solar dynamic spectra c. vocks and g. mann 1. spectrum of the quiet sun: first results 2. how to...

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