Question
Download Solution PDFWhich of the following statements is/are correct about the variation of magnetic declination?
Statement I: Magnetic declination is more at magnetic poles and less at equator.
Statement II: Magnetic declination is more in the summer than in the winter.
Statement III: Magnetic declination is more at night and less in the day.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Statement I: Magnetic declination is more at magnetic poles and less at equator.
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True.
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Magnetic declination is the angle between true north and magnetic north.
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Near the magnetic poles, this angle becomes large and erratic.
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Near the magnetic equator, the deviation is generally smaller and more stable.
Statement II: Magnetic declination is more in the summer than in the winter.
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True
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In summer, the Earth's ionosphere experiences more solar radiation, which increases magnetic activity.
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As a result, there is more fluctuation in the magnetic field, leading to a slightly higher magnetic declination.
Statement III: Magnetic declination is more at night and less in the day.
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False.
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Daily (diurnal) variation is minor, and during daytime, solar radiation affects ionospheric currents, causing slightly more variation than at night—not the other way around.
Additional InformationMagnetic Declination
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It's the angle between true north (geographic north) and magnetic north.
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Measured east or west from true north.
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Essential in navigation, surveying, and compass correction.
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The Earth's magnetic field is not uniform.
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It changes over time due to movement in the Earth's molten outer core (known as secular variation).
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Declination maps (isogonic charts) are used to track local values.
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Long-term (secular): Slowly changes over years/decades.
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Short-term (diurnal): Slight daily shifts due to solar radiation, but typically <0.1°.
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Sudden changes: Can happen during geomagnetic storms or strong solar activity.
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