Question

Which one of the following options is the primary contributor to the International Geomagnetic Reference Field?

• A. Ionospheric magnetic field
• B. Magnetic field generated in the outer core
• C. Crustal magnetic field
• D. Solar magnetic field

Hint:

The IGRF primarily represents the main field generated by Earth's core. External sources (like ionospheric or solar fields) are considered noise or higher-frequency variations.

Answer 1

The Correct Option is B

Step 1: Understanding the source of Earth's main magnetic field.
The International Geomagnetic Reference Field (IGRF) is a model of the Earth's main magnetic field, which is primarily generated by the geodynamo action in the liquid outer core of the Earth due to the movement of molten iron.
Step 2: Evaluating the options:
(A) Ionospheric magnetic field is a minor, time-varying component.
This is true, but it is not the main source of the Earth's magnetic field.
(B) The outer core generates the main magnetic field—this is the correct answer.
The Earth's primary magnetic field is generated by the motion of molten iron in the liquid outer core through the geodynamo effect.
(C) Crustal fields are smaller and more localized.
Crustal magnetic fields are present, but they are much weaker compared to the Earth's main field.
(D) Solar magnetic fields influence space weather but not the Earth's internal field.
While solar magnetic fields affect space weather, they do not contribute to the Earth's internal magnetic field.