Apparatus and Setup
This lab computes the magnetopause standoff distance across a range of real published solar wind conditions (Lecture 11), then computes ring-current energy via the Dessler-Parker-Sckopke relation for both the real 6 September 2017 storm and the Carrington Event's estimated range (Lecture 12).
Materials and Data
| Condition | n (cm^-3) | v (km/s) |
|---|---|---|
| Quiet solar wind | 6 | 400 |
| Fast (coronal-hole) wind | 3 | 700 |
| CME sheath (storm) | 10 | 800 |
All level 2, standard published OMNI-database climatological/storm-time values. Dst values: Sept 2017=-142 nT (level 2); Carrington range -800 to -1750 nT (live-verified this session).
Procedure
- Compute the magnetopause standoff distance for all three solar wind conditions and confirm the quiet and storm values match Lecture 11's stated values.
- Compute the dynamic-pressure enhancement factor (storm/quiet) and confirm the standoff-distance reduction is proportionally much smaller, illustrating the one-sixth-power scaling.
- Compute the dynamic-pressure enhancement factor that would be required to compress the magnetopause exactly to geosynchronous orbit (6.6 R_E), starting from the quiet-wind dynamic pressure.
- Compute ring-current energy (DPS relation) for the real 2017 storm and for both ends of the Carrington Dst range, and tabulate all three alongside their ratio to the 2017 value.
Analysis and Uncertainty
Discuss why the Carrington Event's ring-current-energy range should be presented as a range with an explicit factor-of-two-plus spread (reflecting genuine, disclosed historical-reconstruction uncertainty), not collapsed to a single "best" number.
Deliverables
- The three-condition standoff-distance table.
- The geosynchronous-compression pressure-factor calculation.
- The three-event ring-current-energy comparison table.
Assessment Criteria
- Correct standoff-distance arithmetic for all three conditions.
- Correctly identified one-sixth-power scaling behavior.
- Correct DPS-relation arithmetic for all three Dst values, with correctly disclosed Carrington range.
References and Provenance
- 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.
- Solar wind climatology: standard published, level 2. Carrington Dst range: live-verified this session; see
materials/ASTR370/reference-log.md. - Generated by
materials/ASTR370/src/generate_astr370_content.py.