Ivan Sergei1 

1 Mira Str.40-2, 222307, Molodechno Belarus

seriv76@tut.by

This article presents the results of radio observations in December 2020, as well as a study of the activity of  Geminids by the  Canadian orbital radar CMOR.

1 Introduction

The observations were carried out at a private astronomical observatory near the town of Molodechno (Belarus) at the place of Polyani. A 5 element-antenna directed to the west was used, a car FM-receiver was connected to a laptop with as processor an Intel Atom CPU N2600 (1.6 GHz). The software to detect signals is Metan (author – Carol from Poland). Observations are made on the operating frequency 88.6 MHz (the FM radio station near Paris broadcasts on this frequency). “The “France Culture” radio broadcast tranmitter (100 kW) I use is at about 1550 km from my observatory; It has been renewed in 1997.

The purpose of the radio observations was to monitor the activity of the main meteor streams to patrol the outburst activity of the Ursid meteor shower, and to check the activity of the sporadic background meteors. Listening to the radio signals 1 to 3 times a day for one hour was done in order to control the level of the hourly activity, as well as to distinguish between periods of tropospheric passage and other natural radio interference.

2 Geminids (GEM#0004)

The Geminid peak activity occurred between 21h and 22h UT on December 13, 2020, with hourly numbers of up to 240 echoes. Also, high flux activity was recorded in the interval 6h-7h UT on December 13. My results agree well with the IMO Meteor Calendar (Rendtel, 2020) which indicated that the peak flux activity was expected between December 13, 08h UT and December 14, 08h UT. The maximum number of meteor echoes heard at maximum was up to 330 echoes per hour. Since the radio method captures fainter meteors than the visual method, the peak is a day earlier than the traditional visual maximum (fainter particles encounter the Earth earlier than larger particles). Figure 1 Shows the maximum of minor meteor showers in black, medium activity showers in blue, variable activity showers in green and the major meteor shower in red.

Figure 1 shows the maximum of minor meteor showers in black, medium activity showers in blue, variable activity showers in green and the major meteor shower in red.

Figure 1 – Radio meteors echo counts at 88.6 MHz for December 2020.

 

Figure 2 – Heatmap for radio meteor echo counts at 88.6 MHz for December 2020.

Figure 2 – Heatmap for radio meteor echo counts at 88.6 MHz for December 2020.

Figure 3. - The result of calculating the hourly numbers of echoes of meteors by listening to the radio air for December 2020.

Figure 3 – The result with the calculated hourly numbers of echoes of meteors by listening to the radio signals for December 2020.

Figure 4. Number of meteor echoes at 20-minute intervals on December 22, 2020 from automatic radio observations

Figure 4 – Number of meteor echoes at 20-minute intervals on December 22, 2020 from automatic radio observations.

3 Ursids (URS#0015)

The Ursid meteoroid stream is one of the major showers at the end of the year in the month of December. For 2020, there were some dust trail encounters predicted based on the calculations by J. Vaubaillon, P. Jenniskens, E. Lyytinen and M. Sato for the period of December 22 03h – 22h (UT). (Rendtel, 2019).

The Ursid (#0015) maximum was recorded at 11h30m-12h30m UT (λʘ = 270.80° to 270.84°) on December 22, which agrees well with the predicted data. The hourly number of radio echoes heard was up to 150 per hour, while the one recorded by the Metan program was about 100 signals. This can be explained by the fact that the method with listening allowed to hear more very weak echoes, which cannot be registered by the program because of the settings for the threshold of triggering. If you reduce the threshold for the detection of music and speech signals, the program starts to record false detections, thus distorting the real picture of what is happening in the radio atmosphere. The threshold in the Metan program is set optimally as a result of many years of experimental observations. The total amount of time listening for meteor echoes in December was 62 hours. 

4 Fireballs

For the fireball activity statistics, I have selected signals from the log-files with a peak power of less than 10000 as being fireballs. Signals with a peak power of less than 10000 are an overlap of the echoes of one or two neighboring FM station, which results in random triggers in the Metan program.

For fireballs activity statistics, I have selected signals from log-files with a peak power of less than 10,000 as being fireballs. Signals with a peak power of less than 10,000 are an overlap of the echoes of two or one neighboring FM station, which leads to random triggers in the Metan program. Figure 5. Daily activity of radio fireballs in December 2020

Figure 5 – Daily activity of radio fireballs in December 2020.

Table 1 shows a list of the most powerful radio fireballs signals with Max>30000 , which were registered at night.

Table 1 – List of the most powerful radio fireball signals with Max>30000 in December 2020. Bck: Background signal level, Thr: Radio signal triggering (detection) threshold, L: signal duration ( sec.), A: amplitude signal power, Max: peak signal level, Noise: noise level.

Date and Time Bck Thr L A Max Noise
10.12.2020 23h01m19s 8083 3000 119.380 271003.940 35232 1270
11.12.2020 05h58m26s 6477 3000 15.080 80773.640 34389 1225
13.12.2020 23h22m52s 9030 3000 22.180 118066.700 31258 1817
14.12.2020 02h31m07s 8224 3000 9.780 49966.680 38715 2381
14.12.2020 16h19m26s 8988 3000 22.980 156795.060 34868 4370
14.12.2020 19h42m53s 8387 3000 13.980 44260.960 31884 3447
16.12.2020 01h00m22s 10072 3000 35.660 169521.720 33088 2221
16.12.2020 04h31m11s 9992 3000 16.540 194550.580 30689 870
21.12.2020 05h39m23s 8444 3000 12.280 74019.760 31289 1915
22.12.2020 04h09m56s 6925 3000 15.480 54248.320 32469 813
23.12.2020 02h31m42s 8298 3000 14.880 65045.100 35442 853
26.12.2020 04h05m32s 9382 3000 13.020 118174.320 30849 1142
28.12.2020 19h04m54s 7171 3000 18.280 102208.420 36636 3256
30.12.2020 00h35m44s 8369 3000 12.260 86668.620 30255 2258
30.12.2020 01h30m45s 8431 3000 10.680 70792.420 33978 3275

5 Geminids from CMOR data

The images were analyzed by CMOR radar ((Brown ,2005) data, the images were stored several times during the day. The SNR value determined by the MaximDL photometry software with correction modifications (R,Y,G) was used to determine the activity level. A manual search was performed to detect the most optimal SNR value. SNR values were obtained by moving the cursor over the radiant image on the radar maps. General formula for calculating the shower activity level:

SNRact = SNR1 + R + Y + G, where SNR1 is the total SNR level of the white and pink radiant area, R is the size in pixels of the radiation area on the radar maps, marked in red, Y is the size in pixels of the radiation area, marked in yellow on the radar maps, G is the size in pixels of the radiation area, marked in green on the radar maps. 

Geminids from CMOR data. The SNR value determined by the MaximDL photometry software with correction modifications (R,Y,G) was used to determine the activity level. A manual search was performed to detect the most optimal SNR value. SNR values were obtained by moving the cursor over the radiant image on the radar maps. General formula for calculating the shower activity level: SNRact = SNR1 + R + Y + G, where SNR1 is the total SNR level of the white and pink radiant area, R is the size in pixels of the radiation area on the radar maps, marked in red, Y is the size in pixels of the radiation area, marked in yellow on the radar maps, G is the size in pixels of the radiation area, marked in green on the radar maps. Figure 6 – The Geminid activity according to CMOR. (Signal -to-Noise Ratio – SNR is defined as the ratio of signal power to the background noise power).

Figure 6 – The Geminid activity according to CMOR. (Signal -to-Noise Ratio – SNR is defined as the ratio of signal power to the background noise power).

 

The maximum flux activity is recorded between 11h on December 13 and 9h on December 14, which is slightly earlier than the calculated time of the peak activity. This can be explained by the fact that radar observations are more sensitive and the Earth first crosses a swarm of smaller particles. A dual radiant flux structure appeared in late November, merging into a single radiant on December 5.

 

Figure 7– Geminid radiant position 14 December 2020 09 h 15 m UT according to CMOR.

Figure 7 – The Geminid radiant position 14 December 2020 09h15m UT according to CMOR.

Acknowledgment

I would like to thank Sergey Dubrovsky for the software they developed for data analysis and processing of radio observations, the team of the CMOR radar for making their observations public available. I thank Karol from Poland for the Metan software. I thank Jean-Louis Rault for the information about the FM transmitter in France. Thanks to Paul Roggemans for his help in the lay-out and the correction of this article.

References

Jones J., Brown P., Ellis K. J., Webster A. R., Campbell-Brown M., Krzemenski Z., and Weryk R. J. (2005). “The Canadian Meteor Orbit Radar: system overview and preliminary results”. Planetary and Space Science, 53, 413–421.

Rendtel Jurgen (2020). “Meteor Shower Calendar”. IMO.