The Next Generation in Solar Flux
Monitoring
Ken Tapping
ken.tapping@nrc-cnrc.gc.ca
DRAO
F10.7 Flux
Monitors
Calibration
Horns
Next Generation Solar
Flux Flux Monitor
Solar Radio Monitoring Programme
DRAO, Penticton, Canada
Flux Monitor 1
(Secondary)
Flux Monitor 2
(Primary)
Dual Horn Calibration System
FM#1/FM#2 Flux Ratio
1.03
1.02
1.01
FM#1/FM#2
1
0.99
0.98
0.97
0.96
6
6.5
7
7.5
8
Month in 2011
8.5
9
9.5
Six-Month running
means
Six-month running
standard deviations
( F10.7 ) 0.446 ( N S ) 2 exp( 0.027 ( N S ))
66
F10.7 and
Sunspot
Number
( F10.7 ) 0.2299 ( N S )1.3255
0.25
0.2
2(O-P)/(O+P)
0.15
0.1
observed proxy
2
observed proxy
0.05
0
-0.05
-0.1
1945
1950
1955
1960
1965
1970
1975
1980
Year
1985
1990
1995
2000
2005
2010
2015
Where Does F10.7 Come From?
Corona
Bright emission
from thermal
electrons trapped
in strong magnetic
fields overlying
sunspots.
Free-Free emission
from thermal plasma
Concentration Trapped
in Active Region
Magnetic Fields
Photosphere and Below
S-Component Spectrum (Flux Density)
400
Initial NGSFM
Operating
Wavelengths
350
Flux Density (sfu)
300
Quiet
Active (Thermal)
Active (Thermal + g-r)
250
200
Possibilities for
the additional
wavelengths
150
100
50
0
0
5
10
15
20
Wavelength (cm)
25
30
35
Next Generation Solar Flux Monitor Requirements
• To make precise flux determinations at enough wavelengths for the
spectrum of the S-component to be obtained.
• What would happen if we integrated over the whole spectrum,
accommodating all the amplitude and peak frequency variations? Is
that even possible in the DRAO electromagnetic environment?
• To monitor the Sun with high time resolution for identification of
bursts and perhaps reconnection events associated with the lift-off
of coronal mass ejections.
• To provide a degree of redundancy for on-going data checks and to
increase fault tolerance.
• To reach at least the calibration and data quality standards currently
used with F10.7. This will require using identical measurement
techniques on identical equipment.
NGSFM Antenna
The Day We Put it Together
Antenna Arrangement
Angular diameter of the patch of dish “seen” by
the horn (horn diameter is d:
D
x
Diameter of patch of dish seen by the horn:
Beamwidth of antenna at that wavelength:
x
f
D
H
d
Beamwidth is independent of wavelength until x=>D
We want a beamwidth of about 5 degrees. This
will require d/f = 0.09 (f 10d). For a feed 10cm
in diameter, we want a dish with a 1m focal
length and to give a 5-degree beam at the longest
wavelength (30cm), a diameter of more than 3.6m
57
H
f
57
d
H
57
x
d
57
f
Ultimate Objective
4-m Dish (112 GHz)
Focus Box
(x) front-end
(y) front-end
* Under Construction. Will be
used for a while at Queen’s U
for interference studies and
then shipped to DRAO for solar
observations
Piggy-Back Log
Periodic Antenna
(0.1-1 GHz) ETH,
Switzerland**
** Under
Discussion
(x) Receiver Box
PC-104
(y) Receiver Box
PC-104
High Time
Resolution
Spectrometer
(1-18 GHz)
(Queens U.)*
“Callisto” High
Time Resolution
Dynamic
Spectrometer
Receiver
(0.1-1 GHz), ETH,
Switzerland*
Supervisor
Computer
Network
NGSFM-RX (One Polarization)
To Queen’s U.
Spectrometer
Coax from Focus
Box to Receiver Box
Splitter
1.4 GHz
(2.8 GHz)
4.9 GHz
8.4 GHz
10.6 GHz
Broadband
(1.4-8.4 GHz)
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
Band-Pass
Filter
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
GaAsFET
Amplifier
Demodulator
/Digitizer
Demodulator
/Digitizer
Demodulator
/Digitizer
Demodulator
/Digitizer
Demodulator
/Digitizer
Demodulator
/Digitizer
PC-104
To Supervisor
Trials Using the Broadband Test Receiver
NGSFM – First Light: 20110908
Broadband Tests: 20110908
(1.5 - 8.5 GHz)
6
Overload
5.5
Small Flare
5
RX Output Voltage
4.5
4
Calibrations
3.5
3
??
2.5
2
1.5
0
1
2
3
4
5
6
7
8
9
10
11
Time in Minutes
12
13
14
15
16
17
18
19
20
Calibration
•
•
The NGSFM cannot be intrinsically
calibrated. An absolute calibration standard
is needed for each wavelength. This can be
handled using separate calibration horns
attached as outriggers to the existing horns.
The 21cm calibration will be using the lower,
spare horn, which means its beam will be a
bit fat.
Calibrating the broadband measurements is
more problematic. The current idea is to
take the spot measurements made using the
horns, fit a curve, integrate under it and use
that to calibrate the broadband flux.
3cm
4cm
10.7cm
21cm
6cm
Finally…
• Operations with the NGSFM are due to start in 2013.
• The existing flux monitors, producing F10.7, will continue
to operate. The F10.7 capability of the NGSFM will be a
backup and an additional fixing point for crosscalibration.
• We have no plans to terminate the existing flux monitors
when the NGSFM enters service. The NGSFM will
simply become FM#3.
F10.7
What’s Right About It
•
•
•
•
It is a very good indicator of the
general level of solar magnetic
activity.
It is a successful basis for proxies
for various solar emission
components and solar
parameters.
It is easy to measure and monitor
with high objectivity. It is highly but
not totally observer-independent.
We have a consistent, continuous
database covering more than 60
years.
What’s Wrong With It
•
•
•
It contains contributions from at
least two emission components
(thermal free-free and thermal
gyroresonance). The former is
related to plage and the latter to
sunspots.
It is not therefore fully clear what it
is an index of.
Since sunspot and plage area are
not consistently proportional to
one another, this can degrade its
applicability to proxies (as our
needs get tighter and tighter).
The Problems With F10.7
•
•
•
For better proxies, and science, we need to separate the contributions from
thermal gyroresonance and thermal free-free emission. The former makes
the bump in the spectrum and the latter the monotonic decrease with
increasing wavelength. To separate them requires the spectrum, not a
single-wavelength measurement.
During the solar activity cycle, the spectrum of the S-component changes
both amplitude and to a small extent, the wavelength of the spectral peak. A
single-wavelength measurement reflects both variations inseparably.
There are occasionally contributions by non-thermal emission mechanisms,
which are often hard to eliminate.
Although we want to keep our current measurements of F10.7 going
indefinitely, it would be very useful if we could measure the S-component
spectrum, and provide additional indices hopefully reflecting the
contributions by different emission mechanisms.
The S-Component Spectrum
Solar Radio Spectrum
100000
Active Sun
Quiet Sun
Series3
10000
106 K Black Body
Flux Density sfu
1000
S=Component = Difference
100
104 K Black Body
10
F
2k
2
( , t )Tchrom (1
(t , ))Tcor
1
0.1
0.1
1
10
10.7 cm
Wavelength (cm)
100
1000
Specification for the NGSFM
• Antenna half-power beamwidth to stay in the range 3 – 5 degrees
over the wavelength range 21 – 3 cm (1.4 – 10 GHz).
• Multi-wavelength operations: 21cm, 10.7 cm, 6cm, 4 cm, 2.8 cm and
“broadband”.
• Dual orthogonal linear polarization (not primarily for science, for
redundancy and backup).
• Three precise flux determinations a day plus a “continuous record”
from sunrise to sunset, for each polarization and wavelength.
• Time resolution in continuous record better than 10ms, target is
1ms.
• Modular system that can be duplicated totally or in part in the
construction of other instruments.
Next Generation Solar Flux Monitor Requirements
• The changes we want to monitor can be quite subtle. The best way
to monitor them would be to use a single antenna for all the
wavelengths, with an antenna beamwidth that is (fairly) independent
of observing wavelength. This will make it more likely that any small
perturbation would apply to all wavelengths, so that the ratios are
less likely to be affected.
• We need to apply a common approach to calibration for all
wavelengths. Again this is best met using a single system for all
wavelengths.
• Assuming there are always some sort of linearity/dynamic range
issue somewhere, a common design theme for all wavelengths
would make it easier to identify deviations.
An Under-Illuminated Dish
As the wavelength
changes, so does the
fraction of the
antenna, so that to a
first order, the
beamwidth of the
feed/antenna
combination remains
unchanged.
Ultimate Objective
Piggy-Back Log
Periodic Antenna
(0.1-1 GHz) ETH,
Switzerland*
4-m Dish
(1-12 GHz)
Focus Box
* Under
Discussion
“Callisto” High
Time Resolution
Dynamic
Spectrometer
Receiver
(0.1-1 GHz), ETH,
Switzerland*
Main
Receiver
Box
Computer(s)*
Computer(s)
Network
** Under Construction. Will be
used for a while at Queen’s U
for interference studies and
then shipped here for solar
observations
High Time
Resolution
Spectrometer
(1-18 GHz)
(Queens U.)**
Computer(s)
F10.7
Monthly Means
300
Sunspot Number
F10.7
Flux in sfu or Sunspot Number
250
200
150
100
50
0
1945
1950
1955
1960
1965
1970
1975
1980
Year
1985
1990
1995
2000
2005
2010
2015
Comparison of FM#1 and FM#2 Flux Values
160
150
140
130
FM#1
FM#2
Flux Density in sfu
120
110
100
90
80
70
60
50
6
6.5
7
7.5
8
Month in 2011
8.5
9
9.5