Hot flow anomalies (hfas) are kinetic phenomena observed near the earth's BOW shock that are marked by greatly heated plasmas and substantial flow deflection. The objective of the proposed research is…

This federal contract award, valued at $519,608.28, was granted to the University of Alaska Fairbanks (UAF) Grants and Contracts Administration Division by the Shared Services Center (a civilian federal agency) to conduct research on "Hot Flow Anomalies (HFAs)" near the Earth's bow shock. The objective is to understand the microphysics of HFAs, which are kinetic phenomena marked by heated plasmas and significant flow deflection. The research will leverage data from the Magnetospheric Multiscale (MMS) spacecraft mission to analyze particle distributions, wave activity, and boundary dynamics within HFAs. This contract supports the goals of the Heliophysics Decadal Survey to discover and characterize fundamental processes within the heliosphere and understand the Sun's interaction with the solar system. There is no set-aside designation for this grant, which is awarded directly to UAF as the prime contractor. UAF, as the flagship research university for the state of Alaska, has significant expertise in areas such as Arctic studies, climate science, and geophysics that enable it to contribute valuable scientific research to federal agencies.

Hot flow anomalies (hfas) are kinetic phenomena observed near the earth's BOW shock that are marked by greatly heated plasmas and substantial flow deflection. The objective of the proposed research is to understand the microphysics of hfas. The specific science questions include: 1. What is the internal structure of hfas? 2. How do ION and electron distributions differ in hfas at different evolution stages? 3. How does particle heating occur inside hfas? We will use publicly available data from the four magnetospheric multiscale spacecraft, which are unique in that these multiplesatellite constellations and unprecedented time resolution. There are already over 400 BOW shock crossings encountered by MMS which provide excellent opportunities to study hfas occurring near the BOW shock. We will mainly use the ION and electron data including velocity distribution functions and moments, magnetic field and electric field data. We propose to use the following data analysis methodology. The microscopic currents inside hfas will be calculated using the curlometer technique based on magnetic field measurements from four spacecraft. Assuming the current density is constant over the tetrahedral volume formed by the four spacecraft, IT can be estimated based on ampere's law. The normal direction of various boundaries associated with hfas will be determined by minimum variance analysis (MVA) and four spacecraft timing method. The velocity of boundary motion will also be calculated by the four spacecraft timing method. When the outer boundaries of hfas are shocks, the normal directions will be determined by the coplanarity method. Two-dimensional cut (vperp-vpar plane) of the threedimensional ION and electron distributions at different locations inside hfas and at different evolution stages will be analyzed. The ION distributions will be used to identify the evolution stage of hfas. For young hfas, there are two populations, a solar wind beam and a population reflected from the earth's BOW shock. For mature hfas, there is a single hot distribution. The wavelet analysis of the magnetic field and electric field data will be used to identify both the high frequency (e.g., lower hybrid waves) and low frequency (ULF) waves that may contribute to ION and electron heating inside hfas. We will compare the observations with simulations on particle heating that has been published (e.g., cairns and mcmillan, 2005; daughton ET AL., 2004). This proposal addresses the goals of "discover and characterize fundamental processes that occur both within the heliosphere and throughout the universe" and "determine the interaction of the sun with the solar system and the interstellar medium" as stated in the heliophysics decadal survey since hfas are fundamental processes that operate throughout the heliosphere, including particle energization and kinetic effects upon bulk plasma parameters. Hfas are universal phenomena that are associated with shock waves in plasmas that are found in many environments, from the solar atmosphere to distant galaxies. Hfas can significantly modify the solar wind-magnetosphere interaction, generate shocks, and energize particles efficiently. In addition, one of the major science goals of the MMS extended mission (second dayside phase) is to study the foreshock phenomena including hfas. References: cairns, i. H., and b. F. Mcmillan (2005), electron acceleration by lower hybrid waves in magnetic reconnection regions, phys. Plasmas, 12, 102110, DOI:10.1063/1.2080567. Daughton, w., g. Lapenta, and p. Ricci (2004), nonlinear evolution of the lower‐hybrid drift instability in a current sheet, phys. REV. Lett., 93(10), 105004, DOI:10.1103/physrevlett.93.105004