Year: 2024
Type: article
Abstract: The present study compares a single‐band chorus wave against a banded chorus wave observed by Van Allen Probes at adjacent times, and demonstrates that the single‐band chorus wave is associated with an anisotropic electron population over a broad energy range, while the banded chorus wave is accompanied by an electron phase space density plateau and an electron anisotropy reduction around Landau resonant energies. We further compare banded chorus waves with different spectral gap widths, and show that a wider spectral gap is associated with electron isotropization extending to higher energies with respect to the equatorial Landau resonant energy. We suggest that early generated chorus waves isotropize electrons via Landau resonant acceleration, and the waves that propagate to higher latitudes isotropize electrons at higher energies. The isotropization extending to higher energies leads to a larger spectral gap of new chorus waves after electrons bounce back to the equator.
DOI: 10.1029/2023ja031893
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,880
Awards: CAREER: Exploring Mysterious Whistler Mode Waves in Earth's Plasmaspheric Plumes, The Generation of Banded Chorus Waves in the Earth's Radiation Belt, G1542932375, G1564080852, G200029281, SCIENCE GOALS AND OBJECTIVES THE OVERARCHING GOAL OF THIS PROPOSAL IS TO UNDERSTAND THE CHARACTERISTICS OF THE IONOSPHERIC CURRENTS OF RECONNECTION-GENERATED FAST FLOWS THAT CAUSE EITHER GLOBAL SUBSTORMS OR LOCALIZED PSEUDO BREAKUPS. SPECIFICALLY WE AIM TO QUANTITATIVELY ASSESS BOTH THE LOCALIZED AND GLOBAL RESPONSES OF EQUIVALENT IONOSPHERIC CURRENTS (EICS) AND FIELD ALIGNED CURRENTS (FACS) TO DIFFERENT TYPES OF FAST FLOWS: WITH OR WITHOUT GLOBAL SUBSTORMS; WITH DIPOLARIZATION FRONTS OR SLOWED FLOWS IN THE BREAKING REGION. THE SPECIFIC SCIENCE QUESTIONS THAT WILL BE ADDRESSED ARE: 1. WHAT ARE THE TYPICAL CHARACTERISTICS OF THE IONOSPHERIC RESPONSE OF EICS AND FACS TO DIFFERENT TYPES OF FAST FLOWS? A. HOW DO THE IONOSPHERIC CURRENTS VARY IN LATITUDE LOCAL TIME INTENSITY WITH DIFFERENT FLOWS? B. UNDER WHAT CONDITIONS DO CURRENT VORTICES APPEAR AND WHERE DO THESE VORTICES APPEAR WITH RESPECT TO THE HARANG DISCONTINUITY? 2. WHAT ARE THE TYPICAL CHARACTERISTICS OF DIFFERENT TYPES OF FAST FLOWS? A. DO THE FLUX TRANSPORT RATE AND ENTROPY OF FLOWS DETERMINE WHETHER A GLOBAL SUBSTORM CAN BE TRIGGERED? B. ARE THE CHANGES IN THE LOBE MAGNETIC FIELD STRENGTH AND OPEN LOBE MAGNETIC FLUX DIFFERENT FOR DIFFERENT TYPES OF FLOWS? 3. WHAT ARE THE POTENTIAL PHYSICAL QUANTITIES THAT DETERMINE WHETHER A FAST FLOW WILL TRIGGER A GLOBAL SUBSTORM OR A LOCALIZED PSEUDO BREAKUP? METHODOLOGY THE PROPOSED PROJECT WILL COMBINE THE FIELD AND PARTICLE DATA OF FAST FLOWS OBSERVED BY NASA S THEMIS VAN ALLEN PROBE (VAP) AND MMS; IONOSPHERIC EICS AND CURRENT AMPLITUDES (I.E. A PROXY FOR THE FACS) OBTAINED FROM THE SEC METHODS; AND A NEURAL NETWORK MODEL OF THE IONOSPHERIC CURRENTS TO ADDRESS THE ABOVE IMPORTANT SCIENCE QUESTIONS. MORE SPECIFICALLY 1. USING EXISTING LISTS OF FAST FLOWS AND SUBSTORM ONSETS GENERATED BY OUR TEAM [CHU ET AL. JGR 2015] WE WILL CATEGORIES FAST FLOWS WITH AND WITHOUT GLOBAL SUBSTORMS; FAST FLOWS WITH DIPOLARIZATION FRONT AND SLOWED FLOWS IN THE BREAKING REGION. 2. USING THE HIGH SPATIOTEMPORAL RESOLUTION DATA OF EICS OBTAINED FROM THE SPHERICAL ELEMENTARY CURRENT SYSTEM (SEC) METHOD BY OUR TEAM [WEYGAND ET AL. JGR 2011] WE WILL DEVELOP A NEURAL NETWORK (NN) MODEL OF THE IONOSPHERIC CURRENTS WHICH PROVIDES FULL LOCAL TIME COVERAGE. THIS MODEL RESOLVES THE PROBLEM THAT PERIODICALLY NO DATA ARE AVAILABLE ON THE NIGHTSIDE WHEN THE MAGNETOMETERS ARE LOCATED AT OTHER LOCAL TIMES AND GREATLY INCREASES THE NUMBER OF CONJUNCTIONS WITH SATELLITES. 3. USING THE MODELED IONOSPHERIC CURRENT DATA WE WILL CONSTRUCT THE CHARACTERISTICS OF THE IONOSPHERIC RESPONSE TO DIFFERENT CATEGORIES OF FAST FLOWS. 4. FOR DIFFERENT CATEGORIES OF FAST FLOWS WE WILL STUDY THE CHARACTERISTICS OF THESE FLOWS (ENTROPY AND FLUX TRANSPORT RATE) AND THE MAGNETOSPHERIC RESPONSE (CHANGE IN THE LOBE MAGNETIC FIELD AND AMOUNT OF FLUX RELEASED BY THE TAIL RECONNECTION). RELEVANCE TO THE DECADAL SURVEY GOALS AND THE H-SR PROGRAM OUR PROPOSED PROJECT DIRECTLY ADDRESSES THE MOST IMPORTANT QUESTIONS IN MAGNETOSPHERIC RECONNECTION WHICH IS CURRENTLY ONE OF NASA S HIGHEST PRIORITIES. THE PROPOSED RESEARCH IS HIGHLY RELEVANT TO GOAL 2 FROM THE HELIOPHYSICS DECADAL SURVEY WHICH IS TO DETERMINE THE DYNAMICS AND COUPLING OF EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS . THE PROPOSED PROJECT PERFECTLY FITS THE SCOPE OF HELIOPHYSICS SR PROGRAM., THE EARTH S INNER MAGNETOSPHERE IS A COMPLEX, DYNAMICAL, HIGHLY-COUPLED SYSTEM THAT IS CONTINUOUSLY DRIVEN BY THE SOLAR WIND, AND THE VARIOUS STRUCTU, NONLINEAR WAVE PARTICLE INTERACTIONS AND EXCITATION OF WHISTLERS, G4253589487, G4570898830, G4818969583, G6428057298, G6594388985, G6771806772, G7851056492, G7888998993, G8013478594, G8846283912, G925054966
OpenAlex ID: W4402899300