EMIC waves and associated relativistic electron precipitation on 25–26 January 2013

Abstract

Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (EMIC) waves and associated relativistic electron precipitation (REP) observed on 25–26 January 2013. Among all the EMIC wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe‐B detected significant EMIC waves at L = 2.1–3.9 and magnetic local time (MLT) = 21.0–23.4 for 53.5 min from 2353:00 UT, 25 January 2013. Meanwhile, BARREL‐1T observed clear precipitation of relativistic electrons at L = 4.2–4.3 and MLT = 20.7–20.8 for 10.0 min from 2358 UT, 25 January 2013. Local plasma and field conditions for the excitation of the EMIC waves, wave properties, electron minimum resonant energy Emin, and electron pitch angle diffusion coefficient Dαα of a sample EMIC wave packet are examined along with solar wind plasma and interplanetary magnetic field parameters, geomagnetic activity, and results from the spectral analysis of the BARREL balloon observations to investigate the two types of events. The events occurred in the early main phase of a moderate storm (min. Dst* = −51.0 nT). The EMIC wave event consists of two parts. Unlike the first part, the second part of the EMIC wave event was locally generated and still in its source region. It is found that the REP event is likely associated with the EMIC wave event.

Pitch Angle Scattering of Sub‐MeV Relativistic Electrons by Electromagnetic Ion Cyclotron Waves

“…While there have been good reasons to believe that EMIC waves can strongly affect ultrarelativistic electrons with energies above 2 MeV (Meredith et al, ; Shprits et al, ), it has been less clear how EMIC waves could affect sub‐MeV relativistic electrons. Yet recent observational results have suggested that precipitating electrons may have such low energies (Hendry et al, ; Millan et al, ; Zhang et al, , and references therein). The Hendry et al () results, using a very large database of precipitation events observed by the POES spacecraft (see also Carson et al, ; Hendry et al, ), are particularly important.…”

“…This mechanism has been considered by some researchers to be an important loss mechanism for radiation belt electrons (Millan & Thorne, ; Shprits et al, ). Recent experimental results include simultaneous observation of EMIC waves and relativistic electron precipitation (Blum et al, ; Clilverd et al, ; Hyun et al, ; Kersten et al, ; Li et al, ; Miyoshi et al, ; Rodger et al, ; Zhang et al, ).…”

The Rapid Responses of Magnetosonic Waves to the Compression and Expansion of Earth's Magnetosphere

“…Moreover, the bursts of ultralow‐frequency waves, electromagnetic ion cyclotron waves, plasmaspheric hiss, and whistler mode chorus waves have been observed during the magnetospheric compression period (Fu et al, ; Li, Yu, Cao, & Yuan, ; Li, Yu, Cao, Wang, et al, ; Yu et al, ). The enhanced waves or the gradual change in magnetic field can further affect energetic particles in the radiation belt (Li et al, , , ; Li, Yu, Cao, & Yuan, ; Li, Yu, Cao, Wang, et al, ; Ni et al, ; Thorne, ; Zhang et al, ).…”

Rapid Loss of Radiation Belt Relativistic Electrons by EMIC Waves

“…The POES system at low altitudes ∼800 km (Evans & Greer, ) are usually expected to monitor the radiation belt electron precipitation (Horne et al, ; Turner et al, ; Zhang, Halford, et al, ). On 27 February 2014, data of six POES satellites (MetOp‐2/A, MetOp‐2/B, NOAA 15, NOAA 16, NOAA18, and NOAA 19) were available (Figure ).…”

“…Wave‐driven pitch angle scattering can reduce the altitudes of electron mirror points, and collisions with atmospheric particles yield the precipitation loss of electrons. The primary characteristic of radial loss is a radially peaked PSD profile (Turner et al, ; Mann et al, ), while the main evidences for local loss are the flat‐top PAD characteristic (Usanova et al, ; Engebretson et al, ; Su et al, ; Shprits et al, ) and the wave‐related electron precipitation observed at low altitudes (Lorentzen et al, ; Millan et al, ; Miyoshi et al, ; Tsurutani et al, ; Breneman et al, ; Zhang, Halford, et al, ).…”