 2010
First solar spectrum: HBA
Quiet Sun: 11 September 2009
• Thermal emission
• Rayleigh-Jeans: I f2
Again broad max.,lot of RFI…
4th Solar KSP Workshop, 08.-09. November 2010
Antenna sensitivity: HBA
4th Solar KSP Workshop, 08.-09. November 2010
Normalized spectrum
Plot:
• Dashed line: Itensity
• Solid line: I / f2
Clear evidence forthermal emission
4th Solar KSP Workshop, 08.-09. November 2010
Normalized spectrum
Plot:
• Dashed line: Itensity
• Solid line: I / f2
Clear evidence forthermal emission
4th 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
4th 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
4th 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
4th 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
4th 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