Statistical survey of storm-time energetic particle precipitation

Journal Pre-proof Statistical survey of storm-time energetic particle precipitation Xingbin Tian, Yiqun Yu, Chao Yue PII:

S1364-6826(20)30024-9

DOI:

https://doi.org/10.1016/j.jastp.2020.105204

Reference:

ATP 105204

To appear in:

Journal of Atmospheric and Solar-Terrestrial Physics

Received Date: 10 June 2019 Revised Date:

22 December 2019

Accepted Date: 26 December 2019

Please cite this article as: Tian, X., Yu, Y., Yue, C., Statistical survey of storm-time energetic particle precipitation, Journal of Atmospheric and Solar-Terrestrial Physics (2020), doi: https://doi.org/10.1016/ j.jastp.2020.105204. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd.

Statistical survey of storm-time energetic particle precipitation Xingbin Tian1, Yiqun Yu1,2*, Chao Yue3 1

School of Space and Environment, Beihang University, Beijing, China

2

Key Laboratory of Space Environment Monitoring and Information Processing,

Ministry of Industry and Information Technology, Beijing, China 3

Department of Atmospheric and Oceanic Sciences, University of California, Los

Angeles, California, USA.

*Corresponding author: Yiqun Yu ([email protected])

Abstract Energetic particles precipitation, which transmits energy from the magnetosphere to the ionosphere, represents an important coupling process between two systems. In this study, we investigate the spatial distribution and temporal evolution of medium-energy (tens to hundreds of keV) energetic particle precipitation (both ions and electrons) with NOAA/POES observations. We found the following results: (1) During storm time, both energetic electron and proton precipitations exhibit dawn-dusk asymmetry in the equatorial plane, possibly caused by plasma waves that are excited and then interact with energetic electrons and protons at different local times. (2) The energetic proton precipitation appears to contain greater energy flux than electrons in storm time, which is contrary to the low-energy particle precipitation where the electrons carry the dominant precipitation energy. (3) The depth of the earthward inner boundary of precipitation in statistics is linearly correlated with geomagnetic activity levels, represented by the SYM-H index.

Key Points: 1.

Medium-energy (tens to hundreds of keV) energetic precipitation of electrons and protons both exhibits global asymmetry.

2.

Energetic proton precipitation appears to contain more energy flux than electrons, different from the scenario in low-energy particle precipitation.

3.

The Earthward extension of precipitation linearly correlates with the storm intensity measured by SYM-H index.

1. Introduction During geomagnetic storm time, various plasma waves can be excited, which subsequently lead to the acceleration or loss of charged particles in the magnetosphere via wave-particle interactions [Arnoldy et al., 1982; Belian et al., 1992; Summers and Thorne, 2003; Yue et al., 2009; 2019; Zong et al., 2009; Newell et al. 2009; Ni et al. 2008; Zhou et al., 2015; Foster et al., 2014]. The resonant interactions between the particles and waves can not only result in the energization of particles in the near-Earth region [e.g., Zhang et al., 2010, Albert, 2004; Jordanova et al., 2001; Kersten et al., 2014; Yu et al., 2019; Yue et al., 2016; An et al., 2017], but also deplete magnetospheric populations [Jordanova et al., 1997, Burton et al., 1975, Søraas et al., 2002, Ebihara et al., 2004; Liemohn et al., 2005; Ilie et al., 2017; Zaharia et al., 2008]. For example, electrostatic electron cyclotron harmonic (ECH) and upper-band whistler-mode chorus waves play important roles in interacting with electrons at energies of 100’s eV-10 keV [Ni et al., 2016; Newell, 2009]. Electromagnetic ion cyclotron (EMIC) waves can pitch-angle scatter electrons at relativistic energies [Thorne and Kennel 1971; Summers and Thorne 2003; Summers et al. 2007; Ma et al. 2016; Ni et al. 2015]. In addition, lower-band whistler-mode chorus and EMIC waves can also scatter electrons and protons respectively at intermediate energies of 1 keV–100 keV [Ni et al., 2016]. Following pitch angle scattering process, particles can move along magnetic field lines down to the upper atmosphere, representing an important loss mechanism of charged particles from the magnetosphere [Kennel and Petschek, 1966; Schulz, 1998 Zhang et al., 2015; Newell, 2009, 2010; Yu et al., 2018]. On the other hand, the precipitation provides important energy source for drastic changes in the upper atmosphere. Particles with different energies can impact on different altitudes in the ionosphere-thermosphere system [Fang et al., 2008] and cause different effects. While low-energy (E< 10 keV) particle precipitation is generally associated with diffusive aurora [Newell et al., 2009, 2010], energetic (>10 keV) particles can penetrate to lower altitude and are responsible for the pulsating aurora [Johnstone 1978; Sandahl et al. 1980; Kasahara et al. 2018; Miyoshi et al. 2015] or discrete aurora [Newell et al. 2009].

Turunen et al. [2016] studied a single event of pulsating aurora and found that energetic particles precipitating down to the atmosphere could create excessive amounts of odd nitrogen and odd hydrogen, leading to ozone destruction in the mesosphere and upper stratosphere. Yu et al. [2018] simulated the effects of magnetospheric electron precipitation on the ionosphere and found that energetic electrons with E>30 keV cause remarkable enhancement of ionization in low-altitude atmosphere (~ 80 km, the D region) and generate an extra layer of Pedersen conductivity. It is suggested that as a result of highly energetic electron precipitation, the Pedersen current system in the ionosphere and its closure with the magnetosphere are more complicated than thought before. In view of the importance of the precipitation in the ionosphere-thermosphere system, identifying the driving sources and understanding the effects of particle precipitation have been a long-lasting scientific topic. Earlier studies have examined the spatiotemporal dynamics of low-energy particle precipitation [e.g., Newell et al. 2009] under different geomagnetic activity levels as well as energetic electron precipitation [e.g., Rodger et al, 2008; Meredith et al., 2011; Ma et al., 2018], but the relative importance of energetic particle precipitation between electrons and protons during storms still lacks systematic understanding. Therefore, this study aims to examining the temporal evolution and global spatial distribution of both energetic (tens to hundreds of keV) electron and proton precipitation during storm time and understanding the dependence on geomagnetic activity levels using POES measurements. 2. Data sets The precipitation data of energetic electrons and protons are obtained from the NOAA's Polar Orbiting Environmental Satellites (POES) with the time resolution of 16 s. The six satellites are Sun-synchronous low-altitude polar orbiting spacecraft and have identical instrumentation. Their orbital period is about 102 min, resulting in 14.1 orbits each day. We use the particle measurements from the Medium Energy Proton and Electron Detector (MEPED) that measures high-energy integral electron fluxes in

three energy bands (>30, >100, and >300 keV) and proton fluxes in six energy bands (30-80keV, 80-240keV, 240-800keV, 800-2500keV, 2500-6900keV and >6900 keV) [Ødegaard et al., 2017]. The detector consists of two telescopes, which pointing approximately parallel (0° telescope) and perpendicular (90° telescope) to the local magnetic field line, respectively. The 0° telescope views approximately outwards along the local zenith, detecting precipitating particles, whereas the 90° telescope is mounted perpendicular to the 0° telescope, measuring the geomagnetically trapped particles [Smith-Johnsen et al., 2017]. The POSE data files also include the International Geomagnetic Reference Field (IGRF)-determined L shell values. The six spacecraft orbit across different MLT sectors, allowing us to construct global maps of the particles with high spatial and temporal resolution [Søraas et al., 2018]. Figure 1 shows the mapped positions of the satellites’ orbits in the magnetic equator, covering different MLT sectors during the storm event of May 31, 2013. To achieve the equatorial spatiotemporal distribution of particle precipitation during the storm event, the energetic electron and proton flux data from all satellites are sorted into bins of ∆T = 2 hours and ∆R = 0.5 Re by averaging the flux in each bin. Note that since these energetic particles are measured at the satellite height, we cannot differentiate whether the electrons are scattered from the magnetosphere or they are accelerated by potential drops along magnetic field lines and FACs. Therefore, these precipitating electrons may be related to either diffuse or discrete aurora.

3. Results 3.1. Spatiotemporal dynamics of storm-time particle precipitation We firstly select a shock-driven storm event on 31 May 2013 to study the energetic particle precipitation. Figure 2 (a-f) shows the solar wind conditions and geomagnetic indices obtained from the OMNI data. Before the shock arrival at 16:18 UT 31 May 2013, the interplanetary magnetic field Bz, AE index, SYM-H index, solar wind proton density and pressure are nearly zero. After the shock, the solar wind pressure increases

from 0.5 nPa to 10 nPa, the AE index increases to around 1500 nT, and the SYM-H index reaches a minimum of -130 nT at 07:48 UT 1 Jun 2013. The system then begins the storm recovery phase after 08:25 UT for more than 2 days. Figure 3 shows the precipitation flux for electrons of 30
inner boundary of the precipitation migrates outward with its intensity nearly remained, similar to the behavior of 30-100 keV electrons. We note that previous studies examined the dynamics of radiation belt electrons at sub-relativistic energies during the geomagnetic storms by using NASA's Van Allen Probes [Shi et al., 2015; Geoffrey et al., 2016; Turner et al., 2019; Kilpua et al., 2019; Zhao et al., 2019]. These studies on energetic electrons with similar energy range (10s-100s keV) mainly focused on the trapped electron population, rather than precipitating electrons. They found that the response of these radiation belt electrons reveals clear energy, magnetic activity, L shell and MLT dependence during the storm [Shi et al., 2015; Turner et al., 2019; Zhao et al., 2019]. For example, the 10s keV electron flux is enhanced at all L‐shells (2.5 ≤ L ≤ 6) during the storm main phase and then quickly decays during the early recovery phase. The 100s keV electron flux is enhanced at lower L‐shells (~3 ≤ L ≤ ~4) and then decays in the recovery phase [Turner et al., 2019]. Since these trapped populations provide the source for the precipitation populations, their dynamics to some degree is similar to that of the precipitation population. Figure 5 displays protons precipitation flux of 306). These precipitating protons are probably scattered by EMIC waves that are believed to be mostly generated near the plasmapause boundary in the night-to-dusk sectors following ion injections and subsequent westward transport

[e.g., Jordanova et al., 2001; Jun et al., 2019a; 2019b]. As the convection electric field becomes more intense, the plasmapause shifts inwards and so as the wave location. Note that the flux of 30-80 keV proton precipitation is clearly much higher than that of the 30-100 keV electrons in most MLT sectors, by nearly one order of magnitude. We integrate both the 30-80 keV proton flux and 30-100 keV electron flux over area in each MLT sectors, as shown in Figure 7, in order to compare the number of precipitating energetic particles down to the ionosphere. It shows that more protons are precipitated than electrons at sectors of 15
In addition to the above case study, we further statistically investigate the precipitation flux of 30-100 keV electrons (Figure 8) from 18 storm events during 2007–2014. using epoch analysis technique, in order to understand the general precipitation dynamics of energetic particles in response to storms. The epoch zero time is chosen at the Dst minimum of each storm within an interval of -24 to 72 hrs to include the time from pre-storm to post-storm. Among these storms, the weakest storm has a SYM-H minimum of -50 nT, and the strongest one has a minimum SYM-H at -137 nT. The average SYM-H index is minimized around -80 nT with a long recovery phase. Four times intervals are selected to represent the pre-storm (-24 to -12 h), storm main phase (-12 to 0 h), early recovery phase (0 to 24 h), and late recovery phase (24-48 h) in the L-MLT circular plots shown in Figure 8k. The pre-storm energetic electrons precipitation in average shows dawn-dusk asymmetry with weak precipitation in the noon-to-dusk sector but particularly strong precipitation on the dawn side. During the storm main phase when the SYM-H index drops quickly, the intensity of electron precipitation is enhanced greatly, with the spatial distribution remained like in the pre-storm. The most intense precipitation occurs in the dawn sector between 4
energy content of the energetic particle precipitation. This is different from the low-energy particle precipitation in which electrons are the major carriers. 3.2. Dependence of the precipitation inner boundary on the SYM-H index As shown above, the inner boundary of the particle precipitation evolves with the storm phases. To study the correlation between the inner boundary of the precipitation and the geomagnetic activity levels, we identify the inner boundary of precipitation in each MLT sector by searching the location where the flux intensity is abruptly increased by two orders of magnitude from its adjacent earthward location. Figure 10 exhibits the relationship between the L-position of precipitation inner boundary and SYM-H index in different MLT sectors denoted by colors for 30-100keV electrons (Figure 10 (a)) and 30-80 keV protons (Figure 10 (b)) in the 31 May 2013 storm. Linear regression analysis shows that the precipitation inner boundary almost linearly increases with the SYM-H index with the correlation coefficient exceeding 0.5 in most MLT sectors. This means that the more intense the storm is, the deeper the precipitation inner boundary penetrates. This is consistent with the physical processes following tail plasma injection during storms [Søraas et al.,2003]. As the source plasma is transported inward under an enhanced convective electric field that erodes the outer region of plasmasphere and results in an inward movement of the plasmapause, plasma waves generated near the plasmapause boundary appear more earthward, hence leading to more precipitation therein during disturbed time. Furthermore, when all of the 18 storm events are included, the median value of L-position of the precipitation inner boundary statistically exhibits a linear relationship with the SYM-H index in most MLT sectors (Figure 11). Linear regression analysis shows that the correlation coefficient can exceed 0.85 in most MLT sectors. While observing the scatter plots carefully, it is found that the inner boundary location can reach L=3 as long as the SYM-H index is below zero, whereas it is mostly in the outer region (L>4) for SYM-H>-50 nT. We further investigate individual

storm

events

including

weak

(SYM-H>-50

nT),

moderate

(-100
linear relationship remains in each storm. That is, despite the intensity of a storm, the inner boundary can still penetrate as deep as L=3 during storm main phase and exhibits a linear relationship with the SYM-H index in that particular event. Even during a weak storm (SYM-H>-50 nT), the inner boundary of precipitation could shift to inner zone when the SYM-H index decreases. These results imply that the location of the precipitation inner boundary is not only linearly related with the intensity of the storm measured by numerical indices (i.e., SYM-H index), but also correlated with storm phases. The intensity of the storm (measured by the SYM-H index) is determined by the energy content of the ring current, the strength of which depends on the combined effects of convective electric field and source populations [Yu et al. 2014; Fok et al. 2001]. A large convective electric field without sufficient supply of source plasma may not lead to an enhanced ring current [Yu et al. 2014], but can still drive erosion of plasmasphere and push the plasmapause boundary inward. In other word, the plasmapause can migrate to lower L region even during weak storms. This is probably the reason why the inner boundary of precipitation can be very close to the Earth even under weak storms as mentioned above. 4. Summary In this study, we investigated the dynamics of both energetic electron and proton precipitations during storms and analyzed the correlation of the precipitation boundary with geomagnetic activity levels using NOAA/POES observations. Some major results are summarized as follows: 1. Precipitation of energetic electrons of 30
2. The energetic proton (30
Data

Center

(NGDS)

for

providing

NOAA

POES

data

(https://satdat.ngdc.noaa.gov/sem/poes/data/processed/swpc/uncorrected/avg/cdf/) and the OMNIweb (http://omniweb. gsfc.nasa.gov/) from NASA Goddard Space Flight Center for providing the solar wind/interplanetary field data, SYM-H index and AE index. References Albert, J., 2004. Using quasi-linear diffusion to model acceleration and loss from wave-particle interactions. Space Weather 2, 1-6.

An, X., Yue, C., Bortnik, J., Decyk, V., Li, W., Thorne, R.M., 2017. On the parameter dependence of the whistler anisotropy instability. Journal of

Geophysical Research:

Space Physics 122, 2001-2009. Arnoldy, R., Moore, T., Akasofu, S.I., 1982. Plasma injection events at synchronous orbit related to positive dst. Journal of Geophysical Research: Space Physics 87, 77-84. Belian, R., Gisler, G., Cayton, T., Christensen, R., 1992. High-z energetic particles at geosynchronous orbit during the great solar proton event series of October 1989. Journal of Geophysical Research: Space Physics 97, 16897-6906. Burton, R.K., McPherron, R., Russell, C., 1975. An empirical relationship between interplanetary conditions and dst. Journal of geophysical research 80, 4204-4214. Ebihara, Y., Fok, M.C., Wolf, R., Immel, T., Moore, T., 2004. Influence of ionosphere conductivity on the ring current. Journal of Geophysical Research: Space Physics 109. Echer, E., Alves, M., Gonzalez, W., 2004. Geoeffectiveness of interplanetary shocks during solar minimum (1995-1996) and solar maximum (2000). Solar Physics 221, 361-380. Evans, D.S., 1974. Precipitating electron fluxes formed by a magnetic field aligned potential difference. Journal of Geophysical Research 79, 2853-2858. Fok, M.C., Wolf, R., Spiro, R., Moore, T., 2001. Comprehensive computational model of earth's ring current. Journal of Geophysical Research: Space Physics 106, 8417-8424. Foster, J., Erickson, P., Baker, D., Claudepierre, S., Kletzing, C., Kurth, W., Reeves, G., Thaller, S., Spence, H.E., Shprits, Y., et al., 2014. Prompt energization of relativistic and highly relativistic electrons during a sub-storm interval: Van allen probes observations. Geophysical Research Letters 41, 20-25.

Ilie, R., Daldor_, L.K., Liemohn, M.W., Toth, G., Chan, A.A., 2017. Calculating the inductive electric field in the terrestrial magnetosphere. Journal of Geophysical Research: Space Physics 122, 5391-5403. Jordanova, V., Farrugia, C., Thorne, R., Khazanov, G., Reeves, G., Thomsen, M., 2001. Modeling ring current proton precipitation by electromagnetic ion cyclotron waves during the may 14-16, 1997, storm. Journal of Geophysical Research: Space Physics 106, 7-22. Jun, C.W., Yue, C., Bortnik, J., Lyons, L., Nishimura, Y., Kletzing, C., 2019a. Emic wave properties associated with and without injections in the inner magnetosphere. Journal of Geophysical Research: Space Physics 124, 2029-2045. Jun, C.W., Yue, C., Bortnik, J., Lyons, L., Nishimura, Y., Kletzing, C., Wygant, J., Spence, H., 2019b. A statistical study of emic waves associated with and without energetic particle injection from the magnetotail. Journal of Geophysical Research: Space Physics 124, 433-450. Kennel, C.F., Petschek, H., 1966. Limit on stably trapped particle fluxes. Journal of Geophysical Research 71, 1-28. Kersten, T., Horne, R.B., Glauert, S.A., Meredith, N.P., Fraser, B.J., Grew,R.S., 2014. Electron losses from the radiation belts caused by emic waves. Journal of Geophysical Research: Space Physics 119, 8820-8837. Kilpua, E., Turner, D., Jaynes, A., Hietala, H., Koskinen, H., Osmane,A., Palmroth, M., Pulkkinen, T., Vainio, R., Baker, D., et al., 2019. Outer van allen radiation belt response to interacting interplanetary coronal mass ejections. Journal of Geophysical Research: Space Physics 124, 1927-1947. Liemohn, M.W., Ridley, A.J., Brandt, P.C., Gallagher, D.L., Kozyra, J.U.,Ober, D.M., Mitchell, D.G., Roelof, E.C., DeMajistre, R., 2005. Parametric analysis of nightside conductance effects on inner magnetospheric dynamics for the 17 april 2002 storm. Journal of Geophysical Research: Space Physics 110.

Liu, X., Liu, W., 2014. A new plasmapause location model based on themis observations. Science China Earth Sciences 57, 2552-2557. Liu, Y., Zong, Q.G., 2015. Energetic electron response to interplanetary shocks at geosynchronous orbit. Journal of Geophysical Research: Space Physics 120, 4669-4683. Ma, Q., Li, W., Bortnik, J., Thorne, R., Chu, X., Ozeke, L., Reeves, G.D.,Kletzing, C., Kurth,W., Hospodarsky, G., et al., 2018. Quantitative evaluation of radial diffusion and local acceleration processes during gem challenge events. Journal of Geophysical Research: Space Physics 123, 1938-1952. Ma, Q., Li, W., Thorne, R.M., Bortnik, J., Kletzing, C., Kurth, W., Hospodarsky, G., 2016. Electron scattering by magnetosonic waves in the inner magnetosphere. Journal of Geophysical Research: Space Physics 121, 274-285. Meredith, N.P., Horne, R.B., Lam, M.M., Denton, M.H., Borovsky, J.E.,Green, J.C., 2011. Energetic electron precipitation during high-speed solar wind stream driven storms. Journal of Geophysical Research: Space Physics 116. Meredith, N.P., Horne, R.B., Thorne, R.M., Anderson, R.R., 2009. Survey of upper band chorus and ech waves: Implications for the diffuse aurora. Journal of Geophysical Research: Space Physics 114. Miyoshi, Y., Oyama, S., Saito, S., Kurita, S., Fujiwara, H., Kataoka, R.,Ebihara, Y., Kletzing, C., Reeves, G., Santolik, O., et al., 2015. Energetic electron precipitation associated with pulsating aurora: Eiscat and van allen probe observations. Journal of Geophysical Research: Space Physics 120, 2754-2766. Newell, P., Sotirelis, T., Wing, S., 2009. Diffuse, monoenergetic, and broadband aurora: The global precipitation budget. Journal of Geophysical Research: Space Physics 114.

Ni, B., Thorne, R.M., Zhang, X., Bortnik, J., Pu, Z., Xie, L., Hu, Z.j., Han,D., Shi, R., Zhou, C., et al., 2016. Origins of the earth's diffuse auroral precipitation. Space Science Reviews 200, 205-259. Rodger, C.J., Clilverd, M.A., Green, J.C., Lam, M.M., 2010. Use of poes sem-2 observations to examine radiation belt dynamics and energetic electron precipitation into the atmosphere. Journal of Geophysical Research: Space Physics 115. Schulz, M., 1998. Particle drift and loss rates under strong pitch angle diffusion in dungey's model magnetosphere. Journal of Geophysical Research: Space Physics 103, 61-67. Shi, R., Summers, D., Ni, B., Fennell, J.F., Blake, J.B., Spence, H.E.,Reeves, G.D., 2016. Survey of radiation belt energetic electron pitch angle distributions based on the van allen probes mageis measurements. Journal of Geophysical Research: Space Physics 121, 1078-1090. Soraas, F., Aarsnes, K., Oksavik, K., Evans, D., 2003. Ring current intensity estimated from low-altitude proton observations. Journal of Geophysical Research: Space Physics 107, SMP-30. Soraas, F., Sandanger, M.I., Smith-Johnsen, C., 2018. Noaa poes and metop particle observations during the 17 march 2013 storm. Journal of Atmospheric and Solar-Terrestrial Physics 177, 115-124. Summers, D., Ni, B., Meredith, N.P., 2007. Timescales for radiation belt electron acceleration and loss due to resonant wave-particle interactions: 2. evaluation for vlf chorus, elf hiss, and electromagnetic ion cyclotron waves. Journal of Geophysical Research: Space Physics 112. Summers, D., Thorne, R.M., 2003. Relativistic electron pitch-angle scattering by electromagnetic ion cyclotron waves during geomagnetic storms. Journal of Geophysical Research: Space Physics 108.

Thebault, E., Finlay, C.C., Beggan, C.D., Alken, P., Aubert, J., Barrois, O.,Bertrand, F., Bondar, T., Boness, A., Brocco, L., et al., 2015. International geomagnetic reference field: the 12th generation. Earth, Planets and Space 67, 79. Thorne, R.M., Kennel, C., 1971. Relativistic electron precipitation during magnetic storm main phase. Journal of Geophysical research 76, 4446-4453. Turner, D., Kilpua, E., Hietala, H., Claudepierre, S., O'Brien, T., Fennell, J., Blake, J., Jaynes, A., Kanekal, S., Baker, D., et al., 2019. The response of earth's electron radiation belts to geomagnetic storms: Statistics from the van allen probes era including effects from different storm drivers. Journal of Geophysical Research: Space Physics 124, 1013-1034. Turunen, E., Kero, A., Verronen, P.T., Miyoshi, Y., Oyama, S.I., Saito,S., 2016. Mesospheric ozone destruction by high-energy electron precipitation associated with pulsating aurora. Journal of Geophysical Research:Atmospheres 121, 11,852-11,861. Yu, Y., Jordanova, V., Welling, D., Larsen, B., Claudepierre, S.G., Kletzing, C., 2014. The role of ring current particle injections: Global simulations and van allen probes observations during 17 march 2013 storm. Geophysical Research Letters 41, 1126-1132. Yu, Y., Jordanova, V.K., McGranaghan, R.M., Solomon, S.C., 2018. Self-consistent modeling of electron precipitation and responses in the ionosphere: Application to low-altitude energization during substorms. Geophysical Research Letters 45, 6371-6381. Yu, Y., Liemohn, M.W., Jordanova, V.K., Lemon, C., Zhang, J., 2019.Recent advancements and remaining challenges associated with inner magnetosphere cross-energy/population interactions (imcepi). Journal of Geophysical Research: Space Physics. Yu, Y., Ridley, A.J., 2009. Response of the magnetosphere-ionosphere system to a sudden southward turning of interplanetary magnetic field. Journal of Geophysical Research: Space Physics 114.

Yu,

Y.Q.,

Ridley,

A.J.,

2011.

Understanding

the

response

of

the

ionosphere-magnetosphere system to sudden solar wind density increases. Journal of Geophysical Research: Space Physics 116. Yue, C., An, X., Bortnik, J., Ma, Q., Li, W., Thorne, R.M., Reeves, G.D., Gkioulidou, M., Mitchell, D.G., Kletzing, C.A., 2016. The relationship between the macroscopic state of electrons and the properties of chorus waves observed by the van allen probes. Geophysical Research Letters 43, 7804-7812. Yue, C., Jun, C.W., Bortnik, J., An, X., Ma, Q., Reeves, G.D., Spence,H.E., Gerrard, A.J., Gkioulidou, M., Mitchell, D.G., et al., 2019. The relationship between emic wave properties and proton distributions based on van allen probes observations. Geophysical Research Letters 46, 4070-4078. Yue, C., Zong, Q., Wang, Y., 2009. Response of the magnetic field and plasmas at the geosynchronous orbit to interplanetary shock. Chinese Science Bulletin 54, 4241. Zaharia, S., Jordanova, V., Thomsen, M., Reeves, G., 2008. Self-consistent geomagnetic storm simulation: The role of the induced electric fields. Journal of Atmospheric and Solar-Terrestrial Physics 70, 511-518. Zhang, B., Lotko, W., Brambles, O., Wiltberger, M., Lyon, J., 2015. Electron precipitation models in global magnetosphere simulations. Journal of Geophysical Research: Space Physics 120, 1035-1056. Zhang, J.C., Kistler, L., Mouikis, C., Dunlop, M., Klecker, B., Sauvaud, J.A., 2010. A case study of emic wave-associated he+ energization in the outer magnetosphere: Cluster and double star 1 observations. Journal of Geophysical Research: Space Physics 115. Zhao, H., Johnston, W., Baker, D., Li, X., Ni, B., Jaynes, A., Kanekal, S.,Blake, J., Claudepierre, S., Reeves, G., et al., 2019. Characterization and evolution of radiation belt electron energy spectra based on the van allen probes measurements. Journal of Geophysical Research: Space Physics.

Zhou, C., Li, W., Thorne, R.M., Bortnik, J., Ma, Q., An, X., Zhang, X.j.,Angelopoulos, V., Ni, B., Gu, X., et al., 2015. Excitation of dayside chorus waves due to magnetic field line compression in response to interplanetary shocks. Journal of Geophysical Research: Space Physics 120, 8327-8338. Zong, Q.G., Zhou, X.Z., Wang, Y., Li, X., Song, P., Baker, D., Fritz, T.,Daly, P., Dunlop, M., Pedersen, A., 2009. Energetic electron response to ulf waves induced by interplanetary shocks in the outer radiation belt. Journal of Geophysical Research: Space Physics 114. Figure captions

Figure1. The mapped location of NOAA POES 15, 16, 18, 19 and MetOp-02 satellites in the magnetic equator during May 2013.

Figure2. Figure 2(a-f) show the IMF Bz, the absolute value of solar wind Vx components in the GSM coordinate, AE index, the proton number density, SYM-H index as well as solar wind pressure.

Figure 3. The plot exhibits logarithmic flux of 30-100keV electrons as L versus UT at different MLT sectors: (00-03), (03-06), (06-09), (09-12), (12-15), (15-18), (18-21), (21-24). The plots cover the time interval form 31 May 2013 to 03 June 2013. The lines represent plasmapause boundary determined by the Liu et al. model [Liu et al., 2015].

Figure 4. The plot exhibits logarithmic flux of 100-300keV electrons with the same format as Figure 3.

Figure 5. The plot exhibits logarithmic flux of 30-80keV protons with the same format as Figure 3.

Figure 6. The plot exhibits logarithmic flux of 80-250 keV protons with the same format as Figure 3.

Figure 7. The integrated flux of 30-100 keV electrons and 30-80 keV protons at different MLT sectors. The plots cover the time interval form 31 May 2013 to 03 June 2013.

Figure 8. Superposed epoch analysis of 30-100 keV electrons precipitation during 18 storms. (a-h) are superposed electron precipitation in the same format as in Figure 3. (i-j) show the superposed AE index and SYM-H index with the red line represents the median value, the blue and green line respectively represent the 25th and 75th percentiles of the corresponding parameters. (k) shows the MLT/ILAT distribution of precipitation at selected time intervals: (i) the

pre-storm (-24 to -12 h), (ii) storm main phase (-12 to 0 h), (iii) early recovery phase (0 to 24 h), and (iv) late recovery phase (24-48 h), respectively.

Figure 9. Superposed results of precipitation flux of 30-80keV protons in the same format as Figure 8.

Figure 10. Relationship between the inner boundary (L-position) of particle precipitation and the SYM-H index at different MLT sectors for (a) 30-100keV electrons and (b) 30-80 keV protons.

Figure 11. Statistical result of the precipitation inner boundary vs. the SYM-H index during 18 storm events. Blue points represent the median value, with 25th and 75th percentiles as the error bar. Black lines represent the linear regression analysis of the median value of L-position of the precipitation inner boundary and the SYM-H index. (a-h): electrons (30-100 keV); (i-q): protons (30-80 keV).

1.

Medium-energy (tens to hundreds of keV) energetic precipitation of electrons and protons both exhibit global asymmetry.

2.

Energetic proton precipitation appears to contain more energy flux than electrons, different from the scenario in low-energy particle precipitation.

3.

The Earthward extension of precipitation linearly correlates with the storm intensity measured by SYM-H index.