Earth Science — Size of the Magnetosphere (Dayside) Approximately how far does the Earth’s magnetosphere extend on the dayside, measured from the planet and commonly quoted in general geography references?

Introduction / Context:
The magnetosphere is the region dominated by Earth’s magnetic field, deflecting the solar wind. Its size is not fixed; it compresses on the dayside and stretches into a long magnetotail on the nightside. General-knowledge sources often quote a rounded dayside extent figure for quick recall in exams.

Given Data / Assumptions:

• The question asks for a typical dayside extent in kilometers “above the Earth’s surface.”
• Rule-of-thumb distances are acceptable for GK (not a precise, variable boundary).
• We exclude tail distances, which are far larger.

Concept / Approach:

On the dayside, the magnetopause is commonly around 10 Earth radii (Re) from Earth’s center under average solar-wind pressure. One Re ≈ 6371 km. A rounded figure many primers present is ~64,000 km (order of 10 Re), acknowledging variability. Therefore, among the choices, ~64,000 km “above the surface” is the accepted school-level answer, despite the technical nuance that 10 Re is measured from the center (giving a slightly lower height above the surface).

Step-by-Step Solution:

Recall 1 Re ≈ 6371 km; 10 Re ≈ 63,710 km.Map to rounded GK figure ≈ 64,000 km.Select the nearest provided option.

Verification / Alternative check:

Introductory geoscience texts and exam guides typically cite “about 64,000 km on the dayside” and “hundreds of thousands of km into the tail on the nightside.”

Why Other Options Are Wrong:

9600 km / 8000 km: Far too small; within the plasmasphere and inner magnetosphere only.None of the above: Not needed since a suitable rounded value is present.

Common Pitfalls:

Confusing center-to-boundary distance (in Re) with height above surface; GK answers typically use a convenient round km figure without that distinction.

Final Answer:

64,000 km above the Earth's surface