Technical improvements and possibilities to observe solar oscillations with the small Metsähovi...
-
date post
20-Dec-2015 -
Category
Documents
-
view
218 -
download
2
Transcript of Technical improvements and possibilities to observe solar oscillations with the small Metsähovi...
Technical improvements and possibilities to observe solar oscillations with the small
Metsähovi radiotelescope
Juha Kallunki
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?