11:00 AM - 1:00 PM
[PEM11-P01] Multi-event analysis of simultaneous pulsating aurora and microburst observations with ground-based fast auroral imager and FIREBIRD-II CubeSats
Keywords:pulsating aurora, mircroburst, cubesat
We report the relationship between pulsating aurora and relativistic electron microburst using multi events of simultaneous observations of ground-based fast auroral imagers and the FIREBIRD-Ⅱ CubeSat.
A pulsating aurora is known as one of the diffuse aurorae that blinks in seconds to tens of seconds, and it is generated by precipitation of ∼5–∼30 keV electrons. A microburst is the periodic and short durational precipitation of ∼MeV energy electrons. These two phenomena have similar spatiotemporal features. Otherwise, the energy of the electrons is different between them. Recent theoretical study predicts that chorus waves propagating along the field line generate ∼10 keV electron precipitation and the microburst at the different latitudes on the same field line, that is, both pulsating aurora and microbursts are same product of the chorus wave particle interactions. Showing the relationship between them is of important because it suggests that the pulsating aurora can be an indicator of high-energy electron descent that affects the mesosphere such as microburst. In this study, we examined the data taken by ground optical auroral EMCCD imagers (100 Hz sampling, BG3 grass filter) and high-energy electron data (∼220 keV to >1 MeV) obtained by a low-altitude (433 ~ 632 km) satellite FIREBIRD-II CubeSat to clarify the relationship between pulsating aurora and microburst. We report the results of one case study (Case 1) and multi event analysis of five cases in this presentation.
In Case 1, we analyzed the simultaneous observation event on October 8, 2018 by the EMCCD camera installed at Pokar Flat Research Range (PFRR) and FU3 of FIREBIRD-II and. Near 11:50:50 UT on October 8, 2018, FU3 passed over multiple pulsating aurora patches observed by PFRR. At this time, FU3 observed a microburst 7 seconds after the start of the emission timing of the pulsating aurora. At the same time, the Arase satellite and Van Allen Probes (Radiation Belt Storm Probes-B: RBSP-B) were located at the low latitude from the FU3. From the wave and particle measurement data, it was suggested that both the pulsating aurora and the microburst were generated by electrons that resonated with the chorus waves. It was speculated that the timing difference between the pulsating aurora and the microburst was caused by the oblique propagation of the chorus waves, the resonance energy of the chorus waves, and the spatial distribution of the electrons at the magnetosphere.
In addition, we compared five simultaneous observation events of the ground EMCCD camera and FIREBIRD-II, including the analysis events in Case 1 and Kawamura et al. (2021). As a result, the pulsating aurora of all five events was accompanied by internal modulation, the L value was 6.0 or less, and the shape of the patch was clear. Since the magnetic activity of these events was high, it was considered that the generation of pulsating aurora accompanied by microburst requires the injection of high-energy electrons into the internal magnetosphere associated with the magnetic storm. From this analysis, the following two conditions could be derived for the conditions of the pulsating aurora with microburst. (i) High-energy electrons are generated by injection into the inner magnetosphere, electrons that are the source of pulsating aurora and microburst exist in the magnetosphere, and resonance conditions with chorus waves are satisfied. (ii) Chorus waves propagate to high magnetic latitudes. At this time, the place where the pulsating aurora and the microburst are generated in the ionosphere is different due to the difference in the propagation direction of the chorus wave.
In the future, in order to more understand the conditions and characteristics of the pulsating aurora with and without microburst, it is necessary to study the simultaneous observation of particles, optics, and waves and we have to do statistical analysis by the simultaneous observation events with high time resolution.
A pulsating aurora is known as one of the diffuse aurorae that blinks in seconds to tens of seconds, and it is generated by precipitation of ∼5–∼30 keV electrons. A microburst is the periodic and short durational precipitation of ∼MeV energy electrons. These two phenomena have similar spatiotemporal features. Otherwise, the energy of the electrons is different between them. Recent theoretical study predicts that chorus waves propagating along the field line generate ∼10 keV electron precipitation and the microburst at the different latitudes on the same field line, that is, both pulsating aurora and microbursts are same product of the chorus wave particle interactions. Showing the relationship between them is of important because it suggests that the pulsating aurora can be an indicator of high-energy electron descent that affects the mesosphere such as microburst. In this study, we examined the data taken by ground optical auroral EMCCD imagers (100 Hz sampling, BG3 grass filter) and high-energy electron data (∼220 keV to >1 MeV) obtained by a low-altitude (433 ~ 632 km) satellite FIREBIRD-II CubeSat to clarify the relationship between pulsating aurora and microburst. We report the results of one case study (Case 1) and multi event analysis of five cases in this presentation.
In Case 1, we analyzed the simultaneous observation event on October 8, 2018 by the EMCCD camera installed at Pokar Flat Research Range (PFRR) and FU3 of FIREBIRD-II and. Near 11:50:50 UT on October 8, 2018, FU3 passed over multiple pulsating aurora patches observed by PFRR. At this time, FU3 observed a microburst 7 seconds after the start of the emission timing of the pulsating aurora. At the same time, the Arase satellite and Van Allen Probes (Radiation Belt Storm Probes-B: RBSP-B) were located at the low latitude from the FU3. From the wave and particle measurement data, it was suggested that both the pulsating aurora and the microburst were generated by electrons that resonated with the chorus waves. It was speculated that the timing difference between the pulsating aurora and the microburst was caused by the oblique propagation of the chorus waves, the resonance energy of the chorus waves, and the spatial distribution of the electrons at the magnetosphere.
In addition, we compared five simultaneous observation events of the ground EMCCD camera and FIREBIRD-II, including the analysis events in Case 1 and Kawamura et al. (2021). As a result, the pulsating aurora of all five events was accompanied by internal modulation, the L value was 6.0 or less, and the shape of the patch was clear. Since the magnetic activity of these events was high, it was considered that the generation of pulsating aurora accompanied by microburst requires the injection of high-energy electrons into the internal magnetosphere associated with the magnetic storm. From this analysis, the following two conditions could be derived for the conditions of the pulsating aurora with microburst. (i) High-energy electrons are generated by injection into the inner magnetosphere, electrons that are the source of pulsating aurora and microburst exist in the magnetosphere, and resonance conditions with chorus waves are satisfied. (ii) Chorus waves propagate to high magnetic latitudes. At this time, the place where the pulsating aurora and the microburst are generated in the ionosphere is different due to the difference in the propagation direction of the chorus wave.
In the future, in order to more understand the conditions and characteristics of the pulsating aurora with and without microburst, it is necessary to study the simultaneous observation of particles, optics, and waves and we have to do statistical analysis by the simultaneous observation events with high time resolution.