MWA “burst mode”: Nov 2008 Solar 32 T Observations Vasili Lobzin and Iver Cairns, School of Physics, University of Sydney Canberra 19/1/2009 I. Context II. Observations & Interpretation III. Summary
Jan 18, 2016
MWA “burst mode”: Nov 2008 Solar 32 T Observations
Vasili Lobzin and Iver Cairns,
School of Physics, University of Sydney
Canberra 19/1/2009
I. ContextII. Observations & InterpretationIII. Summary
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
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
“Burst Mode” Solar Obs: 20 Nov 2008
f (MHz)
0
328
04:00:30.804:02:26.8Time
• Vertical, variable signals? Bands of noise? Interference signals? • Any natural signals ….?
Spectra: averaging & background subtraction
• (Left) Averaging & (top) background subtraction structure in interference
• Vertical signals not solar type IIIs since:
1. no freq drift &
2. don’t have Δt ↑ as f ↓
0
f
328MHz
Time (2 mins)
AVG
MWA “vertical signals”: no analogues at Culgoora interference
• No similar bursts in Culgoora (NSW) data (duration or appearance)
noise at MWA
0
f
328MHz
Time (2 mins)
57
180MHz
18
Culgoora lightning (storm near Sydney)
57Freq
18
75
180MHz
MWA “vertical signals”: impulsive local interference
• Δf ~ 100 – 300 MHz spikes ~ 10 - 3 ns duration.
• 50 sweep (0.05s) averages, then subtract background periodicity ≈ 3.6 Hz
• Intensifies with other interference.
0
f
328MHz
Time (2 mins)
0 10 20 30 40 50 60 70 80 90 100-2
-1.5
-1
-0.5
0
0.5
1
time, array index
0 1 2 3 4 5 6 7 8 9 1010
11
1012
1013
1014
frequency, Hz
Pow
er S
pect
ral D
ensi
ty
65
“signal energy”
Frequency (Hz)
power spectrum
Vertical signals intensify with other interference
65
Freq
0
75
328MHz
mwa1, files 400-499, averaging over 100 sweeps + background subtraction
time, array index
freq
uenc
y, a
rray
inde
x
10 20 30 40 50 60 70 80
50
100
150
200
250-1
0
1
2
3
4
5
6
7
8
9x 10
5
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 ~ 3 -10 ns in duration.
• Desire to remove interference sources for future burst mode observations.