1. Understand how coronal structures become the ambient solar wind.

    1. How does the young solar wind flow and evolve on global scales?

      Ulysses/SWOOPS data obtained over several years (white lines) overlain on sample Enlil solar wind simulation (left=solar minimum; right=solar maximum).


      Objective 1A

      PUNCH quantifies day-to-day global evolution of the ambient solar wind flow. PUNCH performs a minimum of two sets of velocity measurements at several radial positions per day, based on deep-field images collected every few minutes that are 10-30 times more sensitive than current coronal and heliographic imagers. These unprecedented daily global velocity maps will spur a broad range of science through a determination of:

      • Solar wind acceleration from outer corona to inner heliosphere and the changing boundaries between fast/slow solar wind;
      • Solar-wind theory ground truth via model-independent, global flow measurements;
      • The large-scale context necessary to relate coronal structure to in-situ measurements;
      • Global conditions through which transient structures propagate

    2. PUNCH resolves the enigmatic shift from striated corona to flocculated solar wind (Deforest et al., 2016), and tracks puffs from their coronal origins (Viall & Vourlidas, 2015).


      Objective 1B

      PUNCH measures the development of turbulence in the young solar wind. By tracking a wide range of microstructures in the solar wind as they form, evolve, and propagate from outer corona into the heliosphere, PUNCH will determine the origin of solar-wind variability (solar vs. intrinsic variability), and observe the possible development of an inertial range of turbulent scales in the young solar wind. This provides critical insight into where and how kinetic energy becomes available to drive a turbulent cascade and mix and heat the solar wind far from the Sun. 3D polarization analysis is employed to reduce ambiguity between feature evolution and observational effects.

    3. MHD simulation of solar wind with Alfven surface shown as black line (Cohen, 2015).


      Objective 1C

      PUNCH maps the evolution of the critical Alfven surface, beyond which the plasma and field lines cannot retract back to the Sun. By measuring inbound vs. outbound waves (e.g., Deforest et al., 2014; Tenerani et al. 2016) in time sequences of imaged intensity, PUNCH will map this source surface of the heliosphere for the first time, enabling:

      • Remote sensing of surface shape, complexity and evolution;
      • Measurement of the Alfven speed at the surface via direct measurement of bulk speed;
      • Discrimination between solar wind models, and "big-picture" context for the Parker Solar Probe (PSP) and Solar Orbiter (SO) missions

  2. Understand the dynamic evolution of transient structures in the young solar wind.

    1. How do coronal mass ejections (CMEs) propagate and evolve in the solar wind?

      CME structure expands and evolves from Sun to Earth (Deforest et al., 2013)


      Objective 2A

      PUNCH capabilities reveal previously inaccessible evolution of the substructure of CMEs as they propagate through the heliosphere. Through its blind-spot eliminating FOV, resolution, sensitivity, and 3D-localizing 3D polarimetric capability, PUNCH resolve long-standing mysteries of CME origin, variability, and geoeffectiveness.

    2. CIR

      Objective 2B

      PUNCH is unique in its ability to observe both early and late manifestations of CIRs. Through a FOV wide enough to encompass both eastward and westward directed views, PUNCH moves beyond a planar perspective, enabling a 3D understanding of CIR formation and evolution (Tappin & Howard 2009). 3D polarization analysis is employed to localize CIR structure.

    3. SOHO/LASCO C3 CME difference image reveals distortion caused by variation in propagation speed (Tappin and Simnett, 1997).


      Objective 2C

      PUNCH provides a cross-scale picture of shock dynamics. By using spatial irregularities and brightness variations to an unprecedented degree of spatiotemporal resolution, shock formation, shock-turbulence interaction, and large-scale instabilities may be explored (Odstrcil & Pizzo, 2009). The role of solar-wind variability on interplanetary shock behavior is revealed by PUNCH, with implications for particle acceleration and radio emission. 3D polarization analysis is employed to localize shock structure.