Solar Physics & Radiation Flashcards

High-speed solar wind streams of about 700–800 km/s mainly originate from which solar feature?

Answer: Coronal holes

Coronal holes have open magnetic field lines that allow fast, low-density solar wind to escape.

The F10.7 solar activity index measures solar radio flux at what frequency, and in what unit?

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.

How does galactic cosmic ray flux at Earth vary with the solar cycle?

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.

Corotating interaction regions (CIRs) tend to recur at Earth with what approximate period?

Answer: About 27 days

Long-lived coronal holes rotate with the Sun, so their stream interfaces return about once per synodic solar rotation.

The South Atlantic Anomaly is a concern for low-Earth-orbit spacecraft mainly because of which particles?

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.

What is the approximate angle of the Parker spiral interplanetary magnetic field relative to the Sun–Earth line at 1 AU?

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.

What does it mean when a coronagraph observes a 'full halo' CME?

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.