1. MWA “burst mode”: Nov 2008 Solar 32 T Observations
Vasili Lobzin and Iver Cairns,
School of Physics, University of Sydney
Context
Observations & Interpretation
Summary
Canberra 19/1/2009

2. I. Context for “Burst Mode” Solar Obs
MWA has strong solar, heliospheric, and ionospheric science objectives
Burst Mode:
0 – 328 MHz spectra, 256 * 1.28 MHz channels
1 spectrum per 0.78 μs every 1 ms (0.938 ms)
“engineering” mode, but great for solar science
Highest known cadence, resolution and bandwidth
Imaging?
17 and 20 November 2008, close to local noon.

3. Solar Radio Bursts

4. II. “Burst Mode” Solar Obs: 20 Nov 2008
mwadas1,2,&4, each 16 pipes,~ 600 files
~ 04:00:30 – 04:02:27 (~0.1 s accuracy)
Power spectrum summed over all pipes 

5. “Burst Mode” Solar Obs: 20 Nov 2008f
(MHz)
328
04:00:30.8
Time
04:02:26.8
Vertical, variable signals? Bands of noise? Interference signals?
Any natural signals ….?

6. Spectra: averaging & background subtractionf
328
MHz
(Left) Averaging & (top) background subtraction  structure in interference
Vertical signals not solar type IIIs since:
no freq drift &
don’t have Δt ↑ as f ↓
AVG
Time (2 mins)

7. MWA “vertical signals”: no analogues at Culgoora  interference18 f 57
328
MHz
Time (2 mins)
180
MHz
No similar bursts in Culgoora (NSW) data (duration or appearance)
 noise at MWA

8. Culgoora lightning (storm near Sydney)18 75
Freq 57
180
MHz

9. MWA “vertical signals”: impulsive local interference65 f
“signal energy”
328
MHz
Time (2 mins)
power spectrum
Δf ~ 100 – 300 MHz  spikes ~ ns duration.
50 sweep (0.05s) averages, then subtract background  periodicity ≈ 3.6 Hz
Intensifies with other interference.
Frequency (Hz)

10. Vertical signals intensify with other interference65 75
Freq
328
MHz

11. III. Summary
“Burst mode” data should be attractive for solar work (very high cadence, wide bandwidth).
Analysis of 2 mins of 20 Nov 32T data show
Noise & interference bands,
Vertical signals that don’t appear to be natural:
No analogues in Learmonth & Culgoora data;
3.6 Hz periodicity in energy;
They intensify with other interference;
 likely impulsive signals ~ ns in duration.
Desire to remove interference sources for future burst mode observations.