SWP Solar Physics & Radiation 5

Question 1

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

Accepted Answer

Coronal holes

Answer

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?

Accepted Answer

2800 MHz, in solar flux units (sfu)

Answer

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?

Accepted Answer

It is highest near solar minimum and lowest near solar maximum

Answer

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?

Accepted Answer

About 27 days

Answer

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?

Accepted Answer

Energetic trapped protons from the inner Van Allen belt

Answer

Earth's weak field over the South Atlantic lets the inner proton belt dip to LEO altitudes, which causes single-event upsets.

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