# Assessment Instructions: Problem Set 04 — CME Transit and the Parker Wind

## Inputs to Inspect
Student submission, this problem set, the solution key, the corresponding lecture slides/notes, and the referenced dataset(s) under `materials/ASTR370/data/`.

## Grading Standard
Award credit for correct method and units first, then for the specific numeric result. A student who shows correct reasoning with a small arithmetic slip should receive most of the available credit; a student with a correct-looking number but no visible derivation steps should not. Because this is a 300-level quantitative solar physics and space weather course, full marks require a genuine derivation wherever the problem set asks for one, and a genuinely reasoned (not merely asserted) interpretation wherever the problem asks for scientific judgment (e.g., honestly characterizing an order-of-magnitude estimate's uncertainty, or a historical reconstruction's disclosed range).

## Problem-Level Criteria
- Problem 1: verify the inverse speed-time scaling is confirmed numerically.
- Problem 2: verify correct r/r_c conversion for Mercury's orbit and correct numerical root-finding.
- Problem 3: verify the direction of the critical-radius temperature dependence (cooler -> larger r_c) is derived from the 1/c_s^2 scaling, not guessed.
- Problem 4: verify the qualitative direction of the time-constant sensitivity is correct (longer time constant -> shorter transit time).

## Resubmission Policy
Students may resubmit within one week of receiving feedback. A resubmission must show a corrected derivation, not only a corrected final number, and should reference the specific feedback comment it addresses. Regrade to a maximum of 90% of the original point value unless the error was a grading mistake.

## Common Errors to Flag
- Sign errors in the r_c vs temperature scaling (claiming a hotter corona gives a larger critical radius).
- Choosing the wrong root of the Parker wind transcendental equation (subsonic instead of transonic branch) for r>r_c.
- Reversing the direction of the time-constant sensitivity in Problem 4.