SWP Solar Physics & Radiation 5 — Questions and Answers
Question 1: High-speed solar wind streams of about 700–800 km/s mainly originate from which solar feature?
- Active-region sunspots
- Coronal holes (Correct answer)
- Helmet streamers
- Prominences
Correct answer: Coronal holes
Coronal holes have open magnetic field lines that allow fast, low-density solar wind to escape.
Question 2: The F10.7 solar activity index measures solar radio flux at what frequency, and in what unit?
- 245 MHz, in pfu
- 10.7 GHz, in W/m²
- 1420 MHz, in jansky
- 2800 MHz, in solar flux units (sfu) (Correct answer)
Correct answer: 2800 MHz, in solar flux units (sfu)
F10.7 is the 10.7 cm (2800 MHz) flux in sfu, where 1 sfu equals 10⁻²² W m⁻² Hz⁻¹.
Question 3: How does galactic cosmic ray flux at Earth vary with the solar cycle?
- It does not vary with solar activity
- It is highest near solar minimum and lowest near solar maximum (Correct answer)
- It peaks only during the declining phase
- It is highest near solar maximum
Correct answer: It is highest near solar minimum and lowest near solar maximum
A stronger, more turbulent heliospheric magnetic field at solar maximum shields the inner heliosphere from cosmic rays.
Question 4: Corotating interaction regions (CIRs) tend to recur at Earth with what approximate period?
- About 24 hours
- About 27 days (Correct answer)
- About 11 years
- About 6 months
Correct answer: About 27 days
Long-lived coronal holes rotate with the Sun, so their stream interfaces return about once per synodic solar rotation.
Question 5: The South Atlantic Anomaly is a concern for low-Earth-orbit spacecraft mainly because of which particles?
- Neutral atmospheric oxygen
- Solar wind alpha particles
- Auroral electrons below 10 keV
- Energetic trapped protons from the inner Van Allen belt (Correct answer)
Correct answer: Energetic trapped protons from the inner Van Allen belt
Earth's weak field over the South Atlantic lets the inner proton belt dip to LEO altitudes, which causes single-event upsets.
Question 6: What is the approximate angle of the Parker spiral interplanetary magnetic field relative to the Sun–Earth line at 1 AU?
- About 45° (Correct answer)
- About 0°
- About 10°
- About 90°
Correct answer: About 45°
Solar rotation combined with a ~400 km/s radial solar wind winds the field into a spiral that is roughly 45° at Earth's orbit.
Question 7: What does it mean when a coronagraph observes a 'full halo' CME?
- The CME is directed roughly along the Sun–Earth line, either toward or away from Earth (Correct answer)
- The CME is narrow and travels in the ecliptic plane
- The CME came from a polar coronal hole
- The CME is too faint to have any geomagnetic effect
Correct answer: The CME is directed roughly along the Sun–Earth line, either toward or away from Earth
Ejecta that expand in all directions around the occulting disk are traveling near the line of sight, so disk imagery is needed to tell front-side events from back-side ones.
