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

kallunki@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?