Extend this unit's transit-time and Parker-wind tools to new speeds, radii, and coronal temperatures.
Compute the naive constant-speed transit time for a hypothetical CME twice as fast as the real 6 September 2017 event (2 x 1571 = 3142 km/s), and compare it to the real event's naive transit time computed in the lab.
Mercury orbits at approximately 0.39 AU. Numerically solve the Parker transonic wind equation for u at r=0.39 AU (convert to r/r_c using the critical radius from this unit's data) and report the wind speed in km/s. State whether it is faster or slower than the wind speed at 1 AU computed in the lab, and explain why using the equation's r-dependence.
Recompute the coronal sound speed and critical radius for a somewhat cooler corona (T=1.0e6 K rather than this unit's 1.5e+06 K), and state whether the critical radius moves closer to or farther from the Sun as a result.
Using the drag-based deceleration functional form from the lab but with a time constant of 25 hours instead of 15 hours, describe qualitatively (no need to fully re-derive the arrival time numerically) whether this longer time constant would predict a faster or slower approach to the ambient wind speed, and hence a shorter or longer predicted transit time.
Submit a complete derivation with equations, units, labeled quantities, and a short narrative interpretation for each problem. Show every step; a correct final number without a visible derivation receives partial credit at most, and quoting a lecture number without adapting it to this problem's specific inputs receives no credit for that step.
OpenStax Astronomy 2e (local extracted reference copy: references/openstax-astronomy-2e-extracted.txt) covers the Sun in Chapter 15 ("The Sun: A Garden-Variety Star"): 15.1 The Structure and Composition of the Sun, 15.2 The Solar Cycle, and 15.3 Solar Activity above the Photosphere. Chapter 15’s section numbering was cross-checked directly against its own embedded figure numbering this session (Figures 15.1 through 15.24 all appear under their matching section headers with no offset), so this citation is verified against the local extracted text rather than extrapolated by analogy from a prior course. OpenStax’s treatment throughout Chapter 15 is descriptive and qualitative; nearly every quantitative derivation in this course (the hydrostatic solar-atmosphere/scale-height argument, the sunspot magnetic-pressure balance, the Parker solar-wind critical-point argument and its numerical transonic solution, flare free-energy budgets, the Chapman-Ferraro magnetopause standoff distance, and the Dessler-Parker-Sckopke ring-current/Dst relation) goes well beyond OpenStax Astronomy 2e’s introductory level; each lecture states explicitly where this course extends beyond the assigned reading.
materials/ASTR370/data/ where referenced above.