Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective
Year: 2023
Type: article
Abstract: We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or $\Delta L\sim 0.56$ Δ L ∼ 0.56 ) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at $L\sim 5-7$ L ∼ 5 − 7 at dusk, while a smaller subset exists at $L\sim 8-12$ L ∼ 8 − 12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an $L$ L -shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of $\sim 1.45$ ∼ 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.
Source: Space Science Reviews
Authors: V. Angelopoulos, X.-J. Zhang, A. V. Artemyev, D. Mourenas, E. Tsai, C. Wilkins, A. Runov, J. Liu, D. L. Turner, W. Li, K. Khurana, R. E. Wirz, V. A. Sergeev, X. Meng, J. Wu, M. D. Hartinger, T. Raita, Y. Shen, X. An, X. Shi, M. F. Bashir, X. Shen, L. Gan, M. Qin, L. Capannolo, Q. Ma, C. L. Russell, E. V. Masongsong, R. Caron, I. He, L. Iglesias, S. Jha, J. King, S. Kumar, K. Le, J. Mao, A. McDermott, K. Nguyen, A. Norris, A. Palla, A. Roosnovo, J. Tam, E. Xie, R. C. Yap, S. Ye, C. Young, L. A. Adair, C. Shaffer, M. Chung, P. Cruce, M. Lawson, D. Leneman, M. Allen, M. Anderson, M. Arreola-Zamora, J. Artinger, J. Asher, D. Branchevsky, M. Cliffe, K. Colton, C. Costello, D. Depe, B. W. Domae, S. Eldin, L. Fitzgibbon, A. Flemming, D. M. Frederick, A. Gilbert, B. Hesford, R. Krieger, K. Lian, E. McKinney, J. P. Miller, C. Pedersen, Z. Qu, R. Rozario, M. Rubly, R. Seaton, A. Subramanian, S. R. Sundin, A. Tan, D. Thomlinson, W. Turner, G. Wing, C. Wong, A. Zarifian
Institutions: University of California, Los Angeles, The University of Texas at Dallas, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, CEA DAM Île-de-France, Johns Hopkins University Applied Physics Laboratory, Oregon State University, St Petersburg University, California Institute of Technology, Jet Propulsion Laboratory, Space Science Institute, University of Oulu, Boston University, Deloitte (United States), Microsoft (United States), University of Chicago, SpaceX (United States), Los Alamos National Laboratory, Planet Labs PBC (United States), Tyvak (United States), Apple (United States), Zipline International (United States), Lucid Motors (United States), California State University, Fullerton, The Aerospace Corporation, Stanford University, Mercedes-Benz Research and Development North America (United States), Geosyntec Consultants (United States), Juniper Networks (United States), Teledyne Technologies (United States), NSWC Corona Division, The Ohio State University, Amazon (United States), University of California, San Francisco
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,490
Funders: National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, California State University, Montana State University, Nuclear Safety and Security Commission, Nanjing Institute of Technology, Jet Propulsion Laboratory, Goddard Space Flight Center, University of Colorado Boulder, Air Force Office of Scientific Research, Air Force Research Laboratory
Awards: G1799348198, G2048821276, G2676722403, G3115651459, G3450036804, Collaborative Research: Causes and Consequences of Relativistic Electron Precipitation as Revealed by the CubeSat Mission ELFIN’s Pitch-Angle Resolved Loss Cone Measurements, G3648211085, Collaborative Research: NSFGEO-NERC:Conjugate Experiment to Investigate Sources of High-Latitude Magnetic Perturbations in Coupled Solar Wind-Magnetosphere-Ionosphere-Ground System, CubeSat: Electron Losses and Fields INvestigation (ELFIN), THE ELFIN-STAR (ELFIN*) CUBESAT WILL RESOLVE THE ROLE OF ELECTROMAGNETIC ION CYCLOTRON (EMIC) WAVES FOR (AND DETERMINE THE RATE OF) RELATIVISTIC ELECTRON PRECIPITATION DURING STORMS. FROM A NEAR-POLAR (I>65O) LOW-EARTH (400KM ALTITUDE) ORBIT ELFIN* WILL PROVIDE UNIQUE PITCH-ANGLE- AND ENERGY-RESOLVED SPECTRA OF RELATIVISTIC ELECTRON FLUXES WITHIN THE LOSS CONE TO DETERMINE WHETHER THEY BEAR THE CHARACTERISTIC SIGNATURES OF EQUATORIAL SCATTERING BY EMIC WAVES. COMPARING ITS OBSERVATIONS WITH DIFFUSION MODELS FOR EMIC CHORUS MAGNETOPAUSE SHADOWING AND OTHER LOSS MECHANISMS ELFIN* WILL ESTABLISH WHETHER LOSSES ARE DOMINATED BY EMIC WAVES OR ARE DUE TO OTHER PROCESSES. ENERGETIC PARTICLE DETECTOR (EPD) ELECTRON MEASUREMENTS (0.1-5MEV) AT RESOLUTION 11.25O (0.4O 0.8O AT THE EQUATOR AT L=5-7) RESOLVING THE LOSS-CONE INCLUDING TRAPPED PARTICLES ACHIEVE CLOSURE. IF EMIC WAVES PROPAGATE TO THE IONOSPHERE ELFIN* S MAGNETOMETER (MAG) WILL ALSO DETECT THEM (DESIRED BUT NEITHER NECESSARY NOR SUFFICIENT FOR CLOSURE). ELFIN* S INTEGRATED DATA ANALYSIS APPROACH AND RAPID DISSEMINATION STRATEGIES VIA THE SPACE ENVIRONMENT DATA ANALYSIS SYSTEM (SPEDAS AN OFF-SPRING OF THEMIS) OPTIMIZE SCIENCE YIELD AND ENSURE WIDEST COMMUNITY BENEFITS. ELFIN* S POTENTIAL IS COMPOUNDED BY CONJUNCTIONS WITH CONCURRENT EQUATORIAL MISSIONS IN 2016 (THEMIS RBSP ERG MMS) THAT WILL COMPLEMENT ITS UNIQUE LOSS-CONERESOLVING SPECTRA.OUR SIMILAR PROPOSAL TO NSF IN 2012 (ELFIN) IS ONE OF TWO FRONT-RUNNERS BUT HAS NOT BEEN SELECTED (YET) DUE TO PROGRAMMATIC CONSIDERATIONS IN A TOUGH FISCAL ENVIRONMENT. IF ELFIN IS SELECTED BY NSF WE HEREBY PROPOSE UNDER H-TIDES TO EXECUTE ELFIN* S STAR OPTION. ELFIN* WILL BUILD AN IDENTICAL SATELLITE TO NSF S ELFIN AND RELEASE IT ON THE SAME LAUNCH VEHICLE INTO A FORMATION ORBIT WITH ITS TWIN. SPRING-SEPARATION PROVIDES A NATURAL VARIATION OF THE INTER-CUBESAT DISTANCE WITH A FULL-ORBIT LAP ONCE PER 30DAYS.ELFIN* S SMALL-SEPARATION RADIATION BELT CROSSINGS (0-15MIN 33% OF THE TIME) WILL RESOLVE THE TEMPORAL VARIABILITY (LOSS-CONE FILL RATE) AND SPATIAL EXTENT OF THE RELATIVISTIC ELECTRON PRECIPITATION AND DETERMINE ITS AGREEMENT WITH EQUATORIAL EMIC WAVE DIFFUSION RATES OVER TIME SCALES COMPARABLE TO SUCH DIFFUSION (MINUTES). THUS FOR AT LEAST 2 STORM-TIME PRECIPITATION EVENTS OVER ITS BASELINE (6- MONTH) MISSION ELFIN* WILL DETERMINE THE GLOBAL ROLE OF EMIC WAVES ON RADIATION BELT PRECIPITATION. A RADIATION MARGIN OF>2 AND EMPHASIS ON PARTS SELECTION FOR A>1YR DESIGN-LIFE IS EXPECTED TO DOUBLE THIS SCIENCE YIELD TO>4 STORMS.ELFIN* RESOLVES A FUNDAMENTAL SPACE- AND PLASMA-PHYSICS QUESTION RELATED TO RELATIVISTIC ELECTRON SCATTERING AND LOSS IN THE OUTER RADIATION BELT. ITS STAR OPTION IF EXERCISED WILL DETERMINE THE GLOBAL EFFECTS OF SUCH SCATTERING. FOR PURPOSES OF UNDERSTANDING SPACE WEATHER AND FUNDAMENTAL PLASMA PROCESSES DETERMINING STORM-TIME OUTER BELT ELECTRON LOSS RATES AND MECHANISMS IS JUST AS IMPORTANTAS DETERMINING ACCELERATION OR TRANSPORT. ELFIN* IS THEREFORE KEY IN THE HELIOPHYSICS DISCIPLINE S ASPIRATION BOTH FOR A COMPREHENSIVE NATIONAL SPACE WEATHER PROGRAM AND TO UNDERSTAND FUNDAMENTAL MICROSCOPIC PHYSICS AS WELL AS THE GLOBAL SYSTEM BEHAVIOR AS RECOMMENDED BY THE 2012 HELIOPHYSICS DECADAL SURVEY. ELFIN* DIRECTLY ADDRESSES ALL THREE STATED HELIOPHYSICS OBJECTIVES (IN THE 2010 SMD SCIENCE PLAN) TO UNDERSTAND: THE FUNDAMENTAL PHYSICAL PROCESSES OF THE SPACE ENVIRONMENT HOW TECHNOLOGICAL SYSTEMS ARE AFFECTED BY SOLAR VARIABILITY AND DEVELOPING THE CAPABILITY TO PREDICT EXTREME AND DYNAMIC CONDITIONS IN SPACE . THESE ALSO TIEDIRECTLY TO HELIOPHYSICS SCIENCE GOALS #2 AND #4 LISTED IN THE DECADAL SURVEY (P-S2). ELFIN* S APPROACH TO ADDRESS LOSSES SYSTEM-WIDE BY INTEGRATING ITS UNIQUE DATASET WITH THOSE OF OTHER NASA MISSIONS ADDRESSES THE PRIMARY RECOMMENDATION OF THE DECADAL SURVEY(FIG. 1.2) FOR SYSTEM-SCIENCE WITH THE INTEGRATED HELIOPHYSICS SYSTEM OBSERVATORY., G5295504614, G54188565, At the Cusp of the 21st Century: The Next Generation of Geospace Research Facilities at South Pole and McMurdo Stations, G5561424898, G5683993009, G5953495884, Time Domain Structures Driven by Whistler and Kinetic Alfven Waves in a Laboratory Plasma, G7307739112, Combined Effects of ElectroMagnetic Ion Cyclotron (EMIC) and Whistler Mode Waves on Relativistic Electron Scattering in the Earth's Inner Magnetosphere, G830101876, G8389910058
OpenAlex ID: W4383906054