Capstone: GIC Risk and Course-Long Synthesis
Conservative ratio = 500/375 = 1.33, implied GIC scaling factor = sqrt(1.33) = 1.15 -- both smaller than the lab's original values (ratio 1.87, factor 1.37), illustrating that even a more conservative reanalysis still implies a substantially elevated (not merely comparable) GIC risk relative to the modern benchmark.
| Criterion | Points |
|---|---|
| Correct ratio and sqrt-factor arithmetic | 8 |
| Correct comparison to the lab's original values | 7 |
The equivalent Unit 6 quantity would be the Carrington Event's estimated Dst itself (rather than the 2017 event's published -142 nT). Given the genuine, disclosed uncertainty between the two published estimates (-800 nT conservative vs -1750 nT), a defensible choice is to headline the full estimated range rather than a single number, explicitly noting which study each endpoint comes from -- exactly the disclosure practice this course's own lectures and labs follow.
| Criterion | Points |
|---|---|
| Correct identification of the Dst quantity as the Unit 6 equivalent | 5 |
| Reasoned, non-overclaiming choice of range-vs-single-number presentation | 5 |
Doubling the line length doubles the total GIC magnitude at fixed geoelectric field (since GIC ∝ E x length in this simple resistive model). High-latitude grids like Quebec's are both longer (spanning greater distances) and experience larger geoelectric fields during storms (since auroral/ring-current-driven magnetic disturbances are strongest at high geomagnetic latitude), so both factors compound to increase their GIC risk relative to shorter, lower-latitude grids.
| Criterion | Points |
|---|---|
| Correct linear length-scaling statement | 5 |
| Correct compounding-factors explanation for high-latitude grids | 10 |
Example full-credit answer: "The Sun's hydrostatic interior structure (Unit 1) sets the stage for the dynamo-driven magnetic cycle and sunspots (Unit 2), whose stored free magnetic energy powers flares (Unit 3); a flare's associated CME propagates through the Parker solar wind (Unit 4) until it compresses Earth's magnetosphere and drives a ring current measured by Dst (Unit 6), whose rapid field changes ultimately induce the geomagnetically induced currents that can collapse power grids (Unit 7)."
| Criterion | Points |
|---|---|
| At least four units named in correct order with correct one-clause physical link between each | 15 |
Award full marks for correct method, units, and a numeric result consistent with the arithmetic shown (allow reasonable rounding). Verify that the student re-derives the number for this problem's specific inputs rather than quoting a lecture example without adaptation. Watch specifically for unit-conversion errors (Gauss vs Tesla, nT vs T, km/s vs m/s, hours vs seconds), for comparative-magnitude statements given in the wrong direction, and for level-1/level-2/level-3 data-provenance conflation (e.g., presenting the order-of-magnitude flare free-energy estimate as a precise measurement, or presenting a Carrington-Dst estimate as a directly measured historical value) -- these are the most common sources of mistakes in this course.