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 FM#1/FM#2 Flux Ratio 1.03 1.02 1.01 1 0.99 0.98 0.97 0.96 6 6.5 7 7.5 8 8.5 9 9.5 Month in 2011
Six-Month running means Six-month running standard deviations
( F 7) 0.446 ( N S ) 2 exp( 0.027 ( N 10. S )) 66 F10.7 and Sunspot Number 1.3255 ( F10.7) 0.2299 ( NS )
2(O-P)/(O+P) 0.25 0.2 0.15 0.1 0.05 0 2 observed observed proxy proxy -0.05-0.1 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Year
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
Flux Density (sfu) S-Component Spectrum (Flux Density) 400 350 Initial NGSFM Operating Wavelengths 300 250 Quiet Active (Thermal) Active (Thermal + g-r) 200 150 Possibilities for the additional wavelengths 100 50 0 0 5 10 15 20 25 30 35 Wavelength (cm)
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: H 57 d x D f H d Diameter of patch of dish seen by the horn: Beamwidth of antenna at that wavelength: Beamwidth is independent of wavelength until x=>d x f H 57 D 57 57 x d f 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
Ultimate Objective 4-m Dish (1-12 GHz) Focus Box (x) front-end (y) front-end (x) Receiver Box (y) Receiver Box PC-104 PC-104 * Under Construction. Will be used for a while at Queen s U for interference studies and then shipped to DRAO for solar observations High Time Resolution Spectrometer (1-18 GHz) (Queens U.)* Supervisor Computer Piggy-Back Log Periodic Antenna (0.1-1 GHz) ETH, Switzerland** ** Under Discussion Callisto High Time Resolution Dynamic Spectrometer Receiver (0.1-1 GHz), ETH, Switzerland* Network
NGSFM-RX (One Polarization) To Queen s U. Spectrometer Splitter 1.4 GHz (2.8 GHz) 4.9 GHz 8.4 GHz Band-Pass Filter Band-Pass Filter Band-Pass Filter Band-Pass Filter 10.6 GHz Band-Pass Filter Coax from Focus Box to Receiver Box Broadband (1.4-8.4 GHz) 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
RX Output Voltage NGSFM First Light: 20110908 Broadband Tests: 20110908 (1.5-8.5 GHz) 6 Overload 5.5 5 Small Flare 4.5 4 Calibrations 3.5 3 2.5?? 2 1.5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time in Minutes
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 6cm 21cm
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 What s Wrong With 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. 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.
Flux Density sfu The S-Component Spectrum 100000 10000 Solar Radio Spectrum 10 6 K Black Body Active Sun Quiet Sun Series3 1000 S=Component = Difference 100 10 4 K Black Body 10 1 2k F (, t) T (1 ( t, )) 2 chrom T cor 0.1 1 10 100 1000 0.1 10.7 cm Wavelength (cm)
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* Callisto High Time Resolution Dynamic Spectrometer Receiver (0.1-1 GHz), ETH, Switzerland* 4-m Dish (1-12 GHz) Focus Box Main Receiver Box ** 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.)** * Under Discussion Computer(s)* Computer(s) Computer(s) Network
Flux in sfu or Sunspot Number F10.7 Monthly Means 300 Sunspot Number F10.7 250 200 150 100 50 0 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Year
Flux Density in sfu Comparison of FM#1 and FM#2 Flux Values 160 150 140 130 120 FM#1 FM#2 110 100 90 80 70 60 50 6 6.5 7 7.5 8 8.5 9 9.5 Month in 2011