Results of comparative analysis of the SEP events and the microwave bursts observed by 2÷24 GHz and 4÷8 GHz spectropolarimeters in 2010÷2016
We compared the data of the microwave burst catalog obtained by BBMS [Zhdanov, et al., 2011] with the SEP event catalog obtained by Wind/EPACT [Miteva, et al. 2018]. Microwave observations are available only from 2010, and it is limited by local day time (0÷10 UT). There are 172 events in the SEP event catalog in the period 2010 to 2016. Only 39 events from them took place between 0 and 10 UT that could be observed by the spectropolarimeters. We carried out an analysis of 39 events and found that the 18 events are typical microwave bursts. In the remaining 21 cases, three events were related with very weak flares (B8.1, C1.2, C4.6), seven events had no microwave features, we could not reveal the solar flares associated with another seven events, and for four events, microwave observations finished earlier than 10 UT. We focused further on the 18 events associated with microwave bursts. We processed the data, plotted the microwave spectrum and determined the following parameters for each event: the flux value at maximum; the frequency of spectral maximum; presence and sign of the polarization and the frequency of the maximum polarization value. The spatial distribution of the microwave bursts indicates to more active northern hemisphere (Fig. 1).
 |
|
| a) | b) |
Fig. 1 SEP source mapping; circles are positions of microwave bursts; sizes of circles depend on both strength of the microwave flux and the degree of polarization. |
|
Table 1 shows the obtained results. The peak frequencies of the microwave bursts vary within 2 GHz and 10 GHz. The circular polarization in microwave emission was found in 10 of the selected events. We did not reveal any dependence between the position of the solar origin of the SEP event and the sign of circular polarization. Further analysis of the selected and processed data will allow getting additional information about the properties of microwave emission of SEP event origins.
| NO | Date (yyyy‑mm‑dd) |
Time (UT) | GOES class | Fluxmax (sfu) | Fmax (GHz) | V/I (%) |
Fmax V (GHz) | Position |
|---|---|---|---|---|---|---|---|---|
| 0 | 2011-02-15 | 01:44 | X2.2 | 1000 | 8 | no | no | S20W10 |
| 1 | 2011-06-07 | 06:16 | M2.5 | 800 | 6.5 | no | no | S21W54 |
| 2 | 2011-08-09 | 07:48 | X6.9 | 2000 | 10 | no | no | N17W69 |
| 3 | 2012-01-23 | 03:38 | M8.7 | 8000 | 4 | +10 | 4 | N28W21 |
| 4 | 2012-03-07 | 01:05 | X1.3 | 7000 | 9.4 | -30 | 3.7 | N22E12 |
| 5 | 2012-05-17 | 01:25 | M5.1 | 600 | 5 | no | no | N11W76 |
| 6 | 2013-03-15 | 05:46 | M1.1 | 120 | 1.5 | -15 | 7.5 | N11E12 |
| 7 | 2013-05-15 | 01:25 | X1.2 | 1600 | 7 | -18 | 6.5 | N12E64 |
| 8 | 2013-06-21 | 02:30 | M2.9 | - | - | - | - | S16E73 |
| 9 | 2013-11-02 | 04:40 | C8.2 | - | - | - | - | S23W04 |
| 10 | 2014-02-20 | 07:26 | M3.0 | 500 | 6 | +20 | 6 | S15W73 |
| 11 | 2014-12-17 | 04:25 | M8.7 | 800 | 7 | -30 | 13 | S20E09 |
| 12 | 2015-06-18 | 00:33 | M1.2 | 60 | 2 | -20 | 2 | S16W81 |
| 13 | 2015-06-21 | 02:06 | M2.6 | 1100 | 7.5 | no | no | N13E10 |
| 14 | 2015-06-25 | 08:02 | M7.9 | 4500 | 9 | +10 | 17 | N09W42 |
| 15 | 2016-03-16 | 06:34 | C2.2 | 8 | 3.5 | no | no | N12W88 |
| 16 | 2016-04-18 | 00:14 | M6.7 | 400 | 6 | -8 | 9 | N12W62 |
| 17 | 2016-07-23 | 05:00 | M7.6 | 850 | 2.5 | +20 | 10 | N05W73 |
References
Miteva R., Samwel S. W., Costa-Duarte M. V., The Wind/EPACT Proton Event Catalog (1996÷2016),
(2018) Solar Physics, 293, no. 2, article id. 27, 44.
Zhdanov D.A., Zandanov V.G., Broadband microwave spectropolarimeters,
(2011) Central European Astrophysical Bulletin, 35, 223-227.
