Description
Introduces solar structure, magnetic activity, sunspots, flares, coronal mass ejections, the solar wind, heliophysics missions, magnetospheric response, and space weather impacts on technology (the official catalog description). Every physical tool developed in this course — the hydrostatic solar-atmosphere scale-height argument, the sunspot thin flux-tube magnetic-pressure balance, the Parker solar-wind transonic critical-point derivation (solved numerically), flare free-energy budgets from magnetic reconnection, the Chapman-Ferraro magnetopause standoff-distance formula, and the Dessler-Parker-Sckopke ring-current/Dst relation — is derived from first principles and then applied to real data: real Solar Cycle 24/25 sunspot-number records (SILSO/WDC-SILSO), the real 6 September 2017 X9.3 flare/CME/G4-storm case study (AR 12673), the historic 1859 Carrington Event, the Parker Solar Probe mission, and real SDO/SOHO instrumentation; see reference-log.md for full data provenance, including which datasets were live-verified via direct web fetch this session versus drawn from standard published literature.
Learning Outcomes
- Derive the hydrostatic scale-height relation and apply it to the Sun's photosphere and corona, and explain the unsolved coronal-heating problem.
- Describe the Babcock-Leighton solar dynamo qualitatively and interpret real Solar Cycle 24/25 sunspot-number data.
- Derive the thin flux-tube magnetic-pressure balance condition for sunspots and distinguish it from the Biermann convective-suppression mechanism responsible for sunspot darkness.
- Explain magnetic reconnection as a flare energy-release mechanism, estimate an active region's order-of-magnitude free energy budget, and apply the GOES flare classification scheme to a real, extensively documented flare (AR 12673, 6 September 2017).
- Derive and numerically solve the isothermal Parker solar-wind transonic critical-point equation, and compute CME transit times, contrasting naive constant-speed estimates with real observed transit times.
- Describe the complementary techniques of remote sensing (helioseismology, coronagraphy) and in-situ measurement (Parker Solar Probe) used to observe the Sun and solar wind.
- Derive the Chapman-Ferraro magnetopause standoff-distance formula and the Dessler-Parker-Sckopke Dst/ring-current-energy relation, and apply both to a real modern storm and to the historic Carrington Event.
- Explain the physical chain connecting space weather to real technological impacts: satellite atmospheric drag, radiation hazards, ionospheric disturbance, and geomagnetically induced currents in power grids.
Textbook and Materials
Primary reading: OpenStax Astronomy 2e (free, openly licensed; local extracted reference copy under references/openstax-astronomy-2e-extracted.txt). The Sun is covered 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 15.1–15.24 all appear under their matching section headers with no offset), rather than extrapolated by analogy from a prior course. Because ASTR 370 is an upper-division elective, nearly every quantitative topic here (the hydrostatic scale-height derivation, the sunspot magnetic-pressure balance, the Parker transonic wind solution, flare free-energy budgets, the Chapman-Ferraro standoff distance, and the Dessler-Parker-Sckopke relation) goes well beyond OpenStax Astronomy 2e's introductory, descriptive level; each lecture's slides and notes state explicitly where this course extends beyond the assigned reading.
Assessment
| Component | Weight |
|---|---|
| Problem sets (7) | 30% |
| Labs (7) | 30% |
| Midterm exam (Lectures 1–7) | 15% |
| Final exam (cumulative, emphasis Lectures 8–14) | 20% |
| Participation and reading checks | 5% |
Lecture, Lab, and Problem-Set Cadence
The course runs 14 lectures, 7 labs, and 7 problem sets — a matched 1:1 biweekly cadence in which each lab and its paired problem set both follow the same two-lecture block, following the ASTR 230/310/320/340/350/360 matched-cadence precedent for a standard-format 3-credit, 14-lecture elective. This choice was confirmed against the actual lecture content, not assumed from file counts alone: the course is organized into seven thematic units of exactly two lectures each (Solar Interior and Atmosphere; Solar Magnetism and Sunspots; Solar Flares; Coronal Mass Ejections and the Solar Wind; Heliophysics Missions and Diagnostics; the Sun-Earth Connection; Space Weather Impacts on Technology), and each unit's two lectures develop exactly one self-contained physical toolkit that its paired lab and problem set then apply to real data — a natural, unambiguous two-lecture-per-lab grid, directly following ASTR 360's precedent of choosing the matched cadence specifically because the course's thematic units are each exactly two lectures long. This is documented explicitly here, rather than left implicit, because a solar physics and space weather course could in principle have been paced unevenly (e.g., a longer flares/CMEs block and a shorter missions block, as some prior courses in this curriculum have done for uneven thematic units); this course's seven sub-topics divide naturally into balanced two-lecture pairs, so the matched cadence was chosen deliberately rather than by default. A single real event — the 6 September 2017 X9.3 flare from active region 12673, its associated CME, and the resulting G4 geomagnetic storm — is used as a running case study across Units 3, 4, 6, and 7, explicitly flagged in Lecture 06 as an illustrative worked example rather than a statistically typical event.
| Lab/PS Unit | Lectures | Lab | Problem Set | Topic | Thematic Unit |
|---|---|---|---|---|---|
| 1 | 1–2 | Lab 01 | PS 01 | Solar hydrostatic structure and scale heights | Unit 1: Solar Interior and Atmosphere |
| 2 | 3–4 | Lab 02 | PS 02 | The solar cycle and sunspot magnetic pressure balance | Unit 2: Solar Magnetism and Sunspots |
| 3 | 5–6 | Lab 03 | PS 03 | Flare free energy and the AR12673 case study | Unit 3: Solar Flares |
| 4 | 7–8 | Lab 04 | PS 04 | CME transit time and the Parker wind's numerical solution | Unit 4: Coronal Mass Ejections and the Solar Wind |
| 5 | 9–10 | Lab 05 | PS 05 | Remote-sensing geometry and Parker Solar Probe in-situ prediction | Unit 5: Heliophysics Missions and Diagnostics |
| 6 | 11–12 | Lab 06 | PS 06 | Magnetopause compression and ring-current energy | Unit 6: The Sun-Earth Connection |
| 7 | 13–14 | Lab 07 | PS 07 | Capstone: geomagnetically induced currents and the full flare-to-grid chain | Unit 7: Space Weather Impacts on Technology |
Revision Policy
High standards apply to all graded work. Problem sets and labs may be revised and resubmitted once for improved credit within one week of return, provided the resubmission includes a short change note identifying what was corrected and why (see each problem set's assessment instructions for full criteria).
Prerequisites Check
PHYS 172 (a calculus-based mechanics/electromagnetism sequence course) and ASTR 230 (Stellar and Galactic Astrophysics) are required as prerequisites because this course's quantitative toolkit builds directly on tools developed in both: the linear-perturbation and conservation-law derivation habits (PHYS 172) needed to follow the Parker wind's critical-point argument and the Chapman-Ferraro pressure-balance derivation, and the radiative-transfer, hydrostatic-equilibrium, and stellar-structure reasoning (ASTR 230) directly reused here for the solar hydrostatic scale-height derivation and the general habit of applying first-principles physics to a specific, real star. Students who completed ASTR 230 will recognize the hydrostatic-equilibrium and scale-height derivations in Lecture 01 as the same tools applied to stars in general, now specialized to the Sun; students arriving via PHYS 172 will recognize the Parker wind's critical-point analysis and the magnetopause pressure balance as directly analogous to standard mechanics/fluids/electromagnetism techniques applied here to astrophysical plasma.