juha kallunki kallunki@kurp.hut.fi metsähovi radio observatory
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Technical improvements and possibilities to observe solar oscillations with the small
Metsähovi radiotelescope
Juha Kallunkikallunki@kurp.hut.fi
Metsähovi Radio Observatory
Metsähovi small radiotelescope • Total intensity
measurements• Facts:
– Diameter: 1,8 m (beam size: 81,6 arc min)
– Center frequency: 11,2 GHz– Band: 1 GHz– two different sample record
interval• Since 2001• To detect solar flare
”fishing float”• Average level of total
intensity
Recent technical upgrades and studies
• Solve technical problems– weather effects mechanical improvements
– calibration some method to do calibration– pointing renewing the pointing algorithm– ”inner oscillations”
• To study possibility to observe solar oscillations
Observations (1/2)
• About 100 observation days --> selection based on stability of intensity (weather, power outages, service…), between 2007-2008 (May-August) period of low solar activity
• Each day, period of 8 hours (the highest elevation)
• 50 samples per second one second average• FFT analysis• Cold and hot load measurements
Observations (2/2)
Antenna inner oscillations• 10-15 days with hot load (ideal
attenuator) ambient temperature• Same measurement principle• All values are in relative units• Also with cold load (sky)
measurements• Amplitudes of inner oscillations are
less than 5% for the typical level of solar oscillations
• Possible reasons:– EMC– Reflections– Mechanical vibrations– etc.
extremely difficult to say exact reason
0 – 5 min(1540)
5 – 10 min
(2820)
10 – 15 min
(4960)
Avg. 12,9 29,6 55
Min. 5 10 30
Max. 20 50 100
Classification of solar oscillations
• Own classification • Choosing the highest
amplitude at certain interval
• We have been concentrated to study oscillations in interval of 3-15 minutes.
Interval Class
2 - 4 min 3 min
4 - 7,5 min 5 min
7,5 – 12,5 min 10 min
12,5 - 17,5 min
15 min
Solar oscillations (1/2)
Solar oscillation (2/2)
3 min 5 min 10 min 15 min
Avg. 770 1540 2820 4960
Standard deviatio
nσ
46 83 171 358
Bigger antenna vs. small antenna (1/2)
• big antenna (36,8 GHz; 2,5 arcmin)• some comparison during solar flares• big antenna: track of active area• small antenna: whole disk
Bigger antenna vs. small antenna (2/2)
• Big antenna • Small antenna
Conclusions
• possible to observe solar oscillations with small antenna
• of cource it is not possible to say about coordinates of the flare, for that we need to use some other observation instruments, for example big antenna
• in case of solar flares can be seen similarities between small and big antenna
Future works
• more observations (”active periods”)• simultaneous observations with big and
small radiotelescopes• possible technical improvements
– radome– dicke radiometer– etc.
The EndQuestions?
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