# Space Weather Effects from Observations by Moscow University Cubesat Constellation
## 4 Solar Energetic Particle Injection into Polar Cap  
A rather intensive solar flare of an X1.0 class occurred on 28 October 2021 at 15:17 UTC in the active region AR12887, located near the center of the solar disk, AR coordinates S28W01. It led to an acceleration of charged particles, i.e., protons and electrons. Charged particle counters onboard GOES satellites were detected on 28 October 2021, increasing fluxes of protons in a wide energy range (see Figure 3), while the electron detector onboard ACE satellite--increasing sub-relativistic electron flux. As could be seen from Figure 3, the second increase in the solar cosmic ray (SCR) flux was observed on 1 November 2021. It was associated with an M1.5 class flare that occurred on 1 November at 01:45 UTC, also in AR12887. A day later, on 2 November, a long-term flare again (M1.7 class) occurred in AR12887, with which a coronal mass ejection (CME) was associated. This CME turned out to be the so-called \"cannibal\", absorbing slower CMEs from previous flares. This CME may additionally accelerate SCR protons and electrons. As a result, a short increase in SCR  
Figure 2: Electron flux \(J_{\rm e}\) distribution on McIllwine parameter \(L\) before, during **(top panel)** and after **(bottom panel)** geo-magnetic disturbances late November–early December 2021. Color of curves corresponds to the color of dates presented on the panels. fluxes was observed around midnight from 3 to 4 November, both according to the ACE and GOES data. During the considered time, the DeCoR instrument on the Norbi satellite also recorded increases in energetic charged particle fluxes in the polar caps. Time dependences of DeCoR counting rates in two monitoring channels, which correspond to the detection of events predominantly in CsI(Tl) crystal and plastic scintillator, respectively, are presented in Figure 4. As it was mentioned above, events in CsI(Tl) are caused by the detection of gamma quanta with energies greater than 100 keV, while events in plastic scintillator--by the detection of electrons with energies greater than 300 keV. However, it is necessary to note that the plastic scintillator is also sensitive to protons with energies more than several MeV, which can penetrate through the aluminum layer of 150-micron thickness, which covers the detector input window. The CsI(Tl) scintillator can also detect electrons with energies of more than hundreds of keV due to bremsstrahlung, although its efficiency is much less than the efficiency of detection of gamma quanta with the same energies. It means that protons can input counts in the electron channel (plastic), while sub-relativistic and relativistic electrons--are in the gamma channel CsI(Tl). The curves presented in Figure 4 were recorded with a time resolution of 1 s for three-time intervals corresponding to the period before charged particle flux variations connected with solar flares, i.e., 25 October 2021, after the first SCR flux increase, i.e., on 29 October and before the SCR flux increase caused by CME, i.e., 3 November. As it could be seen from the figure before the SCR events, it was a typical picture of count variations along with the low altitude and high inclination orbit (see top panel of Figure 4). There are so-called latitude dependences quite visible in both channels, which are caused by the detection of local gamma quanta and electrons produced by energetic particles of galactic cosmic rays. Moreover, rather intensive maxima are clearly visible at the moments when the satellite crosses the outer radiation belt of the Earth. What is important is that in the quiet period, the time dependences of counts in both channels are rather flat in the polar caps, and the corresponding counting rates are much less than in the outer belt. The situation changed drastically after the first SCR event, i.e., 29 October. As we can see from the middle panel of Figure 4, counting rates increased significantly in the polar caps and became of the same value as in the outer belt, which practically ceased to appear on time dependencies.