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